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What determines the rate at which a cam will rip out?
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Onlyoriginal


Sep 26, 2012, 2:19 AM
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What determines the rate at which a cam will rip out?
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Is there anything when buying a piece of protection, that shows when it will rip out of the wall?
Like how much force is needed to pull it outa the wall?

Does the strength of the protection have anything to do with this?


jowybyo


Sep 26, 2012, 5:15 AM
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Re: [Onlyoriginal] What determines the rate at which a cam will rip out? [In reply to]
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No....the force required to fail a placement is based on the strength of the rock, the friction between the rock and the gear, and the overall quality of the placement itself.

Protection does come with a rating for it's ultimate strength, but this is the force required to break the gear not rip it from rock.

-Joe B.


andrewluke


Sep 26, 2012, 5:15 AM
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Re: [Onlyoriginal] What determines the rate at which a cam will rip out? [In reply to]
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It all depends on the rock.


patto


Sep 26, 2012, 6:14 AM
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Re: [Onlyoriginal] What determines the rate at which a cam will rip out? [In reply to]
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In theory and in most of the time in practice a cam will either pull at very light loads ie a tug with your hand. Or hold until the rock or cam breaks.

The exception is when the cam is close to the threshold of slipping but not at it. In this case a cam may slip at lower loads due to flex and compression of the cam lobes.


Of course if the cam is not aligned with the direction of the fall and moves when loaded then that can significantly affect outcomes.


acorneau


Sep 26, 2012, 6:24 AM
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Re: [Onlyoriginal] What determines the rate at which a cam will rip out? [In reply to]
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One should also mention that it has been shown that even for the most bomber of placements most will only hold ~10kN before ripping out.


USnavy


Sep 26, 2012, 9:38 AM
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Re: [patto] What determines the rate at which a cam will rip out? [In reply to]
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patto wrote:
In theory and in most of the time in practice a cam will either pull at very light loads ie a tug with your hand. Or hold until the rock or cam breaks.
I dont know what theory you are studying. Every cam I have ever pulled on a bounce test while climbing aid held static bodyweight. It was not until I started bounce testing the piece that it pulled. Also, most of the cams I have ripped on a fall would have likely held bodyweight as in most cases I could feel the piece tug on the rope before ripping. But, many of those cases involved the rock breaking right under the lobes, so I guess that would fall into your exception clause. Anyway, just because a piece will withstand a tug from your hand does not mean it will arrest a lead fall.


(This post was edited by USnavy on Sep 26, 2012, 9:41 AM)


Partner cracklover


Sep 26, 2012, 9:58 AM
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Re: [patto] What determines the rate at which a cam will rip out? [In reply to]
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patto wrote:
In theory and in most of the time in practice a cam will either pull at very light loads ie a tug with your hand.

In theory, perhaps, but in practice, this couldn't be more wrong. Tons of placements look anywhere from bomber to scary-as-fuck, and will hold more than a hard tug, but less than full strength.

GO


petsfed


Sep 26, 2012, 10:12 AM
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Re: [cracklover] What determines the rate at which a cam will rip out? [In reply to]
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cracklover wrote:
patto wrote:
In theory and in most of the time in practice a cam will either pull at very light loads ie a tug with your hand.

In theory, perhaps, but in practice, this couldn't be more wrong. Tons of placements look anywhere from bomber to scary-as-fuck, and will hold more than a hard tug, but less than full strength.

GO

And this is due almost entirely to the coefficient of friction changing following the destruction of the rock's surface when the cam is loaded.

Patto is not wrong, its just that confirmation bias and a complex reality tend to obscure the theory he's pointing out. The point was that if you look only at the tangent angle and how close the crack is to parallel, but ignore the rock quality of the placement, you'll get a bimodal failure distribution, with peaks at fall-strength and light-tug-with-your-hand. That doesn't mean there isn't a gray area, just that what puts a placement into that gray area has a lot to do with the rock quality. That is, a placement that might fail well above a body-weight load in good, high friction rock might fail at well below body-weight in slick or crumbly rock. If you only compare similarly hard rock, then cams placed in the rock with the higher coefficient of friction will fail less than those in slicker rock in otherwise identical placements.


