Forums: Climbing Information: The Lab: Re: [cracklover] More Alien Test Results (Lots of pics, very bandwidth intensive): Edit Log




jt512


Jun 18, 2009, 5:27 PM

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Registered: Apr 12, 2001
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Re: [cracklover] More Alien Test Results (Lots of pics, very bandwidth intensive)
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cracklover wrote:
3 - All of the Aliens tested had an effective cam angle greater than the angle of the other cams. This means that before deformation of the cam lobe even begins, the cam is closer to the point of reaching the critical angle of 35 degrees. The higher the starting angle, the less metal needs to be deformed to reach the critical point. Which again, means less force required.

Even if the method of measuring the affect of the misdrilled axles on effective cam angle is imprecise, there's little doubt that in almost all of these samples, it resulted in a larger starting cam angle. Perhaps we don't have enough precision to predict the variance from cam to cam, without laying the lobes flat on a scanner bed, but on average, they were pretty consistently off in the direction of too high a cam angle.

We have no evidence that cam angle in this sample is predictive of failure load. I have conducted a regression of failure load on cam angle, adjusted for strength rating, and the p-value for cam angle is 0.81. Cam angle is completely insignificant in the sample. Its effect has either been obliterated by measurement error, is swamped out by the harness issue, or a combination of both; or, its effect is physically insignificant, as long as the angle is sufficiently less than the critical angle. I suspect that its effect really is insignificant or that what little effect there is has masked by the hardness issue. Regressing failure load on hardness, again adjusting for strength rating, the effect of hardness on failure load is in the expected direction (harder is better). The effect is not statistically significant, but the p-value is 0.12, low enough to suggest that the effect may be real, but that we need a bigger sample size to detect it.

Jay


(This post was edited by jt512 on Jun 18, 2009, 5:36 PM)



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Post edited by jt512 () on Jun 18, 2009, 5:35 PM
Post edited by jt512 () on Jun 18, 2009, 5:36 PM


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