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qtm
Jul 3, 2009, 5:24 PM
Post #26 of 27
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Registered: Apr 8, 2004
Posts: 548
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Just a note, I started this thread after the 2006 recall for the braze issue on dimpled aliens. I'd purchased a recall-era non-dimpled alien which hadn't been fallen on, and wanted to ensure that the head wasn't going to pop off under body weight. It's a simple rig composed of materials that most of us would probably have lying around, to ensure the braze wouldn't fail.
All superseded by Arics tests, but it's great others are still doing their own tests and coming up with new methods of testing.
The flat webbing is a great idea. I'd thought about using scissor jacks (still with a loop around the axle, not placed in a crack). The problem was the cord fuse was so elastic it would require two scissor jacks to keep the sides even, and would need to be mounted on cinder blocks to deal with the stretch... not a very stable test rig. The single jack and jack stand with the flat webbing is a great idea.
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cracklover
Jul 8, 2009, 5:01 PM
Post #27 of 27
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Registered: Nov 14, 2002
Posts: 10162
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Since this thread has been resurrected, I'll post my DIY test here, too:
Put a spectra sling around a big rock (~40 lbs). Haul big rock above the cam with ~ 2 feet of static material plus fuse connecting them. Make sure the Alien is in a good placement that doesn't stress the stem. Drop the rock.
So the attachment is: rock -> spectra sling -> biner -> nylon fuse -> biner -> alien. Then factor 2 the rock onto the alien. When dropped, the nylon fuse breaks, unless the placement was poor, in which case, the alien rips out. Or, of course, if there's a manufacturing defect, the cam itself would fail, but I haven't seen that yet.
The fuse I used in my first set of tests was: PMI 3mm Tech Cord. They rate it with a minimum breaking strength of 1.7kN. I made a loop of it tied with a double fishermans. If the MBS is exact, it should fail at just about 3kN. Though if there's a safety margin on the cord, It might put as much as 4kN of force on the cam before failing. It usually failed at the knot.
For my second set of tests I found a 3mm tech cord from Sterling, rated with an MBS of 2.6kN (perfect!) A loop of that should get me a force of around 4.5-5.5kN.
By the way, the biner on the cam takes very little abuse, but all the other gear takes plenty (because it hits the ground with the rock). After a few test rounds, with a big rock falling on it, the spectra sling and the biner attaching it to the fuse (which fall to the ground each time) were pretty beat up. After about 10 tests, the spectra sling finally gave up the ghost completely. So if you feel like playing along these lines, don't use your favorite gear. Oh, and the cams look great after the test. Certainly some fairly deep gouges in the lobes if they're set up against a crystal but nothing troubling.
Here's a video of a test session:
http://www.youtube.com/watch?v=jMeGtWjmS54
GO
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