Partner cracklover


Sep 26, 2012, 11:07 AM
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Re: [petsfed] What determines the rate at which a cam will rip out? [In reply to]
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petsfed wrote:
cracklover wrote:
patto wrote:
In theory and in most of the time in practice a cam will either pull at very light loads ie a tug with your hand.

In theory, perhaps, but in practice, this couldn't be more wrong. Tons of placements look anywhere from bomber to scary-as-fuck, and will hold more than a hard tug, but less than full strength.

GO

And this is due almost entirely to the coefficient of friction changing following the destruction of the rock's surface when the cam is loaded.

Patto is not wrong, its just that confirmation bias and a complex reality tend to obscure the theory he's pointing out. The point was that if you look only at the tangent angle and how close the crack is to parallel, but ignore the rock quality of the placement, you'll get a bimodal failure distribution, with peaks at fall-strength and light-tug-with-your-hand. That doesn't mean there isn't a gray area, just that what puts a placement into that gray area has a lot to do with the rock quality. That is, a placement that might fail well above a body-weight load in good, high friction rock might fail at well below body-weight in slick or crumbly rock. If you only compare similarly hard rock, then cams placed in the rock with the higher coefficient of friction will fail less than those in slicker rock in otherwise identical placements.

No, it's just plain silly. You're calling an "exception" nearly every single fall that happens in the real world. I doubt there are many real falls (not counting just slumping onto the piece) that do not cause the cam to either move somewhat, or crack, crush, or dislocate some crystals.

I suspect that the true failure load of cams in the field would be not so much your "bimodal distribution" (with peaks at light tug with your hand and the strength stamped on the cam) but more like a high peak around the rated failure, and then a gradual slope from the strength stamped on the cam down.

There are so many factors that impact the failure strength of the cam, and so many imperfect placements that work "well enough".

GO


(This post was edited by cracklover on Sep 26, 2012, 11:10 AM)


petsfed


Sep 26, 2012, 12:08 PM
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Re: [cracklover] What determines the rate at which a cam will rip out? [In reply to]
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I think anybody experienced in placing gear would agree that simply looking at the geometry of the placement, and not the rock its placed in, would consistently result in bad placements. Patto's statement only refers to the geometry of the placement. So does mine.

The gray area comes from the fact that we're not simply looking for parallel placements when placing cams, but also situations that prevent walking, that have good rock, that don't result in a junk placement if they walk, etc.


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Sep 26, 2012, 2:06 PM
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Re: [petsfed] What determines the rate at which a cam will rip out? [In reply to]
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petsfed wrote:
I think anybody experienced in placing gear would agree that simply looking at the geometry of the placement, and not the rock its placed in, would consistently result in bad placements. Patto's statement only refers to the geometry of the placement. So does mine.

The gray area comes from the fact that we're not simply looking for parallel placements when placing cams, but also situations that prevent walking, that have good rock, that don't result in a junk placement if they walk, etc.

The point I'm trying to make is that all my experience leads me to suspect that many placements (at least for cams roughly an inch and a half or smaller), placements you and I use every day and call good enough, are squarely in that "gray area".

These placements would, if subjected to a serious fall, fail at significantly below the rated strength of the cam. The reasons are myriad, and not worth going into here. The point is that the notion that a cam is either "good" or "bad" in the real world is simply silly and misleading.

Sure, I could find you placements where I'd bet good money that the cam would fail at it's rated strength, but in the real world, such placements are often nothing more than a pipe dream, and we go with what's "good enough".

The only scary thing, to me, is that I bet that most people wouldn't know the difference between a "good enough" placement and a truly bomber one. Fortunately, it rarely matters, since most of us don't go around taking big whippers most of the time.

