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el_layclimber
Mar 4, 2009, 6:58 AM
Post #51 of 177
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I am going to number the pictures above here 1-8, starting at the top.
In pic #2 above, there are scrapes on the outside, non-contact face of the cam. How did that get there? That should not have happened in a normal placement or fall.
Imagining the forces that would cause the cam to bend as in pics 3,4, 7 and 8 it seems as if the cam had forces applied to it in the opposite direction that they should in a fall. Imagine putting the cam in a vice until it was crushed - it should have bent the other way.
Pics 5 and 6 show a nick to the bottom/inside edge of the cam lobe - again, this part of the cam should not come in contact with the rock. If we imagine the cam in an overcammed position in a crack, the forces that would be applied could explain why the cam is bent contrary to the expected direction.
These two pics also show another view of the nick on the outside (non-functional) face of the cam.
I think this is a case of user error. Camming devices are deceptive in that they appear easy to use and seem to cover a wide range in smaller sizes is actually similar to that of a nut or hex, and requires a great deal of expertise to place properly.
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ersatz_radio
Mar 4, 2009, 7:32 AM
Post #52 of 177
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vegastradguy wrote: btw- the pictures from the top definitely show major deformation of the axle...definitely send the cam back to OP.
Don't think this is the case. Ignore the springs and just look at the nuts at the end of the axle and the part in the center where the cable attaches. They appear to be straight. The springs create the illusion of a bent axle because they are not parallel to the axle.
If it was bent, it would be bent in the opposite direction of the way it appears to be bent. The outer lobes would have more torque on the axle and it would bend so that the outer lobes spread and the inner lobes come together. Go look at the camalot pull test thread to see what I mean.
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rightarmbad
Mar 4, 2009, 12:08 PM
Post #53 of 177
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This may just be a case of the cam slipping when placed exactly on the join between the 2 lobes, have witnessed that myself in slippery rock. But the cam did grab after it slipped to a slightly different place.
What puzzles me is that the contact points are not symmetrical, causing me to think that this placement was biased to one side to begin with.
All manufacturers warn against this type of error.
Really do need placement pictures to draw any meaningful conclusions.
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vegastradguy
Mar 4, 2009, 4:36 PM
Post #54 of 177
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ersatz_radio wrote: vegastradguy wrote: btw- the pictures from the top definitely show major deformation of the axle...definitely send the cam back to OP. Don't think this is the case. Ignore the springs and just look at the nuts at the end of the axle and the part in the center where the cable attaches. They appear to be straight. The springs create the illusion of a bent axle because they are not parallel to the axle. If it was bent, it would be bent in the opposite direction of the way it appears to be bent. The outer lobes would have more torque on the axle and it would bend so that the outer lobes spread and the inner lobes come together. Go look at the camalot pull test thread to see what I mean.
after a second look, you might be right- although, i have to say that despite not being an engineer, this cam doesnt look kosher to me- just seems like theres a little too much with it that isnt aligned.
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shoo
Mar 4, 2009, 5:02 PM
Post #55 of 177
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el_layclimber wrote: In pic #2 above, there are scrapes on the outside, non-contact face of the cam. How did that get there? That should not have happened in a normal placement or fall.
I suspect that the cam actually rolled over while it failed. We know that the cam was not pulled in the direction in which it was set. The placement was likely about as thick as the expansion of the cam. When pulled sideways, an edge of the cam caught before the cam could swivel, causing it to roll. The side edges may have had some contact with the crack after the roll, and may even have "caught" a little, scraping the side and squeezing the outer lobes to the center.
In any case, without a picture of the placement and a clear picture of the fall, this is worthless.
Furthermore, Navy fell out of the direction of pull. This is poor placement, not poor construction.
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billcoe_
Mar 4, 2009, 5:21 PM
Post #57 of 177
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jt512 wrote: Kerwin, that is a very elitist attitude. This is America. This is a democracy. Anybody can make climbing equipment, anybody can test climbing equipment, and so can anybody else. You, on the other hand, seem to be implying that it would be preferable for such tasks to actually be undertaken by individuals possessing relevant knowledge, training, and skill. You should be praising USNavy for the effort he has put into contributing to the climbing community, not castigating him for no other reason than his results were meaningless. Haven't you ever heard of giving an A for effort? Jay
Hi JT! Welcome back. Curt was doing the heavy lifting while you were slacking off.
