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climbingjones
Trad climber
grass valley,ca
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Topic Author's Original Post - Jan 13, 2007 - 09:48pm PT
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Obviously there is a debate on how to equalize an anchor. I prefer to use a cordelette (or long sling) joining 3 or more pieces with the sliding "W" method. A former partner used to argue that the correct way was to knot a figure 8 knot at the supposed "perfect" angle. To me this can load only one piece when the anchor is loaded at a different angle than thought due to many variables, such as the belayer putting some pull on it in an un-thought of angle, or a fall that puts force on it in a different angle. Plus, since you dont know when your climber might fall or what angle they might put on it. The sliding "W" takes all of those variables into account and distributes the weight evenly when weighted. I would be interested to hear others thoughts.
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TGT
Social climber
So Cal
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Jan 13, 2007 - 10:00pm PT
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Howza bout a good place to brace your feet and a hip belay?
Bomber!
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climbingjones
Trad climber
grass valley,ca
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Topic Author's Reply - Jan 13, 2007 - 10:01pm PT
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Seriously AC? Clove hitching does not equalize them. My reference to 'obvously' was due to the arguments between me and the aforementioned partner. But I would assume that there is a debate? We seem to argue everything here. And that is good, more minds, more opinions, more solutions. I guess. Just looking for input.
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climbingjones
Trad climber
grass valley,ca
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Topic Author's Reply - Jan 13, 2007 - 10:03pm PT
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As long as the hip belay includes a hemp rope TGT. Maybe a foot jam? I like yer style.
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clustiere
Trad climber
Durango, CO
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Jan 13, 2007 - 10:10pm PT
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be sure to absorbe shock through letting the rope slip around the waist..!!
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climbingjones
Trad climber
grass valley,ca
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Topic Author's Reply - Jan 13, 2007 - 10:10pm PT
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Yeah. I thought. How to place the biner. Sliding or tied off knot? That was my question. I guess I did not simplify it enough. Sorry for the confusion. Just trying to get some climbing related talk going here. No confusion for me. I think the way I outlined is the way. Just trying pick some brains.
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Climber 46
Social climber
Ottawa, Ontario
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Jan 13, 2007 - 10:18pm PT
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I haven't seen Largo's new book yet, but my current practice is to tie a figure 8 so there is no extension of the power point if one of the anchor pieces were to fail. It is possible that the new book will provide updated info....Anyone out there know?
Cheers,
Doug
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cintune
climber
Penn's Woods
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Jan 13, 2007 - 10:21pm PT
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This is one of those potentially endless debates, but either way, screamers are great insurance.
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climbingjones
Trad climber
grass valley,ca
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Topic Author's Reply - Jan 13, 2007 - 10:21pm PT
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It was cool, sorry freezing. The ice is so hard. Rare for this area. Just bouldered some smaller stuff. Some short solos as my partner couldnt make it. Shoe-d around a bit. Scoping for tomorrow. Headed to some FAT formations at Rainbow tomorrow, maybe the tracks near 20 and 80 junction. With the partner this time.
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john hansen
climber
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Jan 13, 2007 - 10:22pm PT
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Any one got a diagram showing a sliding W? I think I know how the tied off figure eight looks.
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 13, 2007 - 10:28pm PT
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boy, this topic was flailed to death on rc.com and then that dead horse was beaten repeatedly...
...John Long's latest edition of the Anchors book has some new data from anchor equalization schemes that everyone should read.
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Beer 46
climber
Mountain Room
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Jan 13, 2007 - 10:58pm PT
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"Equalization"
The bad news is: It's impossible.
The good news is: It's unnecessary (nearly always).
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climbingjones
Trad climber
grass valley,ca
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Topic Author's Reply - Jan 13, 2007 - 11:26pm PT
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Unnecassary? Are you serious? Then why not just use one piece at an anchor? Perfect equalization might be unatainable, but some form of an attempt should be made. Otherwise you are using just one piece, no matter how many you have placed. Please explain.
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Tom
Big Wall climber
San Luis Obispo CA
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Jan 13, 2007 - 11:42pm PT
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The sliding W allows the power point to move down before equalizing the remaining anchors if one fails. This means that a pseudo shock-load hits the remaining anchors.
The figure-8 does load the anchors unevenly, depending on the direction of the load and how much care is taken in tying it. However, if one anchor fails, the others are not as severely loaded during the transition from three to two points.
I only climb walls, which means heavy haul bags. I would never use a sliding W for a wall anchor. Having a haul bag break loose and suddenly fall half a meter onto a few meters of perlon cordelette is not my idea of safe climbing.
A sliding W for equalizing a single aid placement (two or three bad pins, all tied together) is not a bad idea, because the load is shared among the bad pieces. The idea here is that none of the pieces is strong enough, so the concept of statistical strength is used to move up past the bad section. If one of them rips, well, that's why they call it A4/A3 loose.
If your belay pieces are so bad that you need to equalize them with a sliding W, you are on A6, which is beyond the scope of rational climbing, and this forum is not the place to find out how to stay alive.
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climbingjones
Trad climber
grass valley,ca
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Topic Author's Reply - Jan 13, 2007 - 11:47pm PT
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No Tom, I dont use the sliding "W" for aid anchors. Free anchors only. When loaded I have witnessed the sliding "W" move and while doing so I can see that the load is being distibuted evenly. I think there is usefullness to both methods. Different situations require different applications.
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WBraun
climber
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Jan 13, 2007 - 11:49pm PT
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Always equalize, be redundant, make your anchors 10 to one safety factor, visualize your power points, good job, and now have fun.
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the Fet
Knackered climber
A bivy sack in the secret campground
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Jan 13, 2007 - 11:53pm PT
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The sliding W is the most effective thing to equalize 3 pieces, you can back it up with another longer cord or sling tied with an 8 or overhand so it doesn't extend much if one piece blows. On that A6 pitch.
I haven't had the chance to get Largo's new book, but in the rc.com thread he mentions the sling/cord tied with an 8 doesn't equalize, most force is on the shortest arm.
I've been using a sliding X with limiter knots (good equalization, little extension) on the two best or closest pieces. And a seperate sling to a third piece, slightly loose, if I think I need it.
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climbingjones
Trad climber
grass valley,ca
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Topic Author's Reply - Jan 13, 2007 - 11:57pm PT
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That is the way that I do it Fet. Seems bomber. Total confidence I feel. The figure 8 does load unevenly, no matter how well you anticipate to load direction.
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the Fet
Knackered climber
A bivy sack in the secret campground
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Jan 14, 2007 - 12:13am PT
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I've been using this trick to shorten the sling for the third piece. I leave my sliding X with limiter knots pretied, so I usually don't have to tie any knots at the anchor. Very fast.
I don't use it like the picture. The way I use it, the quickdraw in the picture is replaced with a sliding X with limiter knots.
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rgold
Trad climber
Poughkeepsie, NY
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Jan 14, 2007 - 12:22am PT
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Here's a summary of the equalization discussion.
There is a sort of Heisenberg Uncertainty Principle for equalization: It is impossible to obtain equalization with no-extension under anchor point failure. The only way to genuinely equalize the load to multiple anchors is to have some sort of pulley system. But if an arm of a pulley system fails, there will be extension.
Until recently, most climbers used fixed-arm set-ups that cannot equalize in theory and do not equalize in practice. Such anchors are distributed anchors, not equalized anchors, and there is a chance that if loaded to anchor point failure, the load will be applied sequentially to single points rather than divided amongst them.
Pulley systems that allow for large extensions if a single piece fails are undesirable, so the challenge of practical equalization is to produce a pulley component with relatively little rope or webbing in it so that not much extension is possible.
There are three further challenges here.
One is that you don't want to burn up too much gear at belays. Many of the systems proposed on the rc.com extravaganza use five or six biners, not counting the power point attachments, for a three-point anchor. That's ten to twelve biners from your rack devoted to a pair of belay stations, too much unless you're on a big wall and lugging the kit that goes with it.
The second challenge, a much more daunting one, is friction. A pulley system won't equalize if the frictional losses around components are too great.
The third challenge is complexity. A system should be highly adaptable and deploy rapidly with little or no potential for disasterous mistakes.
There is a another challenge, advanced by Largo, that anchoring solutions should be obtained with simple gear like slings and cordelettes. I haven't listed this as one of the challenges to be met because I think the only way to make real progress is to concoct some specialized gear. Although I am deeply sympathetic to any aversion to gadgetry, I also have to admit, looking at all the mechanical doo-hickies hanging from my harness, that we are several decades past anything like true economy of gear.
Largo's equalette meets the challenges for two-point anchors, but is a half-measure for three (or more) point anchors. The sliding W mentioned by climbingjones fails both the friction test and the extension test and so is a poor candidate for a solution in my opinion.
Most climbers are happy with their fixed-arm rigging, but that could change if equalizing solutions for multiple anchors are devised, solutions that meet the three challenges listed above.
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Beer 46
climber
Mountain Room
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Jan 14, 2007 - 12:23am PT
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Do as Werner sez.
Seriously though, Mr. Goldstone has mentioned some of the difficulties in actually achieving "equalization". In the real world, it aint gone to happen.
Some people seem fixated on the idea of equalizing, thinking it's always required. Nonsense. Equalization is actually a relatively new idea (last 30 years or so). The fact is the gear is strong enough (usually) without equalization. In most cases, you want more than one piece to provide backup for the unexpected, not because one isn't strong enough.
Of course, there are exceptions, in which case, load sharing (a far more accurate term) strategies are called for. If you're in such a fix, you should also be thinking about other survival strategies, like "Don't Fall".
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Rocky5000
Trad climber
Falls Church, VA
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Jan 14, 2007 - 12:38am PT
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Clever sling-shortening, though by instinct I get queasy when sling material rubs against itself. Not a factor, though, on this minor scale. Just keep a paranoid eyeball glued to it.
There is no perfect anchor, ever; it's an unlimited opportunity for creativity. If you have two really strong pieces, you can make it simple and quick, if the force vector is fairly definite. If all you have is marginal garbage, you have to pull out all your tricks and go nuts - screamers, cordlettes, sliding W with backups to brass micronuts duct-taped onto a rugosity - whatever. If if if. Although it's fun to browse J. Long's many interesting photos of anchors, I never remember any of that when I'm up there; I have to respond to whatever unique weirdness is thrown at me, and do it right.
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WoodySt
Trad climber
Riverside
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Jan 14, 2007 - 01:53am PT
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How do you equalize one point. I don't know what you're talking about here.
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climbingjones
Trad climber
grass valley,ca
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Topic Author's Reply - Jan 14, 2007 - 01:57am PT
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Can you use yer lips?
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Beer 46
climber
Mountain Room
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Jan 14, 2007 - 02:31am PT
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How do you equalize one point?
How do you clap one hand?
Questions for Werner?
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Trusty Rusty
Social climber
Tahoe area
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Jan 14, 2007 - 02:33am PT
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"Knots" in an equal system obviously work in one direction, but once loaded with 2 Haul Bags, 3 swine & 10 cheap Wine Boxes, only a Hindu Monk could untie the mess. Dan's wrong bro, sliding Cordelette is better for loads, just make sure the cord is beefy.
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Tom
Big Wall climber
San Luis Obispo CA
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Jan 14, 2007 - 03:41am PT
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I would suggest that WBaun is the expert, here.
Anybody who claims to have better experience, prove it.
I am not a worshipper of false gods, but W is neither false nor a God.
He is simply a man who has proven himself.
I don't know what God is thinking, but I think he likes W.
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Tom
Big Wall climber
San Luis Obispo CA
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Jan 14, 2007 - 04:18am PT
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"and now have fun." - WBraun
Well, there it is.
We'd forgotten.
Climbing is supposed to be fun.
I didn't climb because it wasn't fun. 18 years.
Werner, You're the Best:
The Reminder: Have Fun.
I had fun last time I climbed.
Thanx.
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s. o.
Trad climber
academia
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Jan 14, 2007 - 07:35am PT
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A Few thoughts:
I have heard of the figure 8 knot refered to as static equalization.
ditto to rgold and Tom
If a piece fails in the "sliding W" the powerpoint on the achor will drop causing a dynamic load to the rest of the anchor.
The angle between pieces is far more important than the anchoring system used. It is possible and easily done that the individual points have more force exerted on them than if they were the only point in the system. This happens with useing a runner, short cordelette, or having the anchor spread over a large area.
The figure 8 knot increases these forces by increasing the angle.
In the rare case that your cordelette breaks or your knot sucks, or you make a mistake clipping the "w" correctly; your anchor may fail.
Most important: use bomber gear for your anchor - if your anchor fails it is most likely because the RURP, micro nut, and bush you built into an anchor failed.
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Largo
Sport climber
Venice, Ca
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Jan 14, 2007 - 10:32am PT
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"Some people seem fixated on the idea of equalizing, thinking it's always required. Nonsense. Equalization is actually a relatively new idea (last 30 years or so). The fact is the gear is strong enough (usually) without equalization."
I would argue this point--at least a little. The rigging challenges are much greater today than they were when I first started climbing, over 30 years ago. Back then, we slugged titanically strong (and easy to use) chromolly pegs into the rock. It mattered little how we tied them off as even one or two was often good for the whole anchor. Trying to achieve the same brute strength with passive camming devices presents another magnitude of difficulty hence the modern day need trend toward equalizing.
JL
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rgold
Trad climber
Poughkeepsie, NY
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Jan 14, 2007 - 10:45am PT
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Mr. Goldstone has mentioned some of the difficulties in actually achieving "equalization". In the real world, it aint gone to happen.
I do not believe this. The equalette already works for two anchor points, and I think it is just a matter of time before there are acceptable solutions in general. But the solutions cannot be achieved by fixed-length arms.
Equalization is actually a relatively new idea (last 30 years or so). The fact is the gear is strong enough (usually) without equalization. In most cases, you want more than one piece to provide backup for the unexpected, not because one isn't strong enough.
I agree with Largo that equalization has become more important as individual pieces of gear have become both less strong and harder to evaluate. As for the gear being strong enough without equalization, I would submit that we really don't know, because so few belay anchors have ever been subjected to a severe test. I wouldn't be shocked to learn that, say, 10% of all gear belay anchors will not survive a factor-2 fall onto the belay.
Of course, there are exceptions, in which case, load sharing (a far more accurate term) strategies are called for.
One of the reasons to pursue equalization as a general strategy is that a party, yes even an experienced one, may be unaware that it is in one of these exceptional cases.
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dirtineye
Trad climber
the south
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Jan 14, 2007 - 11:56am PT
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I'll just add very slightly to what Rgold said in his last sentence:
Most people who got into a serious jam, and got injured or even maybe died, were probably not thinking, "Gee, I'm really in trouble here. This looks bad, I'd better be careful.", right before the shyte hit the fan.
But I guess if you are going to climb over anchors that seriously need equalization to be good, you have to ask youself, "How much lipstick does it take to make a pig kissable?".
I'm not against equalization or even agaist doing dumb things while climbing, I just like to know when I'm doing it, although, as Rgold pointed out, sometimes you really don't know.
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WoodySt
Trad climber
Riverside
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Jan 14, 2007 - 12:04pm PT
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Just pick up a good sized rock; drop it on the flat; sit behind it; wrap your legs around it and enjoy your partner's screaming and sputtering when he or she arrives.
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andanother
climber
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Jan 14, 2007 - 05:43pm PT
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did rockclimbing.com go offline again?
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Nick
climber
portland, Oregon
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Jan 14, 2007 - 07:22pm PT
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I hate to throw even one cent into the ring on such a discussion, but at the risk of pointing out something obvious. My daughter came home from college a month or so ago with a copy of Largo's new book and one of these equalette things. It looks like a good solution except the arms are too long and you have to tie them up all the time. So, I tied a bowline on a bight into each end and viola. Easy to rack. Two bolts, just clip and go. Four pieces, separate the loops and adjust their length, instant equalization. It worked well for us. If your anchor was all in one vertical crack clove hitches might be better.
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s. o.
Trad climber
academia
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Jan 14, 2007 - 10:13pm PT
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"How much lipstick does it take to make a pig kissable?"
poetry
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healyje
Trad climber
Portland, Oregon
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Jan 15, 2007 - 04:33am PT
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As Ed said, this whole business got flogged to death on rc.com and the horse buried, dug up, and buried several more times just before Largo put out his latest anchor book. The discussion is still there, but due to choices rc.com made that included eliminating in-line photos, the thread isn't quite what it was. That could be good or bad depending on your perspective. Recreating it all here seems ill-advised at best. Largo, haven't had a chance to look at your book but the rc.com discussion was interesting most of the time...
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climbrunride
Trad climber
Durango, CO
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Jan 15, 2007 - 04:35am PT
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Well, this might not be rcN00B.com, but I'm a gear weenine with a science background, so I like a gear discussion every once in a while...
All of the above could be the correct anchor. It just depends on where you use it. For toproping on nice, bomber anchors, where we are climbing left, right, center, etc. on the same rope, a self-adjusting setup like the sliding-W, or linked, equalized slings seems appropriate. You can always get highly gear intensive and clip a loose backup sling to a couple pieces, to minimize extension in case of gear failure.
I can't remember how many times I've found nothing but crap from which to build an anchor. In those cases, I try to get 3 pieces carefully equalized and tied-off with an overhand (not 8) knot on my cordalette. Then, if I can, I still get another one or three pieces to buff it out. Then I very carefully stand, or painfully hang, so I load the anchor just right. If I'm really lucky, I can belay off my wiast and hold most of the load on my legs, should my second take a slip. (Kind of an "improved Spencer Tracy belay" - painful on the kidneys when he falls, but less chance I take flight.) Once I'm all set up and ready to go, I yell those words any second just loves to hear from his belayer, "DON'T FALL!"
EDIT: Thanks for letting me got that gear discussion out of my blood. I don't use that other site, so I had lots of pent-up energy waiting to jump on a tech-weenie topic. Even though I really did't say much, I think I'm now satisfied. Thank you.
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 15, 2007 - 10:19am PT
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Back in the day it was not uncommon to belay off a single, well placed pin. While that was not redundant, it often was overkill safe, especially for the types of climbs that were being done by the majority of climbers. It helped that taking a lead fall was not a part of the the climbing mentality back then.
The introduction of passive climbing protection forced a major rethinking of the whole anchor system. Building a safe anchor became an exercise in finding multiple placements which were usually "serial," that is, you tied off one piece to another to another to you. You were counting on one of the pieces holding if the loaded piece blew out.
When cams came out they were incorporated into these redundant systems. While equalizing was known, it wasn't practiced widely (I believe) until John's book made the case. I remember looking at some of his "bad example" photos with much recognition... and I personally worked hard at an "equalized" anchor system which was very clean. The cordolette idea made the whole system neat and easy to critique vs. the tied of slings, etc, of old systems.
As rgold points out, however, there are not a lot of well understood tests of anchor systems, either failed or successful. The tests recently done for the latest edition of John's book point out a major problem for cordolette equalization, but also studied other anchor tie off systems.
In the end, it is important to remember many of the hard learned lessons:
1) the anchor system should be redundant and each point as secure as possible, ideally each point able to sustain a factor 2 fall
2) it is important that the whole anchor system be considered, especially to avoid a factor 2 fall right off the belay by placing anchors to "protect the belay"
3) rock has finite strength and anchor protection should be placed, as much as possible, in a way that does not depend on a single rock feature... e.g., don't put all you pieces behind the same flake... a "redundant system" includes the material you are anchoring in also...
The analysis of the cordolette forces shows that if each of the arms of the cordolette are the same length, then it works to equalize... if they are not the same length then there are higher forces on the anchors attached with the shortest cordolette arm. This might be entirely acceptable if you consider it when you arrange your anchor attachment, but you have to be aware of the fact that the anchor is not equalized in such a configuration.
Other ways of anchor attachments are valid, as they always have been. The point is to do the "what if" analysis whenever you set up the anchor.
And most importantly, you should keep foremost in your mind that the anchor must be good enough to secure you and your partner in the event of a fall. You life depends on it, always.
Constructing a safe anchor is not impossible, and cordolette or not, constructing a safe anchor always required careful attention.
Once you can do this, you can go out and have fun.
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dirtineye
Trad climber
the south
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Jan 15, 2007 - 10:48am PT
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I do believe that,"Kissable Pig", would make an excellent route name, and I have just such a line in mind.
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bwancy1
Trad climber
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Jan 15, 2007 - 11:53am PT
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I have been using a webolette for a few years now. I equalize as best I can, and tie a figure 8. By leaving the figure 8 a little "loose", there is enough give in the knot to compensate for slightly imperfect lengths on the three legs. I think that an anchor like this would auto-equalize fairly well when loaded.
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rgold
Trad climber
Poughkeepsie, NY
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Jan 15, 2007 - 01:28pm PT
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The analysis of the cordolette forces shows that if each of the arms of the cordolette are the same length, then it works to equalize
...if the cordelette has been tied exactly right. Any errors would have to be partially compensated by give in the knot (completely unpredictable) or stretch in the material (which is one reason why nylon is preferable to spectra).
The so-called "equal arm" situation is essentially three pieces in a horizontal crack. If either the left or right piece fails, the entire load is transferred to the middle piece with no load at all distributed to the other piece. This sets up the "cascade failure" scenario in which each piece in succession is required to bear the entire load.
The other problem with fixed-arm rigging is that it only distributes when the load is applied directly downward (or in whatever direction the rigging has been tied for). If the leader falls on one side or the other of the belayer, then when the rope comes taut the downward fall will be turned into a pendulum. This change of direction comes with a very high acceleration and so it is very reasonable to expect that such a fall will impose a high load on the belay that is not straight down, the direction the anchor was tied for. This load will have to be born by one of the outer single pieces of the anchor, and so will also set up the cascade failure scenario.
The usual response to these observations is that if things are really this bad, why aren't parties regularly plunging to their death? The answer, in my view, is that it is very rare that an anchor is tested.
Here is another way to look at the situation. Suppose there was a way to achieve practical equalization with directional tolerance, a way that was as easy to deploy as a cordelette. Wouldn't it be sensible to adopt such a method and thereby eliminate or at least significantly reduce potential scenarios such as the ones above?
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wootles
climber
Gamma Quadrant
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Jan 15, 2007 - 02:20pm PT
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The analysis of the cordolette forces shows that if each of the arms of the cordolette are the same length, then it works to equalize
Actually... no.
I did the drop tests for Largo's book and it may be pointed out in there that even when the legs of the cordelette were tied as near to perfectly equal as I could get them there was still significant differences in the force to each anchor. It should also be noted that it was easy to judge the direction of pull for each drop because I was using a guided mass where the pull, obviously, was in the same spot every time.
It's all in the book and as much as you all love to bust on rc.com everything is pretty well covered over there, that is if you can wade through the 1000 or so impertinent posts.
Constructing a safe anchor is not impossible, and cordolette or not, constructing a safe anchor always required careful attention.
I think this is a point that may have been missing in the discussion on rc.com. There seemed to be too much black and white thinking and that will only limit your 'bag of tricks' to building a safe anchor.
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Thom
Trad climber
South Orange County, CA
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Jan 15, 2007 - 06:17pm PT
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Man, this topic HAS been beaten to death 10x over...
I do believe the argument AGAINST the "sliding W" or any self-equalizing anchor set-up goes something like this:
If any single piece fails, the remaining pieces are shock-loaded as the anchor re-equalizes itself, thus requiring the remaining pieces to be "bomb-proof" to prevent their failure also. Since one does not know which of the pieces will fail, when using any self-equalizing system, we must be certain that EVERY piece is "bomb-proof" thus negating the need to use a self-equalizing system to begin with.
Someone needs to do some testing:
Rig up a tied-off, 3-piece cordelette anchor with the appropriate angles to promote equalization throughout the system; then, release one of the pieces and record how the weight transfers to the remaining pieces via the cordelette. I doubt there is much difference between the two.
Maybe hang 3 scales from a beam, rig the cordelette, hang a weight on the power-point, and record the weight on each scale; then, cut one of the cords and watch how the weight transfers.
I'd do it myself but don't have the equipment.
Cheers,
T.
Edit: haven't read the book, just saw the above posts and apparently somone has done some testing (finally) with the cordelette system. Guess I'll have to obtain said book to see the results. t.
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healyje
Trad climber
Portland, Oregon
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Jan 15, 2007 - 06:44pm PT
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It's a testament to the new RC forum software that you can do a "show all" on that thread. The pictures have been replaced with links to them and I'd recommend you right-click on those links and do "Open in a new window" so you keep your place in the thread easier. I'd also recommend you consider all the ideas more from a component perspective versus accepting or rejecting whole anchor designs. There are a lot of interesting ideas presented and many good ones are not necessarily in the best anchor proposals (imho). On the whole it was a pretty worthy exploration of the space even if later in the thread the conversation suffers a bit here and there...
RockClimbing.com: [url="http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?do=post_view_flat;post=1306133;page=1;sb=post_latest_reply;so=ASC;mh=25;guest=3555152" target="new"]Improved sliding x: Is it really safer?[/url]
P.S. Please do not rouse the sleeping beast that is that thread. Let that poor damn horse rest in peace - it went through hell for the cause...
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rhyang
Ice climber
SJC
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Jan 15, 2007 - 07:05pm PT
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I read JL's new book over the holiday, and was quite amazed. I'd like to experiment with the equalette more, since it seems like a useful technique.
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WBraun
climber
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Jan 15, 2007 - 08:26pm PT
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So Cjones
Still sliding on that W?
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rgold
Trad climber
Poughkeepsie, NY
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Jan 15, 2007 - 08:55pm PT
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Man, this topic HAS been beaten to death 10x over...Someone needs to do some testing
The trick now is to keep up with the beatings...which is why, Joe's urgent pleas not withstanding, there still appears to be some use in these discussions. And although the rc.com thread is gargantuan, there are a number of fundamental questions still unanswered and perhaps even unposed, primarily because that thread was, perhaps prematurely, about solutions.
So I'm gonna take up my club and administer another some more whacks for time number 11. In partial justification, the points made here have not been made in the rc.com thread. [Edit: This claim is overblown. In particular, GoClimb repeatedly raised the question about the effect of the belayer falling during anchor extension in the rc.com thread.] Nonetheless, they're probably of interest to only a few folks out there; to the rest I apologize for blabbering on so, but suggest that there may be something worth considering in the final two points.
In the case at hand, testing has been performed for a two-anchor equalized system (the equalette) with a drop of a bit under 5". The results, reported in the rc.com thread---which almost no one can bear to read---and reiterated in JL's anchor book, pp 190--191, are that the extension makes little difference in the peak loads.
I'm not exactly sure what question one should be asking for this situation, but I think it is this: If a fixed-arm system (e.g. cordelette) has one arm fail and all the load is transferred to the other anchor(s), how does the peak load in that situation compare to what happens if a sliding system fails and transfers the load to the same anchor(s)? I don't think this question has been answered yet. JL? Wootles?
