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Grigri impact force on protection .... 16-Jul-2005 At 10:24:20 PM cheesehead

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>is it just speculation that a gri gri causes more forces, or have people
>actually performed a test? i guess, that until a test is done, its all
>just a myth.....call on mythbusters!!

It makes sense that a gri gri system loads greater force through the rope/pro. In the same controlled fall/belayer/dynamic or 'rigid' belaying, the grigri locks instantaneously* as opposed to a tube or stooge-plate or Munter hitch, which cannot lock as quickly and allow a more dynamic braking - ie, lower deceleration.

Whether this force difference is significant, or is substantiall lower than the difference between a static/dynamic belayer (etc) is a different issue. I believe that any situation where you're using (or should be) screamer style draws will be effected by the difference in belay force.

*Instantaneous is a cool word that was invented to counter the fact that 'insant' is an abused word. There is no such thing as 'instant'. In the case of deceleration (such as, for example, when belaying a lead fall), it is imposible to stop something in no time flat (ie, rope through belay device). This would mean infinite deceleration thus infinite force (for those who didn't make paper aeroplanes all through calculus class) on the rope. Rather, since a grigri stops rope 'straight away' as far as we're concerned, we say instantaneous.

To run your test, get your mate to fall from precisely** the same height above a bolt. Use a fast running video camera to essentially measure how far he wings it AND how long 'till he stops moving (or reaches the bottom of his stroke, or first bounce if you like).
Do it stacks of times with each belay device on test. Then get a nerd to use the time/distance numbers and tell you the relative force on the rope. Using the same rope counters the rope stretch part of it.

**Precisely or exactly doesn't exist either (not in science/eng anyway).

right, that's my big HECS debt justified.