Forums: Climbing Information: The Lab: Re: [ptlong2] Impact force vs. fall length, fixed fall factor: Edit Log




jt512


Jul 14, 2011, 9:17 AM

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Registered: Apr 11, 2001
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Re: [ptlong2] Impact force vs. fall length, fixed fall factor
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ptlong2 wrote:
shockabuku wrote:
I would still like to see some data on a case where these other factors aren't involved.

These data are taken from a paper by Martyn Pavier. The selected drops were performed with a 70kg steel mass and the belay was tied off. It appears that with the "other factors" removed the length of fall has no significant effect on maximum tension, at least over this limited range.



For real life falls I would wonder about the effects of belay device and belayer behavior.

Maybe I'm missing something, but that chart of the Pavier data doesn't seem to address the original question—what is the relationship between the fall length and the maximum impact force for a given fall factor—very well. The only fall factor where we have data for multiple fall lengths is 1.00. Here the impact force increases slightly as the fall length increases from 1 to 2 m. However, at FF = 0.90 there appear to be three drops of the same length, whose range of impact forces appears to be about the same as the range at FF = 1.00, so what could be interpreted as an increasing relationship here could be due to random error.

It seems like what we need in order to answer the original question is a dataset with multiple drops at a constant fall factor over a greater range of fall lengths.

Edit: Is the impact force in the chart for the "climber's" side of the rope? Have you compared the Pavier data to that predicted by the "standard" model? Do you know the rope modulus or impact force rating of the rope?

Jay


(This post was edited by jt512 on Jul 14, 2011, 9:25 AM)



Edit Log:
Post edited by jt512 () on Jul 14, 2011, 9:25 AM


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