52 



- AND DESIGN 



sunk key F. It is also good pmotioe to ArM ' k on 



to the shaft The process of shrin I :>t- of l.onn^ out 



the crank a little sm:illrr than th.- shaft, and thru I, 

 which causes it to expand sulii. -imtly to go on to the si. 



milk cools, it shrinks anil grips t In- shaft iirnily. Tin- 

 K may also \*> shrunk on to tin- .-rank pin. (In- latt. r b 



d over as shown in fig. 17. 



A good plan to adopt in preference to the shrinking process 

 is to force the parts together by hydraulic pressure. Thi* 



. 47 



method is adopted for placing locomotive wheels on their axles, 

 and for putting in crank-pins. As to the amount of pressure 

 to be used, the practice is to allow a force of 10 tons for every 

 inch of diameter of the pin, axle, or shaft. 



Instead of being riveted in, the crank pin may )* prolonged 

 and screwed, and fitted with a nut. Another plan is to put a 

 cotter through the crank and the crank pin. 



The distance from the centre of the crank-shaft to thr 

 centre of the crank- pin is called the radius of the crank. The 

 4ltrow of the crank is twice the radius. In a direct-acting 



