Machine for applying Bending <Sf Tioisting Moments. 497 



piroted to rotate around a line intersecting the axis of the 

 specimen and perpendicular thereto, and this method o£ 

 pivoting must also be adopted at the horizontal lever. This 

 arrangement only differs from that of the perfectly freely 

 suspended arrangement shown by fig. 1 (PI. XI.) infixing one 

 point of the rod, and this has the indirect advantage of stilling 

 ■vibration which is troublesome in the freely suspended bar. 



The arrangement described above is carried into effect in 

 the manner indicated by figs. 2, 3, 4, and 5, showing the 

 apparatus in side elevation, end elevations, and plan 

 respectively. 



The various parts are supported in a built up frame con- 

 sisting of two planished steel shafts, A secured in cast-iron 

 cross frames, B mounted on four standards, one of which 

 latter is adjustable in height to secure steadiness on an uneven 

 floor. Upon the steel shafts are two castings C. D, each of 

 which has a cylindrical bearing E encircling one of the 

 shafts and resting with a flat face F in line contact with the 

 other shaft, and secured in position by a cross-bar Gr threaded 

 on studs. This connexion is perfectly rigid, since it removes 

 all degrees of freedom and it is readily released by simply 

 turning back one of the cross-bar nuts, leaving the casting- 

 free to slide into a new position. It also has the advantage 

 that no accurate fitting is required for the supporting frame. 

 The casting C carrying the worm-wheel gear W has trunnion 

 bearings H at right angles to and intersecting the axis of 

 the specimen. The bearings are fitted with friction rollers, 

 and when the machine is used simply for torsion the worm- 

 wheel is kept in a vertical position by an arm I keyed to the 

 bearing H and locked in position by a thumb-screw. A 

 weight J attached by an arm to the second bearing balances 

 the pivoted casing in all positions. 



The weigh levers are supported from a vertical standard 

 K of the frame D by a wire L, terminating in a thin plate 

 M with a keyhole slot encircling the spindle N. Formerly 

 a roller bearing was used for this spindle, but this is an 

 unnessary refinement as the friction is extremely small, and 

 can be easily taken into account. The casting supported in 

 this way has three levers, P, Q, and R, the first two of which 

 are for the application of twisting moments S, and the third 

 R, in the line of the specimen, is for applying a bending 

 moment. 



All the loading levers are provided with knife-edges S, 

 fig. 6, of circular form, made by turning an ordinary Whit- 

 worth nut down to form a disk with a V-shaped edge. These 

 disks carry rings T with wide angled V-shaped recesses on 



Phil. Mag. S. 6. Vol. 17. No. 100. April 1909. 2 M 



