Forums: Climbing Information: General: Re: [Syd] Quick and dirty test: What happens during shockloading? : Edit Log




jt512


Dec 29, 2012, 3:09 PM

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Registered: Apr 11, 2001
Posts: 21890

Re: [Syd] Quick and dirty test: What happens during shockloading?
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Syd wrote:
JimTitt wrote:


Even in the shorter falls used in lab experiments which are the only ones we get full data for the time from initially tensioning the rope to the peak force is substantially longer than you are talking about, around 200ms is probably reasonable.

Based on ? I have seen a graph but I'm damned if I can find it.

In reply to:
If you look at US┤s lower graph (which is a longer, lower FF)you┤ll see the belayer had about 500ms from tension to peak and probably over a second if he saw the fall.

In fall of 20 to 30 ft, the belayer has about 1300 ms from fall to peak. The point is the time to react and how to precisely synchronise his jump with the peak.

As USNavy says, you can define the peak as an even shorter period.

Try standing on a flat surface in belay stance and as quickly as possible, jump as high as possible. You might raise your CG by a couple of inches. That is, by a dynamic belay jump, you might be able to reduce the energy of the climber's fall by perhaps 1% or so ... if you time your jump precisely to the millisecond.

Belayers are better off forgetting about jumping to give an active dynamic belay, and locking off the rope correctly and focussing on not tripping or hitting the wall if on an indirect belay.

You don't know what you're talking about. But you're right about one thing:áif you're too uncoordinated to time the jump properly, you're better off just standing there and locking off, since jumping too early results in a harder catch than if you just stand there like an idiot and lock off.

Better yet, offer to let someone who knows what they're doing belay.

Jay


(This post was edited by jt512 on Dec 29, 2012, 3:10 PM)



Edit Log:
Post edited by jt512 () on Dec 29, 2012, 3:10 PM


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