GO


sween345


Sep 26, 2012, 2:26 PM
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Re: [Onlyoriginal] What determines the rate at which a cam will rip out? [In reply to]
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 Only,

This will explain it....http://www.bigwalls.net/climb/camf/index.html


patto


Sep 26, 2012, 3:45 PM
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Re: [cracklover] What determines the rate at which a cam will rip out? [In reply to]
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cracklover wrote:
No, it's just plain silly. You're calling an "exception" nearly every single fall that happens in the real world. I doubt there are many real falls (not counting just slumping onto the piece) that do not cause the cam to either move somewhat, or crack, crush, or dislocate some crystals.

It all depends on the situations and the rock you climb. The rock I climb on doesn't have "crystals".

The majority of my trad climbing is done on strong, fine grained homogeneous rock. This minor means that rock failure pretty much wont occur so that rules out one failure mode. Movement isn't a big deal if the crack is fairly regular and the cam is placed very close to the line of fall. This leads smooth slippery cracks as the main failure mode (low coefficient of friction). In practice at this crag most cam failures are of this type.

Contrast this with say course rock climbing. Coefficient of friction here is normally significantly higher so straight forward slipping is rare. Breaking of crystals and ripping out pulling rock with it is the common failure mode.


curt


Sep 26, 2012, 3:54 PM
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Re: [Onlyoriginal] What determines the rate at which a cam will rip out? [In reply to]
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Onlyoriginal wrote:
Is there anything when buying a piece of protection, that shows when it will rip out of the wall?
Like how much force is needed to pull it outa the wall?

No.

Onlyoriginal wrote:
Does the strength of the protection have anything to do with this?

No.

Curt


patto


Sep 26, 2012, 4:01 PM
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Re: [cracklover] What determines the rate at which a cam will rip out? [In reply to]
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cracklover wrote:
The point I'm trying to make is that all my experience leads me to suspect that many placements (at least for cams roughly an inch and a half or smaller), placements you and I use every day and call good enough, are squarely in that "gray area".

These placements would, if subjected to a serious fall, fail at significantly below the rated strength of the cam. The reasons are myriad, and not worth going into here. The point is that the notion that a cam is either "good" or "bad" in the real world is simply silly and misleading.

Sure, I could find you placements where I'd bet good money that the cam would fail at it's rated strength, but in the real world, such placements are often nothing more than a pipe dream, and we go with what's "good enough".

The only scary thing, to me, is that I bet that most people wouldn't know the difference between a "good enough" placement and a truly bomber one. Fortunately, it rarely matters, since most of us don't go around taking big whippers most of the time.

GO

Comments like these make me think you climb on really shit rock. I place cams all the way down to the Green ZERO, which is 1/3 of an inch. (Though I haven't falled on greeny.)

Here are some real world tests of trad gear. The sandstone where this gear was placed is renowned for its poor quality for trad gear. (though it isn't as bad as really shitty sandstone.)
http://www.sanguma.org/...ructo/placements.php

Your comments that decent most cams can hole light falls but not big whippers are simply not true for decent cams good rock.


petsfed


Sep 26, 2012, 5:16 PM
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Re: [patto] What determines the rate at which a cam will rip out? [In reply to]
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I can't speak for cracklover, but if you actually believe that all the things you don't have to consider aren't a MAJOR factor in piece quality, then you really need to travel more, or you misunderstood my defense of your statements.


patto


Sep 26, 2012, 5:39 PM
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Re: [petsfed] What determines the rate at which a cam will rip out? [In reply to]
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petsfed wrote:
I can't speak for cracklover, but if you actually believe that all the things you don't have to consider aren't a MAJOR factor in piece quality, then you really need to travel more, or you misunderstood my defense of your statements.

I'm not sure what you mean here... Maybe I wasn't clear in my above statements.

I have travelled a fair bit and climbed in different locations, different countries and on different rock. I've never had gear pull on me when resting on it or falling. I try not to fall too regularly, I took a couple of whippers on cams last time I was in Yosemite.


bearbreeder


Sep 26, 2012, 6:16 PM
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Re: [Onlyoriginal] What determines the rate at which a cam will rip out? [In reply to]
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Onlyoriginal wrote:
Is there anything when buying a piece of protection, that shows when it will rip out of the wall?
Like how much force is needed to pull it outa the wall?

Does the strength of the protection have anything to do with this?

as pointed out the answer is no ...


