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billcoe_
Jan 3, 2008, 3:30 AM
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My thoughts are that what Joseph is saying is correct. When you think back to when Friends were new and the only cam on the market, there was all kinds of similar issues with them.
Stems failing in horizontal edges and seemingly good placements failing when fallen on are 2 examples. People accepted their limitations and eventually everyone learned to utilize the tool so it was productive and good.
Those cams are still being made, called Forged Friends, they are made damn near exactly as they were then (colored now). They are one of the more inexpensive cams out there and they are still in use all over the place today. Most people are aware that placing a solid stem Friend in a horizontal pocket and leaving the stem overhanging the cliff edge just sticking out is a poor placement unless you did a Gunks Tie off. It is obvious with a near immediate look at the product. 
However, when new, the things were plugged in exactly that way and usually failed when fallen on. The holes there were originally put in to lighten the product, now folks put a piece of kevlar or tech cord and short tie it to reduce the leverage over an edge like I described.
The point is to utilize the tool so it works for you. Back to Link Cams, you do not want it to have to pivot, just like you do not want a forged friend to be hanging over an edge without tieing it short. Sure, the cam MAY pivot, but it may jiggle to a point where it will not, and a fall on it will put pressure on these pins and points. Now, they've tested this cam 6 ways to Sunday and they fielded tested it for a long time before we could drool all over them in retail stores as well. More than the Forged Friends ever were tested. They hold up and work great for what they are, which is utilization of that magnificent range.
I am actually surprised that there have not been more issues and problems, It seems to me that a lot of newer climbers use this tool. Older climbers have lots of cams and not much need for more, although some of us older gear whores ran out and grabbed a few, but I know lots of experienced dudes who didn't for a variety of reasons. When one doesn't climb a lot, it can be difficult to always grab the correct size, these minimize that issue so that noobs and dudes (like Moi) who are on the couch a lot with business or family obligations love showing up and grabbing the correct piece while sketched and on lead. This is the go-to piece for many new people when it absolutely looks grim on lead. Furthermore, many of this newer generation have no fear of either placement or gear failure and readily yell "take" right after totally trashing out and plugging in that single cam between them and the dirt on what they call "trad" climbs. Plug and slump. Plug and slump. Shake and go again. Shake and go again. "TAKE". (I think this is insane btw, but thats another rant)
Yet for all that, and I see these cams all over the place, we have this single issue.
Reread Josephs post. Just utilize the tool properly. Align the stem when you place it, try to find a good crack that doesn't open up in back, and utilize good runnering so it will not move or walk.
simple.
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billcoe_
Jan 3, 2008, 3:35 AM
Post #252 of 388
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I still may sell mine to pocket the $.
The Metolius cams are significantly lighter, I rarely grab the incorrect one, and I love the fact that when you put one in the rock, it will hold if you fall on it possibly more than any other cam.
The joys of being a gear whore....
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curt
Jan 3, 2008, 3:36 AM
Post #253 of 388
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healyje wrote: ...I'm afraid you're just not getting it - the rotational forces associated with pivoting are exactly what's likely to break the links. If you can't place one of these babies so the stem is [statically] in line with the ancticipated forces of a fall then it's the wrong cam to choose for any such placement. Any rotation of the cam at all is a highly risky affair, particularly in any rock rougher than Creek splitters. Never placing these cams in placements which allow stem leveraging and/or rotation should be the primary takeaway from anyone reading this thread.
Although it's always a good idea to place any cam such that the stem is oriented in the direction of an anticipated fall, the likely failure mechanism for this particular cam (as posited by rgold and based on Vaino Kodas' data) is completely different from the issue of rotation. The likely failure mechanism here was force multiplication due to the flared nature of the placement.
Curt
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healyje
Jan 3, 2008, 4:34 AM
Post #254 of 388
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curt wrote: The likely failure mechanism here was force multiplication due to the flared nature of the placement.
Due to half the cams not holding (being leveraged out) and then having lateral forces applited to the fragile cam lobes / links. Any sideways pressure on the those linked lobes - for any reason - is going to be bad. Rotating or leveraging are simply the two most common ways such loads can be applied to a link cam lobe assemblies. I would be stunned to find out a single solid cam lobe would have broken versus pulled in the same placement if it could be recreated exactly.
