RIEHLE TORSION MACHINE. 



moment is recorded in foot-pounds directly without any 

 calculation. The specimens used in this machine are made 

 with square ends, and are held in a self-centering grip. 



The twist is put upon the specimen through a power- 

 d riven speed cone working on to a train of gearing. 

 Specimens up to K in. diameter and 20 in. long can be 

 tested in this machine. The longitudinal movement of 

 the loose headstock is up to 12 in. There is a graduated 

 circular scale attached to the loose headstock by means of 

 which the angle twisted through by the specimen under 

 test is indicated. 



The accompanying illustration. Fig. 100, represents an 

 improved form of torsion machine made by Messrs. 

 Kiehle. This machine is capable of applying a twisting 

 moment of 250,000 inch-pounds. The power is applied 

 through a system of compound levers, and the end of 

 specimen at which the twisting moment is applied is held 

 in a set of toggle grips, supported by a parallel system of 

 levers, which arrangement completely neutralises any 

 stress except that exerted by the specimen. Specimens 

 up to 10 ft. long can be tested in this machine. 



116. Observations on Torsional Testing Machines. 



From the above descriptions it will be gathered that there is 

 considerable variety in the arrangement of torsional testing 

 machines. Many of the details are defective. In 

 all probability the best arrangement for the measure- 

 ment of the twisting moment is that of a simple 

 lever carrying a constant load whose position 

 can be varied. This is the most convenient method, 

 besides being more accurate than using a constant arm 

 and spring instead of a deadweight. Whatever the magni- 

 tude of the jockey weight it can be perfectly balanced in 

 its zero position by means of a counter-weight, its move- 

 ment along the arm can be measured with a great degree 

 of accuracy, and the weight itself, when once it is stan- 

 dardised, remains practically invariable. A spring, such 

 as the one that would be used to take the place of a dead- 

 weight, besides depending for its readings on a previous 

 calibration with known weights, may possibly become 

 affected by constant use, and the value of its readings 

 changed ; and, if this does happen, there is nothing to 

 indicate that an error has arisen. A compound lever 

 arrangement, such as the one used on the Riehld machine, 

 makes it possible to use small weights and renders the 



