WBRDER TESTING MACHINE. 



53 



load W to the second lever. The first lever is bell-cranked, 

 and therefore the position of the specimen is horizontal. 



III. The accompanying sketch, Fig. 20, is intended _ to 

 represent the principle upon which machines work which 

 utilise fluid pressure for the measurement of the load. 

 The best example of this type of machine is the Emery 



FIG. 20. 



machine, whose use is almost entirely confined to America. 

 This machine is said to possess extraordinary sensitiveness, 

 and to be very easy to use and manipulate. 



In the diagram the straining cylinder is at B, S is the 

 specimen, whose right-hand end is attached to a 

 diaphragm or flexible piston in what is virtually a 

 shallow cylinder of large diameter at A. The total 

 pressure upon this diaphragm is transmitted as the load 

 to the specimen ; and the magnitude of this pressure, and 

 therefore of the load, is measured by conveying the fluid 

 to a smaller diaphragm, which again acts upon a system of 

 measuring levers and balance weights. This is a hori- 

 zontal machine. 



In all the machines which have been mentioned, the 

 load is applied and the stretch of the specimen taken up 

 by means of an hydraulic ram. The weighing appliances 

 and the hydraulic ram are at opposite ends of the specimen 

 in the case of the Wicksteed, Greenwood, Adamson, and 

 Emery machines. The Werder machine alone of those 

 which have been mentioned has both at the same end of 

 the specimen, the other end being rigidly fixed to an abut- 

 ment attached to the bed of the machine. 



Before proceeding to compare these various machines 

 and to discuss their respective advantages and disad- 

 vantages it will be well to describe them in detail. 



*THE WERDER TESTING MACHINE. 



24. The Werder machine has been described as the one 

 in which tests have been made, excelling in precision and 



*Unwin's " Testing of Materials," p. 128 



