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




USnavy


Jan 3, 2013, 10:42 PM

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Registered: Nov 5, 2007
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Re: [Syd] Quick and dirty test: What happens during shockloading?
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patto wrote:


And I believe there has been other good research to support this. Dynamic belaying was found produce only very minor reductions in peak load.
Maybe research done by high school kids. Any reputable research done by anyone that knows what they are doing will show the opposite of what you claim, except in extremely low fall factor scenarios.
Syd wrote:


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 .
That is completely incorrect. You are overthinking it. Dynamic belaying is not as much of a precision art as you believe it is. Close is good enough. You dont need to time things to the millisecond.

Syd wrote:
patto wrote:
I completely agree with this.

And I believe there has been other good research to support this. Dynamic belaying was found produce only very minor reductions in peak load.

Thanks patto.

I've done some experiments to support this. The maximum effect of a dynamic belay is the instant the belayer's feet leave the ground. The fastest time I recorded was 800 millisecs from the instant a climber yells or is seen to fall, to the belayer's feet leaving the ground in an active hop. 200 ms later, the belayer is headed for the ground again (unless he is yanked upwards of course). Another 200 ms and the belayer is adding to the impact on the climber.

A "typical" free fall of 20 feet takes 1200 ms. In the next 200 ms, the climber falls another 8 feet. For a dynamic belay to work, the belayer has 400ms to calculate the amount of slack, how far the climber will fall and hence exactly when to jump.

To put things into perspective, "the blink of an eye" is 300 to 400 milliseconds. That is, the belayer must literally do the above calculations in the blink of an eye. If he's a blink of an eye out, he adds to the impact on the climber.

In summary, dynamic belaying is a myth. It might make you feel good in that you fool yourself into thinking you are helping but it's useless.
Allow me to show you what actually happens when you give a dynamic belay and when you dont. I tested this at my local crag using standard belaying techniques found in use by any experienced sport climber.



Fall 1: - Dynamic catch 13 total 3.09 kN
Fall 2: - Static catch (belayer just stood there) 10 total 3.75 kN
Fall 3: - Running belay (belayer yanked in slack and ran backwards) 7 total 3.91 kN


(This post was edited by USnavy on Jan 3, 2013, 10:49 PM)



Edit Log:
Post edited by USnavy () on Jan 3, 2013, 10:46 PM
Post edited by USnavy () on Jan 3, 2013, 10:48 PM
Post edited by USnavy () on Jan 3, 2013, 10:49 PM


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