To Figure The Diameter Of Pulleys


Suppose a motor runs 1500 R.P.M. and is fitted with a 4" pulley. Suppose also, a main shaft should run 300 R.P.M.



Then, 1500 : 300 :: x : 4;


Or, 300x = 6000,


x = 20, or the diameter of the large pulley on the main shaft.




Suppose again that a line shaft runs 300 R.P.M., and a counter shaft 600 R.P.M. The counter shaft has a pulley 4" in diameter. The pulley on the line shaft must then have a diameter of 8".



300 : 600 :: 4 : x;


Or, 300x = 2400,


x = 8"




Suppose the cone pulley on the counter shaft runs 600 R.P.M.; a lathe spindle runs 2200 R.P.M., when connected with the small cone pulley which has a diameter of 3". The large cone pulley has then a diameter of 11".



600 : 2200 :: 3 : x


Or, 600x = 6600;


x = 11"






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