Moreover, I think result reported by JL has to be understood properly. Those tests were conducted by dropping a weight directly onto the anchor. In such a test, the length of rope involved becomes important for understanding the results.
As is now well-known, the load on the anchor depends on the fall factor. When the anchor blows, the length of rope remains the same (I'm assuming an equalette made up of extremely low-stretch material that doesn't contribute to energy absorbtion) but the length of the fall increases by the amount of anchor extension. If this extension is very small compared to the amount of rope, then the fall factor barely changes and we wouldn't expect to see much difference in the loads on the anchor. I suspect this is what happened in the tests JL reported; perhaps Wootles could clarify this point.
If, however, the extension in the anchor is significant compared to the length of rope involved, then there could be a big increase in fall factor leading to a much higher anchor load.
In a climbing situation, the load on the anchor is delivered by the tension in the belayer's tie-in, which is usually relatively short. The dynamics of the situation are those of coupled harmonic oscillators (two sections of rope, one section between falling leader and belayer, the other section the belayer's tie-in), and I haven't worked out what would, in theory, happen to the tension in the belayer's tie-in. But it is possible to make some rough estimates by treating the leader's fall and the belayer's fall as if they were not coupled events.
The leader's fall energy is absorbed by the full length of rope involved, and a small extension from the anchor would have a negligible effect on the fall factor and so on the anchor load. But, assuming the fall pulls the belayer off and the anchor extends, the belayer's fall energy has to be absorbed by the short tie-in.
If an 80 kg belayer tied in with two feet of rope with 9 kN impact rating falls 4 inches because of anchor extension, then there is a fall factor of 1/6 with consequent load of about 3.2 kN, a bit less than 720 lbf. So given the showdown I proposed above between the cordelette and the sliding anchor, I'd expect the remaining anchor to have to withstand a somewhat higher load---it is hard to know how good an estimate 720 lbf is.
This effect might be mitigated by the fact extension might allow the extraction of the piece to absorb some fall energy. This point has been argued a lot too; it depends on whether the falling leader's rope can recover during the brief interval when it is unweighted. There are some theoretical reasons to believe this, and I think the data from the drop tests with arm failure suggest it too.
So there is reason to believe that an extension that is small compared to the tie-in length, although it will increase the load on the remaining anchors, has benefits that outweigh the deficits. [Edited.] But there are some caveats worth observing too:
(1) All bets are off if you tie in with slings or daisies. You will then have thrown out the belayer's energy absorber and a small extension might provoke a big load increase. Anyone using an extendible system must tie in with the climbing rope (and indeed this is true for all tie-ins in my opinion.)
(2) If there's a choice of belay positions, The longer your tie-in the better, since you want to minimize the ratio (extension) / (tie-in length).
Sorry Joe, I know you begged me not to do this.
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healyje
Trad climber
Portland, Oregon
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Jan 15, 2007 - 09:00pm PT
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Well, you're far braver than I and it will be interesting to see if it goes (ends) better over here. At least you can post pictures here - I'll grant you that much...
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cintune
climber
Penn's Woods
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Jan 15, 2007 - 09:05pm PT
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There is a way to view the embedded images in the rc thread if you use Firefox. It's a java script posted by melekzek that can't be posted here because the ST server reads it as instructions instead of as text, but for the details see here:
http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?post=1489870
The how-to is in the fifth post down, but the most recent version of the bookmarklet is in the sixth post.
Anyone who can equalize an anchor should be able to follow these directions.
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healyje
Trad climber
Portland, Oregon
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Jan 15, 2007 - 09:10pm PT
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"So there is reason to believe that extension, although it will increase the load on the remaining anchors, has benefits that outweigh the deficits."
As a blanket statement I'd probably disagree with that. Most of the effort on the RC thread was about exploring ways to resolve the competing and mutually exclusive requirements of equalization and extension when building anchors. I thought the result was a bunch of designs that sacrificed one for the sake of the other, or attempted to 'firewall' one from the other to provide a controlled amount of each. After going down those various paths together I haven't seen anything that would lead me to wholeheartedly embrace your proposition...
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rgold
Trad climber
Poughkeepsie, NY
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Jan 15, 2007 - 09:19pm PT
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Joe, I wouldn't agree with my statement as is either. I've edited it to add that the extension has to be small compared to the tie-in length. How small is a matter for experiments if there is anyone around who can do them. How about 1/10?
The smallness requirement means that the system must, as you say, incorporate a way to keep extension low (which is one of the reasons why an ordinary sliding W is not satisfactory). The new point is that the belayer's tie-in should be significantly larger than the extension and should be made with the climbing rope.
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GOclimb
Trad climber
Boston, MA
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Jan 15, 2007 - 10:02pm PT
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There were several excellent solutions proposed on that thread which, while untested by JL's crew, showed slightly more promise than the "accepted" method proposed by JL. Of course, they won't sell any books - which must be why they're considered impertinent. Apparantly the fact that they just might save lives seems not to be as important.
I've been using two of the methods from that thread exclusively since then. I've hauled off 'em, and slept on 'em, too - two people with all our gear, pig, ledge, etc. Slept easy. Neither method has caught a factor two fall. Hope that stays that way. But if one does, I'm as sure that it'll perform admirably as I can be without seeing any hard test data.
GO
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healyje
Trad climber
Portland, Oregon
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Jan 15, 2007 - 10:14pm PT
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Wanna share which ones? Preferrably with a pic of each (if you can find them). And if you were posting over on the rc thread were you doing it under GoClimb there as well (sorry, my memory isn't what it used to be...)?
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climbingjones
Trad climber
grass valley,ca
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Topic Author's Reply - Jan 15, 2007 - 10:33pm PT
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I do like the "W" Werner. But I am not so stuck on it that I will not give other ways a try. I dont "always" use it, but most of the time. Usually for 3 bomber pieces. I still think tying a knot into the same 3 pieces loads it unevenly. If I am faced with a sketchy belay I usually incorporate a mix and match approach. I have been accused of using too much gear on an anchor if I think it is sketchy. But so what? I like to carry lots of weight around anyway. Never been so concerned with saving that 8.34546623 'crucial' ounces. But I dig the discussion that it generated. Even though there are alot who seemed bent that it was being discussed. If you are so bent, or so over it, why did you post? Again.
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David Nelson
climber
San Francisco
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Jan 15, 2007 - 11:17pm PT
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Climbingjones asked a real question, let's not stray off topic for the poor guy, OK?
Listen to Werner B, he knows what he is talking about.
I haven't read the literature, but like the fig 8 because if one anchor pulls, the others are still equally loaded and there should be no shifting. Make sure you believe in the security of each one, don't start telling yourself "Oh, the others will hold." Make sure each one is good.
They may not be equally loaded with an off-angle load, but usually you know where the load will be coming from, and it is usually straight down. If the approach to the belay is from the side, there are some anchors from there, and the load might come from the side if the fall comes lower down, you might add another point that helps to resist a pull from the side.
Keep talking to climbers and listening.
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healyje
Trad climber
Portland, Oregon
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Jan 15, 2007 - 11:28pm PT
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Largo, are you up for starting on the third edition...?
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rgold
Trad climber
Poughkeepsie, NY
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Jan 15, 2007 - 11:46pm PT
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haven't read the literature, but like the fig 8 because if one anchor pulls, the others are still equally loaded and there should be no shifting.
Perhaps there would be some value in reading the literature. Your statement here is false in general.
They may not be equally loaded with an off-angle load, but usually you know where the load will be coming from, and it is usually straight down.
Again, the literature has something to say about this, although not as definitive as in the first case. I think there's a decent chance that there will be a off-angle impact in most cases. Only testing could tell us for sure.
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WBraun
climber
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Jan 16, 2007 - 12:16am PT
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Cjones
Why are people bent about the sliding W? Me don't know. Sometimes in certain situations it will be the way to go. Other times it will not be the way to go.
Totally depends on the type of situation. If there are a lot of dynamic variables in the angles of the power point (way to go) or when the power point angle remains perfectly static (not the way to go).
Gee whiz man it's not so hard to figure this stuff out.
Or is it? That is the first big decision, to accurately "visualize" your power points. Sometimes it also helps considerably to pretension your power points to get the angle/angles of your load/loads.
Let's beat it to death, hahaha
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rgold
Trad climber
Poughkeepsie, NY
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Jan 16, 2007 - 12:23am PT
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There were several excellent solutions proposed on that thread which, while untested by JL's crew, showed slightly more promise than the "accepted" method proposed by JL. Of course, they won't sell any books - which must be why they're considered impertinent. Apparantly the fact that they just might save lives seems not to be as important.
Perhaps this is what Joe was warning about when he suggested not opening this can of worms again. I'm always astonished when people pretend to know other people's motives, especially when they are ready to ascribe the basest motivations to people they don't know for actions they have no basis for judging. I hope you find yourself able to apologize for this one Gabe, it is way out of line, and contributes nothing but rancor to a discussion that might otherwise be useful.
It would be nice if an entity like the American Alpine Club could find a way to either fund or encourage research into anchoring solutions. This would be a substantial undertaking far beyond what could be expected from the author of a climbing book. In the meantime, it should be noted that JL acknowledges the rc.com thread in his book and expresses the view that better methods will ultimately come from the efforts of individual climbers.
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WBraun
climber
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Jan 16, 2007 - 12:37am PT
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Good anchors are really fun to build and present a wonderful challenge to make them solid and robust to the variables that they are encountered.
I love building anchors. I first learned some cool tips from the masters Bridewell and Porter. The Rigging for Rescue course is also an excellent resource although expensive and mostly geared towards rescue situations. That course will open ones eyes toward systems and their dynamics involved towards good solid fundamental anchors.
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WBraun
climber
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Jan 16, 2007 - 12:59am PT
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Hairball back then?
Back then was a blast.
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climbingjones
Trad climber
grass valley,ca
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Topic Author's Reply - Jan 16, 2007 - 02:08am PT
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Werner, I never said that it was hard to figue out. Not for me anyway. Like I said, different situations require different approaches. I was more into hearing how other people did it. I know many ways of building an anchor, making it safe, and equalizing it as best as possible. Not looking to be schooled, I know what I am doing (not dead yet anyway with many anchors built), but I enjoy reading other peoples perspectives. Especially since there are many out there who are smarter than I am with way more experience. You included. I am just enjoying reading about climbing realted topics on this climbing realted website. Go figure.
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Tom
Big Wall climber
San Luis Obispo CA
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Jan 16, 2007 - 02:30am PT
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Largo is right:
"Trying to achieve the same brute strength with passive camming devices presents another magnitude of difficulty hence the modern day need trend toward equalizing." - Largo
His idea that pounded pins are more akin to CalTrans anchors for anchoring whole sections of roadway should not to be lost upon modern alpinists.
In the old days, pounded pins were so bomber, you could belay off one, or two.
But, removing the pins damaged the rock, and the question was: how many more ascents can be done this way?
All things being equal, a clean anchor is not going to be as strong as well-hammered anchor, at least in Yosemite.
A typical belay with a few wedged stoppers, or cams, is not the same as if well-driven pins are used.
Hence, the need to equalize.
But, regardless of the type of anchor, reducing the potential for a shock-load on any of the pieces seems expedient. A sliding W can shock load anchors, but a tied-8, properly tied, will not.
If you're worried about your belay, there is always another way out: climb a few moves up, and then equalize those pieces back down to the belay. How many pieces you need to go up depends on the pitch. I once used six moves above the belay, because the anchor was a loose block.
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ADK
climber
truckee
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Jan 16, 2007 - 02:47am PT
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The only way to prevent shockloading and ensure equalization is to use one piece of gear. Otherwise its situational. ja
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Tom
Big Wall climber
San Luis Obispo CA
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Jan 16, 2007 - 03:58am PT
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"The only way to prevent shockloading and ensure equalization is to use one piece of gear."
I once - once - saw a great idea of one piece of gear at a belay, and I never climbed with that guy again.
I was "shock-loaded" in the brain upon climbing up and and seeing the setup.
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nutjob
Trad climber
San Jose, CA
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Jan 16, 2007 - 04:27am PT
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OK here's a serious question thrown into this mess. Maybe this is what happens over at rc.com (I never wander in that direction).
I studied all the anchor guidance in Freedom of the Hills and the Largo books in the mid-90s. And I was all anal about following the rules when setting up top-ropes and learning on my own with no mentor.
Nowadays on long trad climbs where speed = getting down before dark = not having to bivvy after getting lost... I strongly favor an ultra simple setup. Mostly I set my pieces and clove hitch the climbing rope directly to them in serial (do a sliding X equalization on 2 or 3 pieces if they're crappy). This is really fast and efficient when swinging leads, and requires less gear (e.g. if I forgot a cordalette). Then I belay off of my harness and bear the shock before loading the anchors (hanging belays are different). If need to lead in blocks, tie in with figure 8 on double biners through strong points of harness, then can switch ends of the rope at belays after clipping in to a backup sling on harness.
Aside from the issue of escaping the belay, does anyone have a problem with this setup? I think escaping the belay is not that big of deal if you're in a situation that really requires it (assuming you have some extra slings and biners and you've practiced it), and belaying off harness avoids shock-loading and blowing out crappy anchors.
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Tom
Big Wall climber
San Luis Obispo CA
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Jan 16, 2007 - 04:28am PT
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"I once used six moves above the belay, because the anchor was a loose block. "
Yikes!
Whatup with that?"
Just below the The Shark's Mouth, on Bermuda Dunes.
The teeth were menacing.
Great White Shark, but huge.
Hanging down, sharp, like El Cap now turns into a huge shark there, and those loose sharp flakes are looking like his teeth that are expendible, and if you grab onto them, you fall.
Just above and right of the Slack.
The Shark.
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wootles
climber
Gamma Quadrant
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Jan 16, 2007 - 08:19am PT
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God knows I don't want to get too deep in this topic again but...
There's been a few statements about shock loading and the dangers there of. First we need to define what a shock load is and that's not as easy as it sounds. A simple answer is rapid loading. But how rapid? In normal UIAA drop tests the peak force occurs in roughly 0.11 to 0.17 seconds on the first drop with a new rope. Each successive drop the peak force occurs earlier than the previous. So I would think that shock loading would have to occur sooner than that but then again how high does the force need to be to be considered in the definition of shock load?
I performed tests specifically looking for the theoretical shock loading. I think it's in Largo's book, though I have to confess I have not read it entirely. I feel the tests showed quite conclusively that shock loading from extension is a myth. There are only two dangers I see in regards to extension: potential loss of control of the belay due to redirection and if the belayer is easily startled loss of control of the belayer's bowels. Yes there is a transfer of the force but it does NOT exceed the total sum of the force, obviously. There are far too many variables to calculate what the final force would be but for certain if you are tied to the anchor with a dynamic rope there is no shock loading. That said, I did not test using static lanyards such as daisy chains or Dyneema/Spectra slings. I, and some other people, have conducted other tests that show direct connection with static lanyards is a bad practice. You may be better off with nylon slings but ultimately the rope is your safest option.
So then back to the rapid loading. I'm working from memory here but during the shock loading tests I recall the second peak, the one resulting from the transfer, occurred at a time point roughly equal to twice the time it took to reach the first peak. The first peak occurred earlier than the normal UIAA drop test because of the test method. The method was to use a 'fuse' on one leg of the anchor that would blow before what would have been the normal peak force. For example the first peak would occur at roughly 0.07 seconds and the second, and lower peak, would occur at roughly 0.14 seconds. Those might seem to be super fast but the forces were quite low, under 3kN if I recall. I wish I could find the data. Sterling moved to a new building back in August and the computer that has all that stuff in it somehow got damaged and I haven't tried to retrieve anything from it.
Now for the curve ball... All of this goes out the window in rescue scenarios. When hauling litters extension is potentially a really bad thing. WBraun can probably address this more.
If this horse was the son of God we would be celebrating Easter all year long.
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Largo
Sport climber
Venice, Ca
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Jan 16, 2007 - 11:49am PT
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Gee Willikers, am I really diving back into this . . . again??
Jim wrote: "I performed tests specifically looking for the theoretical shock loading. I think it's in Largo's book, though I have to confess I have not read it entirely. I feel the tests showed quite conclusively that shock loading from extension is a myth."
Maybe a better term is "load multiplication," meaing that somehow in the time that the first piece blows, to the time (fractions of a second) that the second piece starts absorbing the load, said load does not magically increase. In fact, it decreases relative to the amount of energy absorbed by the first piece before it blew out. Meaning if you had initial loading of L3 on the anchor, one piece blows out and absorbs L1, then extends to the second piece, the second piece would be subject to L2 of loading, almost to the pound according to the testing.
The whole thing goes out the window with rescue work because there is no tube/crimp belay device in the equation (through which the load is greatly diminished through rope slippage), no body to fold and give and absorb energy, and most of all, no dynamic rope that stretches upon loading. Here (as is probably the case with big haul bags tethered with static lanyards) it is almost certain that you'd see, not load multiplication, but shock loading, meaning the sudden decelleration of a litter or haul bag could quite possibly bust biners and rip anchors.
JL
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wootles
climber
Gamma Quadrant
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Jan 16, 2007 - 12:07pm PT
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Thanks John. That was a much better explanation than mine. Yeah I forgot to mention the energy absorption of the piece blowing out. I'll keep looking around for the data but I'm pretty sure it's locked up in my computer bone yard. My drop tower and slow pull computers didn't survive the move.
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mingleefu
climber
Champaign, IL --> Denver, CO
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Jan 16, 2007 - 12:54pm PT
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WBraun wrote: "make your anchors 10 to one safety factor"
Are you just being facetious, or is this actual practice in your line of work? How does one go about conceptualizing what a 10:1 safety factor looks like? Or do you just build the anchor ultra-beefy until you have that "feel good" fuzzy inside?
Curious about the concept.
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TradIsGood
Happy and Healthy climber
the Gunks end of the country
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Jan 16, 2007 - 01:07pm PT
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Largo, that explanation of loads and energies is pretty confused.
Meaning if you had initial loading of L3 on the anchor, one piece blows out and absorbs L1, then extends to the second piece, the second piece would be subject to L2 of loading, almost to the pound according to the testing.
Load would certainly be a measurement of force and not energy. The idea that L3 = L1 + L2 is vague as to the definitions of the L's, and likely not right with any reasonable definitions even if you define them to be energy instead of forces.
Measurements are important. One thing that changes after the first piece blows is the elasticity of the rope. It is now "less dynamic", since it will not immediately shrink to its unstretched length.
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 16, 2007 - 10:40pm PT
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god knows I never get this stuff right the first time, but I did do an analysis of the cordolette and the "magic x" equalization of two points and got what I thought was something consistent with the drop tests that wootles did.
My main conclusion from that was basically, don't use stiff slings... nylon slings, as with nylon ropes, have a lower bulk Young's modulus which lowers the force considerably. The difference of lenghts of the arms of the cordolette will cause differnt forces for each of the pieces of protection they are attached to, thus defeating the idea of equalization. However, if you keep this in mind, and if you make sure that the arms are long, rather than short, the differences may be within the margin that your anchors might be able to take.
What you have to be aware of is the cordolette does not equalize.
What I take to be shock loading is simply that the dynamic forces generated have to do with the change of momentum:
F = dP/dt
where P is the momentum... P = m*v and the difference in the momentum is proportional to the velocity that gets stopped, and the time it takes to stop it. This is the same force calculated in the "force factor" equations, so you can get an idea of the dt by first calculating that force, then calculating the change in momentum, and solving the above for dt:
dt = dP/F
When you have a failure of an anchor at some force, some amount of momentum is decreased, which means the falling person has a lower velocity... this sets an upper limit on the force the next anchor will be subject to. This force will be less than the force that would have been generated if the piece that blew wasn't there in the first place.
Anyway, I've had way too much to drink tonight to be at all coherent... another way of thinking about shock loading is to consider how a hammer works. If you push on a nail with the same force you would swing a hammer, you would not press the nail into the wood. But the hammer generates a lot of force because of the the change of momentum over a very short time. F = dP/dt...
That's going to happen in a belay situation. It is possible that practically it is not an issue for blown pieces on a set of closely spaced, closely coupled anchors, but if you had a very long sling connecting the pieces it might be more of an issue.
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GOclimb
Trad climber
Boston, MA
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Jan 17, 2007 - 05:39pm PT
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>> I wrote:
>> There were several excellent solutions proposed on
>> that thread which, while untested by JL's crew, showed
>> slightly more promise than the "accepted" method proposed by
>> JL. Of course, they won't sell any books - which must be why
>> they're considered impertinent. Apparantly the fact that they
>> just might save lives seems not to be as important.
> To which RG responded:
> Perhaps this is what Joe was warning about when he suggested
> not opening this can of worms again. I'm always astonished
> when people pretend to know other people's motives, especially
> when they are ready to ascribe the basest motivations to
> people they don't know for actions they have no basis for
> judging. I hope you find yourself able to apologize for this
> one Gabe, it is way out of line, and contributes nothing but
> rancor to a discussion that might otherwise be useful.
I didn't say he thought the discussion was impertinent, he said that. As for why he would be so dismissive of all ideas but the one presented in the book, I admit - I really can't (and shouldn't presume to) answer that question. But I sure do find the idea of tarring the entire discussion with the dismissive word "impertinent" to be a bit galling. Still, I'll try to remain productive, despite the fact that many find any input (by better minds than mine) so completely valueless.
And by the way, in regards the importance of factoring in the force a falling belayer creates when a piece extends, I could not agree more. As it happens, I introduced that question in the original thread, and (perhaps too) strenuously argued about its importance. I even suggested what I thought was a reasonably simple change to the testing environment to measure this factor. More impertinence on my part, no doubt! ;)
> healyje wrote:
> Wanna share which ones? Preferrably with a pic of each (if you
> can find them). And if you were posting over on the rc thread
> were you doing it under GoClimb there as well (sorry, my
> memory isn't what it used to be...)?
The moniker GOclimb was taken on rc.com, so I'm Cracklover over there.
Here are the ones I'm most taken with for a typical three point anchor. The pros and cons of each are all available in that thread, though I also have my own views on them after using them for a season:
The Mooselette:
The CharlesJMM anchor:
And the two crossed slings:
Werner I ain't, and greater minds and more experienced climbers seem to want this conversation to end, so I'm not going to take the time to detail my thoughts on these unless requested. Briefly, my preference goes from top to bottom, with the Mooselette equalizing the best and being quickest to set up (once you get accustomed to it, and in situations where it's appropriate), CharlesJMM rig being in the middle, and two crossed slings taking the longest to set up, and equalizing the worst.
Cheers,
GO
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rgold
Trad climber
Poughkeepsie, NY
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Jan 17, 2007 - 07:52pm PT
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GoClimb wrote: I didn't say he thought the discussion was impertinent, he said that.
The I-word wasn't used by Largo. It was Wootles who said
...as much as you all love to bust on rc.com everything is pretty well covered over there, that is if you can wade through the 1000 or so impertinent posts.
GoClimb wrote: As for why he would be so dismissive of all ideas but the one presented in the book, I admit - I really can't (and shouldn't presume to) answer that question.
Since the quote isn't from Largo, you are relieved of even presuming to to figure out why he said it. Meanwhile you have let stand your claim
Of course, they won't sell any books...Apparantly the fact that they just might save lives seems not to be as important.
which says that Largo, who never said what you say he said, is by virtue of those misappropriated words more concerned about book sales than human life.
Moreover, even though they aren't Largo's words, the quote itself, far from being dismissive, clearly expresses the author's appreciation for the rc.com thread, even in the face of this site's reflexive inclination to denigrate anything from rcNOOB.com. The I-word supplies a touch of irony and can hardly be read as a "tarring of the entire discussion."
Largo obviously could care less, but I still think a real apology would still be the decent thing to do here, not that decency is particularly high on any list of internet discussion desiderata.
..........
By the way, to return to the topic at hand and highlight a point Largo made previously, in 49 years of climbing I've had to hold one factor 2 fall directly onto the belay. The anchor was a single 1" angle, pounded zealously into a perfect horizontal crack. The belay was, of course, a hip belay.
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healyje
Trad climber
Portland, Oregon
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Jan 17, 2007 - 08:02pm PT
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"By the way, to return to the topic at hand and highlight a point Largo made previously, in 49 years of climbing I've had to hold one factor 2 fall directly onto the belay. The anchor was a single 1" angle, pounded zealously into a perfect horizontal crack. The belay was, of course, a hip belay."
I can't speak to the fall factors involved, but I've held a few hard drops directly on to hip belays. I'm always categorically stunned - stunned - at the number of [smart, experienced] folks who have never hip belayed who don't consider it a "real" belay. For the uninitiated, hip belaying when done right is highly effective, can be fairly technical and is best considered integral with a more technical perspective on stancing than is commonly in evidence today.
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WBraun
climber
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Jan 17, 2007 - 08:20pm PT
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Well ....
To tell you the truth, I'm so glad I don't have to hip belay no more. You have to be so damn attentive to the point of being anal to do it properly so that if a fall does occur that the rope doesn't rip out of my hands.
So glory hallelujah rgold, the one f'ckin pin held. Why did we all even live through that crazy sh#t we did back then?
Now I'm scared to belay without my grigri and have to tie off 10 twigs instead of just one .......
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maldaly
Trad climber
Boulder, CO
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Jan 17, 2007 - 08:25pm PT
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With all due respect....I'm starting to feel like I'm over at rc.com.
Lot's of good stuff here but I'm with nutjob, despite the unfortunate handle. If the rock is good and the anchors sound, I place two down (EQ'd) and one up. Tie in with the rope, twnsion with a clove hitch and swing leads.
I'm not dead yet.
Mal
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rgold
Trad climber
Poughkeepsie, NY
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Jan 17, 2007 - 08:29pm PT
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Now I'm scared to belay without my grigri and have to tie off 10 twigs instead of just one .......
Y'know, I recently tied off ten twigs for a belay anchor and caught a load of flak for it. Man, those twigs were bomber!
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andanother
climber
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Jan 17, 2007 - 08:44pm PT
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Hi,
My name is overkill. I like to beat dead horses.
LOOOOOONG after they are dead I can be found beating their rotting carcasses. That's my thing.
I also like to over-analize the sh#t out of everything. I don't actually climb much, but I spent 2 hours building an anchor in my backyard just so I could post pictures for you guys. Hope you like them. I analyzed them for hours. Then I over analyzed them even more. That's what I do.
I'm the guy that turns 3 pitch climbs into overnight epics. I've had to rappel off of every single grade III I've ever attempted. It gets expensive, but I make some pretty sweet rap anchors. I have photos of every single one of them. I took photos from all different angles so that I could over analyze them upon returning home.
In my world, grade IV doesn't exist. If it's longer than 3 pitches, it is automatically grade VI. I can often be seen hauling 60 pounds of gear up Nutcracker.
Still haven't finished that one. Is the mantle as scary as they say?
