Traddies, don't take your gear for Granite

[Crankmas]

did you say college or third grade, oh that's right we're in Kentucky

[dhoyne]

JB, it's a pun.

I am a metallurgical engineer. I know a whole shitpot about the different manufacturing techniques and the strengths/weaknesses of each.

Just by looking at the pic I could almost say it's not a casting defect. But this is only based off a picture on the net, so I can't really analyze it more.

Brittle is a relative word. So is strong. There's lots of room to play with those terms.

[TradMike]

I can appreciate your concern, Mike, but die casting can actually be a superior process when done correctly. Black Diamond and several other cam manufacturers die cast their cams.

I stand behind my statement that the Cassin Joss Cam is a piece of shit. It’s lobes are made from diecast 383.0F Aluminum. Almost all other cams’ lobes are made from 7075-T6 Aluminum that is CNC machined from 7075 aluminum extrusions. I would like to see the specs and the material that Black Diamond is using for Camalot Jrs. I hope they are not trying to make more profit at the expense of strength because diecast is cheaper.

Here are the specs on both materials with references.

Joss Material = diecast 383.0F Aluminum
http://www.matweb.com/search/SpecificMa ... m=MAC3830F
Ultimate Tensile Strength = 45000 psi
Tensile Yield Strength = 22000 psi
Elongation at Break = 3.5 %
Shear Strength = 27100 psi

Camalot Material = 7075-T6 aluminum extrusions
http://www.matweb.com/search/SpecificMa ... m=MA7075T6
Ultimate Tensile Strength = 83000 psi
Tensile Yield Strength = 73000 psi
Elongation at Break = 11 %
Shear Strength = 48000 psi

The extruded 7076-T6 is nearly twice as strong in ultimate tensile strength, won’t start yielding with over three times the load, deforms almost three times as much before failure and almost twice as strong in shear strength. The numbers speak for themselves. Granted we will never know how the cam was exactly placed and what actually happened but we can make some good assumptions. It’s obvious the cam held well enough to catastrophically fail the lobes. It appears that the neither the axle, the lobes, nor the stem is bent at all. I have seen plenty of pictures of failed cams from severe loading and nothing looks close to that picture.

This is a twisted 7076-T6 cam lobe with the axle failing at 2280 lbs.


Here’s a photo of a cam that failed at 3000 lbs.


I think the UIAA is also to blame. Their testing requirements need to be more stringent. "To pass UIAA specifications, cams need only be tested in the type of placement and direction of pull for which they are designed. They are not required to be tested in other types of placements, or pulled at other angles. A cam made of a more ductile material would be somewhat tolerant of deviations from designed placement and angle of pull, because the lobes will deform substantially before breaking. But the alloy in the Joss cam would deform only slightly before breaking, making it vulnerable to failure under bending or twisting forces on the lobes.” Other cams are, “much better able to take an unusual load and give to the point where other lobes might share the load before breaking.” The Joss Cam, “catastrophically failed (broke into pieces) under the weight of a 140 pound climber on a low fall factor fall.”

Trango
The cams lobes are CNC machined from 7075 aluminum extrusions
Aliens
Cams are machined from 6061-T6 Aluminium extrusions, a grippy alloy.
DMM
Sophisticated machining has allowed DMM to take away all the fat and keep the strength

[wanderer]

.” The Joss Cam, “catastrophically failed (broke into pieces) under the weight of a 140 pound climber on a low fall factor fall.”

The first post says his weight never came on the rope, which I assume came from the belayers testimony. So wouldn't that put the stress level at almost nothing? Is it even possible to come up with a weight that a piece could receive before the belayer would feel it?

[TradMike]

The failure picture for the Cassin Joss Cam also indicates that the cam was loaded properly. It's failure points are very consistent with what a finite element program indicates where the highest stresses are for an over or under cammed cam. The highest stresses are near the axle.

[weber]

Although the photo suggests that the cam may have failed because it was too “brittle”, we would be wise to reserve judgment until all the facts are presented.

Rick

I stand behind my statement that the Cassin Joss Cam is a piece of shit. It’s lobes are made from diecast 383.0F Aluminum. Almost all other cams’ lobes are made from 7075-T6 Aluminum that is CNC machined from 7075 aluminum extrusions...

Thanks, Mike, for taking the time to research this issue and for an excellent presentation of the facts. Now I know I (and probably many others) won't be considering buying Cassin cams!

Rick

[dhoyne]

Thanks for all the tensile specs, I now see you are a sucker for marketing people.

I can certify all the material I sell to a tensile specimen produced from the same lot of material. Does this mean it's all as strong? HELL NO. Strength and ductility can vary from part to part depending on size, heat conditions, and tons of other factors.

Also, machining parts puts a great deal of stress on them. It has a good effect on tensile properties and ductility because of this. Heat treating also changes properties drastically.

I'm not saying that the cam is "shit" as you so eloquently put it. I'm also not saying it's fantastic. Just that you shouldn't base your sole opinions off of a stated number.

[kato]

Just conjecture, but thinking about the apparent contradiction of the belayers claim that the rope was never weighted and the failed cam...
If the rope twisted or knotted below the cam, or otherwise became caught in the biner or sling, so that his weight came only onto the cam and not the belayer, the fall factor would be dangerously high. Combine that with a substandard placement and you have a disaster.

[TradMike]

I am not putting all of my faith in the numbers and I am not a sucker for marketing. I know very well how much induced stress is put in a part that is machined from extruded stock and I also know how much more stress is put in a part that is diecast. Milling off material will not do a great deal of damage because the part is kept cool with lubricant while cutting where as diecast is liquid metal injected into a die and cooled from a much higher temperatures into complex shapes that further induce much larger stresses than what would be in extruded stock material. The Cassin cam is made from both an inferior process and inferior material. The numbers represent best cases for both materials. Line for line the Cassin is SHIT.

[TradMike]

Just conjecture, but thinking about the apparent contradiction of the belayers claim that the rope was never weighted and the failed cam...
If the rope twisted or knotted below the cam, or otherwise became caught in the biner or sling, so that his weight came only onto the cam and not the belayer, the fall factor would be dangerously high. Combine that with a substandard placement and you have a disaster.

I didn't see this anywhere. His belayer said it was "140 pound climber on a low fall factor fall.” He fell 2 to 3 feet above his pro. His belayer didn't say anything about the rope not coming tight.