CREAMERY BUTTJ'R MAKING 193 



Rubber belts are not as desirable for creamery use as 

 leather belts. 



Adjustment of Shafts. To avoid straining a belt the 

 shafts must be parallel. This means that where the inter- 

 mediate and engine are hitched to the same shaft the 

 latter must be placed in position first. The engine and 

 intermediate are then lined up so as to. have their shafts 

 run parallel with the main shaft. When the shafts are 

 parallel the pulleys are easily adjusted so as to have the 

 belts run on the middle of the pulley. 



Lubricants or Oils. These slippery substances act in 

 a two- fold way in minimizing the friction between sliding 

 surfaces : ( i ) by filling up the inequalities of the sliding 

 surfaces, thus preventing interlocking; (2) by allowing 

 oil to slide on oil instead of one solid surface upon 

 another. 



The best oils are those that are entirely free from any 

 tendency to gumminess and it is economy to use only 

 such. Indeed in fast running machinery no other oils are 

 permissible. 



Consistency of Oils. This is determined by the use 

 to which the oil is put. In fast running machinery where 

 there is little pressure on the bearings, as, for example 

 in a cream separator, very thin oil is most serviceable. 

 The reasons for this are ( i ) that only a very thin layer 

 of oil is required in the bearings of such machinery, and 

 (2) that there is some friction produced in one layer of 

 oil sliding upon another, and the thinner the oil the less 

 will be the friction produced in this way. 



The crank shaft of an engine, which runs at a com- 

 paratively low speed and is subjected to more or less 

 pressure, requires a rather heavy oil for best service. 



Hot Bearings. These are most frequently caused by 