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GOclimb
Trad climber
Boston, MA
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Jan 17, 2007 - 09:17pm PT
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> RG wrote: The I-word wasn't used by Largo. It was Wootles who said ...
Yes, it's Wootles who I'm referring to. If that wasn't clear, I apologize. At the time I made my post, I don't believe that JL had even waded back into this morass, so I thought it clear who's post I was referring to.
And I read the statement "...as much as you all love to bust on rc.com everything is pretty well covered over there, that is if you can wade through the 1000 or so impertinent posts. "
As saying: In case you don't want to buy the book, JL, Healyj, RG, and I pretty well spelled out all the research we did in that thread on rc.com. Too bad it was mucked up by all those other impertinent posts.
> RG also said: Since the quote isn't from Largo, you are
> relieved of even presuming to to figure out why he said it.
> Meanwhile you have let stand your claim
>> Of course, they won't sell any books...Apparantly the fact
>> that they just might save lives seems not to be as important.
> which says that Largo, who never said what you say he said, is
> by virtue of those misappropriated words more concerned about
> book sales than human life.
Okay, I apologize for suggesting that. In fact, I was quite impressed that JL came right out and said he felt responsibile for selling an idea that he now believes to be flawed, and he clearly put a huge amount of work into getting this new research done, and promulgating a new idea anchor system that we can all agree is superior to the standard cordelette method. So far as I'm concerned, JL's heart is clearly in the right place. Absolutely no question about it.
I'll just let it go at that.
GO
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Largo
Sport climber
Venice, Ca
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Jan 17, 2007 - 09:20pm PT
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"As for why he would be so dismissive of all ideas but the one presented in the book, I admit - I really can't (and shouldn't presume to) answer that question. But I sure do find the idea of tarring the entire discussion with the dismissive word "impertinent" to be a bit galling. Still, I'll try to remain productive, despite the fact that many find any input (by better minds than mine) so completely valueless."
I think this deserves a sober response. I stated in the new anchor book that the equalette was simply the first of many new possible innovations that tried to address the problem of extension and equalization. I fully expected, and encouraged others, to keep the discussion going in the hopes of fathering new rigging strategies. I recommended the equalette and the quad simply because those were the ones we were able to devise and test (Wottles work here)–both in the lab and in the field–in the limited time we had. The claim that I, personally, consider new wrinkles on this basic strategy as "completely valueless" is something that, apparently, only you believe.
I've stated many times that little if anything in any of my books is catagorically definitive, rather it's merely the most up to date information that I know of per what should and must remain an ongoing investigation.
The other issue is that I am somehow discouraging the climbing community from embracing strategies other than those shown in my books for the fear that such an endorsement would affect book sales. That's an awfully tough pill to swallow, especially considering that the anchors books are speciality items that might, at best, sell about 20,000 copies over a decade. Per hours spent in the research and writing and profits received from such sales, my rate would work out to around 10 bucks an hour, and zero bucks an hour to important contributors like Rich and Craig, as well as many others. I'm glad that for every book sold, perhaps ten or even twenty people read it. That's the point–to get the knowledge out there. It's basically my other work that allows me, and pays for me, so to speak, to work on books (such as Climbing Anchors) that would put me in the poorhouse and my family on the street if I was relying on them for my livelihood.
JL
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GOclimb
Trad climber
Boston, MA
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Jan 17, 2007 - 09:22pm PT
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Andanother: I'm not a particularly fast climber by anyone's measurement, but after placing the gear, this anchor takes me the same length of time to build as a standard cordelette.
GO
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healyje
Trad climber
Portland, Oregon
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Jan 17, 2007 - 09:27pm PT
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Well, 100 posts and not out of the rough quite yet...
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GOclimb
Trad climber
Boston, MA
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Jan 17, 2007 - 09:30pm PT
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Largo, I tremendously appreciate the time, effort, and money put in by you, Wootles, RG, Chiloe, Sterling, etc, for that effort, and also your role in the discussion around it, which I found extremely valuable. I said as much to Jim when I ran into him last year. In fact, IIRC, I volunteered to put in some time in some testing he was talking about doing this winter.
The fact that I found some elements of that discussion extremely frustrating does not in any way reduce my appreciation for your work.
GO
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WBraun
climber
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Jan 17, 2007 - 10:06pm PT
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GOclimb
I'm glad for your input as it brings out good discussion and analysis. You never know what people come up with. There's always subtle nuances that appear in these analysis that surprise us.
In YOSAR, we've tested and analyzed many types of rigging and anchor systems over the years, and I'm always surprised by some of the many different nuances that come up.
I like learning all the stuff there is.
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Rags
Trad climber
Sierra foothills, CA
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Jan 17, 2007 - 10:45pm PT
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Largo wrote, "I fully expected, and encouraged others, to keep the discussion going in the hopes of fathering new rigging strategies.
John, thanx for the work you have done on anchors, and to further the sport and address safety, something many of us consider worthy of discussion. I would hope that you and wootles continue to be available for comment. You are by virtue of your testing, possibly the closest thing to "experts" on the subject.
Discussions such as this might actually stimulate new thinking on an old topic. However, this become tedious because the discussion gets perforated by those that think it a waste of time. In this regard, it is the very act of interjecting meaningless drivel, irrelavant to the topic, that hobbles an intelligent and worthy discussion. Even the marginally relevant misunderstandings detract from the otherwise intelligent analysis and exchange of ideas. If you have nothing of value to add, have some consideration and respect for others, exhibit some self-control, and post to the "nothing thread".
Back to your regularly scheduled program--------------
The point that I find curious is the suggestion that a sliding X or W assumes that all pieces are bomber and won't blow. The ASCA website has this, "While the sliding X does equalize the pieces, it assumes that neither could break, since if one does break, there is severe extension in the system - enough that it would likely cause the carabiners to break."
Obviously the testing has proved this to be a myth. However, it has been my practice to use this arrangement, and the "W", in most of my anchors, including an arrangment that utlized a marginal piece. A knot to shorten extension always seems the simple solution. Since shock loading is now a marginalized concept, why are there still concerns regarding extension at all?
As someone pointed out, a fall of factor 2 is highly unlikely. Redirects and practicing a "soft belay" in the event there is a possibility would seem to mitigate the risk even further. I am suggesting that our techniques are as important as our mechanics.
"How we do" with "what we have" ultimately dtermines the net risk. There needs to be an integration of both in the learning process and evaluation process.
Thanx to all that have "contributed" to the discussion.
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healyje
Trad climber
Portland, Oregon
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Jan 17, 2007 - 10:59pm PT
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Rags, have you read the entire rc.com sliding-x thread? One would hope any discussion here would use that as a starting point versus attempting to cover all that ground again. Comments about the wisdom of doing so here have to do with the seemingly unavoidable landmines of various stripes this topic has invoked at both sites. In my opinion, anyone really committed to such a discussion who hasn't read the rc.com thread in its entirety ought to consider doing so before starting in here in order to understand the lay of the land and the reason for statements of caution.
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 17, 2007 - 11:05pm PT
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I find a perlon cordolette a sweet piece of gear and carry it, and use it, in many situations. I am fully aware of it's limitations and apply it in situations that I think are safe. It is a quick way to setup an anchor.
I have also used the same system as healyje on occasion, tie off on the high piece with a clove-hitch, tie into two lower pieces via a "magic-x"... equalize the clove-hitch and you're good to go.
It also helps to pick a good belay spot appropriate for the gear you got rather than put some jingus pro in an arbitrary place. When I'm leading I'm always looking for the belay spot...
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Rags
Trad climber
Sierra foothills, CA
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Jan 18, 2007 - 02:54am PT
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healyje,
yes I was reading along for quite a while when the thread started. Maybe a review isn't a bad idea. It is possible that I am asking something that may have been answered before. So are others. Isn't that what started this thread?
Restating and reinforcing updated information is exactly what needs to occur for MYTHS, such as the one I quoted from ASCA to be dispelled. In fact, there is other value in reviewing information. The review process often sheds new light that reveals unexpected results. Now I've gone and done exactly what I criticzed, a post of marginal relevance to the topic.
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v10gripper
Boulder climber
Joshua Tree, CA
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Jan 18, 2007 - 03:40am PT
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I'm not going to sit here and read all of the posts in this topic, so this may have already been said.
I have switched out my static cordelette with dynamic cordelette, this aliviates(sp?) some of the factors in a "what if" situation. I think that this helps out both scenarios(sp?) the sliding "w" and the "figure 8" at the "power point". I use a peice of a twin rope. I would bet in the next couple of years you are going to see just about all manufactures(sp?) marketing some sort of similar(sp?) product just for equalizing(sp?) anchors.
sorry about all the"(sp?)'s" but I have had too much to drink to spell properly, or for that matter care that much.
S.Powers
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Degaine
climber
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Jan 18, 2007 - 04:37am PT
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My apologies for continuing the flogging of this dead horse, but I find the discussion interesting and have a couple of comments/questions.
1) I really like this setup:
I’ve used it on many occasion and with the quad as per Largo’s book it seems like a perfectly reasonably anchor, am I missing something? I don’t use it all the time, and like a good Marine I improvise, adapt and overcome depending on the situation.
Goclimb, I can set it up pretty quickly, what is it exactly that you don’t like or what takes you so long?
It’s ironic that the setup you consider to be so quick, I (and apparently a few others?) consider to be complex or time consuming. Guess it’s just a matter of practice and familiarity, right?
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healyje
Trad climber
Portland, Oregon
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Jan 18, 2007 - 04:52am PT
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"I'm not going to sit here and read all of the posts in this topic, so this may have already been said...."
And so it begins...
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wootles
climber
Gamma Quadrant
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Jan 18, 2007 - 07:09am PT
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To GO and others who may have been offended by my 'impertinent' statement. I apologize for being so general. I was referring to the vile ugliness that erupted in a couple of the threads on this topic at rc.com. Ultimately there was more positive discussion and great ideas than impertinence.
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raymond phule
climber
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Jan 18, 2007 - 08:36am PT
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"if you are tied to the anchor with a dynamic rope there is no shock loading."
Everything doesn't seem to be clear yet...
The problem as I see it is about shock loading and the belayer. I dont think the above statement is correct in general, the loading on the ancors depends on the length of dynamic rope between the ancor and the belayer. This lengths could be very short when for example using a cordallete. I believe that I sometimes clip the biner directly into the rope tie in loop (not the harness tie in loop).
The logical step I have seen several times and dont agree with.
Extension is bad if the connection belay belayer is static but it doesn't pose any problem if you have the rope in the chain between belay and belayer.
This is true if the extension is much less than the connection rope. I dont belive that this is always the case and the statement is false otherwise.
Have someone done any testing of the loads on the anchor that also inlude the belayer?
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Largo
Sport climber
Venice, Ca
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Jan 18, 2007 - 11:08am PT
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Degaine--
That set up is bomber so far as the individual placements are bomber. A common misuderstanding is that the rigging determins the holding power of a given anchor. The rigging can only exploit the potential holding power of the individual placements, nothing more.
An interesting side note to the above anchor (the Degaine pic) is that in testing, were were aware of the so-called "clutch effect" that sometimes happens in the Sliding-X and other systems were rope strands are running over in a way that can bind on the biner. Wottles found that by using a big, pear-shaped, anodized biner, with the mouth on top, gate faced outwards, the clutch effect was largely if not entirely eliminated. This is really a point worth noting because it makes a huge difference in the degree of load sharing in an anchor.
JL
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GOclimb
Trad climber
Boston, MA
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Jan 18, 2007 - 11:30am PT
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Degaine,
The pair of sliding-exes is indeed a fair setup. You asked if you are missing anything. I really don't know, as you didn't state the pros and cons as you see them.
Here they are as I see them. I'll take the three-point anchor just for clarity's sake, though all the pros and cons apply for two- or four-point anchors, too:
Pros:
1 - Shares load between all anchor points
2 - Easy to understand and inspect
3 - Requires fairly small amount of gear (one long sling, one short sling, and one biner)
4 - Is fairly resistant to cutting of slings (say by a falling rock). The only point that, when cut, will cause the entire anchor to fail is the small area between the knots at the power-point.
Cons:
1 - Even with no friction, one of the pieces gets half the load, while the other two each get a quarter.
2 - Requires tying, untying, and adjusting four knots.
3 - In testing, the sliding-x has been shown to sometimes bind on itself (the two strands are moving in opposite directions at a pretty good clip), so the dynamic equalization potential is limited.
For reference, here's the pic of the setup Degaine is referring to:
GO
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v10gripper
Boulder climber
Joshua Tree, CA
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Jan 18, 2007 - 11:33am PT
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""I'm not going to sit here and read all of the posts in this topic, so this may have already been said...."
And so it begins... "
and so it ends
S.powers
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GOclimb
Trad climber
Boston, MA
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Jan 18, 2007 - 11:49am PT
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Degaine said "It’s ironic that the setup you consider to be so quick, I (and apparently a few others?) consider to be complex or time consuming. Guess it’s just a matter of practice and familiarity, right?
It is indeed. I now carry my cordelette with those two knots in it already, so all that's required is that I clip the cord into the three pieces, pull the middles down to the power point, adjust the two knots, and I'm done.
By the way, the mooselette doesn't only work as I showed it earlier, with all three pieces lined up nicely in a horizontal. Here's a pic of it where all three pieces are spread out over three dimensions. Note that the foreshortening of the camera angle makes it look like there's a high angle in the cord on the left side, whereas it's really just that the tricam is buried in a rather deep crack.
GO
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G_Gnome
Boulder climber
Sick Midget Land
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Jan 18, 2007 - 11:57am PT
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Damn, I read this whole thread. Anyway, GO I have a question about your last photo.
Would it not be a lot better to have the tied off loop that the central piece is clipped to be much smaller such that the 2 other pieces are clipped in an upward direction so that if one of the side pieces blows the extension is greatly minimized? Seems you could just about eliminate that extension in this case yet you didn't bother to. Are you missing this factor?
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v10gripper
Boulder climber
Joshua Tree, CA
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Jan 18, 2007 - 11:59am PT
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"Damn, I read this whole thread"
That was dumb
S.Powers
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Degaine
climber
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Jan 18, 2007 - 12:07pm PT
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JL and GOclimb, thanks for repsonding to my question!
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Crag Q
Trad climber
Louisville, Colorado
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Jan 18, 2007 - 12:20pm PT
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One of the disadvantages of the mooselette that I can't get over is that it uses 2 more biners than the equalette. So, that's 5 biners instead of 3 (not counting the locker). In a multipitch situation that's 10 biners being used up just rigging anchors (not counting the lockers).
It also appears to be a tad more complicated to setup than a cordolette or equalette based on # of knots tied and biners clipped. It seems that evaluation how your pieces are being loaded would be hard to determine because the extra biners change the direction of the forces.
It might be perfectly great, but I'm going to file the mooselette under "interesting, but no thanks."
K.I.S.S
my $0.02
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GOclimb
Trad climber
Boston, MA
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Jan 18, 2007 - 12:52pm PT
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g_gnome: Would it not be a lot better to have the tied off loop that the central piece is clipped to be much smaller such that the 2 other pieces are clipped in an upward direction so that if one of the side pieces blows the extension is greatly minimized? Seems you could just about eliminate that extension in this case yet you didn't bother to. Are you missing this factor?
To answer that question, I first have to explain how this system extends. Most of the extension goes into re-equalizing the system. So, lets say that right-hand piece is nine inches above the knot. If it rips, the power point only will extend one third the distance, or three inches. So by moving the knot up a few inches, it doesn't change much. I don't mind having three inches of extension in the system.
But why have those three inches at all?
Because if I were to move that knot all the way up, the angles caused by the outer pieces linking to the biner get pretty high. It looks a little like an American Triangle when I do that. I'm not convinced it loads forces like an AT, but, barring testing, why risk it?
GO
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HighDesertDJ
Trad climber
Arid-zona
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Jan 18, 2007 - 12:54pm PT
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Yeah I can't imagine I'd ever use that in real life.
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GOclimb
Trad climber
Boston, MA
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Jan 18, 2007 - 01:07pm PT
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crag_q, if I understand it correctly, a three-piece equalette requires four knots and two locking biners (not counting the biners on the gear), while the mooselete uses two knots and three biners (only one being a locker). Certainly a tradeoff. Not sure how you got to 10!
Anyway, there's are pros and cons to each - no doubt about it. I have played around with them enough so that I think I understand them as well as I can without subjecting them to drop tests with load cells (I wish!) And I've been quite happy using a few of them in all the scenarios I've been in.
But it would be great if more people became familiar with them and played with them on their own. Given all the creative minds out there, I bet we could at the very least stimulate some worthwhile discussions, and at best, come up with a simple hybrid that nearly everyone can love and use. Just be careful, and make sure you know what you're doing before you hang you and your partner's life on it.
GO
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GOclimb
Trad climber
Boston, MA
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Jan 18, 2007 - 01:11pm PT
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The CharlesJMM anchor is extremely simple, doesn't use any extra biners, and is safe against cord breaking/cutting.
GO
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Crag Q
Trad climber
Louisville, Colorado
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Jan 18, 2007 - 01:36pm PT
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Hi Goclimb,
It's obvious you're spending a lot of time thinking about this and looking for new answers to old problems. I respect that. I really enjoyed Largo's new anchor book because it challenged a lot things I held as truths, most of which I had gotten from the previous 2 books.
Anyhoo, you got me on the knots. There's more in the equalette. 2 limiters and 2 clove hitches.
I was getting ten biners because on a mutlipitch climb you'd have an anchor atop pitch one, and another a top pitch two. So, you need gear for 2 anchor setups.
Here's how the inventory racks up for one 3 piece anchor:
mooselette: 1 cord, 5 biners, 1 locker on power point.
equalette: 1 cord, 3 biners, 1 or 2 lockers on power point depending on whether or not you do a sliding -X between the limiter knots.
cordolette: 1 cord, 3 biners, 1 locker on power point.
How's setting up the mooselette in the dark when you're cold, tired and dehyrdrated? I like to keep my systems as simple as possible, so when I'm in that situation I can do the exact same thing I do under ideal conditions.
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Crag Q
Trad climber
Louisville, Colorado
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Jan 18, 2007 - 01:44pm PT
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Another disadvantage that just occured to me with this mooselette is that it doesn't work with 2 anchors. So, you'd have to have a different process for a 2 piece vs. 3 piece anchor. Not to mention when the gear is crap there's also the need to equalize 4 pieces which is no problem for the equalette or cordolette. It's the same process.
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the Fet
Knackered climber
A bivy sack in the secret campground
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Jan 18, 2007 - 02:22pm PT
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The horse is alive and kicking, and some of us enjoy the ride...
I believe the testing showed a small amount of extension was ok (e.g. in a limited knot sliding X). But I would be concerned about a lot of extension (e.g. in a 48" sling sliding W) where the anchor could drop feet instead of inches (and the rope tie in may be short), and also the possibility of being pulled of the belay ledge. So I wouldn't use a sliding W (built with a long sling/cord) without some sort of backup to limit extension. You could always back up the sliding W with a cordelette tied with a single knot or as an equalette, or make the sliding W out of a 1 foot sling with extensions to the pieces (if you really required equalization on 3 sketchy pieces, I would't want to be there :-).
I started using the cordelette with a knot when I became aware of it because I thought it was the quickest, simplest way to build a 3 piece anchor that at least partialy equalized. I used it perhaps 90% of the time. The slidingX thread (due to input from Largo's book) let me know it doesn't equalize. So personally I looked at the sliding X thread as an attempt to find a replacement.
Perhaps there may be a great idea that comes along and solves all the requirments: equalizes 3 pieces, simple, fast, redundant, uses small amount of normal gear. But I think the sliding X thread demonstrated that there are solutions that can do everything but be KISS (simple). I posted the only design on that thread (under username Glowering) that placed equal loads on 3 pieces (33%/33%/33%)(neglecting friction) limited extension, and equalized, and although it was quick and simple for me to setup, I realized it wouldn't be so for the average climber.
One of the primary goals of equalization IMO is load sharing. You don't need exactly the same force on every piece, but if you have a pretty good split between two pieces you've given yourself a much greater margin of safety.
In looking at the equalette I saw a design that does a good job at equalizing on two pieces with 1 or 2 more in backup (i.e. only weighted if primary fails) pieces (that's what I need 90% of the time). And it's pretty simple. However I don't like the idea of tying two or more correctly positioned clove hitches at each anchor (a little time consuming), so now I use a sliding X with limiter knots (pretied) as my primary anchor, load sharing on my two best pieces, with 1 or two seperate backups if needed. I now use this 90% of the time, so basically it's my cordelette replacement. I can set it up faster than anything (besides the cordelette with a single knot) and it's simple enough for all my partners to easily understand.
The possibility of the clutch effect Largo notes above (binding in a slidingX powerpoint causing loss of equalization) can also be mitigated by tying one of the strands between your limiter knots (in a sliding X or equalette with limiter knots) a little longer than the other one. This keeps the strands from interfering with each other. I use a big locking biner for my powerpoint, (which Largo points outs reduces the clutch effect)but I prefer the big end down so I can clip multiple biners into it.
Crappy photo, but hopefully gives the idea:
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GOclimb
Trad climber
Boston, MA
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Jan 18, 2007 - 02:53pm PT
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Another disadvantage that just occured to me with this mooselette is that it doesn't work with 2 anchors. So, you'd have to have a different process for a 2 piece vs. 3 piece anchor. Not to mention when the gear is crap there's also the need to equalize 4 pieces which is no problem for the equalette or cordolette. It's the same process.
The mooselette works with three or more pieces of gear. For fewer than that, no gear shenannigans are necessary. I'd just use a pair of quickdraws, a crossed sling, or the rope, for two pieces (depending on what they were and the configuration). And just a locking biner for a one-piece anchor.
I'm not interested in being the advocate for the Mooselette. It has serious disadvantages that haven't been mentioned here. But so does just about everything, *especially* the old cordelette.
Yes, I put some thought into this the first time around, and I've put some time into using a few of these configurations in the field. I don't mind discussing my findings here - that's one of the things these forums are good for.
GO
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raymond phule
climber
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Jan 19, 2007 - 05:18am PT
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"I believe the testing showed a small amount of extension was ok (e.g. in a limited knot sliding X)."
I believe that the tests where done without anything in the place of a belayer so the test actually doesn't show anything about shock loading if a belayer is included in the belay chain.
The test show that no shock loading occurs due to the falling climber. This is not strange but wasn't well know before.
A falling climber plus "falling" belayer due to extension is definitely going to load the ancors in a different way compared to just a falling climber (as in the test).
The force from the climber might be less due to slipping in the belay device.
The falling belayer is going to load the anchor independent of the falling climber. This load is going to be higher with a stiffer connection between belayer and anchor. 10 cm of climbing rope is not much to soften the connection.
edit: The term shock loading is not god here as rgold pointed out in the other thread. All dynamic forces on a anchor could be considered shock loads. The interesting question is simple if the load is going to be very high if extension happens.
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tito
climber
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Jan 19, 2007 - 06:29am PT
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Rags, have you read the entire rc.com sliding-x thread? One would hope any discussion here would use that as a starting point
one should hope for nothing of the kind. if you had had your way, the whole thread over there would have been killed after 3 posts as people succumbed to your demands that they first read all the past threads on anchor building and JL's book 1 and book 2.
As someone pointed out, a fall of factor 2 is highly unlikely. Redirects and practicing a "soft belay" in the event there is a possibility would seem to mitigate the risk even further.
a factor 2 fall does not produce double the force of a factor 1 fall. a factor 2 fall increases the force on the anchor by 40%. redirecting the belay through the anchor increases the force on the anchor by around 60 percent. if you are concerned about reducing the forces on the anchor, redirecting the belay does not get the job done. the goal is not simply to reduce the fall factor. reducing the fall factor only slightly by redirecting the belay through the anchor will increase the forces on the anchor by almost 60%(catching a fall directly on your waist v. redirecting the belay through the anchor).
other issues come into play as well. can anyone catch a factor 2 fall on their waist? without gloves? or will there be so much slippage through the belay device that the belayer will drop the climber?
I’ve used it [ed. two sliding x's with limiter knots to form a three piece anchor] on many occasion and with the quad as per Largo’s book it seems like a perfectly reasonably anchor, am I missing something?
a majority of force goes to the shorter leg? because it stretches less when the anchor is impacted? that's not a bad thing. if the force were equally distributed to both arms, the force distribution to the three pieces in your picture would be 50-25-25. if 60% of the force goes to the shorter leg, then you could have something like 40-30-30(if the 60% going to the shorter leg was then equally divided between the other two pieces--but once again leg length of the rigging between those two pieces matters). note the better distribution of forces: 50-25-25 vs. 40-30-30. you just have to be aware of that unequal force distribution. when one leg is shorter than the other, you have to be careful not to rig the anchor in such a way that you put 60% on a single marginal piece, which could happen if you had the shorter leg going to one piece. then you would get a distribution of something like 60-20-20, which is worse.
Briefly, my preference goes from top to bottom, with the Mooselette equalizing the best
from looking at that rigging, it doesn't seem like it can equalize well because of all the friction produced by so many strands of cord running across biners. hooking up a portaledge to an anchor and being able to get a good night's sleep does not prove that an anchor is reliable for trad climbing. unless you have test results that show otherwise, one can only assume that anchor won't equalize very well. the more strands of cord running around biners, the harder it is for an anchor to equalize. the two sliding x's with limiter knots would appear to be superior.
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raymond phule
climber
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Jan 19, 2007 - 07:44am PT
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Is it possibly to get any details about John's testing except from the book?
The things I have heard about the test and the results don't quite add up.
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wootles
climber
Gamma Quadrant
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Jan 19, 2007 - 08:29am PT
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What isn't adding up?
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 19, 2007 - 08:42am PT
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It would be nice to have a technical paper desribe the results, with quantitative data, so that others could analyze the tests. I don't know what journal they could be published in, but that would be great if it were possible.
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raymond phule
climber
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Jan 19, 2007 - 09:00am PT
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The test was done with 2 anchoring points, right?
It is often stated that using a cordalette put all force to a single anchor if the legs are uneven in length. This cant be true in general if the anchor points are spaced horizontially apart. The configuration is more important than the lengths of the arms.
The understanding (after reading parts of the threads) of the result of the test seems to go outside what was actually tested.
Some examples.
The above example.
That the equallete equalise 4 points.
That no shock load (high load) happens in a real situation with a belayer.
That the cordalette is bad with 3 points (probably correct but not tested)
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jstan
climber
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Jan 19, 2007 - 09:06am PT
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I must be missing something. We all realize no two anchors have the same strength and we count on our ability to estimate this strength. Why are we trying to equalize the load??
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wootles
climber
Gamma Quadrant
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Jan 19, 2007 - 09:39am PT
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I don't know if this is in the book but thought I'd put it up here as reference. I'm working on digging out some data but as I've mentioned earlier the computer that it is contained in suffered some damage during Sterling's recent move. To tell the truth I'm not even sure where that computer is at the moment or at least which one of the 8 or so hard drives laying around that it's on.
