Forums: Climbing Information: Injury Treatment and Prevention: Re: [jt512] Link Cam Report: Edit Log




healyje


Jan 8, 2008, 8:35 AM

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Registered: Aug 22, 2004
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Re: [jt512] Link Cam Report
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jt512 wrote:
... results of tests carried out under controlled conditions.

"Controlled conditions" is the issue from my perspective given these cams are breaking out in the wild. You pretty much have to expect that one of two scenarios is playing out - that they're failing due to forces which are in-line with an axis perpendicular to the axle or, that they're failing due to lateral forces being applied off that axis. If they're failing due to forces in-line with that axis then there are problems with the design or manufacture - this I do not believe, doubly so after my informal test. But if they're failing due to off-axis lateral forces, then it's more like maldaly's comparison to being able to break biner gates so you shouldn't load them that way any more than you would laterally load a biner gate.

I'm guessing the tests done in 'controlled conditions' simply don't adequately address this issue of lateral forces. Rather than try to come up with a whole series of emulations of placements, I'd far rather see them address the question by just laterally breaking some Link Cam lobes and the unsegmented lobes from a variety of other brands and compare the results. That would answer the now generalized question - for off-axis lateral loads - are the segmented Link Cam lobes weaker, comparable, or stronger than unsegmented lobes? I'd rather extrapolate to the wild from that basic generalized test than from a series of poor specific emulations.

[ Edit: And take a close look at this photo (here I will go speculative as I'm no metalurgist) but this plausibly looks like it could be a case where an outward, off-axis lateral force tried to bend the outer flange out from under the axle end cap and that the inner flange, in tension, sheared on that angled plane in response to the sudden failure of the outside flange axle hole (or vice-versa). Speculative? Yes, but plausible - it would be interesting to see OP's metallurgical analysis of the break. ]



Dingus, yeah I made a only slightly exaggerated conjecture for the sake of getting my point across, but that did get my own curiousity up so I felt I might as well give it a whirl (I got a good deal on it). Not that much different than doing onsight FAs after nothing but a quick look - sometimes you get'em, lots of times you don't - but nothing ventured...

Now, if I can corral the right set up I'll have someone blow both that one and a comparable Metolius with a straight lateral force parallel with the axles using one of the inner cams that I didn't wail on.

[ That, and it's now permanently cold, wet and dark up here and Bill and I have piss else to do with ourselves but break shit for awhile... ]


(This post was edited by healyje on Jan 8, 2008, 10:14 AM)



Edit Log:
Post edited by healyje () on Jan 8, 2008, 8:37 AM
Post edited by healyje () on Jan 8, 2008, 8:45 AM
Post edited by healyje () on Jan 8, 2008, 8:45 AM
Post edited by healyje () on Jan 8, 2008, 9:32 AM
Post edited by healyje () on Jan 8, 2008, 9:33 AM
Post edited by healyje () on Jan 8, 2008, 9:35 AM
Post edited by healyje () on Jan 8, 2008, 9:35 AM
Post edited by healyje () on Jan 8, 2008, 10:10 AM
Post edited by healyje () on Jan 8, 2008, 10:11 AM
Post edited by healyje () on Jan 8, 2008, 10:13 AM
Post edited by healyje () on Jan 8, 2008, 10:14 AM


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