Some of the mechanical belay devices upcoming simply hold the bight of rope in a ' U ' formation so the rope can pass over whatever is connecting you to the rope. In my case, I prefer a 50 Kn steel triple-locking caribiner. It wears much longer than friction hitches and is more predictable with wet rope.
SO, it's the steel caribiner that is taking on the forces and the majority of the friction, the belay device just guarantees proper positioning of the rope and adds a bit more friction. If properly designed, the friction can be adjusted precisely and incrementally with regards to the climber's style, weight and rope type and diameter. Also what lacks on these simple devices is the lockoff ability, hard and soft.
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Originally Posted by George What is "2:1 doubled rope descent" ? |
It's what you're using if climbing on a hitch system. We went over it in detail in past pages. But summarizing, one end of the rope is anchored to you, goes up and over your tie-in point, through friction control and to the ground. The movement of the rope at the tie-in point acts as a 'pully', creating two legs of a mechanical advantage system. You must pass twice as much length of rope through friction control as the distance you descent.
This is in contrast to 1:1 doubled rope descent and 1:1 single rope descent.
Let me catch up with you guys in another day or so. We're still in Mexico, sitting on the bullseye for Cat. 4 Hurricane Dean which will arrive the day after tomorrow (We're a short distance south of Cancun and Cozumel). Our place is under compulsory evacuation, so we must fly out this evening. Hasta luego. Jeem.