Here is a summary that Chiloe wrote up about the analysis of the tests. This may be in the book. While not a full on technical paper it is the best I have right at this moment.
Larry Hamilton
October 4 2006
BRIEF SUMMARY
-----------------------------
Anchor setup | Median absolute
(similar rigs | difference in
combined) | force (kN)
--------------------+--------
cordelette equal | 0.88
X equal | 0.26
cordelette unequal | 3.33
X unequal | 1.00
equalette unequal | 0.41
-----------------------------
In connection with John Long’s new anchors book, Jim Ewing at Sterling Ropes ran a series of drop tests to see how well different setups could equalize the load on the anchors. He started with two basic anchor configurations: equal-length legs (think of two pitons in the same horizontal crack) and unequal-length legs (like two pitons in the same vertical crack).
Cordelettes did a relatively poor job of equalizing the unequal-legs setup. The median difference in force felt by long and short legs was over 3kN. Even in equal-legs setup, the median absolute difference was close to 1kN. A sliding-X, in contrast, reduced the unequal-legs difference to 1kN, and the equal-legs difference below 0.3kN.
Because even the 1kN difference between sliding-X legs is significant, Long, Ewing, and soon others turned their attention to alternatives that might work better than the sliding X. One of these, currently being called the “equalette,” reduced the median difference between unequal-length legs to about 0.4kN.
Most of the other proposed variations have not yet been drop tested. It is possible that due to unforeseen friction some of them, like the sliding X, will prove to equalize better in the living room than in falls.
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raymond phule
climber
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Jan 19, 2007 - 10:00am PT
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Thanks,
what was the total force?
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wootles
climber
Gamma Quadrant
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Jan 19, 2007 - 10:23am PT
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Ok. Here's a small hunk of data but it doesn't include the egualette stuff or the shock loading stuff. I'm done looking for the other stuff for today and won't be able to look again for a couple of weeks.
There's more and I'll post it if or when I find it.
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Chiloe
Trad climber
Lee, NH
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Jan 19, 2007 - 10:47am PT
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The sum of the forces felt by both arms in the main series of cordelette/sliding X/equalette tests ranged from about 4 to 11 kN.
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wootles
climber
Gamma Quadrant
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Jan 19, 2007 - 11:05am PT
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I should mention that in the early stages of the testing, where I believe the above numbers came from, I was using a fresh rope for each of those sets of 3 drops. In later tests I used the same rope sample continuously. So the increases in the forces you see above are due to the loss of elasticity (increase in modulus) of the rope sample. I found that using the same sample of rope not only saved time but delivered more consistent total peak force. After a rope has seen a half dozen or so FF1 drops the elasticity property changes very little if at all. I think I was doing the drops at 3 minute intervals. It also says in the book what mass I used but right now I can't remember if it was 80kg or 100kg.
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raymond phule
climber
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Jan 19, 2007 - 11:24am PT
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Thanks for the info
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Largo
Sport climber
Venice, Ca
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Jan 19, 2007 - 11:50am PT
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The testing we did was always intended to be shared far and wide beyond just being printed in the book. We did everything possible in having it be as scientific as we could, given the time and resources. The numbers were crunched by two nationally recognized statistics gurs who are also climbers, and Wottles is recognized throughout the industry as the most comprehensive tester in the US, with all the fancy UIAA towers and computers and gadgets as well as all the experience. He was recommended to me by Kolin P. at Black Diamond.
Ideally, this kind of testing is an on-going affair that should be carried out by the AAC. That's how it's done in virtually every other country on earth. All private efforts will be limited.
We got the ball rolling, but I can't keep it rolling by myself, nor can Wottles.
JL
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Chiloe
Trad climber
Lee, NH
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Jan 19, 2007 - 12:11pm PT
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and Wottles is recognized
The climber formerly known as Wootles
;-)
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dirtineye
Trad climber
the south
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Jan 19, 2007 - 12:25pm PT
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How much wottle
Would a Wootler wot
If a Wootler would wot wottles?
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GOclimb
Trad climber
Boston, MA
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Jan 19, 2007 - 03:28pm PT
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Regarding this anchor, which I'm calling the two crossed-x slings:
Tito said:
>> I’ve used it [ed. two sliding x's with limiter knots to form a
>> three piece anchor] on many occasion and with the quad as per
>> Largo’s book it seems like a perfectly reasonably anchor, am I
>> missing something?
> a majority of force goes to the shorter leg? because it
What do you mean by shorter leg? There is the same length of webbing on both sides. In general, with crossed-x situations, because the biners act as (approximate) pulleys, the force is the same on a long arm as on a short arm. Look at it this, way - if the force started to get higher on the short arm than it was on the long arm, the sling material would slip through the biner towards the short arm until those forces were equalized again. Does that make sense to you? It is, in fact, why you see relatively good equalization on what the testers called the "unequal" setups.
Tito goes on to say, in regards to the mooselette:
> from looking at that rigging, it doesn't seem like it can
> equalize well because of all the friction produced by so many
> strands of cord running across biners.
In practice, it seems to equalize better than most. So far as I can tell, this is because there is typically only one strand moving through the power point (the movement through the other biners is very small, and not binding). But as Wootles pointed out, seeing this with body-weight or two bodies-weight doesn't tell us much about what might happen from a hard fall. Only a test rig could do that.
{snipped the rest of Tito's analysis, which seemed to be based on a faulty premise}
> hooking up a portaledge
> to an anchor and being able to get a good night's sleep does
> not prove that an anchor is reliable for trad climbing. unless
> you have test results that show otherwise, one can only assume
> that anchor won't equalize very well. the more strands of cord
> running around biners, the harder it is for an anchor to
> equalize. the two sliding x's with limiter knots would appear
> to be superior.
I have no idea why you would assume that. Build one yourself, it's very easy. You can feel that the tension equalizes at least approximately on the strands, and you can feel that even under with body weight, the strands move freely - which is not always the case with the sliding-x, and you can see that there are rarely strands moving in opposite directions to each other, which always happens with the sliding-x.
GO
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Crag Q
Trad climber
Louisville, Colorado
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Jan 19, 2007 - 03:38pm PT
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GOClimb, What route is that in the mosselette picture? It sure looks like Eldo, but I can't match it up in my mind with any route.
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GOclimb
Trad climber
Boston, MA
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Jan 19, 2007 - 03:48pm PT
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Crag_q wrote: GOClimb, What route is that in the mosselette picture? It sure looks like Eldo, but I can't match it up in my mind with any route.
Bingo! Good eye! Yellow ridge, just before the short traverse under the roof around pitch, what, four, I think?
GO
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 19, 2007 - 03:50pm PT
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Thanks wootles and John, great to have this data out in public. I know that it is difficult to find the time to write a formal paper up for a journal, perhaps we can have a productive set of thoughts generated in this shared environment of the Forum...
...I'm between meetings now, but I will post some calculational thoughts I have regarding the results later...
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wootles
climber
Gamma Quadrant
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Jan 19, 2007 - 04:24pm PT
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The climber formerly known as Wootles
;-)
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Largo
Sport climber
Venice, Ca
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Jan 19, 2007 - 04:29pm PT
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I've actually got to go to a meeting now but if someone can scan all the test stuff from the book and post it here, perhaps something more can be wrung from it. I'd don't have a scanner here at my home office.
JL
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GOclimb
Trad climber
Boston, MA
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Jan 19, 2007 - 04:48pm PT
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Jstan wrote: I must be missing something. We all realize no two anchors have the same strength and we count on our ability to estimate this strength. Why are we trying to equalize the load??
Because the person who built the cordelettes that would have tested like these ones in a hard fall...
... probably didn't realize that there was essentially no equalization going on - all of the force of the fall would hit one piece, and, if ripped out, then hit the other piece. Not good.
GO
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jstan
climber
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Jan 19, 2007 - 08:34pm PT
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GOCLIMB:
Do I have it correctly. Your answer is " we are trying to equalize because in this data we failed"?
Just trying to understand. That is OK but does not address my question.
My question was this. If I think I have one piece good for 3000# and another good for 1000# - I should not try to equalize. I should try to put say 2000# on the strong one and 500# on the weak one. If I try to put 1500# on both - one will rip. If I don't equalize the total force the anchor system (the sum of the two) can be substantially increased. If done correctly the total force can be 4000# instead of the 3000# one gets after ripping the poor anchor.
Before you are done this is going to need some mechanical network analysis using stress/strain data for the kinds of nylon used.
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Trusty Rusty
Social climber
Tahoe area
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Jan 19, 2007 - 09:47pm PT
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After jugging up to my picture perfect iron curtain of 69 equalized pins, Dorton calmly stated "minimum 3 & max 5 dude"
With a typ. 500 lb load, equalizing is a must and the "perfect figure eight" is appropriate for walls.
C/Jones. . .that "partner" was right when it comes to wall climbing. . .. but as far as free routes the "sliding W" is probably better.
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john hansen
climber
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Jan 19, 2007 - 10:12pm PT
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This thought just came to me after reading these posts.
It seems that most , if not all, of the systems use 'static' materials.
What if you had a cordellet with dynamic qualities? Like a bungee cord that would stretch to help distribute the wieght to three or more anchors, if not'exactly..' equal, at least with less shock loads.
I know the first question would be "How do you haul the bags or jumar from it ?" It would have to have just enough stretch to make it work. Help me out here....The difference between gold line and modern ropes is amazing. Im sure they have the technology.
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cintune
climber
Penn's Woods
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Jan 19, 2007 - 10:22pm PT
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"What if you had a cordellet with dynamic qualities?"
Yates makes an 8mm "dynamic prussik" cord that sounds like what you're suggesting. Having none of the expertise of the main contributors here, I have no idea how it would work in an anchor, but it's out there.
And there's always screamers.
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climbingjones
Trad climber
grass valley,ca
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Topic Author's Reply - Jan 19, 2007 - 10:26pm PT
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I agree Trusty, walls and free climbs are totally different. What I like most is carrying a roll of duct tape to "back up" anything sketchy. I prefer a triple xyz config. Maybe I should carry some silly putty too. 69 pins though? Good thing he was carrying the gear, eh? Thats alot of slings too. Did he incorporate his underwear into that deal? Cracking a St. Pauly Girl here. You?
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john hansen
climber
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Jan 19, 2007 - 10:30pm PT
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The screamer (unless I am thinking of the wrong product, or they have upgraded it ) relies on stitching ripping out to soften the impact. A bungee cordellet would load gradually without maximum static force's. The more stretch the more it would equalize.
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wootles
climber
Gamma Quadrant
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Jan 19, 2007 - 10:56pm PT
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Dynamic cord won't equalize any better than steel cable. No matter what the materials are, given identical setups, the load ratios will always be the same. Dynamic cord will, however, lower the overall peak force which probably isn't a bad thing.
8mm dynamic prussik cord is nothing more than a hunk of 8mm half or twin rope. You probably won't see much more load reduction with a dynamic 8mm vs a standard 8 or 7mm accessory cord anyway. We're talking relatively short pieces of cord here. Also the tensile strength of dynamic cord/rope is generally less than the equivalent size static due to the internal structure, not that strength would be an issue.
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TGT
Social climber
So Cal
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Jan 19, 2007 - 11:10pm PT
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My firmly braced feet are guaranteed to equalize.
And the rope burned flesh on my backside insures that there will be no shock loading.
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tito
climber
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Jan 19, 2007 - 11:16pm PT
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What do you mean by shorter leg? There is the same length of webbing on both sides..
well, yes, but the big/main sliding x in the picture looks like nylon cord, which has some dynamic properties to it. the second, smaller sliding X looks like an 8mm dyneema sling, which doesn't have much stretch. since the right hand leg of the rigging will stretch less, it will feel more force. maybe i slightly overstated the differences in the amount of force going to each leg, and the real distribution of forces lies somewhere between a setup with equal leg lengths and one with unequal leg lengths.
In general, with crossed-x situations, because the biners act as (approximate) pulleys, the force is the same on a long arm as on a short arm. Look at it this, way - if the force started to get higher on the short arm than it was on the long arm, the sling material would slip through the biner towards the short arm until those forces were equalized again.
in a hypothetical frictionless environment that would be true. but that is not the case when friction is taken into account. as the biner slides across the cord in an effort to equalize the forces, friction fights against the biner. as a result, the biner only succeeds in getting 2/3 of the way to perfect equalization. the same phenomenon occurs when a climber hangs on a top rope. the belayer only has to pull with 2/3 of the force that the hanging climber exerts on the anchor. the friction from the rope running through the anchor point helps the belayer hold the climber up. good when belaying, but bad when trying to distribute forces equally to all the pieces of an anchor.
the more times cord or webbing runs over a biner in a rigging, the more friction prevents the system from equalizing.
But as Wootles pointed out, seeing this with body-weight or two bodies-weight doesn't tell us much about what might happen from a hard fall. Only a test rig could do that.
agreed.
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Trusty Rusty
Social climber
Tahoe area
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Jan 19, 2007 - 11:21pm PT
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Clean Livin CJ. . . . J. Hanson is on to something big . .. .. Flexible American Spirit Summer Porn Squash, vagina stretched ear to ear. . something like a mother who leads 5-4 .. .Chemical Brothers Remix.
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climbingjones
Trad climber
grass valley,ca
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Topic Author's Reply - Jan 19, 2007 - 11:31pm PT
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Dude yeah. A stretchy vagina equalizes everything. Or nothing. Not sure which. But who cares? Maybe this belongs on the "Men and women are different" thread. But whatever. My mother cant lead 5.4 though, she is to into worrying about my goat porn habit. I told her to get a life. But maybe I should just get a goat. Do they eat summer porn squash? Cause I have alot. Maybe enough to equalize an anchor. But only if I use the sliding Dub-ya. No screamers though, there will be plenty of screaming when you see the anchor that I build on top of that ice formation on Sunday.
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john hansen
climber
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Jan 19, 2007 - 11:37pm PT
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With a twenty foot countinous piece of this stuff you you could make a two foot cordelette figure eight anchor could stretch to four or five feet it might be safer .Maybe this could even be applied to extreme free climbing or speed ascents with 'short roping'.
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TGT
Social climber
So Cal
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Jan 19, 2007 - 11:40pm PT
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The answer to all your equalization problems
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 19, 2007 - 11:54pm PT
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I did an analysis of the Cordelette and the Sliding X which end up being extremes in the physical model of a 2-anchor system. I'd be happy to send it anyone...
...in this model I correctly calculated the different performance of the test results.
You all may think this is obvious, but, the way the Cordelette works, each arm works in parallel. This means that when you try to extend the "master point" the stiffness will be determined by the stiffest arm, which is the shortest arm. That means that much more force will be on the short arm then the long one.
The Sliding-X works with both arms effectively in series, so the entire sling extends, reducing the force and equalizing it, except for the friction at the "master point" (the 'biner "pulley"). This is also possible to calculate to get the differential force on the arms.
Here are the details of the calculation... rgold might like to comment on whether or not this makes any sense... I am notorious for goofing up on this stuff...
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GOclimb
Trad climber
Boston, MA
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Jan 20, 2007 - 12:29pm PT
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Tito - that's right - that's why Wootles' test results typically show a 25% difference in peak load between the two arms of the uneven crossed sling.
I simply don't know how large a factor the friction over biners would be for the mooselette in the case of a hard fall. Yes, the cord has to run around three biners - the power point and two out of the three protection biners. But at least it has the potential to equalize pretty well over all three (or more) points.
Compare that to the CharlesJMM anchor, which only has full (potential) equalization within a narrow range of angles, or if all three pieces are within the same plane, or the equalette, which pretty much only equalizes on any two pieces at a time, except within a narrow range of angles where it can equalize over three or more strands.
GO
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ghand
Sport climber
Golden,Colorado
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Jan 20, 2007 - 01:04pm PT
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This guy seems to have forgotten his mooselette!
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Largo
Sport climber
Venice, Ca
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Jan 20, 2007 - 05:42pm PT
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Hey, Ed, if you were to try and break those figures down for us who never got past Cal.2 (and didn't want to even go that far), what would it all mean?
Thanks,
JL
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 20, 2007 - 06:07pm PT
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boy I guess I take up the mantel of "buzz kill" from Roger...
OK, simple...
The stiffness of the arms depends on their length and their "Young's Modulus" which is a constant property of the material (so it is the same independent of what the size of a sling, or the diameter of the rope, etc).
If an arm is shorter, it is stiffer, which means that you need more force to pull it a distance x.
When you tie a cordelette with arms at two different lengths, you are making the shorter one stiffer than the longer one.
When you apply force at the "master point", you are pulling both arms the same distance x, but the force on the short arm is higher than the force on the long arm, thus, the forces are not equalized. This is what the test found.
For the sliding-x, you are applying the force at the 'biner, which is free to slide. The entire sling extends, it is less stiff than either of the cordelette arms because it is longer. When you extend the master point it takes less force to move it x than in the case of the cordelette, and the force is equal in each arm, the 'biner allows the sling to slip around and equalize the forces as long as you neglect the friction of the 'biner sliding at the master point. The test saw this too.
The analysis of these two systems also agree quantitatively with the test, which gives me confidence that the analysis.
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Mighty Hiker
Social climber
Vancouver, B.C.
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Jan 20, 2007 - 08:12pm PT
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Another angle on this subject, so to speak, is the subjective side. Over half of mountain and climbing fatalities in western Canada are due to snow avalanches. A few years ago, 29 died in one winter. (The average is something like ten.) Partly due to that, the various governments decided to put some funding into looking at the subject.
There were already lots of introductory and refresher and intermediate and advanced and professional avalanche courses. Most backcountry skiers were taking them and practising the various skills they learned. Less so snowmobilers, and those being guided - though the latter usually got at least some introductory training.
I'm no expert, but used to teach introductory avalanche (and rock) courses, have been backcountry skiing for decades, and have lost ten or more friends. I've attended various programs on what has been learned, and it may be relevant to this discussion, as far as I understand it.
They've done a great deal of analysis, and looked hard at what's done in Europe and elsewhere. Some of what they've learned, which is being translated into tools for the recreational user, is objective. That is, create tools that can be easily learned and applied to assess risk and make decisions.
Some is what we call subjective. Crudely, that people sometimes do stupid things, often for environmental reasons. They include things like fatigue, poor conditions, lack of nourishment, group dynamics, and even composition of the party. (A party comprised of both males and females is more likely to get into trouble, especially if they're in the 15 - 30 age range. The males almost always end up in the decision making roles, and make poorer decisions.)
This seems to apply to anchors also. A lot depends on the objective factors - how strong and reliable is the gear, how strong is the rock, how well is the gear placed, is it well connected? And the SERENE stuff. And, how well people have learned about both the technical side, and the judgment and experience needed to apply it.
Failing belays aren't exactly common - there was one on the DNB of Middle Cathedral a few years ago, but fatalities are more common for other reasons. Some of it is the influx of new climbers, who're sometimes perplexed by a stance that doesn't have a fixed belay. (I've seen some who couldn't figure out that a healthy large tree in a forest abutting the top of the cliff was a perfectly good anchor.) Perhaps some is how they learn, given that so many now learn in courses.
In terms of constructing belays, we shouldn't forget the non-technical side. That is, are other subjective factors such as those mentioned relevant, and should be climbers learn to be aware of them? After all, how often do we simply think "We're in a hurry/it's getting dark/I'm hungry or thirsty/I need to look like I know what I'm doing so that chick will be impressed/I know what I'm doing even if that old fart says I don't"? Worse still, be affected by these things, but not be aware that we're being affected?
An example is commonly referred to on ST. The novice, setting up a toprope belay. Who may not be receptive to help or suggestion, for pride or similar reasons. (Interestingly, the typical adolescent male may be more receptive to such suggestions from females than males, AOTBE.)
Anyway, just some thoughts.
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TGT
Social climber
So Cal
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Jan 20, 2007 - 10:17pm PT
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All my preceeding posts have been jokes, but have kind of obtusely been generated by this point of view.
1. You can't teach mechanical aptitude.
2. The abillity to visualize the forces involved is not all that common.
3. No rule set can cover every or even a small fraction of belay anchor possibilities, or lack thereof.
Sometimes a good bucket to place your butt in really is good enough.
Sometimes the most complex multi piece anchor isn't.
knowing the difference, is more of a talent and or product of experience than a science project.
Now go forth and analyze the physics for another 170 posts. I'm not doubting the value of the analysis or that we all might learn something, just its practicality,
If you don't have the judgement and eye for the practical application all the theory in the world won't do you any good.
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knudeNoggin
climber
Falls Church, VA
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Jan 21, 2007 - 12:36am PT
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> How much wottle
> Would a Wootler wot
> If a Wootler would wot wottles?
ootles!
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 21, 2007 - 01:59am PT
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TGT - working out the physics taught me something important about setting up ALL anchors. I am probably still not explaining this very well, or maybe it isn't as important to someone else as to me...
...but the trying to understand the tests that were done allows me to generalize the lessons contained in the results.
The lesson? only the sliding-x equalizes a two point anchor. The problem is the extension on a blown anchor. The tests also show that in some situations, the extension of the sliding-x onto one anchor doesn't load as much as feared.
I sometimes use a sliding-x and tie in with the rope on the third anchor. Seems redundant and secure.
A cordelette has real problems when the arm lengths are very different, especially if you have poor anchors. There may be a situation where a cordelette is fine to use, however, especially with nearly equal arm lengths (I know wootles doesn't think so, but here I would probably believe the analysis).
The physical analysis of the two rigs, compared to the test results, allows for a general understanding which is useful, at least to me.
I have to admit, I was completely surprised that the cordelette was so poor in unequal arm anchors. That is worth a lot.
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Chiloe
Trad climber
Lee, NH
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Jan 21, 2007 - 08:51am PT
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The lesson? only the sliding-x equalizes a two point anchor.
I'd qualify that by saying that the sliding-X equalizes better than a cordelette. In the tests, friction proved to be a significant complication for the sliding-X, resulting in a median absolute difference of 1kN between arms in the unequal-length setup (compared with 3kN for the cordelette, but only 0.3kN for the "equalette"). That was the second unexpected result of the tests.
These comparisons, not all of them included in Wootles' data table, are visualized in the graphic that he posted earlier (from John's book):
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GOclimb
Trad climber
Boston, MA
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Jan 21, 2007 - 02:33pm PT
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Chiloe, I have a question about methodology. It relates the the chart in your post, and I'll get to that later.
1 - In the chart Wootles posted (the one where I circled several of the data points) each item got three drop tests, each with increasing values. The average absolute values vary a good bit from test to test.
2 - Wootles mentioned that in later tests, he used a rope that gave pretty consistent force values, and mentioned that the equalette drops were done on that rope.
So my question - were the numbers in your chart taken from those two different sets of drops? The reason why I ask is that for the percentage difference between arms, it seems to make very little difference how much force the anchor felt, so the methodology doesn't matter, but your chart shows delta in absolute value, not percentage value. So the different methodology could produce very different results.
If my point isn't clear, I could give examples.
GO
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rgold
Trad climber
Poughkeepsie, NY
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Jan 21, 2007 - 09:58pm PT
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if you were to try and break those figures down for us...what would it all mean?
I think the simplified answer is the one I gave a few years ago in a thread on rc.com BSX (before the sliding x thread):
In a fixed-arm system, arm tension is inversely proportional to arm length.
So if one arm is double the length of a second arm, the tension in the first arm will be half the tension in the second arm. These results are extremely simple consequences of the assumption that the rigging material obeys, at least approximately, Hooke's Law, but are strictly valid only for the situation when all anchor pieces are in a single vertical line.
Ed's calculations are considerably more complex because he wants to predict the anchor loads from the fall data. I was only interested in the way the anchor load, whatever it might be, will be distributed.
Now predictions based on idealized behavior may or may not be observed in practice. In the field, it is the climber who ties the arm lengths, which of course can never be perfect, and even if they were, the way in which small amounts of slack may or may not be released by the knot is unknown. Moreover, neither my simplistic formulation nor Ed's calculations nor Wootle's drop tests consider the effects of arms radiating from the power point at various angles.
The unequal arms in Wootles' posted chart were of lengths 100 (+/-) 3 cm and 45 (+/-) 3 cm, so the long arm is about twice the length of the short arm. Ideally then, the load measured at the long arm should be about half the load measured at the short arm. In the first two columns of Wootles' chart, this ratio is roughly apparent in about half the trials, rows 4,5,6,9,11,12, and 15, but way off in the other half. The lack of exactitude isn't suprising when one looks at the discrepancies from 15% to 35% in the equal-armed cordelette, which indicate just how hard it is to actually tie functionally equal arms.
What I get from the combined theoretical and experimental results is that equalization is unobtainable in principle when the arm lengths are unequal, but in any case the climber's best efforts to tie a correctly proportioned fixed-arm rig will nonetheless lead to unpredictable and perhaps significant inequities in load distribution. I think that in that post I mentioned above, I also said (and have since repeated) that for fixed arm rigging, you should probably assume that each piece will get the full load in turn. This turned out to be far more appropriate than I imagined, with 6 of 15 attempts at fixed unequal-arm rigging ending up with more than 80% of the load on one piece.
It has often been proposed that stretchier rigging materials would help to compensate for the inevitable small deviations from perfection made when tying fixed-arm rigging. I see little evidence for this in the data; spectra doesn't fare significantly worse in percentage difference in the equal-arm tests than stretchier materials like 7mm cord. The 6 mm cord does seem to provide a levelling effect, I'm not sure whether that cord it is spectra or nylon. The equalizing performance of webbing and cord might also be affected by differences in the way knots in the two emit or retain additional slack.
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cintune
climber
Penn's Woods
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Jan 21, 2007 - 11:05pm PT
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Wouldn't stored elastic energy introduce a whole new variable to deal with?
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rgold
Trad climber
Poughkeepsie, NY
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Jan 21, 2007 - 11:43pm PT
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You mean energy absorbed by stretching the rigging itself? In principle, yes, and I think Ed does this. In the case of a belayed leader fall, my guess is that the climbing rope and belayer tie-in would absorb most of the fall energy, and that neglecting the contribution of the anchor rigging itself would not be a source of substantial error. But this is just a hunch based on having tried once or twice to include such factors in a model only to discover that they made little difference
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Chiloe
Trad climber
Lee, NH
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Jan 22, 2007 - 09:33am PT
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GOclimb:
your chart shows delta in absolute value, not percentage value. So the different methodology could produce very different results.
Within these data, our general conclusions seemed reasonably stable. For example, percentage differences show the same ordinal pattern as absolute differences.
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 22, 2007 - 10:46am PT
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The elastic nature of the material is incorporated into the calculations above. The parameter "K" is the spring constant which defined by the product of the cross sectional area and the Young's modulus Y of the material:
K = Y*A
The force required to increase a sling of length L the distance x is then given by Hooke's law:
F = K * x/L
Where we can use the very good approximation that the material obeys Hooke's law. The agreement of the calculation with the data seem to support this assumption.
