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rgold
Trad climber
Poughkeepsie, NY
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Nov 13, 2006 - 11:04am PT
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"I guess with cams the success rate would be much better, but it would sure be interesting to see the results of such test!"
Yeah, I suspect the test would be an eye-opener. I'd sure like to have my judgement evaluated in this way. But I think you are wrong about the ``success rate'' being better for cams. The factors affecting cam security are more numerous, more complex, and harder to judge than those affecting piton security. However, as far as the actual numbers go, I wonder whether the tests you mention involved climbers judging pitons they themselves had placed, or rather judging pitons already in place. Obviously, the latter is much harder to do, and if the numbers you mention applied to in-situ evaluation, then they aren't quite as shocking.
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kubko
climber
Slovak Republic, Europe
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Nov 13, 2006 - 12:38pm PT
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I wonder whether the tests you mention involved climbers judging pitons they themselves had placed, or rather judging pitons already in place.
The pitons were already place (some of them for a long time) - that was the point of the test to see how reliable is climbers' judgment with regard to in-situ (old) pitons, as old pitons are abundant in many areas in europe and are often relied on by those who choose not to carry a hammer (a majority I would guess) where no clean protection works.
Sorry, I should have made that clear right away.
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BoKu
Trad climber
Douglas Flat, CA
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Topic Author's Reply - Dec 4, 2006 - 06:04pm PT
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Quick update - My wife says a package just arrived from the Ukraine. It can only be my new KROK #3 cam!
Also, last weekend I finally got around to actually breaking some climbing gear with my hydraulic puller:
This new, unused, Rock Empire 20cm long, 12mm wide Spectra dogbone broke at 25.6kn (116% of its 22kn rating). It held at that force for about 30 seconds, during which it made occasional crick and pop noises before suddenly letting loose with bang.
This Omega Pacific bent-gate biner came with a set of Dirtbag quickdraws. It was used for two seasons before testing, and showed only normal wear and tear.
Testing the biner in gate-closed condition to the limits of my equipment (26kn, 108% of its 24kn rating) distorted the spine of the biner slightly, but it showed no other distress. The gate operated smoothly once the force was released.
My policy is to permanently retire any gear tested to over 50% of its rated strength. Therefore, I decided to destroy the biner by testing it in gate-open condition.
The biner broke with a sharp report at 9.2kn, 131% of its rated 7kn gate-open strength.
If I have any spare time next weekend I'll set up the artificial crack I'll use to test the KROK cam. For that test, I'll have a camera handy during the actual test.
Bob K.
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Tahoe climber
climber
Texas to Tahoe
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Cool thread!
Please keep letting us know how the testing goes - particularly if you do catch a manufacturing company lying/making mistakes with their strength specs.
Thanks!
-Aaron
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BoKu
Trad climber
Douglas Flat, CA
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Topic Author's Reply - Dec 11, 2006 - 07:56pm PT
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Well, I've had some time to get a good look at that Petrenko cam. I disassembled it for a good look at the parts, put it back together, and did a pull test up to 7.5 kn. Here are some pictures so far.
The cam in the pull tester, with about 7.5 kn applied. The gauge indicates about 1460 psi; the effective piston area is 1.153 in^2, so the tension is 1460*1.153=1683 lbf = 7.48 kn.
An overall view of my test setup showing the hydraulic pump, the pullback ram, the test chassis, and the test crack. The test crack is a pair of 3/4" steel plates, with the inside surfaces textured with a rough grinder.
A closeup of the cam lobes engaged with the test crack. The unit held fine at 7.5 kn. The crack width is 1.75", which is halfway between the min and max sizes.
I'll post more about the test, but first I need some help. Can anybody who's done cam testing like this drop me a line? I have some questions about how to interpret some of the results I observed.
Thanks, and best regards to all
Bob "BoKu" K.
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Mungeclimber
Trad climber
one pass away from the big ditch
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Dec 11, 2006 - 09:03pm PT
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Rad Boku!
Why not just email the guys at Black Diamond. I'm sure they would help with the configuration, but obviously wouldn't release any 'trade secrets'. Ya never know.
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BoKu
Trad climber
Douglas Flat, CA
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Topic Author's Reply - Dec 14, 2006 - 10:55am PT
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Okay, I've got a new surface to test with. I used an air hammer (like a handheld jackhammer) with a chisel insert to apply a rough knurling to the steel plates of the test crack. That should create enough starting friction to continue testing.
What's going on is that I'm doing test comparisons between the Petrenko Links #3 and the Rock Empire Comet #3. Both cams are geometrically very similar. The size range and cam profiles are almost identical, as is the cam spacing along the axle.
The problem I had was that the Petrenko cam would engage the steel surface for pull testing, but the RE cam would not. So I couldn't do a pull test on the RE to compare the effects of the pull test. I think it might mean that the lobes of the Petrenko cam are softer than those of the RE, but I won't know that for sure without getting Rockwell hardness tests of both cams to compare.
With the steel surface knurled, I can now crank both cams up to 7.5 kn and see how much local yielding there is of the cam lobe surfaces at the contact point. That will provide a good basis for comparison between the two.
Bob K.
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spyork
Social climber
Land of Green Stretchy People
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Dec 14, 2006 - 04:35pm PT
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Hey Bob, cool stuff. I want to see pictures of exploding cams! Action shots!
Save some gear for actual climbing though...
Steve
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Tom
Big Wall climber
San Luis Obispo CA
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Dec 14, 2006 - 06:03pm PT
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I've used plain steel, about 1/2" thick, in a frame with parallel sides. When I first tried uncleaned steel, the residual grease and oil allowed the cams to slide. I cleaned the steel, left it outside a couple of days and allowed it rust. After that, there was no tendency for the cams to slide out. They would lock right up.
You might want to look into getting a load-cell, which mounts in series with the cam and the pulling rig, and you can hook up to a PC to get more accurate data.
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BoKu
Trad climber
Douglas Flat, CA
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Topic Author's Reply - Dec 15, 2006 - 06:37pm PT
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> Hey Bob, cool stuff. I want to see pictures
> of exploding cams! Action shots!
I'll try. But I suspect that most cams will die with a whimper, not a bang.
> I've used plain steel, about 1/2"
> thick, in a frame with parallel sides.
That's basically what I tried, using 3/4" steel that I had on hand. I "conditioned" it with a rough grinding wheel and degreased it. It still wouldn't grip some cams. Hence the knurling.
> You might want to look into getting
> a load-cell, which mounts in series
> with the cam and the pulling rig, and
> you can hook up to a PC to get more
> accurate data.
I'd like to do that, and I may some time in the future. But that's thousands of dollars worth of stuff versus the two-hundred odd dollars my current 25.6 kn +/- 2% setup cost me. Breaking climbing gear isn't lucrative enough to justify the extra expense.
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ExtraBlue
Ice climber
the ford VT
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Sep 15, 2010 - 11:51am PT
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any update on the Krok test?
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Steve Grossman
Trad climber
Seattle, WA
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Sep 15, 2010 - 09:05pm PT
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Find a stoneyard that has guaged granite blocks or have some reasonably uniform blocks cut. You can easily epoxy threaded rod for attachment and use a layer of two part masonary epoxy to wet set your blocks into your steel test armature. The goal is even face compression.
Borrow a video cam!
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