Partner cracklover


Sep 27, 2012, 8:22 AM
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Re: [patto] What determines the rate at which a cam will rip out? [In reply to]
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patto wrote:
cracklover wrote:
The point I'm trying to make is that all my experience leads me to suspect that many placements (at least for cams roughly an inch and a half or smaller), placements you and I use every day and call good enough, are squarely in that "gray area".

These placements would, if subjected to a serious fall, fail at significantly below the rated strength of the cam. The reasons are myriad, and not worth going into here. The point is that the notion that a cam is either "good" or "bad" in the real world is simply silly and misleading.

Sure, I could find you placements where I'd bet good money that the cam would fail at it's rated strength, but in the real world, such placements are often nothing more than a pipe dream, and we go with what's "good enough".

The only scary thing, to me, is that I bet that most people wouldn't know the difference between a "good enough" placement and a truly bomber one. Fortunately, it rarely matters, since most of us don't go around taking big whippers most of the time.

GO

Comments like these make me think you climb on really shit rock. I place cams all the way down to the Green ZERO, which is 1/3 of an inch. (Though I haven't falled on greeny.)

Here are some real world tests of trad gear. The sandstone where this gear was placed is renowned for its poor quality for trad gear. (though it isn't as bad as really shitty sandstone.)
http://www.sanguma.org/...ructo/placements.php

Your comments that decent most cams can hole light falls but not big whippers are simply not true for decent cams good rock.

I climb on a variety of rock, and make a variety of placements in that rock. I'll just give a few examples:

In even the hardest and most parallel of desert sandstone, I'm absolutely sure that a hard fall on a small cam will cause it to track at least a little. Depending on how deep the cam is (some placements are simply shallow, there's nothing to be done about it) that could mean a ripped placement from a hard fall.

In even the hardest granite, you sometimes must make do with a shallow cam in a pin scar. Expecting these to hold a hard fall is wishful thinking. A buddy of mine recently fell and ripped four such cams from their placements - all of which he thought were truck.

Those are just a couple examples of gear that looks - not perfect, but good enough. And these pieces will certainly hold, but will pull out before they break.

BTW, your link does little to bolster your point. There were only two cams tested, and in both cases, they tracked out, undamaged. In one case, it tracked out even though it was behind a bottleneck, which is the one case where a cam should be absolutely solid. So much for your theory that it either comes out with a tug or hold until it breaks or the rock crumbles.

GO


(This post was edited by cracklover on Sep 27, 2012, 8:24 AM)


patto


Sep 27, 2012, 3:53 PM
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Re: [cracklover] What determines the rate at which a cam will rip out? [In reply to]
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cracklover wrote:
In even the hardest and most parallel of desert sandstone, I'm absolutely sure that a hard fall on a small cam will cause it to track at least a little.
Then the rock isn't hard or it is glassy smooth.

If a small cam (and by small I mean Metolius 0 or below) start tracking then its pretty much all over. If its "tracking" then you are going to have lubricating rock dust. If it is slipping or sliding then the lower kinetic friction will likely mean it will continue.

If you are suggesting that a cam moving out and then stopping is common in cam behaviour then you clearly don't understand the mechanics here. Once a cam moves in the direction of fall then in all likelyhood its not going to stop. (Unless you are talking slight compression movement that is visible on all big cams on even a hand tug.)


cracklover wrote:
In even the hardest granite, you sometimes must make do with a shallow cam in a pin scar. Expecting these to hold a hard fall is wishful thinking. A buddy of mine recently fell and ripped four such cams from their placements - all of which he thought were truck.
Your buddy needs to assess his gear placements better.

cracklover wrote:
Those are just a couple examples of gear that looks - not perfect, but good enough. And these pieces will certainly hold, but will pull out before they break.
No they are not.

cracklover wrote:
BTW, your link does little to bolster your point. There were only two cams tested, and in both cases, they tracked out, undamaged. In one case, it tracked out even though it was behind a bottleneck, which is the one case where a cam should be absolutely solid. So much for your theory that it either comes out with a tug or hold until it breaks or the rock crumbles
One cam tracked out leaving scores in the rock. Ie the rock sheared and failed as mentioned in the comments. The other had a wedged block move and it released the cam.