The idea of all these calculations is to equate the energy of a falling mass into the work done to "pull the spring."
This calculation is based on an idealization of the anchor system. I think it shows that to first order (which is good to probably 30% to 50%) that the major aspects of the anchor can be understood in this simple way.
That is impressive. Most "real world" situations are usually not well represented by such idealizations. Anyway, you can take it or leave it... I think the rgold has a wonderful way of expressing the essential features of the analysis. His conclusions are right on.
This physics helps us understand why something behaves the way it does. It's not intended to lead to a solution of the "anchor problem." In fact, it points the way to the likely conclusion that the "anchor problem" cannot be solved, that is, unextendable, equalizing anchor systems may not exist.
If that is true, then we start looking for other solutions for anchor systems.
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rgold
Trad climber
Poughkeepsie, NY
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Jan 25, 2007 - 12:07am PT
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Before asking such questions, it is important to check the sliding x thread on rc.com, where many rigging proposals have been made. I'm fairly sure your set-up hasn't been suggested, and it has a very nice way of dealing with extension in case a piece fails. Nonetheless, I don't think it is likely to be of much interest, for at least the following reasons.
1. It is for two anchors, and the equalette already does a good job with less complexity and more adaptability.
2. The two anchors have to be at the same level. If they aren't, one of the side rope pieces has to be retied. This makes the set-up impractical for many gear anchors.
3. When loaded off the vertical axis, one of the arms can slip down over the gate of the central biner. You'd be well advised to use two biners with the gates reversed there. But now your rigging uses twice the non-power point biners that the equalette needs.
Forget two-anchor rigging. The standard trad anchor is a three-piece anchor. The challenge is to find rigging for this that equalizes effectively, has a small extension if a piece fails and re-equalizes the load if this happens, can adjust to different directions of load, is quick and foolproof to set up regardless of the anchor configuration, and does not require excessive depletion of the party's carabiner supply.
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Largo
Sport climber
Venice, Ca
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Jan 25, 2007 - 10:47am PT
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Rich wrote: "Forget two-anchor rigging. The standard trad anchor is a three-piece anchor. The challenge is to find rigging for this that equalizes effectively, has a small extension if a piece fails and re-equalizes the load if this happens, can adjust to different directions of load, is quick and foolproof to set up regardless of the anchor configuration, and does not require excessive depletion of the party's carabiner supply."
That's exactly right. The solution is looming out there somewhere.
The interesting things about all of this is, to me, not all the number crunching (which guides the results, as it must), but in looking at this as a kind of riddle (which is currently is) waiting to be solved. The criteria has been stated--now meet it.
One thought: The sticking point so far is that with a two-point anchor, both arms of an equalette (or variation thereof) go to a sliding powerpointthat to some extent can shift and redistribute some of the loading once weighted. When strung to three placements, one or the other of the two arms is connected to two placements, while the other arm secures one placement, resulting in unequal loading across the three placements.
The first part of the riddle to figure out is how to rig something that A) still has a sliding powerpoint, and B) distriburtes equal loading to 3 placements.
In other words, how do rig a three-armed system that still has a sliding power point? I'm thinking the bottom of the loops between the three arms (the two "U" sections at the bottom of the sling between the three placements)have to be divided into two unequal strands (and left tied that way), with one strand of each "U" extended down a bit and drapped over the other and clipped off like a regular equalette. Can you picture that??
JL
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 25, 2007 - 11:30am PT
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From what I understand of the equalette, it is functionally in between the cordelette and the slinding-x..
The idealized sliding-x is one long piece of sling which is free to distribute the load over the entire sling.
The cordelette can be thought of as individual slings connected to a single master point, each sling undergoes an identical elongation (thus unequal forces for unequal sling lengths).
I assume the equaletted is in the new edition of the Anchors book, I'll try to find a copy and take a look. Perhaps rgold can describe it functionally here.
My guess is that there may be no ideal way of solving the problem, that every solution will have limitations that will need to be understood... the problem might be more complex than to admit a simple solution.
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bobh
climber
Bishop, California
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Jan 25, 2007 - 12:34pm PT
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The potential for minor-axis loading of the power point biner in the anchor pictured above is something that should really be avoided. As pictured, this is a bad rig. Additionally, both this anchor and the mooselette anchor reduce extension at the expense of putting some 'american-triangle' type force amplification on the lateral anchor points. Something to consider when tabulating the pros and cons of each system.
Interesting discussion. Love your anchor books, John.
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Ksolem
Trad climber
LA, Ca
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Jan 25, 2007 - 01:03pm PT
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This is an interesting discussion with some good examples as well. But, practical application in the field is another story. So I have a question or two for all of you anchor scientists.
First, how often, when you set an anchor system at the end of a pitch, do you really think there is a possibility that one or more of your pieces might pull if loaded?
Also, given the fact that there is a limit to how much stuff one wants or is able to carry up a hard pitch, what would you rather have when you arrive at the belay - 20 ft. of 7mm cord and 6 or 8 extra carabiners, or a couple extra cams and nuts to choose from.. ?
Not to say that equalization is not important, especially if you are in the unfortunate position of having a dicey anchor. But I usually look at the multiple pieces in an anchor as backups. I use the rope to clip in, usually in series without any slack between. Of course I am usually swinging leads, not guiding, so this is not inconvenient. And with only 35 years of this under my belt I guess I am due to get chopped any day now anyway... :-)
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rgold
Trad climber
Poughkeepsie, NY
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Jan 25, 2007 - 02:07pm PT
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Ksolem, I do something similar much of the time, and it wouldn't be surprising to find JL did too. I've never had a piece pop on a loaded anchor, but I do know people who have and have read about others.
But regardless of whether or not it seems likely that gear will fail, perhaps you might change over to something that didn't load your anchor pieces sequentially with the full load if the new method was almost as quick and easy as your series of clove hitches and didn't eat up a good part of your rack for two belays.
Moreover, for better or worse, climbing is heading in the direction of "foolproof" systems that enable people who have not acquired experience through a long apprenticeship to participate. Direct rope tie-ins were replaced by swami belts which where, in turn, replaced by harnesses, which have now been replaced by harness with buckles that don't need to be back-threaded. Belay devices have been followed by autolocking belay devices, nuts by cams, and so on.
Traditionalists scream "foul" when innovations appear, but then, after a sufficient period of abstinence, embrace them. Gear that make things safer for novices typically has found favor with experts. The same thing will happen with rigging systems, if we can together come up with better ways of doing it.
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Ksolem
Trad climber
LA, Ca
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Jan 25, 2007 - 02:25pm PT
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RGold - I don't disagree, and I am not one to cry foul over new innovations.
How about the second question..?
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murcy
climber
San Fran Cisco
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Jan 25, 2007 - 03:16pm PT
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given that the alternative is a bunch of biners and too much fussing, why not have a special piece of gear, a "powerpoint biner", with a main locking compartment for the load and three little closed compartments (maybe with pulleys on them like those dmm revolver biners) for cordalette loops. keep a single, continuous cordalette loop running through all three pulley compartments. clip the three resulting loops of it to your pieces (shortening the cordalette with a butterfly if you like). that's as good equalization as you're going to get and it's instantaneous to set up because you'd keep it pre-tied.
for limiting extension have a bundle of three short "backup" cords with a figure 8 on a bight tied at their mutual end; the bight is kept clipped to (or tied through another special compartment of) the "powerpoint biner". tie the cords off loosely to each piece based on how much extension you want to tolerate.
one big specialty biner, one cordalette that can be a bit shorter than usual (no huge figure 8), one bundle of three cords that's about half a cordalette total in weight. compared to the old cordalette method, a bit heavier, but just about as easy to set up.
i don't know how important this stuff is compared to solid placements and just not screwing up etc., but it is a fun brain teaser.
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 25, 2007 - 03:35pm PT
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maybe I can answer as a scientist...
This is an interesting discussion with some good examples as well. But, practical application in the field is another story. So I have a question or two for all of you anchor scientists.
Practical applications is what we all are trying to get at, if the problem is susceptable to meaningful analysis, then that is a good place to start as it will make the principals important to a successful application apparent.
First, how often, when you set an anchor system at the end of a pitch, do you really think there is a possibility that one or more of your pieces might pull if loaded?
You never know, and experience isn't necessarily the answer. There is a finite probability that your anchors will blow. We do not know what that probability is, however, you cannot calculate a meaningful answer by taking the number of anchors you've set and saying "less than one in N" as this implies that the chance of failure goes down everytime you set an anchor that doesn't fail.
This is the "Challenger" mind set that NASA had, they couldn't calculate the probability of catastrophic failure that made sense, so they set a limit on the number of flights. The reason the calcuation didn't make sense is that they hadn't had a failure in the time they would expect, 1/200 flights... Now we know that is about the correct failure rate.
Same thing with anchors, you don't know if a particular anchor you set would or would not have failed, you never tested it. You don't know how close you've gotten to disaster 'cause the disaster never occured.
Also, given the fact that there is a limit to how much stuff one wants or is able to carry up a hard pitch, what would you rather have when you arrive at the belay - 20 ft. of 7mm cord and 6 or 8 extra carabiners, or a couple extra cams and nuts to choose from.. ?
I think that the initial "concept demonstration" is where we'd like to get to first, then the technology can be refined from there. The cordelette's appeal was the simplicity of setting it up. The cordelette replaced numerous slings, etc, in systems that equalized. If there is a solution to the problem, I'd think it unlikely that the first thing proposed is the ultimate thing we use.
Not to say that equalization is not important, especially if you are in the unfortunate position of having a dicey anchor. But I usually look at the multiple pieces in an anchor as backups. I use the rope to clip in, usually in series without any slack between. Of course I am usually swinging leads, not guiding, so this is not inconvenient. And with only 35 years of this under my belt I guess I am due to get chopped any day now anyway... :-)
We know that equalization is desirable, and we know that it works because it has been used in aid placements as well as to protect leaders, in both cases where a single piece may not hold. The anchor system works best when the load is as distributed over as many pieces as practical, thus no one component is stressed. This is a simple engineering design rule, stay far from the failure point as possible in a multiply redundant system where any one of the redundancies would accomplish the goal of the system.
As for when you will get the chop, the probability of it happening is probably no differnt today as it was 30 years ago... at least not in terms of the knowledge you bring to the table.
Sometimes you roll the dice and you win... fortunately the dice is loaded in your favor, but it is still possible that the dice roll could go against you. We all should keep trying to load them even more in our favor.
That's what this conversation is all about.
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GOclimb
Trad climber
Boston, MA
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Jan 25, 2007 - 03:59pm PT
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Ksolem - the only reason to be concerned with any of this is if there is a possibility of the leader falling onto the belay. For normal lead falls and for bringing up a second I've been perfectly happy with just wedging my fat ass in a crevice, or backing up my two good legs with one really good nut. For that purpose - sure, a few good cloved pieces is perfect.
But this is really all to answer the question of what happens when the leader falls with no gear in.
Or to put it another way - how many of your clove-hitched-in-sequence anchors would you have been comfortable with catching a leader with no gear on the pitch?
Leader is 10 feet up, falls to 10 feet below you, your bottom piece is weighted with a pretty high force - depending on the type of device you're using, perhaps 10-15kN. Can that one bottom piece hold all that force? What if it pops? Then the next piece in sequence feels approximately the same force. You get the idea.
GO
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rgold
Trad climber
Poughkeepsie, NY
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Jan 25, 2007 - 05:04pm PT
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How about the second question..?
I think that an appropriate anchoring system would make it a false dichotomy. But I also agree with you that systems that eat up too much gear are not going to be useful to many climbers.
On the other hand, climbers have, over time, shown almost limitless willingness to carry more gear. The common rack I see nowadays has at least twice as many pieces on it as the rack of nuts we used 30 years ago, and the pieces, cams, are heavier too. I could go on about the other "necessities" climbers now have on their harness that add weight to the enterprise, starting, I suppose, with the harness itself.
So an alternate answer to your question is, if the rigging system is effective enough, climbers will carry it and the extra gear they think they need even if the load is heavier.
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the Fet
Knackered climber
A bivy sack in the secret campground
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Jan 25, 2007 - 05:51pm PT
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In my limited knowledge, I understand the dynamic properties of the rope should limit the max force(in a factor 2 fall) to not more than 12kN, and is about 9kN.
However, if you are using a re-direct at the belay which acts as a pulley you could almost double that force on the biner/anchor to 18kN.
A camalot is rated for 8 - 14 kN.
A closed biner is rated for about 24 kN.
Personally, I think that it's calling it close to fully rely on an anchor without any form of equalization. Say you have a 9kN leader fall on a 14kN camalot, that's a saftey factor of about 1.5 (14kN / 9 kN). And it gets worse if you use a small camalot or a redirect where you could break a piece, or pop it.
Equalizing 2 pieces (with a sliding X with limiter knots, or an equalette) should do a pretty good job at sharing the force. So your almost cutting the force on each piece in half and doubling your safety factor, very easily. So an approximate 50% reduction on the force compared to just 1 piece.
Equalizing 3 pieces is more difficult, time consuming, and probably requires more gear, and you're only getting another possible 17% reduction of force on each piece. (i.e. instead of 50/50 you get 33/33/33. So there's a diminishing return the more pieces you equalize.
For the average trad anchor where the pieces appear solid, I think splitting the force among 2 pieces is probably going to do the job fine (with a 3rd as a backup as needed). You would probably only need to equalize 3 pieces if they weren't solid placements. Then you would probably be an advanced climber and have more options in your bag of tricks for that situation.
So as a replacement for the cordelette, and as the anchor 90% of climbers could use 90% of the time, I think something that equalizes two pieces, simply, with little gear is the way to go.
I'm not giving up on a solution to something simple, that will equalize 3 pieces with minimum gear, but I don't think it's really necessary for most people and situations. And due to the complexity I don't know if there is a simple solution.
A couple points (that have been addressed before but the numbers above reinforce):
*Always tie in with the rope
*A belay redirect should be used judiciously
*Trusting one piece with your life ain't a good idea
*Place a piece above the belay asap
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Mighty Hiker
Social climber
Vancouver, B.C.
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Jan 25, 2007 - 06:19pm PT
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A fascinating discussion, with lots of interesting stuff. I know just enough physics to get the idea, though analysis of dynamic systems is pretty complex.
I'm still not sure what the objective is, or more accurately how equalizing anchors will contribute to it. If the goal is to better understand belay system dynamics, so that climbers learn to build stronger/safer belays, that's good. I suspect that there are other factors that have a greater influence on this, including equipment and environment limitations, and the subjective elements - skill, experience, circumstances.
Looking at it another way, an analysis of climbing accidents may show belay failure well down the list, and that when it does occur, it's more commonly due to inadequate or poorly placed gear, poor rock, and/or the subjective factors. Should we perhaps be looking at those?
More worrisome, a discussion like this can easily lead to some concluding that the solution is fixed anchors - bolts - at all belays. Which in turn can lead to greater evils, such as the grid bolting found in some places, even though the rock offers good natural protection. Those who think that climbing can or should be completely safe are an ever-present risk.
Somewhere I once heard or read that the human body in a sit harness will likely suffer internal injuries or worse if subject to forces of over 12 kN. Hence gear being designed to take roughly twice that force.
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NoRushNoMore
climber
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Jan 25, 2007 - 08:12pm PT
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Assumptions about FF2 load of 12-18kN on the anchor are unrealistic. Even gri-gri slips at about 4.5kN giving max force in the case of belay thru the anchor of about 7.2 kN
And that is only in if you are anchored down. Otherwise you will be sucked into power point and in to the same load position as if you belaying of the hardness: 4.5kN max load on the anchor.
With these numbers in hand whole discussion about load balancing is a waste, all you need is redundancy (any other belay device will give you even lesser numbers to worry about)
Of course there is a case of human funk device but that much you can control instead of overbuilding anchor
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Largo
Sport climber
Venice, Ca
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Jan 25, 2007 - 09:20pm PT
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Ya' all:
Don't want to speak too soon but I will anyhow. Im perilously close to figuring out the equalized 3-point anchor set up (rigged on one standard piece of thin cordage with no shenanagans or gizmos). Gotta few bugs to work out so it may take a few more hours but I'm hoping . . .
This is fun because I always enjoyed physical puzzles.
JL
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cintune
climber
Penn's Woods
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Jan 25, 2007 - 10:01pm PT
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Well, JL, that will deserve a fresh page, so let me do the honors of filling this one out.
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john hansen
climber
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Jan 25, 2007 - 11:03pm PT
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I brought up the idea before for a more springy cordellete that would stretch more and distribute the load. As the first anchor point began to come under load, it would only take a small percentage of the total load before the second piece started sharing the load. As both these "arms" stretched further the third anchor point would also start to come under load.
I know this is more of a force 'distribution' rather then true equalization.
Does this idea make any sense Ed ,and all you other number crunchers on the topo.
And here is another probably stupid idea. Imagine a V shaped piece of fabric about two feet tall and eighteen inces across the top made out of something like they use for trampolines.
At the bottom of the V would be the power point. On top of the 'V' would be a 'W' of three adjustable clip ins. This way as the power point was loaded it would have the same affect as the system above, only greatly enhanced.
Imagine a one pound wieght,connected by three wire cables to three nails driven into the wall so the cables are as close to equal as the eye could see. You drop the wieght ,and one of the anchors will be 'shock loaded' with the full force generaterd by the fall. What would a scale measure that force as...
Now , imagine the same set up only with rubber bands instead of cables. As one slowly comes under load the other points would gradually take a share of the force generated.
Does this make any sense or am I just full of Stienlager?
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 26, 2007 - 12:43am PT
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the impact force grows, at worst, with the square root of the spring constant... for falls that generate much more force than the weight of the climber.
So if you reduce the spring constant by a factor of 4, you will get, at most, a factor of 2 reduction of the force.
If you look at the ST Forum topic physical properties of ropes and slings I reported on several types of ropes and slings:
K = 11.2 kN for a Beal dynamic rope,
K = 24 kN for nylon webbing
K = 30 kN for a 7mm perlon cord
K = 109 kN for a 5mm spectra cord
Using a 7mm perlon cord would provide a smaller impact force than a 5mm spectra cord... by a factor of 1.9 (nearly 2), depending on the magnitude of the fall. For small falls the difference will be smaller.
In my analysis higher up on this thread, the spring constant K of the slingage is a part of the calculation.
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rgold
Trad climber
Poughkeepsie, NY
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Jan 26, 2007 - 10:36am PT
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I brought up the idea before for a more springy cordellete that would stretch more and distribute the load. ...I know this is more of a force 'distribution' rather then true equalization. Does this idea make any sense Ed ,and all you other number crunchers on the topo.
How stretchy do you have in mind? The belayer might be a bit miffed if it turns out he's in for a day of bungee jumping.
More seriously, there appear to be two obstructions to load equalization. One comes from the inevitable practical failure to have the arms exactly the correct length in knotted rigging. Wootles' results illustrate that the resulting inequities can be quite significant. It has been hypothesized that stretchier material will offset unequal arm tensions in this situation. Just how elastic the rigging needs to be before one sees a significant equalizing effect is unknown.
The second obstruction to load equalization comes from unequal arm length. Changing the stretchiness of the rigging might reduce the total load but can make no difference at all in inequities of distribution in this case, so stretchier rigging material cannot provide a comprehensive solution to the equalization challenge.
I don't think one ought to view the anchor rigging itself as part of the fall energy absorbing system, and I don't think one is likely to get much contribution from any standard rigging. Part of the reason is the load is supported not by one strand of the material in a cordelette rig but rather by six, so the anchor is going to be a relatively rigid component of the system.
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Largo
Sport climber
Venice, Ca
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Jan 26, 2007 - 10:48am PT
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Rich wrote: "I don't think one ought to view the anchor rigging itself as part of the fall energy absorbing system, and I don't think one is likely to get much contribution from any standard rigging. Part of the reason is the load is supported not by one strand of the material in a cordelette rig but rather by six, so the anchor is going to be a relatively rigid component of the system."
I suspect that a workable soultion is kind of polymer biner, or doughnut, that we can attatch and tie into at the power point (backed up by a sling, of course). Modern polymers are remarbably strong, and the relative stretch can be controlled in fabrication. This is a possibility worth investigating. A four inch polymer "power ring" that might stretch to, say six or eight inches under extreme loading might bear some interesting results providing it's light and sufficiently durable.
JL
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 26, 2007 - 11:08am PT
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one way to play this game is to take the extremes,
the stretchiest material will have a K = 0 kN,
then the impact force will be: F = 2 mg
twice the weight of the climber.
If the K -> very big,
F ~ mg*sqrt(2*f*K/(mg))
where f is the fall factor = h/L the distance of the fall h divided by the length of rope L.
Now here's a thought and a jump into complexity... you could have multiple polymer rings, each with a different K, in colors, and build a cordelette anchor attached through the rings to the anchors. For short arms you'd put a strechier ring, for long arms a stiffer ring (or no ring).
That would equalize the force...
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cintune
climber
Penn's Woods
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Jan 26, 2007 - 11:55am PT
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The problem I see is that whatever stretches will bounce back, and the bigger the load, the more often, and the bigger potential variation in the angle of pull. This repeated loading and unloading of a "bungeelette" might defeat the purpose with sketchy anchors by walking them right out of their placements. Although I'm starting to sound like a broken record by now, this is the beauty of the screamer. Peak load is limited to ~2Kn, and there's no rebound to add to the uncertainty.
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Brian in SLC
Social climber
Salt Lake City, UT
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Jan 26, 2007 - 12:24pm PT
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I suspect that a workable soultion is kind of polymer biner, or doughnut, that we can attatch and tie into at the power point (backed up by a sling, of course). Modern polymers are remarbably strong, and the relative stretch can be controlled in fabrication. This is a possibility worth investigating. A four inch polymer "power ring" that might stretch to, say six or eight inches under extreme loading might bear some interesting results providing it's light and sufficiently durable.
Hmmm, like a dog chew toy (or the donut ring and chew toy that some folks use to train hand strength with).
Interesting...heck, this might be KISS off the shelf easily available...
Someone oughta go to the pet or grocery store, pick one up and load test it...high loading rate, see the peak load graph type thing.
-Brian in SLC
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rgold
Trad climber
Poughkeepsie, NY
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Jan 26, 2007 - 12:31pm PT
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A screamer only limits the load to 2 kN if the fall energy is completely absorbed by the time it reaches full extension. In general, I think the approximate effect of a fully extended screamer on the subsequent anchor impact is that the anchor load will be that of a five foot shorter fall.
It would follow that screamers can have a significant impact for short falls of a given fall factor, but would probably contribute little to force reduction for long falls of the same fall factor.
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Largo
Sport climber
Venice, Ca
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Jan 26, 2007 - 12:57pm PT
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The "Bungeelette" has a nice ring, but I don't see it like a spring that will vault a belayer to the moon via recoil. The "dog chew" toy is closer to it but I'm just guessing.
I'm just going to have to track down something and start fiddling. The 3-point simple sling perfect equalizing plan I was so high on isn't panning out as I'd hoped. A sliding power point--in practice--works great for two points but add a third point and an change in loading invariably results in one arm going slack. This is caused by the limiter knots, without which we're looking at huge extension if one placement blows. It might be doable but after fiddling with slings for hours last night I'm starting to wonder if it isn't physically impossible to have a self-adjusting system that spans three placements. The odd number--"3"--is the bugaboo.
JL
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 26, 2007 - 01:27pm PT
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ropes are designed not to bounce back...
a ring could also be... note that the ring could be a sling made of a synthetic material designed with a particular K value... doesn't have to be solid plastic...
A sceamer is an "irreversible" example of this sort of thing. I'm thinking more like a special "dog-bone"
where are the material guys?
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 26, 2007 - 01:37pm PT
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here's something!
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jstan
climber
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Jan 26, 2007 - 01:38pm PT
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This observation may/may not be useful. Slings and ropes are not perfectly elastic. Some energy is dissipated in the rope and leads to a rise in its temperature. Do we know how dissipative rope is? If we suppose it were perfectly dissipative the anchor question changes markedly. In that case if one anchor fails the remaining anchor(s) should only have to deal with the portion of the fall remaining. Serial failure of anchors then may be less less problematic.
We know rope is pretty dissipative. I know of no case where the falling climber rebounded to the height from which the fall originally occurred.
Edit:
Ed's graphic apparently tied the system up enough so did not see his suggestion similar to mine. What this does is change markedly the time evolution of the forces in the overall solution to the dynamical problem. It almost looks worthwhile, now, to do the dynamical problem if inelasticity can be incorporated.
You can't count on the material guys. They all just want to have fun.
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rgold
Trad climber
Poughkeepsie, NY
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Jan 26, 2007 - 02:24pm PT
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Slings and ropes are not perfectly elastic. Some energy is dissipated in the rope and leads to a rise in its temperature. Do we know how dissipative rope is? If we suppose it were perfectly dissipative the anchor question changes markedly.
So would all the calculations, which so far appear to agree decently with test results. These calculations assume energy dissipated is negligible. If energy dissipation is a significant mechanism, the concept of fall factor, which is an artifact of elasticity, would probably be out the window.
In that case if one anchor fails the remaining anchor(s) should only have to deal with the portion of the fall remaining. Serial failure of anchors then may be less less problematic.
This would render moot the long-standing internet debate about whether, when a piece blows, the rope recovers significantly before it is stressed again by loading the next piece.
We know rope is pretty dissipative. I know of no case where the falling climber rebounded to the height from which the fall originally occurred.
Right, but that isn't necessarily an indication of dissipation. A more accurate mathematical model for the rope than the simple spring is probably the damped spring---critical damping would result in no recovery from maximal extension without any dissipation of energy and no beneficial effects for sequential loading. However, I have never seen an argument that, in principle, indicates why the rope should behave like a damped harmonic oscillator. Such an explanation, if there is one, might have to refer to the behavior of the polymer molecules themselves under elongation and contraction, rather than the more obvious case of internal friction, which would probably support John's idea better than the damping concept.
The Italian Alpine Club (CAI) has a sophisticated mathematical model for the entire belay chain, modeled in just this way as a system of damped harmonic oscillators.
http://www.caimateriali.org/Eventi/Torino/computermodel.html
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the Fet
Knackered climber
A bivy sack in the secret campground
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Jan 26, 2007 - 04:43pm PT
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For those of you who are interested and missed it on the rc.com slidingX thread, here is an anchor design I came up with that equalizes evenly among 3 pieces (neglecting friction, binding, etc.)(note: center piece gets the same force due to 2:1 pulley effect), limits extension, and uses just a couple extra biners.
Some problems are:
If one pieces fails then the force isn't distributed 50/50 on the remaining pieces.
Not very simple.
Biners placed in the limiter knots are untested.
Friction will limit the equalization.
