TESTING OF FIBROUS ROPES. 261 



fast as the other. This fast gear is used for light wire 

 testing. An automatic arrangement is provided, by means 

 of which the poise-weight is carried outwards along the 

 beam by the falling of a weight. This automatic motion 

 only comes into action when the beam is raised above its 

 normal position by the pull on the specimen. This 

 releases the escapement wheel, which will be seen at the 

 end of the beam, and the weight is allowed to move the 

 poise-weight outwards, and so increase the stress, and with 

 it the strain. 



139. The Testing of Fibrous Ropes. Like wire ropes, 

 ropes made of Kussian, Italian, Manilla hemp, or 

 cotton are all somewhat difficult to handle in a testing 

 machine, on account of the fact that there are few 

 really satisfactory ways of holding the specimens. The 

 length tested may vary from 18 in. to several feet and is 

 practically limited by the capacity of the testing machine. 

 Of arrangements for holding the ends it is found that both 

 knots and splices are practically useless, as when either of 

 these is used the fracture of the rope nearly always takes 

 place at or close to the knot or splice, as the case may be, 

 and not in the body of the rope, which is what is desired. 

 The failures of this kind of holding seem to be due to the 

 sharp curvature of the rope itself, fracture taking place in 

 a manner analogous to the failure of a beam. 



Unwin recommends the attachment used by Kortum 

 for the purpose of holding the ends of a piece of fibrous 

 rope in a testing machine. This is shown on Fig. 128. The 

 holder consists of an outer shell terminating at its upper 

 end in a loop by which attachment is made to the shackle 

 of the machine. The body of this shell is made taper, 

 with the smaller diameter at the outer end. Fitting this 

 taper portion are two gripping wedges, shaped to fit the 

 socket, so that as they are drawn outwards they close 

 inwards. These wedges are also made to taper in the 

 opposite direction on their inside surfaces, which are 

 provided with a number of sharp teeth, so as to penetrate 

 the rope as the wedges are drawn together. When the 

 rope has to be gripped for testing it is only necessary to 

 insert it in the holder and then draw it tight. By this 

 action the wedges are drawn downwards and close in upon 

 the rope, the gripping being tighter at the outer free end 

 than further down, so that the grip on the rope increases 

 from the top downwards. According to Professor Unwin, 



