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TESTING MACHINES. 



considered so suitable for the rougher kind of commercial 

 work as lever machines. 



Of the lever machines the most generally used and 

 popular in the United States are the " Fairbanks," the 

 " Olsen," and the " Riehle " machines. 



The Fairbanks is a vertical machine with a screw 

 gearing attached to the bottom of the specimen, for 

 the purpose of taking up the strain, and a compound 

 lever weighing apparatus for measuring the load. The 

 Olsen machine, whose arrangement is shown diagrammat i- 





FIG. 38. Diagrammatic View of Olsen Testing Machine. 



cally on Fig. 38, is carried on a small square bed plate of 

 box pattern. In this bed plate is carried the gearing used 

 to give motion to four vertical straining screws, which 

 carry the lower crosshead, and draw it downwards when it 

 is desired to take up any stretch which may have occurred 

 in the specimen under test. The gearing is operated in 

 the first place by means of a pair of power-driven pulleys. 

 By means of various arrangements of pulleys, the mov- 

 able crosshead can be moved either up or down, and 

 either at a fast or slow speed, the slow speed being obtained 



