72 SCIENCE OF SUCCESSFUL THRESHING 



so bad that it makes all boilers liable to prime. The throt- 

 tle should be drained in cold weather to prevent damage 

 by frost. 



Leaky Throttles. If the throttle is leaky, see that 

 the valve is put in so that the steam pressure holds it 

 against the seat when closed. Arrows are placed on the 

 body casting and on the valve itself, indicating the direc- 

 tion of the flow of steam to aid in putting in the valve 

 correctly. Leakage may be the result of a sprung valve- 

 body or valve, or both, occasioned by freezing or other 

 causes. The valve itself may have become twisted by 

 someone trying to open the throttle when it was stuck by 

 frost. Leaks can usually be remedied by taking out the 

 valve and filing it on the high places 

 shown by the contact. Use a very 

 fine file and bear lightly, or use emery 

 cloth. File off but little before try- 

 ing the valve for leakage. A second 

 filing will usually be found to suffice. 

 The Governor. The speed of the 

 steam threshing-engine is controlled 

 by a governor, which "throttles" or 

 limits the amount of steam admitted 

 to the cylinder. The essential parts 



FIG. 2O. GOVERNOR. . 



of a throttling governor consist of 

 balls which tend to fly apart by centrifugal action, which 

 movement is transmitted to the valve and partly closes it. 