Onlyoriginal asked a question and I answered by mentioning behaviour in strong cohesive rock. Sure if the rock is really shit failure can occur at lower loads that is long been recognised. But whats your point again?


(This post was edited by patto on Sep 27, 2012, 4:04 PM)


Partner robdotcalm


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patto wrote:
In theory and in most of the time in practice a cam will either pull at very light loads ie a tug with your hand. Or hold until the rock or cam breaks.
.

Earlier testing by Ocean Pacific after the failure of a link cam indicated that tugging on a cam after placement enhanced the holding power of the cam even for poor quality placements. Perhaps this is what's being referred to.

"One interesting thing we noted was how important "setting" the piece was. A simple tug on the gear before it's loaded made a difference in whether the gear held or popped. Even some compromised placements that were spit out when we didn't "set" the piece held fast when the gear was "set" prior to the load”

http://www.rockclimbing.com/..._reply;so=ASC;mh=25;

rob.calm


petsfed


Sep 27, 2012, 6:36 PM
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Ok, now you're waaay off.

In reply to:
If you are suggesting that a cam moving out and then stopping is common in cam behaviour then you clearly don't understand the mechanics here. Once a cam moves in the direction of fall then in all likelyhood its not going to stop. (Unless you are talking slight compression movement that is visible on all big cams on even a hand tug.)

This is a direct result of inhomogeneity of the rock. That is, the rock is not going to have the same coefficient of friction everywhere, and can be affected by a lot of different things. Also, if the rock is not perfectly parallel, then what is insufficient friction for one contact angle may be sufficient friction for another contact angle. It could also be the case that what's causing these short tracking events is that deep in the crack, there's much more lubricating grit, and further out, much less. If you actually believe that the rock will exhibit as much consistency as you claim it does, I've got a bridge I think you might be interested in buying. By and large, cams placed in parallel cracks don't fail, and tracking leads directly to failure. But flaring, shallow, and uneven cracks are where it gets hard and scary, and then all bets are off.

There are climbs in the Moab area of Utah where you can see distinctive tank-tread like marks in the cracks from the shear volume of people whipping on cams in soft rock, and I'd wager a few of those placements failed, but what caused the track marks is the pulverization of the surface, and the movement of the cam to a stronger position.


hugepedro


Sep 27, 2012, 10:45 PM
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O M G

Let's simplify this.

When you were young, did you play with:

1. Legos, Erector Set, and Lincoln Logs (or something similar, I am old, so these specific toys may not be relevant).

or did you play with:

Play Doh, G.I. Joe, and Care Bears

If it was the former, you're probaly ok. If it was the latter, you probably shouldn't be trad climbing.


petsfed


Sep 28, 2012, 12:18 AM
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I played with both.

Strength or weakness?


hugepedro


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petsfed wrote:
I played with both.

Strength or weakness?

You played with Care Bears? That's fabulous.


hugepedro


Sep 28, 2012, 12:34 AM
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petsfed wrote:
I played with both.

Strength or weakness?

No, seriously, I'd say you're prolly ok climbing trad, but I might not want to climb with you and hear all about you're latest existential crisis.


acorneau


Sep 28, 2012, 6:04 AM
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hugepedro wrote:
When you were young, did you play with:

1. Legos, Erector Set, and Lincoln Logs (or something similar, I am old, so these specific toys may not be relevant).

Oh hell yeah!


patto


Sep 28, 2012, 6:35 AM
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petsfed wrote:
Ok, now you're waaay off.
I don't really see how much of that is in conflict with what I have written.

Clearly due to variations in rock particularly in very soft rock movement is possible without totally ripping. But again we are going well into the complex world of friable and variable rock. Not basic cam mechanics.