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patmay81
Mar 4, 2009, 6:16 PM
Post #58 of 177
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curt wrote: billcoe_ wrote: Valarc wrote: His "data" is damn-near meaningless and he's trying to use it to paint a doom-and-gloom picture of Link Cams. It's unfair to OP and insulting to the intelligence of the RC.com reader, whether that reader "presents data" or not. And yet, although incomplete, it is more information than you had yesterday..... Thanks for starting down the road Navy. I just flipped a coin and it came up heads. You now have even more information than you had yesterday. Curt
this is not new information to me, or most people who have been climbing for a while. but it could be new to someone. The only thing I would admonish USN for is his presentation of the information as a factual test, rather than a "hey this cam failed, and this one didn't in this specific placement".
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k.l.k
Mar 4, 2009, 6:35 PM
Post #59 of 177
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jt512 wrote: k.l.k wrote: This is fuckin bullshit, if the Knob is going to post this stuff then it's just Jackass for n00bs, and this thread has zero empirical content. Kerwin, that is a very elitist attitude. This is America. This is a democracy. Anybody can make climbing equipment, anybody can test climbing equipment, and so can anybody else. You, on the other hand, seem to be implying that it would be preferable for such tasks to actually be undertaken by individuals possessing relevant knowledge, training, and skill. You should be praising USNavy for the effort he has put into contributing to the climbing community, not castigating him for no other reason than his results were meaningless. Haven't you ever heard of giving an A for effort? Jay
I apologize.
I retract my earlier comments and congratulate USN on having found his true vocation as a crash test dummy.
I applaud the efforts of the many posters on this site who have not been disempowered by their inability to acquire any sort of competence in climbing, and who are not intimidated by their complete lack of training, technical expertise or aptitude for math, mechanics, or even armchair engineering but who nonetheless show us the power of the human spirit by hurling their bodies onto random bits of poorly placed gear as a way of rising to the top.
I believe that we should recruit an army of Knobbers to march out into the great outdoors, design appropriate victory whippers from the nearest bridge/sport crag/grain elevator/water tower, and test, for the benefit of all of us, the ability of their harnesses to withstand an FF2.
In the name of Science.
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hafilax
Mar 4, 2009, 6:43 PM
Post #60 of 177
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I've got a great over-unity design that needs testing. It will make cold fusion look like polywater.
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jdefazio
Mar 4, 2009, 7:02 PM
Post #61 of 177
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patmay81 wrote: The only thing I would admonish USN for is his presentation of the information as a factual test, rather than a "hey this cam failed, and this one didn't in this specific placement".
Agreed, but he basically trashed OP in the process which was not remotely merited.
What is also concerning, since Navy is presenting this as an objective test, is that when the notion of a poor placement as a mechanism for the damage first comes up,
USnavy wrote: Thats not something that could happen from that minor of a fall, especially when the piece pulls.
Stating his notion of how he thinks it should work.
But then again, after it is mentioned that he is ignoring the very real possibility of placement-related torque putting very large forces on the cam,
USnavy wrote: It’s impossible for the Link Cam to have held a higher impact force because the cam did not yield to the full force of the fall like the C4 did
So rational arguments against Navy's idealization of how the cam should pull are ignored, and the same answer comes out. "That could not happen. That is impossible." With no new argument besides "it doesn't fit with my ideas." I suspect no matter how many times facts are pointed out they will simply bounce off without register because they don't fit into Navy's perception of how it should work.
Not making any direct comparisons, mind you, but this is typically the mindset of crackpots and the like who give you things like "chemtrails", "9/11 was an inside job", and "intelligent design".
/jd
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cracklover
Mar 4, 2009, 7:38 PM
Post #62 of 177
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USnavy wrote: cracklover wrote: It sure sounds, though, like the direction of the fall line was not the same as the orientation of the cam. In such a situation, a fall of factor .3 is *not* a minor fall, as far as the the impact on the cam is concerned. It sounds like the BD cam had two of its lobes ripped out of the placement, such that the final position in which it caught the fall was more in line with the fall line. The cams were orientated in the direction of the anticipated fall. Falling from a distance where my feet was only slightly over the cam with about 25 feet of rope out is a minor fall.
You originally stated that the FF was .3, and that the total freefall distance was 9 feet. That would mean that you fell with 30 feet of rope out. You are now stating that you fell with 25 feet of rope out. Either you miscalculated the fall factor (it's closer to .4 than .3) or else one of your other figures is off.
Assuming the freefall really was 9 feet over 25 feet of rope, as you now state, I change my estimation of the peak force on the sling to around 6.5kN or 1,500 lbs.
Again, if the cam was torqued due to something you did not anticipate about either the placement or the fall (you state that the cams were placed in line with the anticipated force, but also that the BD cam rotated 45 degrees) then that 6.5kN force in the direction of pull could result in very high forces at the individual lobes.
