TESTING MACHINES. 91 



more than any other country, the variety of types of 

 testing machines is great. Single lever and double lever, 

 horizontal and vertical all are used. But in other direc- 

 tions there are certain very definite limitations. Manometer 

 or diaphragm machines are not used except for very small 

 loads, and with the exception of machines with a capacity 

 of up to three or four tons, the load is always applied, 

 and the strain taken up by hydraulic means alone. 

 In other countries this is not so. Manometer machines 

 are used to a not inconsiderable extent both in France 

 and the United States of America. In America almost 

 entirely, and to some extent on the Continent of Europe, 

 screw gearing, worked by either hand or power, is 

 used in place of hydraulic appliances for taking up the 

 strain of the specimens. 



47. Continental Machines. Of these the Werder 

 machine has already been briefly described. An Alsatian 

 machine, the Grafenstaden, has been largely employed 

 for important testing work 1 . It is made in various sizes, 

 some of the larger ones being arranged as compound lever 

 machines and some as single lever. In the Grafenstaden 

 machines the levers are horizontal, and the specimen 

 placed in the machine vertically ; the weighing lever is at 

 the lower end of the specimen, and the appliances for 

 taking up the strain at the top. This latter is of the screw 

 type, the screws used for raising the upper end of the 

 specimen being drawn upwards by large nuts rotated by 

 power-driven gearing. The jockey weight is moved along 

 the weighing lever by means of a screw. 



Another machine, known as the Thomasset machine, 

 depends for its load measurement on the fluid pressure in 

 a closed diaphragm, which is pressed upon by the end of 

 the long arm of a single lever of the second order, whose 

 fulcrum is at the other end, and whose third point is 

 attached to the upper end of the vertically-held specimen. 

 The lower end of this specimen is pulled downward by the 

 water pressure on an hydraulic piston. 



48. American Machines. These are mostly compound 

 lever and screw gearing machines. Formerly hydraulic 

 power was employed for taking up the strain, but this 

 method has given place in most instances to the use 

 of screw gearing for effecting this purpose. A number of 

 manometer machines as exemplified by the Emery 

 machine are also in use. These are said to possess both 

 great accuracy and extreme sensitiveness, but are not 





