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Topic Date User

breaking ALDI climbing gear 6-Aug-2009 At 1:19:26 PM yankinoz

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On 6/08/2009 gfdonc wrote:
>YankinOz wrote:
>>If a leader falls on the first piece of pro I would think the forces
>on the belay device would be the same as that on the leader.
>
>I'm no engineer, but I wager that's not the case.

not on the device itself. yeah, i agree with you.

>Firstly the force on the belay isn't the same as that on the leader, because
>of friction through the runner system which reduces the force, as well
>as the dynamic nature of the rope.

In the case of a fall from the first piece of protection I disagree - there's only one biner between the leader and the belay so i would expect equal forces on both sides of the rope. Add more pro, more biners, more angles, more friction then the force on the belay side would reduce.
I've been lifted off the ground and I'm sure it takes a fair bit of force to pull 70kg off the ground - greater than 7Kn? is that how the works? I've pulled belayers bigger than me off the ground. there's still a lot of force hitting the belay.

>Secondly the force on the belay is mostly on the carabiner that the rope
>is passing around. The belay device is being subjected to enough force
>to introduce friction into the rope, not directly being pulled by the fall
>- assuming of course an ATC-style plate, rather than a figure-8 where the
>device is directly being loaded.
>
>The force on the exit side of the plate is going to be somewhat limited
>by how hard you are holding the rope. Reckon you can pull 10kN one-handed?

no way I can hold the rope without some mechanical aid! The system locks the rope but the force is still there - we take it on our harness. So my question to the engineers - what's the difference between the forces on the leader's harness compared to the belayer's?

>Now time for the real engineers to join the debate ..

I hope so :)