But maybe this will help inspire some more ideas.
I never adopted it into my anchors beyond trying it a couple times because I think equalizing on two good pieces (with a 3rd as backup) is probably good enough, and if I did need to equalize 3 pieces I would use a slidingW and back it up with the rope or something.
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 26, 2007 - 05:05pm PT
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One of the problems with the Italian Alpine Club link posted is that the physical value of the dissipation term is not given. They determined it by fitting to the accelerometer data, but didn't report the fit values.
The model is a spring and a "dash-pot," which has a term proportional to the velocity, do dissipate the energy.
I played around with this a lot to come up with the value of 600M/(m/s) for that constant, this gives a fall trajectory that seems reasonable:
x'(t) is "over" damped, x(t) is undamped
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jstan
climber
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Jan 26, 2007 - 05:42pm PT
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Now why did TIG have to go and kick all this off by mentioning bounce?
When fall factor is less than 2 the biner at the top piece also provides dissipation. For a 180 degree bend at a biner I think a 30% diminution of the force is typically assumed. If you measured the temperature rise in such biner you could get an averaged caloric value for force diminution. Biners get really hot.
If ever there was a problem that cries out for use of the Method of Steepest Descent - this is it. (Just kidding.)
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WBraun
climber
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Jan 26, 2007 - 05:45pm PT
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Just see ..... the Supertopo mathematical science lab in action trying to calculated the external energy of god. At any particular time he can send the results both negative and positive outside the established rules to maintain his supremacy over all those trying to understand him without bhakti submission.
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Gene
climber
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Jan 26, 2007 - 05:59pm PT
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Lots of good stuff, both theoretical and practical.
How common/how many catastrophic anchor failures occur in climbing situations? I can remember fatalities on DNB and on a desert spire over the last 5 to 10 years. Stipulated that there are many others I don’t know about and one is too many, how often do anchors fail in the real world?
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healyje
Trad climber
Portland, Oregon
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Jan 26, 2007 - 06:06pm PT
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ED, WTF? It's pretty and all, could you interpret for us neanderthals...?
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cintune
climber
Penn's Woods
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Jan 26, 2007 - 06:11pm PT
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Werner, wouldn't prapati be more appropriate to this discussion?
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WBraun
climber
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Jan 26, 2007 - 06:20pm PT
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Gene
I would say real world anchor failures are a rarity. But when they do fail there is usually catastrophic results, duh.
Duane Raleigh as I remember had one total failure on the rappel and still lived, of course since he's still with us today. His number was not up.
Another example of the opposite. Some rescue instructor in the SF Bay Area some years ago had just finished setting up the main and belay anchors for a rescue rigging seminar. He was going to demonstrate to his class how if the main anchor system failed the belay system will back up and save the day.
He then took a knife I believe it was, and cut the main line to provide a real world, real time example in action.
Cut he did and immediately the load was transferred to the belay line in which the anchor immediately failed and he fell to his death to the witnessed shocked onlookers. Huh? His number was up.
Yes folks, strange tales from the past annals of life.
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rgold
Trad climber
Poughkeepsie, NY
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Jan 26, 2007 - 08:01pm PT
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Just see ..... the Supertopo mathematical science lab in action trying to calculated the external energy of god. At any particular time he can send the results both negative and positive outside the established rules to maintain his supremacy over all those trying to understand him without bhakti submission.
God has made the desire to understand one of the central defining characteristics of the human race. Did God do this in order to have subjects for practical jokes?
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WBraun
climber
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Jan 26, 2007 - 08:09pm PT
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God has made the desire .....
No no ..... you have made the desire.
This world is created by OUR desire NOT God's desire.
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 26, 2007 - 08:42pm PT
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don't know how to calculate god... leave that for Werner...
as for the plot, it has two cases, one damped, one undamped.
d2x/dt2 is the acceleration
dx/dt is the velocity
 is the position.
the "primed" constant, e.g. x' is for the damped case.
In the differential equation, we have the three terms:
a*d2x/dt2 + b*dx/dt + c
which has the velocity dependent part of the model, which is the damping due to the rope.
jstan and rgold both pointed out that the rest of the anchor system has a significant effect in dissipating the energy of the fall. The analysis in my plot is for a factor 2 fall with the forces borne by the anchor, no slipping, etc.
This is not a realistic representation of a fall, but represents the extreme. It could happen if you were soloing, having tied off your anchor, and ran it out...
The point was to see what a ball park value of the "b" coefficient would be, given our fall experience is that we don't bounce on the rope. I wanted to know how much damping was required.
The constant is the "specific" constant, independent of the rope dimesions.
Maybe too much for the forum.
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cintune
climber
Penn's Woods
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Jan 26, 2007 - 09:09pm PT
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No one appreciates Sanskrit humor anymore. I don't get no sammāna, no sammāna at all, I tell ya.
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 26, 2007 - 10:25pm PT
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The model that the Italian Alpine Club reported has the details for the simulation, but their results are only graphical... the constants determined by their fitting to the experimental data was not provided.
Playing around with some spread sheet program you can match the graphical results at least qualitatively.
Anyway, those of you so inclined could have a bit of fun...(some of us think this sort of thing is fun).
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 26, 2007 - 11:27pm PT
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1 bhakti f. distribution , partition , separation RV. Ta1n2d2Br. &c. (cf. %{kSetra-} , %{bhaGgI-bh-}) ; a division , portion , share AitBr. ; a division of a Sa1man (also called %{vidhi} , of which 7 or 5 are enumerated) La1t2y. [743,2] Sam2k. ; division by streaks or lines Ragh. ; a streak , line , variegated decoration Hariv. Ka1v. ; a row , series , succession , order (%{-tyA} and %{-ti-tas} ind. in succession) RPra1t. ; (ifc.) the being a part of (%{ajbhakteH} , `" on the part of the vowels "') , belonging to Siddh. &c. ; that which belongs to or is contained in anything else , an attribute Nir. Pra1t. ; predisposition (of body to any disease) Car. ; attachment , devotion , fondness for , devotion to (with loc. , gen. or ifc.) , trust , homage , worship , piety , faith or love or devotion (as a religious principle or means of salvation , together with %{karman} , `" works "' , and %{jJAna} , `" spiritual knowledge "' ; cf. IW. 326 RTL. 97) S3vetUp. Bhag. Ka1v. Pur. &c. ; (ifc.) assumption of the form of Megh. 61 ; often w.r. for %{bhaGgi} or %{bhukti} ; (%{-tyA}) ind. not in the regular sense , figuratively S3am2k.
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cintune
climber
Penn's Woods
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Jan 26, 2007 - 11:40pm PT
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Prapati: To throw oneself down.
Get it? I'll be here all week.
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Largo
Sport climber
Venice, Ca
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Jan 27, 2007 - 12:06am PT
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Much as it might be a blast for numbers gurus to crunch the figures, try this one on for size. It's guaranteed to tax your gray matter.
Get a 20-30 foot piece of thin cordage (a big piece of rope makes it easier to see the process and noodle possible solutions). Get three faux anchor points (like weights or a hooks on a wall) and try and devise a rigging system that won't extend too horribly, that uses minimal biners, equalizes the three anchors (perhaps not perfectly but offers substantial load sharing) and can withstand, within practical reason, multi-axis loading. And, is easy and fast to rig.
I've gotten reasonably close but the no-extension part reduces or eliminates the active pully action (the rope self-adjusting when weighted) I sense is required for dynamic self-equalization. It's easy with two points, but the third causes one arm to go slack on anything but a pure downward pull.
A hint: I suspect, but certainly don't know, that the middle strand will have to be a loop, while the two side can more easily be single strands.
This one is a real puzzle, boys . . .
JL
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WBraun
climber
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Jan 27, 2007 - 12:22am PT
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multi-axis loading?
Can't you guys for the life of us just sit still in one place long enough for the damn anchor to hold? WTF are people doing down below?
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rgold
Trad climber
Poughkeepsie, NY
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Jan 27, 2007 - 01:57am PT
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multi-axis loading? Can't you guys for the life of us just sit still in one place long enough for the damn anchor to hold? WTF are people doing down below?
One of those vertical dance routines?
I tried explaining this earlier in the thread. I hope I do better this time. Suppose the leader falls onto the belayer with no intermediate pro in yet. It is possible that the leader will fall from a point directly above the anchor, but it is more likely that she will be on one side or the other.
When the rope comes tight, the leader will pendulum underneath the belayer. At the instant the rope comes tight, the rope forces the leader's directly downward fall path to change direction. This requires force (sharpen your pencils, lads) and I suspect, without having done any calculation, that depending how much rope is out and how far to the side the leader falls, the the force need not be insignificant.
The result would be that the first impact on the belayer will be off the vertical axis, and the subsequent pendulum will load the anchor in a range of directions. If the anchor is rigged with fixed arms, then it is most likely (depending on the configuration) that that initial off-axis load will be applied entirely to one arm---usually an outer arm, and so to just one of the anchor pieces. If an outer arm's anchor piece blows, then most fixed-arm rigging will transfer the entire load to the middle piece, so in this case the pieces will get the full load one at a time without any load sharing---the cascade failure.
Another scenario, involving a "leader fall" from below, is the Tahquitz accident. (I mean this as a scenario; we do not know whether or not there was a catastrophic failure of a belay anchor. The S&R team concluded the climbers fell off the top while the belayer was walking with a cordelette and three pieces tied to the climbing rope which was tied to his harness.)
The accident to the rescue instructor that Werner mentions is a good but tragic example of the fact that even experts are not always able to judge the holding power of their anchors. (If the load and belay anchors were not in a vertical line, there would be a chance for the type of failure described above.) The point of equalization is to maximize our chance of surviving if and when one of our misjudgements---and make no mistake, we all make them---is tested, perhaps in a way (like off-axis loading) that we did not anticipate.
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WBraun
climber
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Jan 27, 2007 - 02:08am PT
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That was beautiful rgold.
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murcy
climber
San Fran Cisco
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Jan 27, 2007 - 02:38am PT
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not to ... well yes, to ...
AHEM! my COMPLETELY IGNORED :-) gizmo solution above equalizes three pieces "perfectly" and allows you to limit extension however you please.
sure it uses a so-far nonexistent device, but hell, belay anchors are kind of important.
plz send royalty checks c/o murcy, sf, ca. thanks.
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Ed Hartouni
Trad climber
Livermore, CA
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Jan 27, 2007 - 03:11am PT
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murcy,
you could do it with three carabiners in series, cords through each also... not sure about the friction though...
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jstan
climber
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Jan 27, 2007 - 05:49am PT
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I too am enjoying this and appreciate Richard's,Ed's, and everyone's ideas. Now where did I leave my damn pencil?
When we used hemp ropes during haying you heard a veritable chorus of complaints as a rope was loaded. During my own tensile machine days I was struck by how noisy a heavily loaded sling can be, and how hard it gets. This leads me to a slipping model for dissipation analogous to a rope running over a biner. Perhaps a rope is composed of structures above and beyond the core and sheath. Might we presume two of these structures have relative motion after the rope has been heavily loaded so there is, if you will, internal sliding friction? (Don't ask me how to fabricate such a structure.) Frictional force would be proportional to normal force and that would be proportional to the instantaneous loading. I would be nervous were I to hold onto our friend,Hooke's Law, at this early stage so I can't claim the frictional force is also proportional to extension. If by some strange chance there is anything to this, the rope itself would have to be modelled on two components. I can't respond right now to Richard's suggestion that the fall factor theory assumes no significant dissipation. So I won't try.
My first year of climbing while in a secure sitting position at the cliff edge, I caught from above one of those pendulum falls of which Richard speaks. The force was comparable to that of a serious leader fall. After it was over I looked around and found someone had untied my anchor. After that I made it a rule not to load my anchors if there was any way at all it could be avoided.
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Largo
Sport climber
Venice, Ca
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Jan 27, 2007 - 11:35am PT
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Murcy Me,
The fun (to me) of this particular challenge is to try and drum up a solution with just the one long piece of cord and no gizmos, do-dads and/or horsefeathers. If we started fudging the criteria I imagine there would be more than a few options. But I do think your "speciality biner" might be a good idea in some cases.
JL
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rgold
Trad climber
Poughkeepsie, NY
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Jan 27, 2007 - 01:19pm PT
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Murcy,
I, for one, rather like your gizmo, especially if the little holes are equipped with rollers, because friction and binding are the two things that seem to defeat the tantalizing cave-man solutions (y'know, nothing that can't be made with the ten essentials and a dead goat) we we are striving to find here.
Unfortunately, it doesn't address the small-extension requirement and so isn't quite ready for prime time just yet.
When it is, make sure it doesn't weigh more than two locking belay biners (needed, for example, for the equalette) and you will soon be the filthy-rich CEO of Equalizers Are Us.
Just remember where you got your start.
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rgold
Trad climber
Poughkeepsie, NY
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Jan 27, 2007 - 01:31pm PT
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After that I made it a rule not to load my anchors if there was any way at all it could be avoided.
Agreed! But fashion is heading in another direction. I regularly see climbers setting up virtual hanging belays on ledges that they could sit down on fully braced. Based on some discussions I've had, I think one of the reasons for this is that newcomers spend a day with a guide to learn about constructing belay anchors and then replicate the set-up they were taught---hanging back on the rope, stacking the slack on the tie-in, belay device on the anchor or belay redirected through the anchor---in every location regardless of its bracing potential.
The fact that fewer and fewer climbers interpose anything between the belay load and the anchor makes it more important than perhaps it used to be to find absolutely optimal anchor rigging techniques.
The Italians whose work I referenced above seem to think that belaying the leader directly off the anchor is a good idea too.
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GOclimb
Trad climber
Boston, MA
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JL said: The fun (to me) of this particular challenge is to try and drum up a solution with just the one long piece of cord and no gizmos, do-dads and/or horsefeathers.
It's been done several times already, and months ago, though perhaps you missed it at the time - no doubt you were quite busy as your book was close to going to press.
The Mooselette, the CharlesJMM anchor, and the Gordolette all accomplish this admirably.
GO
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Trusty Rusty
Social climber
Tahoe area
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C/Jones-
Leading with just two porn vids and a squirt gun, you're hard core! (ok maybe not as hard as the Cisco Grove Sri Lanka coldy)
Appreciate the thread, but I cant even follow your approaches. Dude, your entangled details of equalized belay anchors frost our midgets and confuse the paying clients. So, next time to Earny, bring two turn tables and a microphone. . . at least then, the belly floppers might feel their bucks worth.
A$$ Hole
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Degaine
climber
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Thanks to all for the info in this thread. All useful, even the physics calculations that go way beyond my cursory understanding of the subject.
I have a couple of questions, maybe very stupid, maybe not, but hey, this is the web so I’ll ask them anyway.
Why are we fixated with the idea of three pieces for an anchor? Why not two and why not four?
Since the pre-req for it all is making sure that each piece placed is bomber, why would a two piece anchor and the quad not be sufficient?
Otherwise, a four piece seems to equalize well – ex. two pairs of equalized pieces (sliding x with the right biner to avoid the hitch/clutch) then equalized with the quad.
Why so stuck on three? Why does it have to be three?
Please note: I understand that each anchor situation is different and I adjust my anchor configurations according to the situation. I’ve personally used two pieces, three pieces, four pieces, slings around chockstones and my body well positioned, etc., for anchors.
Please note II: Like Socrates, the only thing I know is that I know nothing, so I’ll admit that maybe this has been already covered in a way that went way beyond me.
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raymond phule
climber
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I agree with degaine. The premises is not fully determined.
What is the max force on an anchor?
Do we really need equalised anchors all the time?
How many pieces is necessary?
What is the worst possibly scenario?
Do we really need to make every anchor so it can take the worst possibly scenario independent how unlikely? How likely is a real class 2 fall (freefalling climber), ad that the rope is stuck so the belay is static and we talk pretty low probability.
I just see an unecessary scenario with even longer lines on nutcracker because everybody is trying to perfectly equalize many pieces of good pro on all belays.
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Gary
climber
Desolation Basin, Calif.
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This is all very interesting, over my head, for sure.
I was lucky enough to be able to talk to Bob Gaines about all this last week. I'd gone back to using webbing for anchors, but he said not to ditch the cordelette just yet. He showed us the quad (very cool) and equalette. We talked pros and cons of sliding Xs and Ws and also anchoring in with the rope with a series of clove hitches.
Unless I misunderstood him, he felt the anchor configuration was not as important as making good placements in good rock.
Like jstan and rgold, I feel more comfortable with a bomber stance than any anchor setup.
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raymond phule
climber
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Do anyone have a picture of the quad?
Why 2 looking biners on the equalette? Wouldn't 1 on one of the strands actually work better?
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Tomcat
Trad climber
Chatham N.H.
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Meanwhile,while this is being resolved.Make your anchor,equalize as you see fit,clip through,move up,place bomber piece on next pitch,hang rope through it,step back to belay,tie/clip in,bring up second TRing them through that higher piece.They are set to go.If it's your lead,pull the rope back through.
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Largo
Sport climber
Venice, Ca
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JL said: The fun (to me) of this particular challenge is to try and drum up a solution with just the one long piece of cord and no gizmos, do-dads and/or horsefeathers.
It's been done several times already, and months ago, though perhaps you missed it at the time - no doubt you were quite busy as your book was close to going to press.
The Mooselette, the CharlesJMM anchor, and the Gordolette all accomplish this admirably.
GO
All have too many do-dads and extras. Moreover, they don't equalize three anchor points--that's the real challenge. Four anchors is easy to get load distribution. Three is perhaps impossible to achieve with one sling.
JL
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Paul Raphaelson
Ice climber
Brooklyn, NY
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I question a couple of the basic premises of the anchor uproar. I'm not the first to ask this, but how vital, really, is equalization? I understand that it's desireable from an engineering standpoint, but we've already established that it's not so easy to get everything we desire ... some compromise are probably in order. If your pieces are sound, then there is a high probability that any one of them could take the full force of a factor 2 fall*. Which leaves the other two pieces available for redundancy. An unloaded backup piece (or two) might in fact be a good thing.
Lack of extension still seems desireable, for a few of the reasons stated (Iike not ripping the belayer off the ledge and adding to the forces/soiled knickers).
A cordelette seems like a reasonable compromise in many situations. What it always brings to the party are speed, simplicity, lack of dependence on gadgetry, and (relative) ease of evaluating.
I look at some of the proposed alternatives, and immediately think No Way. I see serious real world danger in any system whose complexity makes it difficult to evaluate at a glance.
It seems like the cordelette is most out of its element when direction of force can't be predicted at all (traversing pitches, etc.). In these cases something that can dynamically equalize, like the humble X and its derivatives, seems like a better compromise.
I suspect a great danger is that people get so obsessed with rigging that they forget about the idividual protection pieces. We labor over how well the rigging can compensate for changes of load direction without asking how omnidirectional the placements themselves are. I see this all the time. Some pieces are likely to pop when tugged sideways, period ... it makes no difference how sophisticated their connection to the rope is.
Finally, do we have reliable data on actual fall forces generated in factor 2 falls held with a belay device? Not counting Gri Gris and other autolocking/autoblocking monsters, I wonder how much force anyone can really generate at the belay end. These devices work as force multipliers, not as rigid clamps. I remember reading on a rescue site that most people were unable to lower a 400 pound rescue load at all without losing control, using ANY standard belay device. That's less than 2 KN! How exactly are we able to generate 10 KN on a belay anchor, even with the questionable practice of redirecting the rope through the anchor? According to the movie playing in my head right now, belay gloves might be a better idea than a custom piece of hardware for equalized rigging.
*If you have individual pieces that are marginal, like micronuts, or anything in suspect rock, this might be an invitation to equalize that piece with another, using an X, and to use that equalized pair as a single arm of the larger anchor. A traditional practice, and still pretty smart, IMHO
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GOclimb
Trad climber
Boston, MA
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JL said: All have too many do-dads and extras.
None use anything besides overhand knots, clove hitches and biners. In many cases, fewer knots/hitches and biners than the equalette.
Moreover, they don't equalize three anchor points--that's the real challenge.
Yes, actually. They do. The CharlesJMM does not do so as well as the other two, but it does do so over a small range - larger than the range of the equalette, in my limited testing.
Four anchors is easy to get load distribution. Three is perhaps impossible to achieve with one sling.
Not impossible. As I said, it's been done, and those three do it admirably well.
I can post additional pics if you like, but can't do so now, I'm at work.
If you'd prefer to pick this up offline and go to email, I believe the email listed under my supertopo login is correct. Just click on my username in the upper left-hand corner of my post.
GO
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rgold
Trad climber
Poughkeepsie, NY
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"I question a couple of the basic premises of the anchor uproar. I'm not the first to ask this, but how vital, really, is equalization? I understand that it's desireable from an engineering standpoint, but we've already established that it's not so easy to get everything we desire ... some compromise are probably in order. If your pieces are sound, then there is a high probability that any one of them could take the full force of a factor 2 fall*. Which leaves the other two pieces available for redundancy. An unloaded backup piece (or two) might in fact be a good thing."
I think "desirable" is the right term. If you can achieve better equalization than we get now without massive extra complications, then that seems to me to be an unmitigated good thing. But the "if" is a pretty big one.
"A cordelette seems like a reasonable compromise in many situations. What it always brings to the party are speed, simplicity, lack of dependence on gadgetry, and (relative) ease of evaluating."
All true. In fact, tying in directly with the rope is even better. But fixed arm rigging is inferior in the equalization department. The question is whether there is a better alternative.
"I look at some of the proposed alternatives, and immediately think No Way.
Me too.
"It seems like the cordelette is most out of its element when direction of force can't be predicted at all (traversing pitches, etc.). In these cases something that can dynamically equalize, like the humble X and its derivatives, seems like a better compromise.
There seems to be a growing number of tests that suggest that the cordelette is almost never very good, even when the arms are of equal length, so it is never really "in" its element. As for falls directly onto the anchor, they will almost never be directly in line with the power point and so the cordelette will in, this sense, almost always be out of its element.
"I suspect a great danger is that people get so obsessed with rigging that they forget about the idividual protection pieces.
I have much more faith in people's intelligence.
Finally, do we have reliable data on actual fall forces generated in factor 2 falls held with a belay device? No counting Gri Gris and other autolocking/autoblocking monsters, I wonder how much force anyone can really generate at the belay end. These devices work as force multipliers, not as rigid clamps. I remember reading on a rescue site that most people were unable to lower a 400 pound rescue load at all without losing control, using ANY standard belay device. That's less than 2 KN! How exactly are we able to generate 10 KN on a belay anchor, even with the questionable practice of redirecting the rope through the anchor?
Well, we know that belay anchors built by experienced climbers have failed catastrophically in the field. (I think I have heard of five such incidents in the past ten years.) In no cases were the anchors made up of pieces we would think of as marginal before they're placed. So either the forces can in some cases be higher than we expect (perhaps a kink jams or a turn of rope around something adds extra friction), or even very experienced climbers sometimes seriously misjudge the holding power of their anchors. From an engineering perspective, equalization is the best strategy for guarding against such outcomes.
"According to the movie playing in my head right now, belay gloves might be a better idea than a custom piece of hardware for equalized rigging.
I don't know about a better idea, but I think they're a damn good one.
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Largo
Sport climber
Venice, Ca
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"Not impossible. As I said, it's been done, and those three do it admirably well."
When I see more than one loop or one strand going to a primary placement, and instead see a bunch of biners cipped in at weird angles or funky knots and multiple strands running to and fro the power point, I don't even study the thing because I know such a rig will never catch on. But I should probably look at these systems a little closer and get some ideas about how to simplify things.
The rig I'm looking for has a single, sliding power point, single strands going to the three placements connected to the primary placements by ONE biner and one knot. No cross strands up high between placements, and only one limiter knot per strand. Such a rig can be easily arranged and will yield very good equaliization but since the whole things slips and slides and dynamically adjusts, once you place limiter knots this is no longer the case and without the knots the extension problem is grave.
So I'm still looking, but if the cat has been licked according to the above criteria, I'm all ears and eyes.
JL
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Frog Man Junior
Social climber
CA
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I say three peices, 3 slings, and screamers are great! Until they won't stop screaming and the kids are waking up!
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GOclimb
Trad climber
Boston, MA
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When I see more than one loop or one strand going to a primary placement...
All three anchor methods I mentioned have one loop per primary placement.
and instead see a bunch of biners cipped in at weird angles...
The only one of the three I mentioned that could qualify for the above would be the Gordolette. In fact, the CharlesJMM in its standard format has fewer biners than the equalette!
or funky knots...
As I said - only overhand knots and cloves.
and multiple strands running to and fro the power point...
Uh, each of the three has one loop coming out of the powerpoint per protection piece - just like the cordelette.
I don't even study the thing because I know such a rig will never catch on. But I should probably look at these systems a little closer and get some ideas about how to simplify things.
Your choice, of course, but if you don't look at them, you really shouldn't mischaracterize them.
Cheers!
GO
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raymond phule
climber
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"There seems to be a growing number of tests that suggest that the cordelette is almost never very good"
I have only heard of the Long et al tests. Are there any more?
"Finally, do we have reliable data on actual fall forces generated in factor 2 falls held with a belay device?"
My link above has some information.
"Well, we know that belay anchors built by experienced climbers have failed catastrophically in the field. (I think I have heard of five such incidents in the past ten years.) In no cases were the anchors made up of pieces we would think of as marginal before they're placed."
Do you have any information of these cases? I have heard of an accident on the DNB but have zero info.
"So either the forces can in some cases be higher than we expect (perhaps a kink jams or a turn of rope around something adds extra friction),"
The worst possibly case might be if the climber fall onto the belayer. My quess is that a 5 m fall onto the belayer would put a huge force on the anchor and would rip out a perfect 3 piece anchor.
"or even very experienced climbers sometimes seriously misjudge the holding power of their anchors."
People do misstakes.
"From an engineering perspective, equalization is the best strategy for guarding against such outcomes."
I disagree, knoweledge about the problems that could occur might be a better guarding.
Do you really have enough information about the accidents so that you can draw your conclusions? After reading your post I get the impression that 5 good anchors, 3 good pieces in good rock that backup each other with no huge extension, for example using a cordellete, completely failed. Do we really know this?
The reason for failure could be many things. Bad pro, pro that anly could take a force in one direction, an anchor with a large extension. The climber might have taken a 10 m fall onto the belayer. Not enough pieces.
Edit: Here is some info about the DNB accident
http://www.supertopo.com/climbing/thread.html?topic_id=20228&msg=20402#msg20402
Seems like a long class 2 fall onto the belay and that the rock might have been suspect. Extension could also have been an issue. An equalised anchor would probably have been good there.
edit: here is another one
http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?do=post_view_flat;post=509416;page=1;mh=-1;guest=5506676;sb=post_latest_reply;so=ASC
Seems like the second made a traversing fall on a cordellete and the belay ript. The belayer might have been connected to the belay with a static sling (special knot, prussik) and the pieces might have been less than perfect. Sounds definitely like a strange acident and might have shown a failure of a cordallete in practice where an equalized anchor might have hold. Edit: Seems to be more uncertainties about the accident than I first thought.