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murf
Jan 3, 2008, 3:04 PM
Post #255 of 388
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curt wrote: healyje wrote: ...I'm afraid you're just not getting it - the rotational forces associated with pivoting are exactly what's likely to break the links. If you can't place one of these babies so the stem is [statically] in line with the ancticipated forces of a fall then it's the wrong cam to choose for any such placement. Any rotation of the cam at all is a highly risky affair, particularly in any rock rougher than Creek splitters. Never placing these cams in placements which allow stem leveraging and/or rotation should be the primary takeaway from anyone reading this thread. Although it's always a good idea to place any cam such that the stem is oriented in the direction of an anticipated fall, the likely failure mechanism for this particular cam (as posited by rgold and based on Vaino Kodas' data) is completely different from the issue of rotation. The likely failure mechanism here was force multiplication due to the flared nature of the placement.
Looking at the pictures of the placement, my guy feeling is that something additional happens with multiple of the lobes touching. That is, for example in this picture:
The middle and top lobes are touching on the top, and the middle and lower in the bottom. Of all the placements of these types of cams at JT that I have seem (granted, a very limited number ), I would have difficulty predicting which lobes would take the force of a fall.
-Murf
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dingus
Jan 3, 2008, 3:15 PM
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healyje wrote: I don't need to back it up with anything - all I have to do is look at one of them - that the reality presented when one does is escaping folks like you is beyond me,
Fine. One look is all you need.
DMT
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dingus
Jan 3, 2008, 3:21 PM
Post #257 of 388
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billcoe_ wrote: Back to Link Cams, you do not want it to have to pivot, just like you do not want a forged friend to be hanging over an edge without tieing it short.
Where do you obtain this technical backup behind the 'you do not want it to pivot.'
Because the Omega Pacific response suggests you didn't get it from them.
Is this opinion, as with Joeseph, or is there something more to this?
OP said the cam broke because it could not pivot.
The notion that this cam must be placed exactly perpendicular to the line of force is thus far backed up with 'ALL IT TOOK WAS ONE GLANCE.' Whoo boy, that's some wicked analysis!
Do you have something more?
Cheers and thanks
DMT
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billcoe_
Jan 3, 2008, 4:09 PM
Post #258 of 388
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dingus wrote: billcoe_ wrote: Back to Link Cams, you do not want it to have to pivot, just like you do not want a forged friend to be hanging over an edge without tieing it short. Where do you obtain this technical backup behind the 'you do not want it to pivot.' Because the Omega Pacific response suggests you didn't get it from them.
No, in fact I had said earlier that what they claim to have happened is a stunner that needs to be further examined: ie, that a flared placement can multiply the forces on the cam. As Rgold posted that Cassin where it appears some other unexplained force crushed the lobes on a Cassin cam, well, draw you own conclusions.
We don't have all of the data and facts, I totally agree with you about that. However, I don't think there is anything wrong with changing our behavior until all of the technical details gets sussed out. It was what folks did early on with forged friends for instance. They shared data and stories just like this one, like cam stems breaking in horizontal placements when you fell - and people would act based on what they thought was a best course of action. It may seem obvios to you and everyone in the world now, but it was learned over time. OP had tested for a sizeways force, but not a sideways force in a flared placement I suspect.
At some time, the mfg or someone like Fish, will look and test all this further, until then you have to guess based on available data.
If you chose to ignore all of this and not act in a manner the details appear to suggest, I'm fine with your choice, I will make my choices as well.
Warm regards Dingus!
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dingus
Jan 3, 2008, 4:27 PM
Post #259 of 388
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billcoe_ wrote: If you chose to ignore all of this and not act in a manner the details appear to suggest, I'm fine with your choice, I will make my choices as well. Warm regards Dingus!
Thank you for the well considered response billcoe. I have nothing more to add or qualify.
DMT
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cracklover
Jan 3, 2008, 4:57 PM
Post #260 of 388
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healyje wrote: Baja - great post, thanks for going out and getting us a better look at it all. cracklover wrote: 1 - because of the huge range of the LC, it will almost always be able to pivot better. In *most* cases where I have a blind placement, this is a good thing, 2 - Any piece of gear has its weak point. In the LC, it's the connections between lobes. Cracklover, I would say your points 1 and 2 are in conflict and that exactly because those links are weak is why you don't want these cam to pivoting under any circumstance if you can avoid it.
