Study on mechanical conditions of the looseness of the outer wires of ropeway haulage ropes

In 1991, the haulage rope of the “Aiguille du Midi” ropeway in Chamonix had to be replaced some weeks after it had been put into operation. It could not be used any longer because scattered over several hundreds of metres of rope were dozens of loose outer wires. The replacement rope was subjected to the same phenomena after nine years of operation. The authors report on a study designed to measure and calculate wire stresses in order to try to determine the mechanical conditions causing the looseness of the outer wires of a test rope subjected to tension and torsion. The calculation results showed that the helical outer wires formed into the rope tructure are subjected to a bending stress, which corresponds to their straightening, resulting in a compressive force and a linear “back pushing” load. The measurement results showed that a few outer wires have in fact a rather variable behaviour in the rope structure as far as the lowest tensions are concerned and that some of these wires are even subjected to a bending stress greater than the value of the conventional stress to the limit of elasticity.

Author(s): J. Dubuisson and M. Cantin