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another anchor failure rant
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sactownclimber


Mar 21, 2006, 7:10 PM
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. . . and unbelievably easily stupidly avoidable . . .

That was quite an adverb linkup . . .


stymingersfink


Mar 21, 2006, 7:59 PM
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Yeah, I know that the breaking strength is not the same as how much force it takes to rip the gear. That probably takes significantly smaller amounts of force than actually breaking the cam. Meaning the statistic is even scarier. It scares me that in a really hard fall, a cam holding would be mere luck. Because it seems like it would be pretty easy to create that much force with long falls.

try to avoid setting yourself up for long falls, especially over suspect placements or soft stone. (seen the video of gear ripping down at the Creek?) on the other hand, did you see footage of Potter taking 50' whippers onto a .3 (or some rediculously small) camalot while working the Tombstone? He had a lot of rope out to absorb the impact forces generated. They had the footage on the BDEL.com site for a while, I'm not sure they still do, but poke around there you might find it.


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I think it is entirely possible to exert 15kN in a high factor fall. But I've never heard of a guy climbing on a dynamic rope snapping his spine even in a hard fall.

the whole 15kn thing?

to pass uiaa cert the rope must keep impact forces <12kn during the initial drop test, so no, you shouldn't ever see 15kn forces at the harness. where you may see them is at the top piece, as someone has mentioned above.

I've been told that the most force a human body can sustain without serious damage beginning to occur is ~1000lbs, which is in the 4kn range. I once took a 24" daisy fall which resulted in 0 (zero) damage to the daisy. This would indicate to me that I generated less than the 3kn the individual pockets are rated to. It wrenched my hips and back in ways I'd not yet felt, and would care to never again.

In a safety video I had to watch at work they were showing the forces generated by a 176lb dummy in a 6' static fall. Somewhere in the neighborhood of 4,800lbs! Their argument was always use a load-limiter when clipping off. (DUH!)


ridgeclimber


Mar 22, 2006, 2:41 PM
Post #28 of 41 (4762 views)
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Re: another anchor failure rant [In reply to]
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Yes, of course we always try not to set ourselves up for long, high-factor falls. But sometimes we can't. What about pitches that are very runout right from the get-go?

Thanks for those stats, they are helpful. But they don't refute my point. While the force on the harness may never reach 15kN, the force on the top piece can, as you said. And 15kN is the breaking strength. You can start ripping cams at much lower forces. Seems to me, if you're on a very runout pitch, and take a big factor-two fall on an all-cam anchor, you stand a very good chance of ripping some or all of your anchor placements. And that's scary.


antiqued


Mar 22, 2006, 3:51 PM
Post #29 of 41 (4762 views)
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Yes, of course we always try . While the force on the harness may never reach 15kN, the force on the top piece can, as you said. And 15kN is the breaking strength. You can start ripping cams at much lower forces. Seems to me, if you're on a very runout pitch, and take a big factor-two fall on an all-cam anchor, you stand a very good chance of ripping some or all of your anchor placements. And that's scary.

It should be scary, but it is still not a good chance. Your belayer, ATC, GriGri, etc will not hold up it's end of the bargain most of the time. The brake end of the rope must kink, loop or get caught somewhere in order to prevent slippage and therefore reduction in force on the belay anchors to (2-friction)* (slip load). Common lit numbers 2-5kN. (Tom Moyer reported 1800 lbs (8kN) of slip load for an ATC with an iron shackle, not a biner, held with both hands with gloves on. )

Something must cause a static belay for these fearsome FF2 forces to appear. Wanna stack your rope nicely now?


ridgeclimber


Mar 22, 2006, 6:41 PM
Post #30 of 41 (4762 views)
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I don't know about you, but my rope has a hell of a lot of kinks and loops. If your point about that is correct, I don't want it killing me. My point is that these nasty FF2 forces can happen. And when they do, cam anchors can start ripping.


clmbnski


Mar 23, 2006, 9:16 AM
Post #31 of 41 (4762 views)
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My point is that these nasty FF2 forces can happen. And when they do, cam anchors can start ripping.

A lot of things 'can' happen but think about how likely is it that it will happen.
An anchor wont necessarily rip if it sees a FF2 force. Pro is more likely to pull higher on the pitch where the force on the top piece is ~1.6X max force.

With good equalization it will easily hold a factor 2 fall assuming decent sized pro and an 80kg climber. But equalization is a bit hard to achieve. That is why the sliding x thread is 50 pages long.

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Can a FF2 fall generate this much force? [15kN] It would depend, but I'd venture a guess that it could...

Look at the impact force of the rope, unless you are much heavier than 80kg you are not going to get much over the impact force and on new ropes that can be as low as 9kN

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What about big runouts, or zippering gear? In this case, you can't protect well. What if you zipper your gear and fall directly on to an all cam anchor? You can generate enough force that the entire anchor blows.

You could runout the entire pitch and fall 2 times the length of the pitch and it would generate no more force than climbing up 10 feet and falling 20. Remember the force generated is related to the fall factor which is a ratio.


ridgeclimber


Mar 23, 2006, 12:02 PM
Post #32 of 41 (4762 views)
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You're not going to see forces over the impact force of the rope on the climber, but you can see forces greater than that on the pro.

