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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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