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Oh, even Cassin knows how bad the Joss cam is. They have discontinued the Joss line and replaced it with guess what, milled 7075-T6. Dhoyne, come back with some facts to back up your statements. Yes, strength and ductility can vary from part to part depending on size, heat conditions, and tons of other factors. Show me these factors in the two cam materials and processes I talked about and try to prove how the Cassin comes even close to comparing.

As long as we're speculating on things we know very little about... The original post implies one of two things. The poster's comment about the rope not drawing tight could mean two things. Either the rope tightened, broke the cam and then never drew tight again or it could mean that the piece just popped before it took anywhere enough weight to break it. The comment, "His weight never came on the rope," suggests to me that it wasn't the climber's fall the broke the cam; it was the cam's fall.

The poster also mentions that the piece may have walked. I don't know anything about this crack, but if the piece walked into a wider part of the crack that narrows before it comes all the way out, it certainly may have opened enough to umbrella. On the other hand, if it was a simple flaring crack it might have been well on it's way toward walking all the way out and sliding back down the rope to join its friends. I don't think it would have broken two lobes that way though.

Just a thought or two.

Rick and Mike, thanks for all the info. It's easy for us to not be as informed as we should be.

Was it a bad placement? maybe. Would it have held if it was better material? maybe. I am just ranting because someone selected a cheaper process at the sacrifice of strength for the benefit of profit and someone is dead. In the following link, the belayer states that all four cam lobes show smashing and scraping. It seems like they were all in contact with the rock but were probably loaded sideways causing a twisting in the lobes. The brittle diecast material couldn't handle the strain. The 7075 probably could have because its three times better in that respect.

Here's a link to some good discussions about the failure.
http://helpdesk.rockclimbing.com/forums ... hp?t=80081

Here's the real problem:

Finally, in spite of Boston's reputation, I toproped the climb after the accident, and there are, in fact, two perfectly good vertical cracks that take a nice sized nut about 3 or 4 feet below the horizontal where the cam was placed. It could have been backed up twice.

(from rc.com)

Dhoyne, come back with some facts to back up your statements. Yes, strength and ductility can vary from part to part depending on size, heat conditions, and tons of other factors. Show me these factors in the two cam materials and processes I talked about and try to prove how the Cassin comes even close to comparing.

I never said that they compare. If you actually read my post you would know this. I'm not one of those people that loves to waste my day doing research on stupid things. Though it sounds like so much fun to debate material properties, I'm going to let you whine and blame the material when the cam was obviously placed wrong and not backed up.

A good mechanic never blames his tools. He also doesn't buy old, used K-mart brand tools from a yard sale because they're cheaper and expect the same quality as Snap-On or Mac. I sure wouldn't trust a discontinued $10 cam (http://www.sierratradingpost.com/produc ... e_no=69277) with my life.

my fiancee is a materials engineering grad student specializing in Steels and is now digging up research about all this as we speak. I assume she knows a good deal about it since she mainly focuses on stress fractures. You'll probably see her post later (frznow)

Sound disheartening that Cassin won't even return his calls. Most other manufacturers would stand behind their equipment.

haas wrote:my fiancee is a materials engineering grad student specializing in Steels and is now digging up research about all this as we speak. I assume she knows a good deal about it since she mainly focuses on stress fractures. You'll probably see her post later (frznow)

Lady engineers rock! Married one 38 years ago, and she's the light of my life.

(Plus, she's handy to have around when I need a complex algorithm developed for a computer program.)

Rick

I'm a metallurgical engineering student (and I'm very interested in this topic!) so take this for what it's worth....

The picture of the Cassin cam that failed shows a brittle-type fracture surface. 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. Aluminum is a ductile material and doesn't usually break like that - instead it plastically deforms (see the other pictures of failed cams in the post by TradMike) like pulling apart some silly putty slowly. There's no way to tell how the cam failed without checking the true compositon of the metal (not relying on the specs from marketing), finding any internal flaws, determining if the material underwent any phase changes that would weaken it, etc.

It's stuff like this that makes school fun.

WOW, I re-read the last post on gunks.com and it stated that he was only 2ft above the cam when he fell. "A cam placed two or three feet below the point from which he fell failed (broke)"