DAIRYING 



45 



with the separator by the manufacturer. In order to obtain this 

 speed it is necessary to provide a pulley of a certain diameter 

 on the line shaft from which the intermediate is run. This dia- 

 meter is found by multiplying the diameter of the driven pulley 

 by its speed and dividing this product by the speed of the driver. 

 Such a calculation may be illustrated by assuming that the small 

 pulley on the intermediate is five inches in diameter, and makes 

 910 revolutions per minute, and that the line shaft has a speed 

 of 300 revolutions per minute. The diameter of the pulley needed 

 on the line shaft is then found by multiplying 5 by 910, which 

 gives 4550. Dividing this by 300 gives 15 inches, which is the 

 diameter of the pulley needed. 



The line shaft pulley should have a flat face at least six 

 inches wide and the belt which connects it to the intermediate 

 should be at least 2^ inches wide when power cream separators 

 are used. The speed indicator on power machines should always 

 be in place and in good repair. Frequent observations of the 

 speed should be made during each run, as losses of fat in the skim 

 milk caused by irregularity of the bowl speed, may amount to 

 a considerable figure. 



With hand machines the number of turns of the crank may 

 be regulated by using a watch to time the turns per minute. 



301. The following table * shows the effect of variations in 

 speed of a hand separator bowl on the efficiency of skimming 

 milk. The figures represent the average of 12 trials in each case. 



Per cent, fat 



* Indiana Experiment Station, Bulletin 116. 