I don't follow your logic at all. A well placed and slung cam won't rotate out of line with the fall. Whether it's a LC or a standard cam. However, a cam placed blindly or quickly or when you run out of slings, may be placed sideways or get rotated into that position due to rope drag. So what happens when that cam is fallen on? The cam with a much wider expansion range has a better chance of re-orienting itself due to the rope pulling it into line. The standard cam has a higher chance of hitting a constriction that it cannot rotate through.
None of the above has *anything* to do with the cam-to-cam connection point, the weak link. The above basically means that in any case where pivoting into line is a *good* thing (I.E. most of the time) you're better off with a LC.
The point about the cam-to-cam connection being the weakest link is only an issue if that link is so far below the norm that it will *cause* failures, as opposed to having the failure cast upon it. (Every chain has some weakest link, obviously.) As Dingus pointed out, the data that will answer that question is unknown at this point. Though OP's point about their cams lobes being strong certainly suggests that they believe that the weak link is probably strong enough that it will not *cause* failure.
Are you suggesting that the fact that a LC will rotate past obstacles better than a cam with a smaller range somehow *puts* force on the lobe connection point? If so, you need to back that up, as I don't see any reason to think so.
GO
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billcoe_
Jan 3, 2008, 9:11 PM
Post #261 of 388
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cracklover wrote: The cam with a much wider expansion range has a better chance of re-orienting itself due to the rope pulling it into line.
Assuming that is true, (it may or may not be true that these self-align better than other cams) as it's the "go-to" piece for noobs and fat oldsters like me, it got placed blindly and wildly and as the greasing and wailing and knashing of teeth starts at the crux as the fall happens, it doesn't rotate....
now what?
See first post again.
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cracklover
Jan 3, 2008, 9:40 PM
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I'm sorry if I'm being dense, bilcoe_, but I don't get your point. So you place it poorly, and despite the fact that it has a better chance of aligning into a good position, it doesn't, and it fails. I fail to see how you could anticipate a better outcome from another cam.
Or, to put it another way, knowing what we now know (thanks to RG's post) would you want to fall on this poorly oriented Camalot?
I most *definitely* wouldn't.
In short, it still seems to me that the LC is a valid "go to" piece for desperate placements. We just know a little more about its limitations now.
By the way, I don't have a vested interest in that question, as I don't own any LCs myself.
GO
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billcoe_
Jan 3, 2008, 10:25 PM
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cracklover wrote: ...knowing what we now know (thanks to RG's post) would you want to fall on this poorly oriented Camalot? [image]http://i9.photobucket.com/albums/a91/seanismyhero/flaredpods5d.jpg[/image] I most *definitely* wouldn't.
Me either. Thats my point. I think we agree here, put them in correcly oriented and do not expect them to rotate or put in another cam. The Metolius cams, as they have less angle, may not present as much outwards force. I have never heard of one failing like this, ever. I suspect testing will bear some what we see in the real world out, but as Dingus says, it's just speculation right now. Metolius cams have been around for a long long time. I heard of somebody taking a free climbing screamer on the smallest aid piece (4kn rating) and it failed, but otherwise, they don't.
(as Bava java posted- and thanks for the great pics too)
"In the same pod, the Link Cam can also be placed with the stem down: too)
The stem-down placement went in with a nice fit. Not tricky or anything, compared to the straight-in placement. It's there. And the narrowing lower half of the pod can be seen to offer a nice constriction. The stem-down placement didn't budge when yanked, and I didn't see any reason it'd pull given how well the lobes sat inside the pod in that orientation, with stem straight down. "
Lots of words for a small point, and sometimes ya just got to plug and go or you'll be flying, thats when I'd try for the Metolius or BD (or Alien, either CCH or the new Metolius ones coming out this month).
I agree with Dingus, like to see more testing in flares. Till then, this is but a minor unusual and interesting blip, and life goes on eh?
Take care
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philbox
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Jan 3, 2008, 10:55 PM
Post #264 of 388
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The only time I have ever had a linkcam slip in a crack was when I placed it in a parralel sided crack. The hinge joint was in contact with the crack sides, the linkcam slid down the crack until it got a little wider and then it held. At the time I made a note to never ever place the cam such that those hinge joints were the principle point of contact with the rock surface. I had reported this somewhere as well and I can dig this up given enough time.
