WIRE ROPE TESTS* 



255 



of several of the wires at a point which is between the two 

 holding sockets ; sometimes one or two of the strands fail ; 

 it is not often that the rope as whole breaks at once. If 

 the ends are not held in a satisfactory manner, the rope 

 may be pulled out of one of the sockets, or the fracture 

 of a number of the wires may take place inside the socket 

 through unequal tension. 



When a length of rope is tested it is usual to test 

 also a number of the wires which go to make up 

 the rope, and to compare the combined strength of 

 these with the strength of the rope itself. Wires 

 must not be taken at random from the rope, but if 

 all the individual wires forming the rope are not tested all 

 those making up one strand are to be tested, and the 

 combined strength of these, multiplied by the number of 

 strands, gives the nominal strength of the rope. By doing 

 this the one soft wire in each strand is tested along with 

 the others of the strand, and not several, as might be the 

 case if the wires were selected at random. 



The testing of these individual wires may be most 

 conveniently performed in a special wire testing machine 

 or a smaller type of general testing machine. Many 

 machines are made to suit the special requirements of 

 wire manufacturers. For wire testing, wedges are used, 

 for holding, with the gripping surfaces -finely cut. When 

 the wires of a rope are being tested there is no need to 

 take any other measurements than the breaking loads. 



The following is an example of a complete test 

 given by Mr. Biggart in his paper on wire ropes. 

 This rope was one made by Messrs. Bullivant, and con- 

 sisted ol crucible steel wires. 



TENSILE TEST OF A STEEL WIRE ROPE.* 



This is a fairly good sample of a test of such a wire 

 rope. There are six strands in the rope, so it is to be 



* Minutes of proceedings of the Institution of Civil Engineers, vol. ci. 



