GREENWOOD MACHINE. 81 



When the machine is to be used for crushing or cross- 

 breaking tests, the same principle as the one already 

 described is employed. A third crosshead is put on the 

 bed between the movable one and the straining cylinder ; 

 and this is connected by two extra links to the first-motion 

 lever crosshead. So that, when pressure is applied to the 

 ram in the cylinder, the movable crosshead is pulled by the 

 screws against the third crosshead through the specimen, 

 the load being measured as before by the force transmitted 

 to the weighing levers through the two extra links. 



Fig. 31(a) shows a plan view of the arrangement of 

 this machine for crushing. Here M is the small crosshead 

 attached to the first-motion lever linked to the extra cross- 

 head N by the rods LL. The specimen to be crushed 

 is placed between the plates at P and J, J being on the 

 loose crosshead. 



Fig. 31(6) shows a plan of the cross-breaking gear. M is 

 the small crosshead attached to the first-motion lever. N 

 is the extra crosshead linked to M by the rods L L. The 

 beam to be tested (here shown dotted) rests upon two sup- 

 ports K K at the end of a beam C C, and is pulled against 

 the central V piece at J, attached to N. The beam C C 

 is connected by the screws with the straining ram. 



At the end of a test the water is released, and the 

 straining ram brought back to its initial position by means 

 of a chain and balance load, which will be seen hanging- 

 beneath the bed on Fig. 30. 



This machine has been specially designed for general 

 testing, and for accommodating specimens up to 6 It. in 

 length. In addition to what has been described, there is a 

 gear provided for carrying out torsion tests. This will be 

 described later. 



40. so-ton Greenwood Testing Machine. Commercial 

 Type, for Shorter Specimens. This machine is illustrated 

 on Fig. 32. It will be seen that the machine occupies less 

 space than the one last described, in fact it has been 

 designed especially for compactness. It takes in specimens 

 up to 24 in. long in tension, and 12 in. long in compression. 

 There is a beam for testing under transverse stresses whose 

 supports are 3 ft. apart. 



Apart from the bed of the machine being shorter than in 

 the case of the machine shown on Fig. 30, additional com- 

 pactness is obtained by having the second lever, which carries 

 the travelling weight, placed directly above the machine 

 instead of projecting beyond its end. Two links are taken 

 G2 



