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




JimTitt


Dec 29, 2012, 10:49 PM

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Registered: Aug 7, 2008
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Re: [Syd] Quick and dirty test: What happens during shockloading?
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Syd wrote:
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.

I donīt jump, donīt recommend it and donīt expect anyone to do it. Nor would I teach it. That was USNavyīs idea and how he achieves this I have no idea, heīs probably younger, more athletic and has better reactions than me.
Since I weigh over 200lbs my belayers generally give me a dynamic belay whether they want to or not, when Iīm belaying I try to give a dynamic belay if required by relaxing towards the tension of the rope as shown in the Petzl cartoon. Mostly I donīt bother since the bottom of the cliffs where I mostly climb are an upward slope which makes things awkward and anyway Iīd probably spill my coffee by moving fast.

The amount of movement required is very low to reduce the peak force, six inches or a foot at the belayer end makes a huge difference and probably wants to be given at an early stage in the arrest of the fall. If you timed it to coincide with the absolute peak force then you are far too late as there is a time delay through the whole process.

If I need to give a soft catch to reduce the swing into the rock then itīs a whole different concept and process (and belay device generally).


(This post was edited by JimTitt on Dec 29, 2012, 10:51 PM)



Edit Log:
Post edited by JimTitt () on Dec 29, 2012, 10:51 PM


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