|
|
Forums:
Climbing Information:
The Lab:
Re: [angry] More Alien Test Results (Lots of pics, very bandwidth intensive):
Edit Log
|
|
jt512
Jun 16, 2009, 5:39 PM
Views: 9686
Registered: Apr 12, 2001
Posts: 21904
|
angry wrote: Aric, I know you're trying to alert us to a safety issue but really, you've proven the reliability of aliens.
Well, there is a lot of variability in terms of how their strength, as measured by Aric, compared with their rated strength. The mean of (measured strength) / (rated strength) * 100% was 89.4% with a standard deviation of 16.0%.
The average is dragged down by the smaller cams. The two black Aliens in the sample had the lowest numbers (54.7% and 63.6%), and one of the two blue Aliens in the sample had the third lowest (69.8%).
The 13 Aliens in the sample that were rated for 2700 lbf did the best. They attained 98.0% of their rated strength, on average, with a standard deviation of 11.1%. The mean strength in this subsample was 2647 lbf, with a standard deviation of 300 lbf, giving a coefficient of variation of 11.3%, which is alarmingly high, and indicates the opposite of your conclusion. These data do not "prove the reliability of Aliens." They suggest the contrary.
In reply to: Clearly they are tested on a different surface than you've got and that accounts for all but 2 of the failures.
If Aric's testing has produced results equivalent to UIAA testing—and I'm not saying that it has—then the correct 3-sigma rating for the 2700-lbf-rating Aliens should be in the neighborhood of 1750 lbf. How can you state that such a large discrepancy is "clearly" due to different testing surfaces?
Jay
(This post was edited by jt512 on Jun 16, 2009, 6:33 PM)
|
|
|
Edit Log:
|
|
Post edited by jt512
() on Jun 16, 2009, 6:33 PM
|
|
Post edited by jt512
() on Jun 16, 2009, 6:33 PM
|
|
|
|
|
|