But on most rock if you cam starts moving and pulverising rock I wouldn't be placing bets on it. Crazy


Partner rgold


Sep 28, 2012, 7:29 AM
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Re: [patto] What determines the rate at which a cam will rip out? [In reply to]
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I'm as or more fond of theory as the next guy, but the elementary theory of cam function is indeed so removed from reality to be of primarily academic interest. It is true, in the elementary theory, that a cam that will hold a tug should hold a big fall, but as has been pointed out over and over, that theoretical result bears no relation to a much more complicated reality.

The problems with the elementary theory begins immediately, with the assumption that there is such a thing as a "coefficient of friction." People write Ph.D. dissertations on the "real" replacements for the naive coefficient of friction concept, which may be appropriate for friction between a pair of highly-polished metal surfaces, but is of questionable relevance for relatively rough aluminum on even rougher rock. The entire concept of coefficient of friction is a convenient empirical observation, but is nothing like a universal physical principle.

Leaving aside the coefficient of friction quaqmire, and assuming some form of solid rock that does not crumble or dispense lubricating micrograins (I'm not sure there is such a form of rock), the failure mode of cams, as anyone who has watched a jig test knows, is due to shear stress failure. The cam surface flattens under pressure, and then the aluminum shears at the contact surface. As a result, in jig tests, one often observes aluminum deposits left on the jig after the cam has failed.

The instant cam deformation begins, which is to say once the lobe material has exceeded its elastic limit, the mathematics involved in describing cam behavior goes out the window and a new analysis is required. This means that, even if the elementary theory is approximately correct for tugging on or just weighting cams, it is no longer even theoretically relevant to cam failure under high loads.

An account of the elementary theory and the sheer stress analysis can be found at http://web.mit.edu/.../cams/cams.body.html


Partner cracklover


Sep 28, 2012, 8:33 AM
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Re: [patto] What determines the rate at which a cam will rip out? [In reply to]
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patto wrote:
cracklover wrote:
In even the hardest and most parallel of desert sandstone, I'm absolutely sure that a hard fall on a small cam will cause it to track at least a little.
Then the rock isn't hard or it is glassy smooth.

Have you ever climbed on good wingate? It sure doesn't seem like you have a clue.

In reply to:
If a small cam (and by small I mean Metolius 0 or below) start tracking then its pretty much all over. If its "tracking" then you are going to have lubricating rock dust. If it is slipping or sliding then the lower kinetic friction will likely mean it will continue.

If you are suggesting that a cam moving out and then stopping is common in cam behaviour then you clearly don't understand the mechanics here. Once a cam moves in the direction of fall then in all likelyhood its not going to stop. (Unless you are talking slight compression movement that is visible on all big cams on even a hand tug.)

As RGold and others have pointed out, you seem to be confused between simple principles and what happens when the rubber meets the road (or real cam meets real rock).

In reply to:
cracklover wrote:
In even the hardest granite, you sometimes must make do with a shallow cam in a pin scar. Expecting these to hold a hard fall is wishful thinking. A buddy of mine recently fell and ripped four such cams from their placements - all of which he thought were truck.
Your buddy needs to assess his gear placements better.
Indeed. But that is exactly my point, and exactly what you are failing to admit. There is a whole range of placements, from garbage to truck. The fact that you won't acknowledge all the ones in the middle does not mean that they do not exist, or that decent climbers don't make such placements all the time. His placements were in the lower to middle part of that range.

Listen to this one more time: every single cam got a hard bounce test (that means it held somewhere in the 1 to 3kN range) but failed under the force of a real fall. According to you, in good Yosemite granite, such a thing should be impossible. My point, for the Nth time, is that there are many many placements that are okay, but not great. They will pull out before the rock or the cam is seriously compromised.

It seems like you have chosen to brainwash yourself into the belief that your gear will always hold a fall, unless that fall is big enough to destroy the piece. I clearly will not convince *you* otherwise, and for everyone else, I'm sure I'm starting to sound like a broken record. So on both counts, I'll give it a rest.

In reply to:
Onlyoriginal asked a question and I answered by mentioning behaviour in strong cohesive rock. Sure if the rock is really shit failure can occur at lower loads that is long been recognised. But whats your point again?

The fact that your black and white version of events does not match reality, and does a disservice to new climbers who are looking for good information.

GO


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