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Largo
Sport climber
Venice, Ca
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Go said: The CharlesJMM is the shite.
Kindly show us how this thing works. I don't have time to search the web for photos.
Thanks, Go.
JL
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the Fet
Knackered climber
A bivy sack in the secret campground
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Why are we fixated with the idea of three pieces for an anchor? Why not two and why not four?
Good question. IMHO 2 pieces of bomber pro equalized seems sufficient. 3 gives you a backup (one of those pieces might not be so bomber after all). Four seems a little overkill, but with any marginal placements 4+ may be the way to go.
Do we really need to make every anchor so it can take the worst possibly scenario... I just see an unecessary scenario with even longer lines on nutcracker because everybody is trying to perfectly equalize many pieces of good pro on all belays.
I prefer all my anchors to be totally reliable. e.g. If a leader fall turns into a self-rescue with two people rapping off the anchor, I want absolute confidence in the anchor. I don't think you always need to perfectly equalize, but equalizing 2 pieces can give you up to twice the strength in about the same amount of time.
Why 2 looking biners on the equalette? Wouldn't 1 on one of the strands actually work better?
Then there'd be no redundancy. One strand of webbing/cord should never break... but neither should a rope or belay loop, and that's happened in the past year.
All (added: Mooselette, CharlesJMM, Gordolette) have too many do-dads and extras. Moreover, they don't equalize three anchor points--that's the real challenge. Four anchors is easy to get load distribution. Three is perhaps impossible to achieve with one sling.
That's true, they share the load, but don't equalize it. The Astroglide will equalize 33/33/33, neglecting friction, but like the Mooselette, CharlesJMM, and Gordolette it is too complex to catch on, and easily visualy inspect (in the dark when you are knackered).
If your pieces are sound, then there is a high probability that any one of them could take the full force of a factor 2 fall*.
No, a small cam could break in a factor 2. Or 10+ year old cam slings could snap, flakes break off, etc.
I see serious real world danger in any system whose complexity makes it difficult to evaluate at a glance.
I agree, and think a sliding W backed up with the rope or slings is probably the way to go if you need to equalize 3 pieces.
If you can achieve better equalization than we get now without massive extra complications, then that seems to me to be an unmitigated good thing. But the "if" is a pretty big one.
rgold hits the piton on the anvil with that statement. By using a sliding X with limiter knots or an equalette (which is almost the same thing) you have acheived pretty good equalization on two pieces, probably coming close to doubling your strength and safety factor, with almost no extra complications (compared to a cordelette).
Equalizing 3 pieces adds a layer of complexity to the problem, that is even more challenging than equalizing 4 pieces. Due to friction, the simple sliding W will probably beat out all other designs at effectively equalizing 3 pieces. There's been a lot of effort (in the rc.com sliding X thread, etc.) to come up with something that will replace the cordelette and; simply, equalize 3 pieces, limit extension, with only one cord. But so far no simple solution.
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raymond phule
climber
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I have thought about this and now I belive that 2 equalised pieces and 1 or maybe 2 pieces as a backup would be a very good anchor. It should be stronger than any non equalised anchor (that have worked good for many years), like using a cordellete, slings or the rope in many cases and it is not that dificult to set up with an equalette or sliding x.
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GOclimb
Trad climber
Boston, MA
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JL, I wouldn't necessarily call the CharlesJMM the best of the rigs, but since you asked.
To do a CharlesJMM rig:
1 - Pull the three loops down into a powerpoint, just like you would for a cordelette.
2 - Put a twist in the line going from the two outside pieces, and clip a biner into the three loops that make up the powerpoint.
3 - Loosely tie overhand knots in the two outside strands.
4 - Pull down on the powerpoint biner to equalize the strands and tighten the knots.
I'll post pics as I have time, very busy at work right now.
Here's an old pic I took of the finished product. Note that I've put extra slack in the strand with the twist so you can see it. Normally it would be taut with the other strands.
GO
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GOclimb
Trad climber
Boston, MA
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I'm not a graphic artist, and due to the limited(!) interest, I'm not going to put a ton of time into this. Anyway, please pardon the fact that these look like crap.
Cheers!
GO
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rgold
Trad climber
Poughkeepsie, NY
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Equalization was embraced as an essential ingredient in anchor construction until it turned out that our methods for achieving it don't even come close in many cases, and since then the discussion of better alternatives is burdened with the question about whether equalization is worth seeking at all. It was necessary when we though we had it, but it became unimportant when it turned out we didn't have it. Hmm.
""There seems to be a growing number of tests that suggest that the cordelette is almost never very good"
I have only heard of the Long et al tests. Are there any more?"
There was a series done by Attaway and reported in a Mountain Rescue conference. The results are not available online, but Attaway's conclusion that the cordelette did not meet their standards for equalization were reported in an online forum. Sorry, I don't have references.
"Finally, do we have reliable data on actual fall forces generated in factor 2 falls held with a belay device? My link above has some information."
A great link, thanks for it. But no useful data on factor-2 falls reported there, unfortunately
""Well, we know that belay anchors built by experienced climbers have failed catastrophically in the field. (I think I have heard of five such incidents in the past ten years.) In no cases were the anchors made up of pieces we would think of as marginal before they're placed."
Do you have any information of these cases? I have heard of an accident on the DNB but have zero info."
Sorry, I'm going on memory. There is the DNB case, the Tahquitz case, a case I read in the AAC accident reports a few years ago, a case Attaway mentions as the motivation for his report on fall impacts, and the case Werner referred to earlier in the thread. The random way this information comes to us suggests the likelihood of other cases we haven't heard about.
In general, there is very little information about what actually happened. In the Tahquitz case, the official conclusion excluded anchor failure as the cause.
""From an engineering perspective, equalization is the best strategy for guarding against such outcomes."
I disagree, knoweledge about the problems that could occur might be a better guarding."
Here I think you are wrong. As you say, peopel make misstakes, even in the presence of knowledge of the problems. They are sometimes wrong about which piece is good. The best strategies are those that minimize potential load to all pieces, are tolerant of off-axis loading, and redistribute the load to remaining pieces if one fails. These are the only available means of coping with the uncertainties that are part of real life.
"Do you really have enough information about the accidents so that you can draw your conclusions? After reading your post I get the impression that 5 good anchors, 3 good pieces in good rock that backup each other with no huge extension, for example using a cordellete, completely failed. Do we really know this?"
No. We know very little about these accidents.
But it is also the case that very few experienced climbers have ever had their anchor judgements subjected to a real test, much less a statistically significant sequence of tests. This means that most climbers really have no basis in reality for judging the strength of their anchors. The tragedy described by Werner earlier in this thread indicates that these claims are not simply hypothetical.
Once again, in the face of this really quite massive uncertainty, equalization is the best strategy, if it can be achieved.
"The reason for failure could be many things. Bad pro, pro that anly could take a force in one direction, an anchor with a large extension. The climber might have taken a 10 m fall onto the belayer. Not enough pieces.
But the effect of all of these things would be mitigated by having an equalized anchor that can adapt to off-axis loads and does not suffer from the possibility of large extensions. Your own analysis of the cases you linked to concludes an equalized anchor might have helped.
In any case, I don't know if there is exactly an "uproar" about all this. It seems to me that a relatively small group of climbers is interested in the intellectual challenge involved, and most others feel that the distributive (rather than equalizing) methods that we have are plenty good enough. It may be that those who are interested will eventually come up with a solution the mainstream will adopt, or it may turn out that the complexities of fabricating equalizing anchors and especially the associated problems of friction will ultimately doom the enterprise to a generally disregarded cult status.
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murcy
climber
San Fran Cisco
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Thanks for posting that, GO!
I'm puzzled, though. The two limiter knots freeze the sum of the lengths of the two outside legs; if they're taut, the powerpoint travels along an ellipse. But then the center strand's length, when taut) is constant, too, and so describes a circle. So it seems to me that apart from the one or two directions at which the circle and ellipse intersect, all the weight will be taken at the powerpoint either by the strand that connects the two knots directly (in which case the center piece is unweighted), or by the two other strands (in which case the center piece gets twice the load of the others, as seems to be the case in your photo). Or am I mistaken?
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rgold
Trad climber
Poughkeepsie, NY
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For those who are interested in such things (perhaps the empty set), I'd like to propose a reappraisal of the effects of a small extension in an anchor.
Conventional wisdom has been that extension is bad because of the "shock load" it would cause. As has been pointed out many times by now, the term "shock load" has never had a proper definition, but forgetting about the shock aspect, certainly the understanding is that the resulting load would be large in the context of possible anchor loads.
I'd like to suggest that maybe conventional wisdom has things exactly backwards; that in fact it is the fixed-arm cordelette that will impose a relatively large load on the remaining pieces, and that by constrast, an anchor that with a small extension will actually produce smaller loads on the remaining pieces than the cordelette would have.
Now "small extension" is ultimately going to need a definition too; my suggestion is that the ratio of extension to the length of belayer tie-in (assuming the belayer uses the rope to tie in)---in other words an H/L ratio for the fall caused by the extension and absorbed by the tie-in---is an appropriate measure of smallness.
Consider what happens if one piece of a cordelette anchor fails. With no extension, the load is immediately transferred the remaining pieces (actually, probably to just one other piece). The rope has no ability to recover during this transfer, precisely because the absence of any extension provides no moment when the tension in the rope is reduced. The net effect is that the remaining piece or pieces get the full maximum impact of the fall, the same impact that would have been delivered to the anchor had it remained intact, but now shared by fewer pieces. Put another way, no benefit is obtained from the energy needed to extract the first piece.
There is an instant in which a shared load is suddenly shared by fewer pieces; this is certainly a candidate for a "shock load" imposed by the cordelette.
Next, consider what happens when a piece fails and there is a small extension. During the instant of extension, rope tension drops to zero. When the load comes on the remaining pieces, they only have to arrest the remaining part of the fall, which clearly involves less energy absorbtion and so a lower peak load. In this setting, the energy involved in stretching the rope up to the point of extraction is removed from the total energy that must be absorbed by the remaining anchor.
This reduction effect is mitigated by the fact that the rope will have been "stiffened" by the first stretching and so will develop higher peak loads, and of course by the added effect of a (low fall factor) belayer fall. Perhaps the load on the anchor will be higher or the same, but it is also entirely possible that a lower anchor load will be observed, precisely as a result of the fact that a small extension allows the extracted piece to function as an energy absorber.
The fact that Wootle's tests essentially showed no "shock load" would be explained by the combination of a very low extension ratio and the energy-absorbing opportunity the moment of extension provided. This analysis would predict that the remaining piece in Wootles tests would have experienced higher loadings when the cordelette was employed. I believe, but am not sure, that some of his data does fit this pattern.
If testing were to bear this out, then small extensions would be viewed as possibly beneficial rather than always harmful, and yet another "benefit" of fixed arm rigging would become questionable.
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rgold
Trad climber
Poughkeepsie, NY
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Very nice insight Murcy. I agree that the CJMM rig never equalizes, in the sense that the probability you hit the two equalizing points is zero.
I don't have the time now to check, but one does wonder whether limiting knots in some of the other three-anchor rigs may also impose geometric constraints on equalization.
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murcy
climber
San Fran Cisco
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rgold writes:
"Consider what happens if one piece of a cordelette anchor fails. With no extension, the load is immediately transferred the remaining pieces (actually, probably to just one other piece). The rope has no ability to recover during this transfer, precisely because the absence of any extension provides no moment when the tension in the rope is reduced. The net effect is that the remaining piece or pieces get the full maximum impact of the fall, the same impact that would have been delivered to the anchor had it remained intact, but now shared by fewer pieces. Put another way, no benefit is obtained from the energy needed to extract the first piece."
I don't get it. If it took energy to yank the piece out, that energy is not going to create force on the remaining pieces. Imagine that it took nearly all the energy of the fall to yank the first piece; the falling climber would be slowed to nearly a stop, and the remaining pieces would have very little to hold. Of course, the rope might not be able to absorb too much more energy, but hey, it was going to have to absorb it all anyway.
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rgold
Trad climber
Poughkeepsie, NY
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"I don't get it. If it took energy to yank the piece out, that energy is not going to create force on the remaining pieces. Imagine that it took nearly all the energy of the fall to yank the first piece; the falling climber would be slowed to nearly a stop, and the remaining pieces would have very little to hold. Of course, the rope might not be able to absorb too much more energy, but hey, it was going to have to absorb it all anyway."
It doesn't take energy to yank a piece out. It takes force. (A very small amount of energy may be consumed by moving the piece a short distance and by generating some heat, but I believe this is negligible compared to the fall energy to be absorbed.)
The so-called "energy absorbed by extracting a piece" is the work done in stretching the rope until the rope tension (force) is enough to break or extract the piece. If that rope tension is not released, and I'm suggesting it won't be with fixed arm rigging, the force, i.e. the stretched rope, will simply be transferred to the remaining piece(s). Further stretching will occur to arrest the fall, at which point the total amount of stretch in the rope will be exactly the same as if the piece hadn't pulled, but now that load is applied to fewer pieces.
If you stretch a 2" rubber band by an additional 1", it doesn't matter how many times you stop while you're doing it. The total energy absorbed will be the energy it takes to stretch the rubber band by 50%, and the tension in the rubber band at the end will be...the tension in a 2" rubber band stretched to 3".
In the case you describe, I'm saying that although the additional rope stretch that occurs on the remaining pieces may be very little, the fact that there has been no release of rope tension means that the remaining pieces will still be subjected to the entire maximum force involved in arresting the fall.
Let's say there is only one other piece and the first piece held while most of the rope stretch was happening. Then the good piece experiences half the total load up until the failure of the bad piece, at which point the load on the good piece nearly instantaneously doubles. Isn't this what people mean by shock loading?
Now on the other hand, if the tension in the rope is released by a small extension in the anchor, then stretching and the build-up of rope tension (= force on remaining pieces) only has to absorb the fall energy remaining, with the ideal result that the remaining pieces experience lower load than they would have with the non-extending anchor.
It's all hypothetical, of course, but it seems quite plausible to me, unless of course I've missed something. I hope someone can test this.
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GOclimb
Trad climber
Boston, MA
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Murcy, that's correct. I said in an earlier post here, as well as in a response to CharlesJMM on the original rc.com thread that the CHJMM anchor only really equalizes between all the pieces within a narrow range, and for exactly the reason you stated so elegantly.
In reality, an elipse is close enough to a circle that within a range, the equalization of the CHJMM is pretty good. It's slightly better than the equalette, in which you immediately unweight one of three pieces completely as soon as you move the centerpoint at all. And of course it's far better than the cordelette, which really only ever weights one piece at a time as soon as you get off center.
This is exactly why the CHJMM anchor was not on the top of my list of anchors, despite its simplicity.
RG wrote: I don't have the time now to check, but one does wonder whether limiting knots in some of the other three-anchor rigs may also impose geometric constraints on equalization.
The Mooselette, multi crossed-sling, and Gordolette do not suffer from this drawback. However the Gordolette has a rather limited range and is awkward to set up.
GO
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GOclimb
Trad climber
Boston, MA
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RG wrote: Next, consider what happens when a piece fails and there is a small extension. During the instant of extension, rope tension drops to zero.
No it doesn't. It drops to the tension of stretching the rope X feet minus the number of inches of extension.
Removing for the moment a falling belayer from the equation (not unreasonable, since in many cases the belayer is on a stance) the force that then comes onto anchor should be very slightly less than the exact force at which the piece pulled out. What is key, however, is that in a two piece anchor that force is *shared* across the two remaining pieces in a dynamically equalizing rig, but is all on one piece in a cordelette.
To put it in simple terms: because it doesn't equalize, a cordelette makes it more likely that
1 - The first piece will rip, because in some cases it feels almost all the load.
2 - If the first piece rips, that the other pieces will rip, because they each feel more force than they would if they were sharing the load.
GO
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rgold
Trad climber
Poughkeepsie, NY
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""During the instant of extension, rope tension drops to zero."
How do you justify this assumption? Is Hooke's Law being thrown out? Or are you saying that the elongated rope shrinks back to its (near) original length during anchor extension? If the rope elongation is large compared to the anchor extension then how can this be? "
Hooke's law is still in operation. I'm saying the elongated rope shrinks some. Tension going to zero is an idealization, although I'm not quite sure how to think about a non-zero the tension in an unloaded rope. The small extension combined with the fact that the rope and climber are falling will limit the amount of recovery before the rest of the pieces engage. A shock-wave calculation made by Ken Cline some years ago on rec.climbing suggested that recovery occurs in extremely short time intervals.
It has been a matter of debate for years whether any real recovery actually happens. In addition to how much recovery might happen in the time interval of an anchor extension, there are the mitigating factors of rope stiffening (we know this happens) and the additional effects of the belayer falling.
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GOclimb
Trad climber
Boston, MA
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RG wrote: Let's say there is only one other piece and the first piece held while most of the rope stretch was happening. Then the good piece experiences half the total load up until the failure of the bad piece, at which point the load on the good piece nearly instantaneously doubles. Isn't this what people mean by shock loading?
Now on the other hand, if the tension in the rope is released by a small extension in the anchor, then stretching and the build-up of rope tension (= force on remaining pieces) only has to absorb the fall energy remaining, with the ideal result that the remaining pieces experience lower load than they would have with the non-extending anchor.
It's all hypothetical, of course, but it seems quite plausible to me, unless of course I've missed something.
I don't know whether you missed it, but it sure sounds like it:
If you have a 20 foot rubber band and stretch it 6 feet, you'll get tension X. Lower the top end 6 inches, and you'll get a tension of X minus a very little bit.
So in your scenario two, the remaining piece feels nearly double the force that extracted the first one.
Of course, that's assuming that the belayer doesn't fall directly onto the anchor. If she does, the anchor may feel significantly *more* force in scenario two than in scenario one.
By the way, if it's an equalizing three piece anchor instead of two piece anchor, when that first piece fails, the other two feel only 50% more force than the first one did, rather than double the force.
GO
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GOclimb
Trad climber
Boston, MA
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RG wrote: Tension going to zero is an idealization
Why? Take a rubber band stretched 50%, and reduce the stretch to 48%, and you say the ideal calculation of the tension in the rubber band is zero?
GO
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rgold
Trad climber
Poughkeepsie, NY
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"If you have a 20 foot rubber band and stretch it 6 feet, you'll get tension X. Lower the top end 6 inches, and you'll get a tension of X minus a very little bit.
Good points. I was thinking of the tension in the belayer's tie-in. What if I have a two-foot tie-in that stretches 8" and an 8" extension in the anchor?
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Largo
Sport climber
Venice, Ca
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I'm fiddling with the CHJMM right now. Once again, the devil is the limiter knots--the "geometric limitation" Rich mentioned. The CHJMM is an elegant idea but it doesn't work as well as hoped because once the limiter knots are set, it dynamically equalizes (within a limited but acceptable range) only in a vertical orientation. Meaning, so long as you are pulling straight down, you're okay within the given range. On the horizontal plane (meaning when you lean out on the rigging, as usually happens on all but hanging belays), the middle piece goes slack.
I'll have to start fiddling with the Moosealette and other two and see if there's not some way to simplify these ideas.
GO, can you be bothered to sketch out those other rigs as well. Thanks,
JL
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cintune
climber
Penn's Woods
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This is getting really interesting. I think this has been posted before in another thread, but here's some stuff that might possibly be useful to test out some of these ideas:
http://www.squid-labs.com/projects/erope/
"Squid Labs has developed an Electronically Sensed Rope - a rope or webbing with integral sensing capability which can be monitored electronically. Our technology can be used to sense wear and load conditions in rope and webbing. We currently work with customers to develop commercial and end-user solutions using our technology, including appropriate sensing elecronics integrated to the application."
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the Fet
Knackered climber
A bivy sack in the secret campground
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Murcy, that's correct. I said in an earlier post here, as well as in a response to CharlesJMM on the original rc.com thread that the CHJMM anchor only really equalizes between all the pieces within a narrow range, and for exactly the reason you stated so elegantly.
I missed this version of the CharlesJMM Anchor (Chuckolette?) on the rc.com thread and thought you (GO) were referring to one of his earlier designs. I played with it a little and it seems like if it's tied like this photo, with extra slack given to the strand with the twist, then it DOES load share good over a good range (if the strand with the twist is only weighted in one piece failure mode). It don't think it "equalizes" since the middle arm looks like it puts 2X the force of the outside arms (25/50/25) but that's ok, if it does everything else good. It equalizes 50/50 if one of the pieces fails.
The main issues I see are: if an outer piece fails a limiter knot pulls through the powerpoint biner, it's a little tricky and time consuming to tie (but not bad).
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WBraun
climber
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So ah mmmmmmmmm
What's behind the blue door?
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GOclimb
Trad climber
Boston, MA
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JL: Not sure how you're setting up your rig - it should make no difference whether you're pivoting around a vertical or horizontal axis.
GO, can you be bothered to sketch out those other rigs as well. Thanks,
Sure, if I have time, will do so tomorrow.
The Fet: I agree with everything you said regarding the CHJMM. I do not know if there is a more efficient way to break it down and build it again, as I have not used it much in the field. From my limited experience, the Mooselette seems much easier, since I just leave the two limiter knots in it. Then all that's required is to clip it into the three pieces, adjust the limiter knots, and I'm good to go.
Werner: What's behind the blue door?
Ah, but Werner, can't you guess? Another anchor, and another blue door, of course!
GO
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raymond phule
climber
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"A great link, thanks for it. But no useful data on factor-2 falls reported there, unfortunately"
The most important info was that you cant put a large force on a rope using an ordinary belay device. This is also true in a class 2 fall. The force on the anchor cant be high except in some special cases. The rope cant slip through the belay device, the climber falling on the belayer, the belayer falls an loads the anchor. Any more possibilities?
"Here I think you are wrong. As you say, peopel make misstakes, even in the presence of knowledge of the problems. They are sometimes wrong about which piece is good. The best strategies are those that minimize potential load to all pieces, are tolerant of off-axis loading, and redistribute the load to remaining pieces if one fails."
I agree
"These are the only available means of coping with the uncertainties that are part of real life."
I disagree about this. Assume that most belayas that fail is due to one problems mention above, rope cant slip, climber falls on the belayer and belyer fall and loads the anchor ( a rigid connection is very bad here). Then are a perfectly equalised anchor better than a non equalised but it might not be enough. Pointing out the main problem is important because it can make people more carefull.
"But it is also the case that very few experienced climbers have ever had their anchor judgements subjected to a real test, much less a statistically significant sequence of tests. This means that most climbers really have no basis in reality for judging the strength of their anchors. The tragedy described by Werner earlier in this thread indicates that these claims are not simply hypothetical."
I agree, but this make it important to try to analyze what actually happens.
"Once again, in the face of this really quite massive uncertainty, equalization is the best strategy, if it can be achieved."
Yes, but the problem is to achieve it. I am also afraid of the load from the belayer due to extension.
"It seems to me that a relatively small group of climbers is interested in the intellectual challenge involved"
It sure can be fun.
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raymond phule
climber
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Interesting thoughts rgold.
The reason for the result is that the maximum force happens when the fallen climber velocity is zero(or there about) because the rope elongation and thus the force is maximum at that time.
My quess though is that the rope is not going to be able to recover fast enough. Isn't a rope very stiff right after a fall? It sure is longer.
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GOclimb
Trad climber
Boston, MA
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JL: GO, can you be bothered to sketch out those other rigs as well. Thanks,
First, the 2 crossed-slings. I don't think you need a sketch, but I just want to reiterate that I think this is an excellent method for distributing the force over three pieces (note, I say distributing rather than equalizing).
Looks like this:
Of course if you wanted to use two anodized big biners at the power-point, you'd get the full non-binding characteristics of the equalette.
-*-*-*-*
To make the mooselette:
1 - Put two overhand knots in the cordelette. These should incorporate the section of line with the joining knot, so as to keep it out of the way. You can do this on the ground. These knots never need to come out.
2 - Place three pieces of gear, and put a loop of the cord through each biner, and pull the centers down to a powerpoint like if you were going to make a standard cordelette. Put the strand with the knots on the middle piece.
3 - Adjust the two limiter knots so that one is down near the powerpoint, and the other is up near the top.
4 - On each side, clip one biner (or draw, if it needs to be longer) between either of the outside strands, and either of the inside strands. Doesn't matter which one, but in the middle, clip it above the upper limiter knot.
That's it.
When I have time, I'll come back and add the Gordolette.
GO
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Degaine
climber
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Thanks for the sketches, goclimb.
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GOclimb
Trad climber
Boston, MA
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Here's the Gordolette. It's pretty cool, but a little too finicky for me. Still perhaps someone with some free time can refine the basic idea.
It's been a while since I've made one, and I drew this up from memory. If I have time this weekend I'll build the real thing and make sure it matches up with my sketch.
GO
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rgold
Trad climber
Poughkeepsie, NY
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Here is an anchoring solution I had sewn up for me recently. Sorry not to have pictures of it in use in the field (I've been out with it for several days of climbing, none with a camera in tow so far). All I have at the moment are the following indoor shots.
The idea is based on something I called the chopolette in the massive rc.com sliding X thread. It generated little interest there, in part because of a biner that had many sliding strands and the feeling that binding of strands would almost certainly destroy its effectiveness in equalizing.
In honor of its gimmicky nature (a source of embarrassment to me and a deal-breaker for Largo and others who believe in the primacy of simple tools) I've dubbed it the Geekqualizer, and admit, with regret, my passage to the Dark Side of gadget worship.
It consists of a commercialy available equalizing module with no crossing strands, and three arms that extend from the equalizing module and are clove-hitched to the protection. Here's what the whole unit looks like:
here's a closeup of the equalizing module and its connection to the arms:
and here is a view of a possible set-up for three pieces at different distances from the power point.
In the last picture, the left arm has been clipped to a far away piece with the loop sewn into its end, while the other two arms have been clove hitched to their biners, after which the end loop has been dropped into the biner as a backup to clove-hitch slippage.
Here is a closeup of the clove hitch and loop backup:
For those increasingly ubiquitous two-bolt anchors, the arms can be dropped and the equalizing module clipped directly to the anchors. The overhand knot at the right shortens the webbing and thereby decreases the extension if one of the bolts fails:
Four-piece anchors can be accomodated by adding a carabiner. The off-axis range is smaller for this set-up and of course there is more friction in the system.
The Geekqualizer wraps up into a small package somewhat smaller than a 7mm cordelette: Wrap-up is very simple and the time is about the same as for a cordelette. Installation time is the time it takes to make three clove hitches.
Advantages:
1. Adaptable to all anchor configurations with consistent installation. Regardless of the placement of the pieces, you rig it up the same way, with no choices or special adjustments. It is easily adapted to two- and four-piece riggings. (I think most of the other methods are tailored to a single fixed number of anchor points.)
