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General Climbing Discussion

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top roping from rap anchors 6-Aug-2005 At 1:54:10 PM Ronny

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The difference is between u bolts and 'p' bolts which are welded rod that only has one shaft going into the rock, and are hence susceptible to being twisted.

Toproping directly off one bolt does not just simply put a single climbers wieght on each bolt. The rope maintains an equal tension over the entire length, including the part between the bolts. This means that the force on the bolt is the resolution of two vectors, one in teh direction of the rope to the climber (or belayer) and one in the direction fo the other bolt. (the two vectors are equal in size). This means that if the bolts are level the resultant force is at 45deg to horizontal. Excluding friction, if the climber is remaining still, there must be an equal weight on the belayers end, and hence the total weight being held up by the anchor is twice the wieght of the climber. Each bolt takes half the weight, but being pulled at 45deg, that makes the total force on each bolt in teh static system about 1.4 timest the wieght of each climber.

The 'death triangle' problem occurs when one bolt fails. (this isn't a real 'death triangle' but as i understand it is the same problem for which death trianbles are named). All of a sudden there is slack in the system (being the amount of rope between the two bolts, and so there will be a shockloading of the remaining bolt. This may not be very much, especially if the bolts are close together, but that is the issue ppl are refering to.

J