RRC Archives

Two separate thoughts:

1. Regarding the comment about how the belayer never felt the rope come tight: the last time I fell on gear (I avoid doing it often, so I remember each one pretty well ), I grabbed the rope below the piece without thinking. I think my belayer did feel something, but the piece held. One major difference here is that I was below (or horizontal with) the piece when I fell, so I wasn't moving very fast when I grabbed the rope (thus no burns). But I'm sure I increased the force on the piece vs. just taking the fall. It's improbable but possible that something like this could have happened in this situation. It would have both increased the shock load on the piece and might have caused the load to be 'out of line' with how the piece was placed. (Damn, the more I think about it the more freaked I am that I grabbed the rope like that!)

2. frzsnow: would a 'side loading' but not especially high impact force loading of cam lobes be likely to cause them to fail in the 'brittle' or 'flat break' way that they did? What I'm thinking is: if you exclude 'side loading' or pre-existing damage/weakness, is it realistic to speculate that the lobes may have failed simply because the piece walked back and was then 'snapped' forward into the crack when the rope came tight on the cam? (If so, then that could happen to any cam, with or without cam stops, if it walks well back into a crack. )

Hmm. Doesn't sound like that was the fall the broke the cam then unless it was ready to blow the next time it was weighted. After looking at that cam another time or two I really have to wonder how reliable that pic is and where it came from. Something here doesn't jive.

frzsnow wrote:So the cam either underwent a huge amount of force in an extremely short amount of time (think of yanking apart a chunk of silly putty which gives you a flat break) or it was previously loaded creating some internal forces that never recovered and the piece failed under a small amount of loading this time.

Would a piece of gear like that be the kind of thing where you could tell the piece was dead just by looking at it?

I took a 3ft daisy chain fall directly onto a .75" cam when the piece I was switching over to popped and it held fine. It about broke my back but the piece held. That's a very severe loading and the cam was sideways when I fell on it.

Check out the broken cam in these pictures. It was placed sideways too.

http://images.google.com/imgres?imgurl= ... s%26sa%3DG

marathonmedic-

Most metallic materials have a limit to the amount of stress they can withstand before plastically deforming - this is the yield strength. When the metal is stressed beyond that point it starts to permanentally deform. Sometimes an object can be stressed to or just below that yield limit and unloaded without anything happening visually. When it is reloaded it will withstand a stress slightly higher than the original yield stress then fail. There's no way to tell if this has happened by simply looking at it.

overhung wrote:Check out the broken cam in these pictures. It was placed sideways too.

Very interesting, the lobes are fine. That's a good cam. The stem took a severe shear loading and failed. That's more what I would expect out of a severely sideways loaded cam.

Usually I just lurk ...

K took a fall off Into the Purple Valley. His top cam pulled. His next piece was low. Rob jumped off the ledge at the base of the climb and that probably saved his life. His head hit the ground at the very end of the rope-stretch. He was lucky and "only" sufferred a concussion. The cam was badly mangled (at the axle?). There was some talk of sending the cam to the manufacturer. Among the more important things I don't remember about this incident is the size of the cam (bigger than hand?), and whether he was wearing a helmet.

The Deal brothers can tell you exactly what happened.

It was a Black Diamond Cam.

tomdarch wrote: if you exclude 'side loading' or pre-existing damage/weakness, is it realistic to speculate that the lobes may have failed simply because the piece walked back and was then 'snapped' forward into the crack when the rope came tight on the cam?

Cams are designed to hold a load with the cam lobes expanding outward. If the cam had walked back into the crack "umbrellering" out then the tips of the lobes would have been the only part of the cam in contact with the rock. If the force of the fall (even a small one) would have put a different type of stress on the lobes, indeed snapping them backwards in the opposite direction that they were designed to hold, in turn causing the fracture. I definitely would agree that this may be what happened - though without specific information on how the cam was placed, the force exerted, etc., there's no real way to say exactly.

Yall are worse than the Warren comision.A cheapo cam failed.BIG SUPRISE!
What bothers me and you all missed is the fact that an overpriced helmit failed to protect from fatal head trauma in a 30 foot fall.

Um, just what kind of protection do you think that helmet was going to give him? They're made more to protect your gourd from falling rocks than to protect it from falling on rocks.