Since then I have stuck to that philosophy. I also attempt adhere to placing cams in the direction of fall and also place draws on them and if out of line will go so far as to place extended trad draws so that the rope does not affect the placement.
Good job on the huge picture analysis, very helpful.
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healyje
Jan 3, 2008, 11:10 PM
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dingus wrote: Where do you obtain this technical backup behind the 'you do not want it to pivot.' Because the Omega Pacific response suggests you didn't get it from them.
Michael says it back near the top of page 6...
michaellane wrote: In reply to: healyje: I strongly disagree with OP if they are saying it would be alright if only the stem had been free to rotate - you might get away with it, but it's a inherently a bad idea to allow the stem to rotate the head under any circumstance as far as I'm concerned. I agree, Joe ... it's not a good practice to place cams poorly and hope they align properly during the fall. What I tried to say was that had this cam been placed at that same angle in a feature which permitted greater rotation of the cam head as the unit came under load, it may have "self-corrected" without issue. But absolutely not ... we don't suggest that placing cams with the assumption or expectation that they'll rotate into proper placement is acceptable. It is always best to place cams deliberately and carefully so that they are properly oriented in direction of load if you fall. Nearly all the time, that means the stem points to the ground and the head is perpendicular to the stem. If that's not always possible, then you have to assess how far "off" that ideal is acceptable. --ML
dingus wrote: OP said the cam broke because it could not pivot.
OP's point was, that it broke because because it could not pivot... - to relieve the lateral pressures on the cam lobe assemblies - i.e. generated by stem leverage. The clear and inherent risk in pivoting / rotating is that if that fragile cam lobe assembly encounters an obstacle in its attempt to rotate - say a small, but significant crystal, peeble, or ridge - then it is going to suddenly brake the rotation and likely break the cam lobe or link.
dingus wrote: The notion that this cam must be placed exactly perpendicular to the line of force is thus far backed up with 'ALL IT TOOK WAS ONE GLANCE.' Whoo boy, that's some wicked analysis!
How's this for wicked analysis? Hold a Link Cam in one hand and with the other take a standard pair of pliers to the end of one of the outer linked lobes. Now, how much lateral pressure would you suppose would be required to break one of those links? My curiosity in any such analysis is primarily centered on the pliers - would I actually need them? Or, could I just break the links with my bare hands fingers?
[ Edit: But I'd still completely trust one in a clean placement... ]
(This post was edited by healyje on Jan 4, 2008, 7:52 AM)
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santoshi
Jan 4, 2008, 6:24 AM
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I found one cracked on my rack and promptly returned all my link cams to REI. Its a good time to sell OP stock.
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medicus
Jan 4, 2008, 7:43 AM
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santoshi wrote: I found one cracked on my rack and promptly returned all my link cams to REI. Its a good time to sell OP stock.
You selling that stock? I'd buy now.
"I found one cracked on my rack... I was in a car crash and my entire rack flew 200 feet before it hit a guard rail, but I'm not sure how it got cracked"
Honestly, finding a cam cracked on your rack does not warrant the downfall of a company.
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blondgecko
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Jan 4, 2008, 9:43 AM
Post #268 of 388
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healyje wrote: How's this for wicked analysis? Hold a Link Cam in one hand and with the other take a standard pair of pliers to the end of one of the outer linked lobes. Now, how much lateral pressure would you suppose would be required to break one of those links? My curiosity in any such analysis is primarily centered on the pliers - would I actually need them? Or, could I just break the links with my bare hands fingers? [ Edit: But I'd still completely trust one in a clean placement... ]
Pliers perhaps. No way are you going to do anything to one of those suckers with your bare hands.
(and yes, I just tried).
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healyje
Jan 4, 2008, 10:59 AM
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blondgecko wrote: Pliers perhaps. No way are you going to do anything to one of those suckers with your bare hands. (and yes, I just tried).
Now that's the spirit! Did you chuck up a pair of pliers to at least get a feel for it all? And you've now at least looked at one close thinking about it - what's your thought on the amount of force it would take to break one of those links - are they fragile, 'normal', or burly in you opinion?
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blondgecko
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Jan 4, 2008, 12:00 PM
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Well, I don't have any pliers, but I extended a lobe out to full stretch, and then did my level best to rip it apart. Ended up with nothing but sore fingers - didn't even see any real deflection, let alone deformation.
