CREAMERY BUTTER MAKING 187 



the rod, but it must not be too tight, otherwise power 

 is lost in friction. If the rod has become scored or rusty, 

 smooth it with emery cloth before packing. 



5. The packing rings in the piston should be kept in 

 good repair. The clicking noise sometimes heard in 

 cylinders is due either to the packing ring wiping over 

 the edge of the counter bore or to its being too narrow 

 for the groove in which it is placed. A ring is needed 

 that fits this groove properly. If the packing ring is too 

 small for the cylinder bore it should be set out by peneing 

 or by tightening the setting out bolts. 



6. When gumminess is noticeable in any of the bear- 

 ings, remove same with benzine and use a purer oil. 



7. When the engine "races" look for the trouble in 

 the governor. 



8. Thoroughly drain cylinder when not in use. This 

 must be done in the winter to prevent freezing. 



HORSE POWER OF ENGINE. 



The horse power of an engine is calculated from the 

 following formula : 



p X 1 X a X n . 



33,000 ~ m which 

 P = Mean effective steam pressure. 

 1 = length of stroke in feet, 

 a = area of piston in square inches, 

 n = number of strokes per minute. 

 H. P. = Horse power. 

 33,000= Number of foot-pounds. 



A foot-pound is one pound raised through one 

 foot of space. 



Length of stroke = twice the length of crank. 

 No. of strokes per min. = twice the number of 

 revolutions. 



