201 i R1KH1.K ToltsloN MA< MINK. 



Crosby indicator, shown in the illustration. When an 

 autographic diagram is to be taken the lever is so arranged 

 t hat it compresses the spring of the indicator as it descends, 

 the amount of the compression being proportional to the 

 moment on the bar. This is accompanied by a movement 



FIG. 99. Deeley's Torsion Test Piece. 



of the pencil, which is of necessity also proportional to the 

 moment. The horizontal motion of the paper drum is 

 effected by a cord connection with the centre, which holds 

 the worm-wheel end of the specimen, and the horizontal 

 movement of the paper is proportional to the angular 

 twist of the specimen. 



i 



115. Riehle Bros. Torsional Testing Machine. Messrs. 

 Riehle Bros., of Philadelphia, make a torsion testing machine 

 of large power, which has some novel details worth con- 

 sidering. The machine consists essentially of two head- 

 stocks, which serve to carry the centres in "which the ends of 

 the test specimen are held. One of these, carrying the centre 

 at which the moment on the bar is measured, is fixed upon 

 the bedplate of the machine, while the other one, carrying 

 the worm-wheel, is capable of being moved along the bed, 

 so that the length of the specimen can be varied. This 

 longitudinal movement is effected by means of a rack and 

 pinion. The twisting moment is determined by having 

 two arms instead of one in the more usual arrangement. 

 These two arms project from the grip-head horizontally on 

 opposite sides, and, by means of an equalising lever below 

 the centre, two equal moments are imposed on opposite 

 sides of the centre. The end of this lever is linked to the 

 knife-edge at the end of the short arm of a second 

 horizontal lever. The end of this again is connected by a 

 vertical link to the short arm of the third lever. This 

 third lever carries the jockey- weight, whose position on 

 the lever serves to indicate the twisting moment on the 

 specimen. So that, in this machine, the moment is applied 

 through a system of three levers instead of one, making 

 the actual weights to be dealt with much smaller, and 

 rendering the manipulation of the machine easier. The 

 graduations on the weighing lever are so arranged that the 



