54 WERDER TESTING MACHINE. 



accuracy those of every other type of machine. Its general 

 arrangement is shown on Fig. 18. The left-hand end of 

 the specimen S is held firmly in grips attached to the rigid 

 frame of the machine, and incapable of movement in either 

 direction. The other end is held by grips, which are 

 attached through links to the knife edge at the end of the 

 small arm of the bell-crank lever. The other knife edge 

 bears on the fulcrum, which is carried upon the outer 

 end of a horizontal ram, working under hydraulic pressure 

 in a cylinder rigidly fixed to the framing of the machine. 



In the Werder machine used by Bauschinger, capable 

 of exerting a pull on a specimen of 100 tons, the 

 fulcrum distance, or the distance between the two knife 

 edges on the short arm of the lever, is only 4 milli- 

 metres (equivalent to about i\in.); and as the long or 

 horizontal arm of the lever is 2,000 millimetres, or 500 times 

 the length of the small arm, a leverage of 500 : 1 is obtained. 



The load on the specimen is controlled by adding weights 

 to a scale pan hung from a knife edge at the outer end of 

 the lever. In order that the full load of 100 tons may be 

 applied, it is only necessary, with this large leverage, to 

 have a load in the scale pan of 



or, 4 cwt. 



As the load upon the specimen is increased by the 

 placing of small weights in the scale pan, and as the 

 specimen in consequence stretches, the lever relinquishes 

 its horizontal position, and becomes inclined downwards. 

 To counteract this and keep the lever floating horizontally, 

 water is pumped into the ram cylinder by means of hand 

 pumps, the ram driven outwards, and the lever restored to 

 its proper position. In order to ascertain when the lever 

 is floating horizontally, a spirit level is attached. 



In addition to its use for tensile testing, special attach- 

 ments can be made for the purposes of compression, 

 bending, and torsion. 



THE BUCKTON-WICKSTEED SINGLE-LEVER TESTING 

 MACHINE. 



25. This, the second of the single-lever machines, has 

 already been shown diagrammatically in Fig. 18, and it.s 

 general principle briefly explained. The simplicity of this 

 principle makes the machine very convenient to use and easy 



