Discussion Topic |
|
This thread has been locked |
Crag Q
Trad climber
Louisville, Colorado
|
|
|
Jan 18, 2007 - 01:36pm PT
|
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.
|
|
Crag Q
Trad climber
Louisville, Colorado
|
|
|
Jan 18, 2007 - 01:44pm PT
|
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 Fet
Knackered climber
A bivy sack in the secret campground
|
|
|
Jan 18, 2007 - 02:22pm PT
|
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:
|
|
GOclimb
Trad climber
Boston, MA
|
|
|
Jan 18, 2007 - 02:53pm PT
|
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
|
|
raymond phule
climber
|
|
|
Jan 19, 2007 - 05:18am PT
|
"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.
|
|
tito
climber
|
|
|
Jan 19, 2007 - 06:29am PT
|
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.
|
|
raymond phule
climber
|
|
|
Jan 19, 2007 - 07:44am PT
|
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.
|
|
wootles
climber
Gamma Quadrant
|
|
|
Jan 19, 2007 - 08:29am PT
|
What isn't adding up?
|
|
Ed Hartouni
Trad climber
Livermore, CA
|
|
|
Jan 19, 2007 - 08:42am PT
|
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.
|
|
raymond phule
climber
|
|
|
Jan 19, 2007 - 09:00am PT
|
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)
|
|
jstan
climber
|
|
|
Jan 19, 2007 - 09:06am PT
|
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??
|
|
wootles
climber
Gamma Quadrant
|
|
|
Jan 19, 2007 - 09:39am PT
|
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.
|
|
raymond phule
climber
|
|
|
Jan 19, 2007 - 10:00am PT
|
Thanks,
what was the total force?
|
|
wootles
climber
Gamma Quadrant
|
|
|
Jan 19, 2007 - 10:23am PT
|
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.
|
|
Chiloe
Trad climber
Lee, NH
|
|
|
Jan 19, 2007 - 10:47am PT
|
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.
|
|
wootles
climber
Gamma Quadrant
|
|
|
Jan 19, 2007 - 11:05am PT
|
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.
|
|
raymond phule
climber
|
|
|
Jan 19, 2007 - 11:24am PT
|
Thanks for the info
|
|
Largo
Sport climber
Venice, Ca
|
|
|
Jan 19, 2007 - 11:50am PT
|
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
|
|
Chiloe
Trad climber
Lee, NH
|
|
|
Jan 19, 2007 - 12:11pm PT
|
and Wottles is recognized
The climber formerly known as Wootles
;-)
|
|
|
SuperTopo on the Web
|
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. 
Let us know!