GO
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cracklover
Mar 4, 2009, 7:56 PM
Post #63 of 177
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Actually, I believe that this test *does* show something, but not what the tester supposes.
What it really proves is that placing cams actually isn't the no-brainer that most climbers think it is. Furthermore, the only way to gain useful knowledge about what makes an adequate cam placement versus one likely to fail, is to place a lot and test them with significant forces. (Edited to add - you don't need human falls to generate these forces!) I suspect that someone with sufficient knowledge could have looked at the placements made by the OP and anticipated some of the problems that resulted.
I learned this lesson accidentally. When the poor QC of CCH Aliens became known, I designed a simple but effective test for all my Aliens, to determine that all were able to hold moderate falls. The test used a fuse of a known breaking strength (some were tested at 3-4kN, while other batches were tested at 4-5).
Well the first thing I discovered was that many of my placements ripped out before the fuse broke! It took some time to develop an eye sufficiently good to recognize a placement and seat it properly to get the cam to hold on the first drop, every time.
Here's some video of one of the tests, in case any of you are curious.
http://www.youtube.com/watch?v=jMeGtWjmS54
Cheers,
GO
(This post was edited by cracklover on Mar 4, 2009, 7:58 PM)
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angry
Mar 4, 2009, 8:02 PM
Post #64 of 177
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jt512 wrote: k.l.k wrote: This is fuckin bullshit, if the Knob is going to post this stuff then it's just Jackass for n00bs, and this thread has zero empirical content. Kerwin, that is a very elitist attitude. This is America. This is a democracy. Anybody can make climbing equipment, anybody can test climbing equipment, and so can anybody else. You, on the other hand, seem to be implying that it would be preferable for such tasks to actually be undertaken by individuals possessing relevant knowledge, training, and skill. You should be praising USNavy for the effort he has put into contributing to the climbing community, not castigating him for no other reason than his results were meaningless. Haven't you ever heard of giving an A for effort? Jay
OK, who stole Jay's computer?
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shimanilami
Mar 4, 2009, 8:15 PM
Post #65 of 177
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jt512 wrote: k.l.k wrote: This is fuckin bullshit, if the Knob is going to post this stuff then it's just Jackass for n00bs, and this thread has zero empirical content. Kerwin, that is a very elitist attitude. This is America. This is a democracy. Anybody can make climbing equipment, anybody can test climbing equipment, and so can anybody else. You, on the other hand, seem to be implying that it would be preferable for such tasks to actually be undertaken by individuals possessing relevant knowledge, training, and skill. You should be praising USNavy for the effort he has put into contributing to the climbing community, not castigating him for no other reason than his results were meaningless. Haven't you ever heard of giving an A for effort? Jay
We have officially entered the Twilight Zone. (Note my new signature.)
(This post was edited by shimanilami on Mar 4, 2009, 8:50 PM)
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jt512
Mar 4, 2009, 8:29 PM
Post #66 of 177
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cracklover wrote: Actually, I believe that this test *does* show something, but not what the tester supposes.
What we can learn from the test is that, based on a sample size of 2, the probability of a cam failing in a poorly characterized "marginal placement" in response to an unmeasured impact force is 0.500 ± 0.487¹; that is, roughly speaking, somewhere between 0 and 1.
Before the test, most competent climbers knew not to trust marginal placements; however, based on these results, I don't think we can make such a blanket statement anymore—the confidence interval is just too wide. It seems that the test may actually have subtracted from our body of knowledge.
Jay
_____________
¹Mean ± 95% confidence interval.
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sungam
Mar 4, 2009, 8:34 PM
Post #67 of 177
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I'm taking 0 as confidence that it will hold, but can it go lower then that?
Confidence that it will not hold, meaning negitive confidence that it will hold?
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angry
Mar 4, 2009, 8:40 PM
Post #68 of 177
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jt512 wrote: cracklover wrote: Actually, I believe that this test *does* show something, but not what the tester supposes. What we can learn from the test is that, based on a sample size of 2, the probability of a cam failing in a poorly characterized "marginal placement" in response to an unmeasured impact force is 0.500 ± 0.487¹; that is, roughly speaking, somewhere between 0 and 1. Before the test, most competent climbers knew not to trust marginal placements; however, based on these results, I don't think we can make such a blanket statement anymore—the confidence interval is just too wide. It seems that the test may actually have subtracted from our body of knowledge. Jay _____________ ¹Mean ± 95% confidence interval.
