Neiv Engine for Riding. 79 



"by means of the sleeves carryiiifj the tubes; provision was also made 

 for a certain amount of lateral displacement. The optical equip- 

 ment of the microscopes afforded a magnification range of from 

 50 to 100 diameters which was found to be ample for all purposes. 

 The steel spindle, carrying the whole system, was supported on the 

 two " dead " centres of the lathe, which were secured in a "locked " 

 position. The cutter frame, supporting the grinding disc and guide 

 pulleys, is seen in a working position immediately in front of the 

 ratchet wheel. During the operation of cutting the teetli the main 

 carriage or saddle of the lathe bed, in the tool holder of which the 

 •e utter frame was clamped, was traversed along the ways of the lathe 

 for the short distance, usually less than an inch, required to com- 

 plete the cut and clear the ratchet. To effect and control this move- 

 ment, the apron mechanism of the lathe carriage was made use of 

 ■iind proved to be both steady and reliable. 



During work upon the ratchet, and particularly near its final 

 stage, pro'^ision was made f(n- protecting the more sensitive and 

 exposed parts of all mechanism likely to l3e affected by heat from 

 Ihe operator's body or other source liable to lead to expansion or 

 contraction owing to temperature changes. The cutting wheel, 

 which was absorbent, was maintained in a moist condition "with 

 kerosene, derived from a sponge pad in contact with its edge. 

 Hence the heat prodiiced by the operation of grinding was reduced 

 to a minimum. 



In the course of the final finishing Avork upon the ratchet wheel, 

 the whole of which was effected with the diamond charged discs 

 already described operating with cuts of .0001 in. or less, a greatly 

 Improved grinding frame (not shown in the photograph) for hold- 

 ing the grindirtg cutters was used. Hence the combined outfit 

 worked with such pi-ecision that it was possible to grind completely 

 round a circle of 540 teeth and find hardly any appreciable loss 

 -upon the wheel cutting edge due to wear, although the operation 

 involved over 2,000,000 revolutions of the grinding disc. A result 

 of such a nature would have been quite impossible without the aid 

 of the special appliances with which it was effected. 



Reference to one or two other details affecting grinding opera- 

 tions may here be made. In order to save time, the angular feed 

 of the ratchet through a tooth space was effected by means of the 

 tangent wheel during four-fifths of the time occupied in the process 

 •of grinding out the teeth. During the finishing process, however, 

 In order to eliminate all stresses, the tangent wheel was thrown out 



