WIRE ROPE TESTS* 25T 



central wire would, in the ordinary course of things, have 

 to bear a greater load than the others, and would snap if 

 of as hard metal, but being of soft annealed metal it can 

 stretch freely without breaking, and so damaging the rope 

 as a whole. 



The arrangement of the rope is most frequently in six 

 strands wound round a central core. This core may be 

 either a similar strand or a piece of tarred hemp strand. 

 This latter arrangement, while decreasing the strength of 

 the rope by one strand, adds very much to its flexibility. 

 Ropes built up of a large number of wires of small 

 diameter, and having a fibrous core, are much more 

 flexible than those made of large wires with wire cores. 



If all the wires in a rope could be subjected to exactly 

 the same tension, providing they were all of the same 

 material, the strength of the rope would be equal to the 

 combined strength of all the individual wires forming the 

 rope. Generally the load which is required to fracture the 

 rope is some ten or fifteen per cent less than the total 

 strength of the wires. This is owing partly to inequalities- 

 in the metal forming the various wires, but chiefly to- 

 the varying tightness of the wires and the consequent 

 unequal load upon them. 



The chief difficulty in carrying out a complete test 

 of a wire rope, or indeed a rope of any kind, lies in 

 finding a satisfactory method of holding the ends. 

 Various means have been tried with more or less success. 

 The usual forms of holders, such as are used for attaching 

 the ends of colliery winding ropes, are generally less strong 

 than the rope itself. Of the many tests made in the 

 direction of finding the most suitable holder, those of Mr, 

 W. Hewitt, of Trenton, N.J.,* are especially interesting 

 and valuable. In the tests carried out by him several 

 forms of fastenings were tried with varying results. Fairly 

 good results were obtained with ordinary thimbles spliced 

 in place. Of these, some were broken in the body of the 

 rope, while in several the failure took place in or near the 

 splice. A number of tests were tried with the ends of the 

 ropes fastened in sockets after the manner usual in wind- 

 ing ropes. These were all pulled out of the sockets and 

 the tests were rendered useless so far as the ropes them- 

 selves were concerned. In this method of holding, the 

 ends of the rope are first frayed out, and the ends of 



* Proceedings of the American Institution of Mechanical Engineers,, 

 1888, page 671. 



