No, and I don't need to; all I need to know is that it isn't going to take much force to break a piece of metal that's less than an 1/8" thick. The type of metal, alloy, heat treatment - they're all irrelevant when you're down under a 1/8" thick...

At this point we're five pages into a similar progression as the LST incident. As this thread has progressed I've been more strident on each successive page about being self-responsible and dealing with reality - not what could / should / ought to be. Trad climbing isn't entertainment or a game, it's life and death in no one else's hands but your own. Coddling isn't going to help - folks need to wake up, ditch the consumer mentality, and stop thinking manufactured gear is somehow 'good' until proven otherwise. Nothing could be further from the truth - climbing history is littered with extremely well-made gear that in use has ranged from deadly to superb once on rock.

And trad climbing definitely isn't for every one; the "constructive criticism" in some case just needs to be 'stick with sport climbing or bouldering'. Even in the '70s before the advent of sport climbing, when everyone trad climbed, I'd say only about 20% of climbers were artisans / craftsman with gear, another 30% or so were competent with it, and the rest were nervously awaiting the birth of sport climbing. The bottom line is folks who can't deal with or get a grip on the harsh realities involved with trad climbing or can't muster the necessary skills and mindset shouldn't bother with it.

Advertisements or other media alerts? Listen to yourself here! Why should they stop there? They should spend all their hard-earned profits to track down each person who owns one of their cams to personally tell them...

Removable carrot bolt hangers come in 2mm thickness with a breaking strength of over 20kN (1/8" = 3mm).

I dunno... Looks to me that a single one of those tabs should be good for at least 6kN in tension. There looks to be ~0.100" of material around the rivet so for calculating the tensile strength of the tab you get something along the lines of (2*(0.063*0.100))*110000=1386 lb-force ~= 6.17kN.

One of the cams broke almost right smack in the middle.

I know, but had they not shaved so much weight off the casting of that part of the cam lobe segment it would have simply shifted the failure to one end or the other and onto the links. A design that had linkages and the strength of a non-segmented cam simply would be bigger and heavier than these already are - it would be like carrying Valley Giants at that point.

However, I suspect the reason for the cam breaking is the same as last time. Cam is in a pod. Climber falls on cam. Cam pivots around top two lobes. Lower two cams rotate further into the crack. Because of the nature of the crack, the angle between the cam lobes and the crack increases as they are torqued in deep, until (as described by RG in the last thread where this happened) the lobes cannot hold the huge force, and break.

I have no doubt. But clamp an inside cam lobe segment in a vice and take a pair of pliers to the end of the outside cam lobe segment and pull 90 degrees to the plane of the cam lobes and tell me how much force is generated down on the axle tab - that's the number of interest. In fact, for the completely non-scientific test I'd say go ahead and do just that to one of the four cam lobes on the cam I sent you and tell us how much effort it took to break it. Sort of like your elbows and knees - amazingly strong they when used in-plane as directed, but only takes about 12 pounds of force to break one if you leverage on it in the wrong direction.

which would put the force needed to snap a tab by pushing on the end of the last link at ~1kN. To be honest, that figure sounds quite low to me so I suspect I missed something (most likely underestimating the cross sectional area and overestimating the long side of the lever).

It's your cam, Joseph, so I'll do whatever you want with it.

[You're missing the point. You keep talking about the tabs as if they are the weakest link in the chain by far, when this whole thread is evidence to the fact that this just isn't so.

So when does it become better to just bring two cams?

Well, I think I'm going to bow out of doing that test. Long story short, I had a couple minutes to kill so did as Healyje asked and tried it my hand with a lobe clamped in a vice. The same sort of fracture happened and I can totally see that much force getting applied in a constrained placement/pod/obstruction/etc and trust that OP is going to give it a long, hard look.

That said, this isn't really news. The one thing I took out of the earlier incident was that you have to be careful with how you place these things and must not let the unfurled lobes get caught on stuff.

-a.

Finally people can stop telling me I am full of crap and actually realize how brittle these lobes are.

If you can break them with a hand and a vice then that says they are definitely not safe in anything but a textbook vertical placement.

I'm not sure anybody has argued that the lobes aren't brittle or weak when pulled sideways. Though many have argued that such weakness is a design limitation and is not a manufacturing problem. Even if material TWICE as strong could be used the cams would still fall far short of the strength required to resist forces in a fall.

Maybe not in this thread.

Um go take a piece of .1" rolled high alloy, medium carbon steel cut to the same shape and see if you can break or bend it by hand.

Well, I think I'm going to bow out of doing that test. Long story short, I had a couple minutes to kill so did as Healyje asked and tried it my hand with a lobe clamped in a vice. The same sort of fracture happened and I can totally see that much force getting applied in a constrained placement/pod/obstruction/etc and trust that OP is going to give it a long, hard look.