2. Zero carabiner cost for two and three anchor points. Other than the always essential biners on the pieces and the power point biner, no other biners are required. Two Geekqualizer anchors consume the minimum of eight biners, whereas two equalette anchors (for three points) require ten biners and two mooselette anchors require twelve biners.
For the occasional four-point anchor, the Geekqualizer requires a total of seven biners, chained equalettes require ten biners, and the mooselette is, I think, out of the running.
3. A consequence of the zero carabiner cost is that there are no biners in the system that might be compromised by unanticipated cross-loading or gate opening. (The sliding X is especially susceptible to a very dangerous configuration if one of the pieces fails.)
4. Very fast installation for all configurations---no limiter knots to tie, adjust, and wrestle with when they become wet, tight, and cold, no potential need to readjust anything as there is with the cordelette, no special circumstances that the system doesn't work for. You clove (or clip) the arms, clip into the power point and you're on.
5. Equalization potential as good and perhaps better than other equalizing methods because of the lack of multiple crossing strands on a biner somewhere. Extension if one piece fails is about four inches.
6. Responds to off-axis loads and redistributes load if a piece fails (as do most equalizing systems).
Disadvantages:
1. Yet another special-purpose item. Although it can be used in other ways in an emergency, it isn't remotely as versatile as a cordelette.
2. Sewn webbing must be inspected and retired when appropriate.
3. Low-stretch material provides little energy-absorbing utility. Tying in to power point with rope is essential for the belayer. Followers who clip in, even temporarily, with a daisy should keep it tight and stay below the anchor. (On the other hand, low-stretch material might behave better when it comes to friction over the various pulley points.)
4. Potential for clove-hitch slippage may be a concern. There are some tests (private communication) that indicate this isn't a problem. Even so, one should be careful to tie the clove hitches without twists in the webbing and should make sure that the hitches are oriented so that the load-bearing part of the knot is close to the spine. (The clove hitch can often be backed up by half hitches around the arm before clipping the end loop to the biner.)
5. Friction. Friction is the reality death-knell of any equalizing system, and this is no exception. I think the elimination of crossing strands should prove to be an advantage (but know of no tests to address this question). There is still friction around all the rings. The worst case is when the strands all make full 180 turns around the rings---three pieces in a vertical crack. If systems such as this have a future, it lies in finding components that will reduce the friction. For example, it would be interesting to know how much difference roller biners on the protection points would make.
Remember, however, that the standards for acceptibility aren't very high, now that we are learning how bad the cordelette is, even with just two equal length arms. My guess is that even with their current levels of friction, the Geequalizer (and many of the other methods) provide equalization on average better than the cordelette provides, together with the advantages of off-axis load adaptibility and redistribution of the load to the remaining pieces if one piece fails.
6. No doubt perspicacious readers will come up with a slew more disadvantages in short order.
What I like about the Geekqualizer so far is that it is fast enough and simple enough for me to use automatically on every anchor. It costs me nothing in time, effort, and gear to use it rather than a more traditional method. The value in this corresponds to my feeling that something terrible is just as likely to happen in mundane casual circumstances as in the midst of some epic, and the instant you need the advantages of equalization, if such a time should come, may not be a moment that you can anticipate and so make special preparations for.
Test results post:
http://www.supertopo.com/climbing/thread.html?topic_id=307091&tn=308
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Ed Hartouni
Trad climber
Livermore, CA
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did you get Wootles to test it?
I'll think about friction later tonight...
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murcy
climber
San Fran Cisco
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nice, rgold!
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GOclimb
Trad climber
Boston, MA
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RG: A few thoughts off the top of my head. Can't replicate it, since I don't have the AE, but maybe I'll see if my buddy Jake who I see a few times a year will let me borrow his sometime.
1 - Looks nice!
2 - The issue of redundancy is a fairly serious one, and this doesn't get full marks. Let me define what I mean by the term redundancy:
A - If any one piece fails, the entire anchor will not fail.
B - If any one strand is cut, the entire anchor will not fail.
So the Geekqualizer passes part A, but gets an incomplete on part B. That is to say, if any of the strands radiating out from the AE are cut, you're fine, but if any of the strands within it are cut, everybody dies.
The CharlesJMM anchor and paired crossed slings do not have this particular failing.
3 - Once we allow ourselves to get geeky, steel rap rings could be substituted in for the biners to give other anchor types similar benefits. In other words, when you say Two Geekqualizer anchors consume the minimum of eight biners, whereas two equalette anchors (for three points) require ten biners and two mooselette anchors require twelve biners. this is comparing apples to oranges. The Mooselette could certainly be made with rings, and if so, would utilize the same number of biners as the Geekqualizer.
4 - As I think I mentioned before, to make a Mooselette on four pieces, all you need to do is pull down the four strands instead of three. It works for any number of placements. You'd simply need to add a biner for each additional strand.
5 - Friction. The Geekqualizer, as you said, has as many as 5 180 degree bends. That's an awful lot of friction. Compare that to: Pair of sliding-Xs - 5; Mooselette - 3 (only one of which typically moves much); CharlesJMM - 2 with a crossed strand, 3 without; equalette - 2. I imagine that this might give a fair approximation of how well each would equalize in the lab and the field.
6 - The fast/easy/idiotproof configuration seems like a huge plus!
Thanks for that!
GO
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johnboy
Trad climber
Can't get here from there
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While some of these other configuraions can't do cross platform (2 piece or 4 piece) anchors, your still left with a 20ft cord that can make up other types of anchors that do work on 2 or 4 piece anchors. I guess what I'm saying is, different situations call for different anchors and a 20 ft cord can do many different things.
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wootles
climber
Gamma Quadrant
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did you get Wootles to test it?
Wootles walks by, hands in pockets, whistling, and avoiding eye contact.
I can see I'm going to have to step up the efforts to get new load cells.
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Ed Hartouni
Trad climber
Livermore, CA
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Feb 10, 2007 - 12:14am PT
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The way that Richard's Geekqualizer works is that the red sling is free to slip and extend under the force of the fall. The slipping is necessary to equalize the forces on the blue slings.
If the red sling is not free to slip then it does not equalize.
The friction can be a large issue. For a sling looped around a ring, the forces can be unbalanced because of the friction. If F0 is the larger force, and F1 the smaller, on each strand of the sling, then the sling will not slip when:
F1 = F0/exp(2*mu*pi)
where mu is the coefficient of static friction and pi = 3.1415...
If mu = 0.4 then F1 = 0.08*F0 or roughly 1/10th the force... put an other way, a 1 lb weight on one side can hold a 10 lb weight on the other.
This is not at all surprising, since that is the way a belay device works.
For multiple bends, these forces multiply, which is GOclimb's point. For a sliding-x there are actually 4 bends, one at each anchor and two at the clip-in 'biner, since the webbing is doubled there. In this case it is a bit more complicated since the normal forces on the inner webbing is increased by the outer webbing. It is possible that this large friction is the reason why the sliding-x did poorly in the Largo/wootles test.
I'll try to measure the static coefficience tomorrow (it's raining in California) to get an idea of how big the problem is...
...my intuition is that the friction is the big problem here.
Of course, one could coat the rings in teflon (or use teflon tape) which would considerably reduce the coefficient. Since this is exponential, it should make a big difference.
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Paul Raphaelson
Ice climber
Brooklyn, NY
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Feb 10, 2007 - 12:15am PT
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I'm looking at variations on the Sliding W.
Besides extension, and lack of redundancy, are there problems with the strands binding? If so, are they catastrophic (rope burning itself) or minor (imperfect equalization due to friction)? If the binding isn't a serious issue, consider this ...
I just did a couple of experiments at home and found that the amount of extension from a typical sliding W setup is actually pretty minor. And it can be greatly reduced by tying one of the strands short (with an overhand or an 8) in order minimize the length of the rigging. You can get some (imperfect) redundancy by tying the rope into the power point biner with a clove hitch, and then backing it up with a figure 8 onto the strongest piece of pro.
Not a perfect setup, but it has some things going for it:
-simple. uses no extra gear, easy to evaluate, faster even than a cordelette.
-excellent equalization, assuming binding of the strands isn't an issue
-extension can be limited to 1 or 2 feet in most cases
-some redundancy is available with minimum effort by using the climbing rope.
On another note, I tried the variation on the sliding W that has overhand knots tied in the outside strands. It didn't work properly. It looked as if it would, but it did not equalize. All the load went onto the outside pieces, and was born by single strands on each side. This is difficult to explain ... I suggest trying it to see what the issue is.
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rgold
Trad climber
Poughkeepsie, NY
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Feb 10, 2007 - 02:14am PT
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"Question: Are you going to use this yourself as a default anchoring tool?"
Yes, for a while anyway. I want to see how much trouble it is in real life.
I don't see myself using the other three-placement anchor systems; they seem tricky to set up, they consume too many biners, I don't understand how they'll perform in all circumstances (there seems to me to be a wrong way to clip the bottom loops of the Mooselette, for example), I'm not sure I can reliably tell from visual inspection when everything is ok, and I don't trust myself to think about any of these things clearly when I'm tired, cold, and in a rush to get down before dark. I don't think any of the ones that purport to equalize three anchor points have fewer friction problems than the Geekqualizer. They may be fine for other people, but I'm a very slow thinker and I make a lot of mistakes on my way to understanding things.
I have very rarely carried a cordelette---mostly I tie in with the rope, so using a special-purpose anchoring gadget is two giant steps in a different direction. But I'll try it out for a season anyway and see what I think after that.
"did you get Wootles to test it?"
There's a chance that Wootles might have a job and a life, and this makes me just a wee bit reticent to ask him to test stuff, especially when he'd need three load cells to see the effect of friction. First I'm going to see if I can stand using the Geekqualizer, 'cause if I can't, why test it? (I'm not concerned about it being worse than the methods I typically use.) In any case, at present I only have two Geekqualizers (under the extremely optimistic assumption that I can convince a partner to carry and use one).
Friction:
I've already said that friction could kill the whole show, and that finding ways to reduce it like Ed's teflon coated rings could be the key to any reasonable success. I'm gonna look into his teflon tape idea....
As for comparisons, I don't think that, for example, the Mooselette fairs any better than the Geekqualizer. In my possibly mistaken reading of Gabe's diagram, the Mooselette appears to have seven bends around biners compared to the five bends around rings in the Geekqualizer. Two of the Mooselette bends are at relatively large angles, in some cases (e.g. the indoor picture posted earlier as opposed to the sketch) so large as to be insignificant, in which case the number of bends could in some cases be effectively as low as 5, the same as the Geekqualizer. However, the Mooselette has three strands interacting and possibly binding at the power point biner, whereas the Geekqualizer has no such interactions. I don't see any a priori way of predicting which might be better, and even if they had the same average performance, the binding potential in the Mooselette and other designs raises the possibilty of bad worst-case performances.
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Ed Hartouni
Trad climber
Livermore, CA
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Feb 10, 2007 - 02:26am PT
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nylon-nylon coefficient is reported to be 0.15 to 0.25, which reduces some of the webbing on webbing binding, but the real problem I think is the increased normal force caused by one strand of the webbing being on top of another over a 'biner or ring.
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Ed Hartouni
Trad climber
Livermore, CA
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Feb 10, 2007 - 02:14pm PT
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The tests for measuring the friction of slingage on 'biners is complete and the conclusions are rather interesting. I believe that they may even be informative.
"Executive Summary"
I'll tell the story here with the technical details below for the geeks out there.
There wasn't much difference in using a big pear 'biner or a regular D... hanging a weight on one side and counter balancing it with a weight on the other you find that a 10lb weight can support a 22lb weight because of the friction. This can complicate a system which depends on the sling to slip around to equalize because 2-to-1 forces have to develop to do it... add more 'biners and you add more imbalance.
The sliding-X was really interesting. Using 9/16" webbing you find one strand sitting on the other. A 10 lb weight held a 65 lb weight statically in this configuration. The perlon sliding-X had the strands sitting next to each other, and the frictional forces were greatly reduced, 10 lbs held 25 lbs, slightly higher than just looping the strands.
If you are going to use the sliding-X, use materials that sit next to each other, not on top of each other! I think the common usage of slings to build a sliding-X should probably NOT be recommended as the equalization properties are defeated.
The tests
The test was conducted by hanging the sling over a 'biner so that the loop made 180º contact with the 'biner. Two weights were hung on either side of the sling. One of the weights was increased until the sling moved. The coefficient of static friction can be calculated by using the formula:
mu = ln(F2/F1)/pi
where ln(F2/F1) is the natural logarithm of the ratio of the greater weight to the lesser weight and pi = 3.1415...
The slings used were a 9/16" wide tubular nylon web, and a 7mm perlon cord.
They were looped both in just a single strand, and in the "sliding-X" configuration.
Two 'biners were used, a large pear 'biner that I use for belaying, rappeling, etc, and a "D" 'biner that I use for "normally" for climbing ropes to anchors, etc. I wrapped Teflon tape on the large pear 'biner to see if it had any effect, it did not.
What I find is that the coefficient of friction is in the range of 0.22 to 0.31 for all slings and 'biner configurations. This gives a force ratio of anywhere from 2 to 2.7 on the 'biner, that is, one strand can have as much as 2 to 3 times the force on it than the other. This would be an issue in a belay rig that is stressed close to the breaking strength of the sling, one side might blow first because the sling isn't able to equalize the force by sliding around the 'biner.
The sliding-X configuration was very interesting. The coefficients were much higher in this case, with the 9/16" sling being in the range from 0.5 to 0.6, able to maintain a force ratio in the range of 5 to 7. This is primarily caused by the fact that one strand of the webbing sits on the other.
The 7mm perlon sliding-X did a better job, the strands sit next to each other. Here the coefficients ranged from 0.29 to 0.4 with force ratios from 2.5 to 3.5.
The data
sling,carabiner,configuration,static,F1 (lbs),F2 (lbs),F2/F1,mu
9/16,large pear,looped,yes,3,8,2.67,0.31
9/16,large pear,looped,no,10,25,2.50,0.29
9/16,D,looped,yes,10,22,2.20,0.25
9/16,D,looped,no,10,25,2.50,0.29
9/17,large pear-Teflon,looped,yes,10,22,2.20,0.25
9/18,large pear-Teflon,looped,no,10,25,2.50,0.29
7 mm,large pear,looped,yes,10,20,2.00,0.22
7 mm,large pear,looped,no,10,22,2.20,0.25
7 mm,D,looped,yes,10,22,2.20,0.25
7 mm,D,looped,no,10,25,2.50,0.29
9/16,large pear,sliding X,yes,10,47,4.70,0.49
9/17,large pear,sliding X,no,10,50,5.00,0.51
9/18,D,sliding X,yes,10,65,6.50,0.60
9/19,D,sliding X,no,10,70,7.00,0.62
7mm,large pear,sliding X,yes,10,25,2.50,0.29
7mm,large pear,sliding X,no,10,30,3.00,0.35
7mm,D,sliding X,yes,10,30,3.00,0.35
7mm,D,sliding X,no,10,35,3.50,0.40
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Paul Raphaelson
Ice climber
Brooklyn, NY
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Feb 10, 2007 - 03:02pm PT
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Has anyone looked at the friction properties of the sliding W?
There's definitely a lot of friction going on. I'm actually less concerned about perfect equalization than I am about what happens if a piece blows and there's extension. I worry that that much cord sliding over itself could cause some burning/shredding ... especially troublesome since the configuration doesn't have built-in redundancy.
If this isn't likely to be an issue, then I'm going to pursue variations on it as a solution.
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Ain't no flatlander
climber
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Feb 10, 2007 - 03:31pm PT
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First, it's "pear" not "pair" though it would be interesting to see how a pair of pears performs. Largo suggests that anodized biners slide better too. Please try your tests with the new generations of 8mm Spectra webbing, which is becoming much more common on many climber's racks.
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Ed Hartouni
Trad climber
Livermore, CA
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Feb 10, 2007 - 04:43pm PT
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my guess is that you can't tell the difference between the spectra and the nylon tube...
I did change the spelling....somedays are just like that though...
the friction is dominated by the schmutz on the surfaces... we all know that a dirty rope has more friction moving in a belay device.
and the 'biner used to be anodized, but if you use them a reasonable amount they aren't pretty quickly.
multiple 'biners also shouldn't change things, the way they work with a belay or a rap is to increase the contact angle, in this set up it probably wouldn't do that (angle would still be pi).
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jstan
climber
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Feb 10, 2007 - 05:23pm PT
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Sloppy, but hey. Good enough for Topo work.
sling---carabiner--------config.----static---F1(#)---F2(#)---F2/F1--mu
9/16-----lg pear--------------looped-----yes-----3----------8-----=2.67-----0.31
9/16-----lg pear------------- looped-----no------10--------25-----2.50-----0.29
9/16-----D---------------------looped-----yes-----10-------22-----2.20-----0.25
9/16-----D---------------------looped-----no------10--------25-----2.50-----0.29
9/17----- lg pear,Teflon---looped-----yes----10--------22-----2.20-----0.25
9/18----- lg pear -Teflon--looped-----no-----10---------25-----2.50-----0.29
7 mm----- lg pear --------- looped-----yes---10--------20-----2.00-----0.22
7 mm----- lg pear ----------looped-----no-----10--------22-----2.20-----0.25
7 mm-----D-------------------looped-----yes----10-------22-----2.20-----0.25
7 mm-----D-------------------looped-----no-----10--------25-----2.50-----0.29
9/16----- lg pear -----------sliding X-----yes--10-------47-----4.70-----0.49
9/17----- lg pear -----------sliding X-----no----10------50-----5.00-----0.51
9/18-----D-------------------- sliding X-----yes--10------65-----6.50-----0.60
9/19-----D---------------------sliding X-----no----10------70-----7.00-----0.62
7mm----- lg pear ---------- sliding X-----yes--10------25-----2.50-----0.29
7mm----- lg pear -----------sliding X-----no----10-----30-----3.00-----0.35
7mm-----D---------------------sliding X-----yes---10----30-----3.00-----0.35
7mm-----D-------------------- sliding X-----no-----10----35-----3.50-----0.40
Does "No" in the static column mean it is a test of sliding friction? If so, I remember coef. static friction as generally being larger than sliding friction. ?
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Jingy
Social climber
Flatland, Ca
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Feb 10, 2007 - 05:31pm PT
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I never do it. I boulder. No fuss no muss.
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Ain't no flatlander
climber
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Feb 10, 2007 - 05:33pm PT
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I suspect the 8mm spectra will test closer to your 7mm cord due to slipperiness and a shape that is nearer to round.
As for anodizing, if it's shown to make a significant difference then that may be an argument for using hard anodizing on locking biners instead of the soft sulfuric anodizing that is currently used. Nobody makes a hard anodized biner...yet.
c'mon AAC, get your feces cohesive and do something useful for a change.
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Ed Hartouni
Trad climber
Livermore, CA
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Feb 10, 2007 - 07:10pm PT
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"No" means it did not hold statically, so the actual value of sliding is somewhere in between those two. Since the range is small, probably smaller than the variations in the coeff. I just bracket the values (usually within about 10% of the total weight)...
I also got a BD dynema sling to see what that's all about, but now I'll have to go back and get a new pear 'biner with anodization... which I don't think is work while. The schmutz factor will dominate any surface preparation.
You used to be able to get a nice nylon pully that fit in the 'biner. Something like that could be made out of teflon (or some other slippery material) and used in this "special" case...
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Ed Hartouni
Trad climber
Livermore, CA
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Feb 10, 2007 - 09:17pm PT
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sorry, the coeff. is calculated assuming static... this gives the range. Usually when I have it slipping, it is just slipping... so I take the range of static mu to be between the "yes" and the "no" values.
It can't be larger than the "no" value.
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cintune
climber
Penn's Woods
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Feb 10, 2007 - 09:21pm PT
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Petzl still makes those pulley wheels to go on ovals. And DMM has their Revolver biners that are rated to something like 10kN (the pulley part, that is.) More gear, yeah, but if you want to reduce friction.....
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rgold
Trad climber
Poughkeepsie, NY
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Feb 10, 2007 - 09:43pm PT
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"Ed, do you think the dynamic coefficient of friction will be low enough compared to the static coefficient to make a difference?
The reason I ask is that the force ratio needed to overcome static friction should occur well before the peak force on the anchor is achieved. Now wouldn't that imply that the cord/slings will be sliding when the peak is reached?"
I think this is a critical point. Somewhere I read a study of the sliding X done by static loading that concluded it was worse than the cordelette at distributing the load. Then Wootle's dynamic tests reached the opposite conclusion, due, I suspect, to precisely the effect DC mentions here.
Here's a reference to the study I mentioned
http://www.t-rescue.com/articles/self_equalising_anchors/index.pdf
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rgold
Trad climber
Poughkeepsie, NY
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Feb 10, 2007 - 10:11pm PT
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I should have mentioned that the Geekqualizer
http://www.supertopo.com/climbing/thread.html?topic_id=307091&tn=285
was subjected to testing, although separate load cells on the three anchor points were not available to quantify the presence or absence of equalization.
The rig withstood 11 falls with an 80 kg weight, at which point the climbing rope failed. the first two falls were factor 1 falls and the remaining nine were factor 1.45 falls. The same piece of rope was used, and so the peak force kept going up, from 6.1 kN on the first factor 1 fall to 8.9 kN on the third fall, which was the first factor 1.45 fall. The rest of the falls, with one exception around 10.4 kN, were all around 11 kN.
On the eighth fall, one arm of the Geekqualizer was purposely cut 50%, on the ninth fall the cut was increased to 80%, and on the tenth fall the cut was increased to 90%. The total load on the ninth and tenth falls was 11.4 kN each time. On the eleventh fall a "fuse" was inserted, but the rope began to cut and extend, ending the test.
Once the loads got up to around 10 kN, the clove hitches tended to slip about 3/4 of an inch.
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Ed Hartouni
Trad climber
Livermore, CA
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Feb 10, 2007 - 10:31pm PT
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what kind of detector does Juan use for his seismometers? maybe they could be used instead of load cells?
I also though that you could use a stress guage on a steel rod that is used as the anchors to measure the dynamic loading.
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WBraun
climber
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Feb 11, 2007 - 12:04am PT
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No those won't work Ed (Juans detectors).
Ed if you need load cells come see me next time you're here in the Valley and I'll lend you mine.
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GOclimb
Trad climber
Boston, MA
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Feb 11, 2007 - 12:41am PT
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rgold said: In my possibly mistaken reading of Gabe's diagram, the Mooselette appears to have seven bends around biners compared to the five bends around rings in the Geekqualizer. Two of the Mooselette bends are at relatively large angles, in some cases (e.g. the indoor picture posted earlier as opposed to the sketch) so large as to be insignificant, in which case the number of bends could in some cases be effectively as low as 5, the same as the Geekqualizer. However, the Mooselette has three strands interacting and possibly binding at the power point biner, whereas the Geekqualizer has no such interactions.
You're quite right that in the Mooselette, (or any configuration with multiple strands through a power-point) the strands at the power-point biner might bind in a hard fall. I've never seen it happen from bodyweight, perhaps because cord strands tend to sit next to rather than on top of each other, or perhaps because all the strands at the power-point are moving in the same direction, or because only one is moving more than millimiters. But with a harder fall, or with a piece blowing - I don't know, that's beyond the scope of my testing.
As for the number of biners with tight bends, take another look. Of the 6 biners, as you say, two of them are at angles that are probably insignificant, and one of them is completely fixed (due to the limiter knots on the middle strand). So there are really only three biner interactions at high angle. Of those three, there's only one strand/biner that moves much. Do folks think it matters how much cord must move through a biner, or is any movement equivalent?
By the way, the CharlesJMM and the Equalette look like they should be big winners on the friction front, unless the tiny-movement theory redeems the Mooselette.
GO
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climbingjones
Trad climber
grass valley,ca
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Topic Author's Reply - Feb 11, 2007 - 01:08am PT
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WOW! Thanks for all of the posts to this thread. I knew there was some discussion to be had here. Though I must admit that I dont understand all of the equations that have been posted. I still feel that the sliding "W" is the best, for a regular free climbing anchor anyway. Tying a know in the system anywhere just limits the distribution of the load. We know that the belay is always shifting if you, as the belayer, are hanging from it. I feel the slider works constantly to evenly distibute the load. The shock loading of one piece blowing is minimal, in my opinion, since we routinely rely on one piece to arrest a fall of much more distance than the resulting "fall" in the event that one piece blows in the anchor. But, I still respect the opinion of you much more knowledgeable folks in the physics of this situation. Thanks again. Keep it coming to make this the most responded to post I have seen. ;)
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murcy
climber
San Fran Cisco
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Feb 11, 2007 - 11:50am PT
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The solution is in today's SF Chronicle!
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rgold
Trad climber
Poughkeepsie, NY
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Feb 11, 2007 - 03:12pm PT
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I bet Werner's got one of those things for rescue rigging. This just shows how useful climbing gear can be when you open your mind to the full potential of uses.
Back to the Mooselette:
"As for the number of biners with tight bends, take another look. Of the 6 biners...one of them is completely fixed (due to the limiter knots on the middle strand). So there are really only three biner interactions at high angle.
It isn't the number of biners with tight bends that matters for friction, it is the number of tight bends in the system. When I look at the Mooselette diagram, I see three movable strands at the power point biner, one from the left anchor to the lower limiting knot, one from the right anchor to the lower limiting knot, and one from the left anchor to the right anchor. These three strands plus the two bends at the left and right anchor biners make for a total of five friction-inducing bends in the system, as well as whatever effects the binding of the three powerpoint strands produces. Moreover, I wouldn't completely discount the friction contribution made by the other two biners; it depends how you rig the Mooselelette.
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GOclimb
Trad climber
Boston, MA
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Feb 11, 2007 - 04:41pm PT
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Regarding the Mooselette: Yup, three moving strands through the powerpoint. What I'm just not clear on is whether or not it matters how much each strand moves. Because two of those strands move only like a millimeter per foot, and typically in the same direction as the main moving strand.
GO
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raymond phule
climber
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Feb 12, 2007 - 07:23am PT
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Nice rig rgold. It should be easy to use. Friction could definitely be on issue with this and many (all?) 3 piece setups.
"now that we are learning how bad the cordelette is, even with just two equal length arms"
The worst load distribution in the equal length arm test was 39%-61% i.e. the force in one of the arms was never less than 39% of the total force. I dont belive that this is that bad.
I think that it should be interesting to see tests performed for a 3 anchor rig, both static and equalising.
The link you posted suggested that friction playes a large roll in a setup like yours. It is hard to say what happens with a larger load and dynamic case. I think friction plays less of a roll then but I am not sure.
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I was a fairly enthusiastic participant in the rc.com thread and there is tons of good stuff in it - I did nothing to attempt to quash it. 
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