In reply to:
With good equalization it will easily hold a factor 2 fall assuming decent sized pro and an 80kg climber. But equalization is a bit hard to achieve. That is why the sliding x thread is 50 pages long.

And without equalization, or even with it, you could start ripping pieces. Mainly cams, I'd say.

In reply to:
You could runout the entire pitch and fall 2 times the length of the pitch and it would generate no more force than climbing up 10 feet and falling 20. Remember the force generated is related to the fall factor which is a ratio.

It wouldn't be a huge difference, but it would be significant. You wouldn't generate exactly the same force for all factor 2 falls. You're accelerating at 10m/s2. Until you reach terminal velocity. The rope can only absorb so much.


ridgeclimber


Mar 24, 2006, 11:58 AM
Post #33 of 41 (4762 views)
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And then there's the dynamic rope factor; after a hard fall, it becomes less dynamic. That means more force on your anchor after ripping gear.


ridgeclimber


Mar 24, 2006, 5:45 PM
Post #34 of 41 (4762 views)
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Alright, this doesn't seem to be going anywhere, so we can branch out into general gear failure. I think the max force on the climber for UIAA drop tests is something like 2600 lbs. But the force on the top piece is significantly more than that, plus more if you're heavy. So it would seem like a FF2 fall could generate enough force to break a cam, not merely rip it. So think how easy it must be to rip even a good cam in a really hard fall. It's actually one of the reasons I go for passive pro when I can. Call me crazy....

Anyone have further thoughts on this?


Partner euroford


Mar 25, 2006, 7:34 AM
Post #35 of 41 (4762 views)
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Re: another anchor failure rant [In reply to]
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Yes, anchor failure is rare that you might even call if a freak thing. That doesn't mean you should be complacent about it. No doubt, caution is one of the reasons that it is rare. However, without actually consulting my back copies, I would guess that at least 100 climbers die from head injuries due to rockfall and/or leader falls (most of whom were not wearing a helmet) for every climber killed by anchor failure.

best response so far by a long shot!!


paganmonkeyboy


Mar 25, 2006, 8:41 AM
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My point is that these nasty FF2 forces can happen. And when they do, cam anchors can start ripping.

this would be why you wanna place a piece to protect the belay asap, imho...something to prevent the f2 you'd be getting 20 feet up and popping off trying to get your first piece in...


ridgeclimber


Mar 26, 2006, 3:57 AM
Post #37 of 41 (4762 views)
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Good point, paganmonkey, and that's why it's important to clip the top piece of the anchor to avoid a FF2 directly on the belayer. But the nature of the climb doesn't always allow a piece right above the anchor to safeguard it. Say you've clipped the top piece of the belay anchor, a cam, as your first piece of gear. There's no pro for a while, you run it out 20 ft, and fall. Bang. Almost a FF2 on your cam. The rope limits the force on the climber to under 2600 lbs, but the top piece gets 1.6 times that (because the belayer's below the cam). Say you generate 2300 lbs. 1.6 times this might be enough to break the cam outright and certainly enough to rip it. Now you have seriously compromised your anchor, and now the belayer has to hold a FF2 directly onto his harness, probably injuring himself in some way. Ugly, huh?

EDIT: One more thing. Since some of the rope's dynamic properties are compromised by the first fall, you have major forces on the rest of the anchor.


patto


Mar 26, 2006, 6:36 AM
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Check out this for some good examples concerning impact force.
http://www.impact-force.info/anglais/impact4.html


ridgeclimber


Mar 26, 2006, 8:07 AM
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God. Even with a low factor fall like that, in the first test, belaying with a grigri can generate 14.35 kN on the top piece; enough to break most cams and more than enough to rip them. An ATC generated about 8.5 kN, but imagine the carnage with a hard FF2. Ouch. Thanks for that link patto. That's sobering.


skinner


Mar 26, 2006, 11:56 AM
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I dunno, maybe it's just me.. but I every time I read another anchor thread, I get the feeling that some people must climb in a perfect world where all the anchors are triple redundant and equalized on bomber placements. For me.. this is rarely the case. I am thrilled when I can actually get in such a text book anchor, but the reality is.. that the rock I climb on rarely offers up such an opportunity.
Climbing is dangerous, that's all there is to it. You try to eliminate what danger you can and minimize the rest. There are situations where things like- long run-outs are unavoidable. If this is not an acceptable risk you are willing to take.. don't do it then! You can always back off and go to the pub instead, or.. you can do something to minimize the risk, like employing screamers. Chances are unless you are airborne the entire way down, you will get hurt if you pop off, that's just reality smacking you around a bit to remind you that you can in fact die doing this sport.
Anyone who thinks you can "eliminate" the risks involved in climbing, should consider another sport.. like ping-pong.. don't forget to wear goggles though! :shock:


ridgeclimber


Mar 26, 2006, 6:10 PM
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Absolutely. Climbing is inherently dangerous. And that's a good point about the main danger in falling not being ripping your anchor but hitting stuff on your way down. But visualize the situation I described in the earlier post, or try out that link patto provided. Petzl also has a good fall simulater. That is scary sh-t. I'm not envisioning perfect super-redundant anchors. I'm envisioning worst case scenario anchor failure probably accompanied by DEATH. Your point is taken, though.

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