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Forums: Climbing Information: The Lab: Re: [healyje] link cam broken when fallen on : Edit Log




USnavy


Apr 18, 2012, 6:35 PM

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Registered: Nov 6, 2007
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Re: [healyje] link cam broken when fallen on
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healyje wrote:
USnavy wrote:
It's kind of an unofficial official statement. Metolius has openly said in e-mails that the pieces are designed for aid only, however they do not state that on their website. I remember reading a thread awhile back where someone complained that they decked when a 0 or 00 ripped. He contacted Metolius and they told him that the 0 and 00 cams were for aid only.


I just checked with their catalog crew and they did at one time annotate those pieces as aid-only. It was probably not the wisest decision to stop pointing out the obvious in their documentation from my perspective.

USnavy wrote:
My partner fell on a 0 Master Cam last season and umbrellaed the cam in its placement, shearing off the cam stops.

As I said, it's physically impossible for a cam - anyone's cam; of any size - to invert and sheer the stops in a good placement - physically impossible.
No it's not impossible, not even close. The guy that fell on the cam took a factor one fall on it. What likely happened is the cam ran out of range and it umbrellaed. That's is not only very possible, it is very likely. It seems so few people seem to realize the serious expansion range limitations of small cams. As I mentioned before, a 00 Master Cam that is placed with the lobes 50% retracted has as much remaining expansion range as a #4 Camalot that is only 4% retracted! So when you are dealing with a cam that has a full expansion range of around 1/4", it's not hard to run out of expansion range on a fall. Here is how it happens: You load the cam until the expansion range runs out, than the piece gets pulled downwards in the crack (even if only a fraction of an inch), and when the rock constricts, the lobes catch and the cam is loaded in its passive mode which immediately rips the stops off.

So normally when the stops rip off, it is because one or more of the lobes were not expanded enough or the rock was crap. However it is very easy to make that mistake. On cams that small, every lobe really needs to be contracted to 80-95%. The problem is that when you are dealing with a piece that small, the crack is going to be very narrow and it is going to be rather hard to properly inspect the back two lobes. Furthermore, a variation of 1/8" in the width of the crack will not be viable to the naked eye, but it could drop the retraction range of one or more lobes by a good 30-70% depending on the cam size, which can made the difference between the piece pulling and it holding. It is for that exact reason why I have always said that small cams are unreliable and should be replaced with RPs when possible. When I am aid climbing I always try to use RPs in any placement smaller than a green Alien. I do my absolute best to avoid using micro cams. Damn near every fall I have ever taken while aid climbing (although admittedly, I haven't taken that many falls) was the result of a really small cam ripping on me.


(This post was edited by USnavy on Apr 18, 2012, 6:47 PM)



Edit Log:
Post edited by USnavy () on Apr 18, 2012, 6:36 PM
Post edited by USnavy () on Apr 18, 2012, 6:37 PM
Post edited by USnavy () on Apr 18, 2012, 6:38 PM
Post edited by USnavy () on Apr 18, 2012, 6:39 PM
Post edited by USnavy () on Apr 18, 2012, 6:45 PM
Post edited by USnavy () on Apr 18, 2012, 6:47 PM


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