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healyje
Jan 4, 2008, 12:12 PM
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Cool, good report, I'll give the same a whirl later today - and the plier test, will have to wait for my daughter to get home to video it and we'll see. So, you're vote is for 'normal' or burly? I guess it's time to bust out the HPDTL (human powered destructive testing lab) and see what one of the rascals will tolerate in the hands of a believer.
Bill, wanna break cams with me to keep me honest (this may prolong the timeframe)...?
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blondgecko
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Jan 4, 2008, 12:37 PM
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healyje wrote: Cool, good report, I'll give the same a whirl later today - and the plier test, will have to wait for my daughter to get home to video it and we'll see. So, you're vote is for 'normal' or burly? I guess it's time to bust out the HPDTL ( human powered destructive testing lab) and see what one of the rascals will tolerate in the hands of a believer. Bill, wanna break cams with me to keep me honest ( this may prolong the timeframe)...?
Well, I'm not going to claim to be anywhere near strong enough to give it a "burly" rating - but I do have a wonderful imprint of a cam lobe on my palm at the moment! Un-augmented human power (at least the power of this puny human) definitely doesn't make a dent on this guy.
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billcoe_
Jan 4, 2008, 3:33 PM
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healyje wrote: Bill, wanna break cams with me to keep me honest ( this may prolong the timeframe)...?
Cool JH! Thanks for the invitation. Wait.....as I own link cams and you don't....oh.... -sorry, just remembered that I'm busy!
Well, I don't know how destroying one would pliers would correlate to climbing falls, but I'd love to get in on building or buying a hydrolic pull-testing device that would test some of these cams in a flared placement.
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healyje
Jan 4, 2008, 9:38 PM
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Bill, I'm on my way out to buy a victim right now. I'm less interested in the flare issue as I don't think it's a great application for these relative to loading one side of a linkage and not the other. As for the pliers, I just want to feel (repeat, feel) just how much force it takes to break / fracture one and I still suspect the answer is, not much. Still want to try and break one fingers only but blondegecko is probably as strong as I am.
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baja_java
Jan 4, 2008, 11:58 PM
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i've fractured one, with bare hands. not joking. i'm very strong. mighty climber. powerful lover
and yes, have sent details, photos, and the fractured cam to Omega Pacific. likely more findings and info to come
and no, wasn't done with a pair of pliers. the Link Cam's steel joint flanges are likely not that flimsy. true, can't say with absolute certainty. more comprehensive testing would be great. but for now, we do have the some informal test results not only from Michael at Omega Pacific:
michaellane wrote: We have tested the assembled links for what we call "over-edge" strength. That is, we set up a perpendicular force on one end of a set of outstretched links with the opposite end anchored, stressed over an obstacle, or edge at the mid-points to test the ultimate strength of the hinge points. For comparison, we also purchased and disassembled competitors' cams (four different brands representing all other major players in cams on the market today) and tested their solid, single-piece lobes in the same manner. Our linkage assemblies fail right in the center of the four other brands: some broke at greater levels of force and some broke at lower levels. We performed multiple tests for each brand. You'll have to trust me that these were brands we all know and trust. Deservedly so, I should add, as none of these failed at levels that would alarm anyone.
but also from Malcolm at Trango (a competitor of OP):
maldaly on Supertopo regarding Link Cam incident wrote: For what it's worth, we tested a bunch of our cams and all of our competitor's cams in an off-axis pull while we were developing them. We wanted to know how they performed if the cams were jammed at an angle and then pulled straight. Basically we simulated the placement in this discussion. Our test fixture is a steel box with steel shims that can be stacked to adjust the width. The face plates, the ones that hold the cam, are faced with a variety of rock types and a range of roughness. What we did was put a spacer in the bottom of the box to hold one side of the cam. When the force was applied the cams was essentially fixed at an angle (about 25°) so there were all kinds of weird loads applied. In all cases, the cams were placed at 75% of their maximum range. In other words, a really, really crappy placement. Surprise, surprise, the Link Cam was the strongest of the bunch and all but one brand went to the cam's minimum rated strength. I won' tell you which cam didn't meet their spec but you could have knocked me over with a feather when I saw the results. Unfortunately this was just one test, there is no standard for this test and we used a very, very small sample set so the results may not be statistically significant. What I think is significant is that all cams are pretty damn strong when blocked in an off-axis pull. For the most part a cam in a placement like the one in question should hold a good load. |
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