And he's back
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adatesman
Mar 4, 2009, 9:28 PM
Post #69 of 177
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USnavy
Mar 4, 2009, 9:35 PM
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cracklover wrote: USnavy wrote: cracklover wrote: It sure sounds, though, like the direction of the fall line was not the same as the orientation of the cam. In such a situation, a fall of factor .3 is *not* a minor fall, as far as the the impact on the cam is concerned. It sounds like the BD cam had two of its lobes ripped out of the placement, such that the final position in which it caught the fall was more in line with the fall line. The cams were orientated in the direction of the anticipated fall. Falling from a distance where my feet was only slightly over the cam with about 25 feet of rope out is a minor fall. Again, if the cam was torqued due to something you did not anticipate about either the placement or the fall (you state that the cams were placed in line with the anticipated force, but also that the BD cam rotated 45 degrees) then that 6.5kN force in the direction of pull could result in very high forces at the individual lobes. GO
What do you mean by "torqued"?
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cracklover
Mar 4, 2009, 9:52 PM
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USnavy wrote: cracklover wrote: USnavy wrote: cracklover wrote: It sure sounds, though, like the direction of the fall line was not the same as the orientation of the cam. In such a situation, a fall of factor .3 is *not* a minor fall, as far as the the impact on the cam is concerned. It sounds like the BD cam had two of its lobes ripped out of the placement, such that the final position in which it caught the fall was more in line with the fall line. The cams were orientated in the direction of the anticipated fall. Falling from a distance where my feet was only slightly over the cam with about 25 feet of rope out is a minor fall. Again, if the cam was torqued due to something you did not anticipate about either the placement or the fall (you state that the cams were placed in line with the anticipated force, but also that the BD cam rotated 45 degrees) then that 6.5kN force in the direction of pull could result in very high forces at the individual lobes. GO What do you mean by "torqued"?
It was pulled in such a way as to produce rotation or torsion on the piece.
GO
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cracklover
Mar 4, 2009, 10:00 PM
Post #72 of 177
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jt512 wrote: cracklover wrote: Actually, I believe that this test *does* show something, but not what the tester supposes. What we can learn from the test is that, based on a sample size of 2, the probability of a cam failing in a poorly characterized "marginal placement" in response to an unmeasured impact force is 0.500 ± 0.487¹; that is, roughly speaking, somewhere between 0 and 1. Before the test, most competent climbers knew not to trust marginal placements; however, based on these results, I don't think we can make such a blanket statement anymore—the confidence interval is just too wide. It seems that the test may actually have subtracted from our body of knowledge. Jay _____________ ¹Mean ± 95% confidence interval.
Ha! But no, I'm serious. It's possible that anyone would have looked at the placements and considered them marginal. But it seems equally possible that the OP, and many others, might have thought the placements to be "fine".
Cams, especially small cams, are not as simple to place well as most people think. Unfortunately, two drops is only enough to discover that you don't know what you think you know, it's not enough to start learning something new.
GO
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ryanb
Mar 4, 2009, 10:38 PM
Post #73 of 177
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jt512 wrote: cracklover wrote: Actually, I believe that this test *does* show something, but not what the tester supposes. What we can learn from the test is that, based on a sample size of 2, the probability of a cam failing in a poorly characterized "marginal placement" in response to an unmeasured impact force is 0.500 ± 0.487¹; that is, roughly speaking, somewhere between 0 and 1. Before the test, most competent climbers knew not to trust marginal placements; however, based on these results, I don't think we can make such a blanket statement anymore—the confidence interval is just too wide. It seems that the test may actually have subtracted from our body of knowledge. Jay _____________ ¹Mean ± 95% confidence interval.
Assume that the placement was not just "marginal" but also suitably marginally distributed and apply Bayes' theorem.
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Valarc
Mar 4, 2009, 10:57 PM
Post #74 of 177
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cracklover wrote: USnavy wrote: What do you mean by "torqued"? It was pulled in such a way as to produce rotation or torsion on the piece.
Erm, US... If you don't even know what the word "torque" means, perhaps you aren't the best choice of person to be testing gear.
I'm not SAYIN', I'm just sayin'
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ladyscarlett
Mar 4, 2009, 10:59 PM
Post #75 of 177
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Sorry, as the a newbie I shouldn't throw stones at the glass house, but really....
jt512 wrote: Haven't you ever heard of giving an A for effort? Jay
Is this like the trophy for participation that the non winning team gets, or school award for good attendance?
Effort gets you the privileged of participating, A's are only for those who both try and succeed above and beyond, I've been constantly told.
USNavy's efforts mean that he now gets to be a subject for discussion, and allowed to participate - but doesn't make what he has to say any more or less valid...the results must speak for themselves. In this case? That would be for all you experts to decide.
On the newbie perspective.. learning interesting stuff about cams...and the viability of a conclusion made off a single data point...,I love seeing science determine what it "good." I learn lots...
cheers
ls
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.... 
