Moreover, even if the belayer hangs on, the burns sustained can range from annoying to exceptionally severe-as in down to the bone. If the belayer cannot maintain full strength grip or even loses control, rope slippage becomes not a safety valve but a liability. I say "potential safety valve" because without gloves, it isn't clear that rope slippage will be controllable. However, in high fall-factor low-friction circumstances, the rope slippage is a potential safety valve that may keep peak loads within the limits sustainable by trad gear, where as the same gear will blow with a Gri-Gri. Since the rope doesn't slip in most climbing falls, there is usually no difference in imposed peak load for a Gri-Gri and ATC-type devices. In summary, as with a number of issues in climbing (equalizing belay anchors, backing up rappels, wearing helmets, etc.), there are practices that are effective a large majority of the time but which may not work well or at all in a very small number of exceptional cases. There is a chance, depending on the rope and other frictional factors, that a Gri-Gri might slip in a factor 2 fall.) Of course, "properly timed" is critical, and given the very large variation in belayer performance in the CAI tests, one has to wonder whether even an experience jumper can regularly reduce peak loads with a Gri-Gri. (Note: a Gri-Gri will not slip in any climbing fall caught by pro. Another set of tests has shown that, with a Gri-Gri, a properly timed belayer jump can result in a decent load reduction to the top pro. These results are for a non-locking belay device for which other force dissipation factors are involved and these apparently mitigate the contribution from belayer lifting.Ĩ. The CAI tests showed that the lifting of the belayer has a relatively minor effect in reducing the peak load to gear, and that only a fraction of the lifting occurs up to the moment of peak load, the majority occuring after the gear has already been maximally stressed. Although I have seen no comparative figures for the BD Guide ATC, I am sure that it has a significantly higher braking factor than the original Reverso had.ħ. ![]() As for the friction supplied by the device, the original Reverso was at the bottom of the heap-in my opinion, it was dangerously inadequate for severe falls. If the additional energy absorbtion of the inertial phase is not enough to stop the fall, then in the next phase the rope is pulled through the belayer's hand under whatever tension the belayer is able to maintain.Ħ. Depending on the position of the brake hand at the moment of impact, this could involve as much as two feet of rope running through the belay device under resistance with no slippage through the brake hand, producing perhaps the energy absorbtion of a Screamer. In the first, or what the CAI calls the inertial phase, the brake hand is pulled up to the belay device. I have slightly oversimplified the discussion of rope slippage here, because there are, in reality, two phases of rope slippage, one of which does not produce burns. The CAI tests also indicate that there is enormous variation in the performance of experienced individual belayers, so much so that it was hard to get useful data from repeated trials. How much rope runs depends on the friction in the system, the amount of friction supplied by the belay device, and the strength of the belayer's hand. Both sophisticated mathematical modeling and extensive practical testing by the Italian Alpine Club (CAI), as well as an extensive historical record of belay testing in the US in the 50's and 60's make it clear that if the belayer is exposed to a high fall-factor situation with few sources of friction, there can be significant amounts of rope running.ĥ. The net effect is that many climbers can climb for years-or even an entire career-and catch many leader falls without ever having the rope run.Ĥ. Even when the fall factors are larger, there are usually enough sources of friction in the system dissipating fall energy so that it is rare for most belayers to experience the rope running. The great majority of climbing falls have low fall factors and do not produce very large loads at the belay device anyway.ģ. ![]() ![]() The result is that more fall energy has to be absorbed by the rope running and so the predictions of rope running are probably on the high side.Ģ. The Petzl simulator (and most theoretical models) use a relatively simple equation that either ignores or only partially accounts for friction through the carabiners and against the rock.
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