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Dynamic belay vs Static belay
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majid_sabet


May 24, 2008, 8:27 PM
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Dynamic belay vs Static belay
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What you guys think about this report ?

Traumatic and overuse injuries to the spine were observed with climbers falling in the rope. The purpose of this study was to investigate the influence of different belaying behaviours and devices on the force measured between rope and harness of a falling climber.

One subject (m = 70 kg) performed standardised falls with a fall factor of z = 0.375. The following situations were tested: static belay at a bolt (1 trail), static belay at the body using a Grigri (1 trial), belay with backward movement of the belayer using a Grigri (1 trial), dynamic belay by a jump using a Grigri (10 trials), dynamic belay using a figure of eight (10 trials), dynamic belay using a HMS-karabiner (10 trials). The force between rope and seat harness was measured by a strain gauge. From the recorded force curves the peak force was determined and compared for the different situations.

For the single static belay at a bolt an about two times higher peak force (4006 N) than the mean peak force of the 10 dynamic trials using the Grigri occurred (2083 N, s = 175.7 N). The differences between different belaying behaviours using the Grigri were as follows: in case of a backward movement of the belayer the peak force was 3887 N which is close to the static trial, in case of no movement of the belayer the peak force was 3267 N, and with a jump of the belayer in rope direction it was 2083 N. The comparison of the belaying devices showed mean peak forces of 2368 N (s = 172.5 N) for the HMS-karabiner, 2197 N (s = 234.0 N) for the figure of eight, and 2083 N (s = 175.7 N) for the Grigri. The difference between HMS-karabiner and Grigri is statistically significant.


http://www.leeds.ac.uk/sports_science/abstracts/climb99/wnachbauer1.htm


gunkiemike


May 26, 2008, 7:13 AM
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Re: [majid_sabet] Dynamic belay vs Static belay [In reply to]
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majid_sabet wrote:

Traumatic and overuse injuries to the spine were observed with climbers falling in the rope.

Don't get the rope behind your leg!


antiqued


May 27, 2008, 10:26 AM
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Re: [majid_sabet] Dynamic belay vs Static belay [In reply to]
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What does "dynamic" belay with an 8 or HMS mean?

Static grigri - 3.3kN
jumping GriGri - 2.1kN
"dynamic" figure 8 - 2.2kN
"dynamic" HMS - 2.4kN


What I find interesting is that the jumping GriGri reduces the impact force to that of what I will assume is typical of regular belaying techniques. If "dynamic" does not mean letting rope deliberately slide through the belay device, then jumping would seem to be an advanced skill, requiring some practice to get a tight standard deviation, producing the same results as just hanging on with other approaches.

If "dynamic" means letting rope slide, then I am impressed that the belayer has mastered all three techniques to arrive at very similar impact forces.

And how much did the belayer weigh?

Basically, I think it is a shame that the Internet can point out all these potentially interesting sources of information that very few can access. I can't find any mention of written proceedings going up the tree at Leeds, but Barnes and Noble will sell you the proceedings on CD for $39.


AeroXan


May 27, 2008, 11:37 PM
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Re: [majid_sabet] Dynamic belay vs Static belay [In reply to]
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it makes sense that dynamic belay techniques would reduce impact force because of increasing time, however, this study sounds far from conclusive.


stymingersfink


May 28, 2008, 11:25 PM
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Re: [majid_sabet] Dynamic belay vs Static belay [In reply to]
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majid_sabet wrote:
What you guys think about this report ?
you either plagerized it, or quoted from it directly.

Aside from a few spelling errors, the grammar was light years ahead of anything we've seen from your keyboard.


stymingersfink


May 28, 2008, 11:27 PM
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Re: [stymingersfink] Dynamic belay vs Static belay [In reply to]
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oh, and if you're gonna throw a web address in a post, the least you could do is make it clickey. It's really not difficult.

http://www.leeds.ac.uk/...mb99/wnachbauer1.htm


brachialis


May 29, 2008, 2:00 AM
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Spelling errors, eh?


swede


May 29, 2008, 5:43 AM
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Re: [majid_sabet] Dynamic belay vs Static belay [In reply to]
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I must say that I doubt this is true. R Messner seems to be a too good name to be true.

Anyways jumping with the grigri should produce lower impact forces. But the abstract do imply that the GriGri is superior, despite not being used in the same circumstances as the dynamic belay devices. If jumping is that important they should have made certain the jump was exactly the same - and for all devices. Sounds like the author wanted a certain result.


Partner j_ung


May 29, 2008, 5:45 AM
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Re: [majid_sabet] Dynamic belay vs Static belay [In reply to]
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majid_sabet wrote:
What you guys think about this report ?

Traumatic and overuse injuries to the spine were observed with climbers falling in the rope. The purpose of this study was to investigate the influence of different belaying behaviours and devices on the force measured between rope and harness of a falling climber.

One subject (m = 70 kg) performed standardised falls with a fall factor of z = 0.375. The following situations were tested: static belay at a bolt (1 trail), static belay at the body using a Grigri (1 trial), belay with backward movement of the belayer using a Grigri (1 trial), dynamic belay by a jump using a Grigri (10 trials), dynamic belay using a figure of eight (10 trials), dynamic belay using a HMS-karabiner (10 trials). The force between rope and seat harness was measured by a strain gauge. From the recorded force curves the peak force was determined and compared for the different situations.

For the single static belay at a bolt an about two times higher peak force (4006 N) than the mean peak force of the 10 dynamic trials using the Grigri occurred (2083 N, s = 175.7 N). The differences between different belaying behaviours using the Grigri were as follows: in case of a backward movement of the belayer the peak force was 3887 N which is close to the static trial, in case of no movement of the belayer the peak force was 3267 N, and with a jump of the belayer in rope direction it was 2083 N. The comparison of the belaying devices showed mean peak forces of 2368 N (s = 172.5 N) for the HMS-karabiner, 2197 N (s = 234.0 N) for the figure of eight, and 2083 N (s = 175.7 N) for the Grigri. The difference between HMS-karabiner and Grigri is statistically significant.


http://www.leeds.ac.uk/sports_science/abstracts/climb99/wnachbauer1.htm

I wish they had thrown in a few other belay devices, since relatively few people I know use figure-8s and Munters.


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