AlexPyro66 Posted November 23, 2012 Share Posted November 23, 2012 Hi everyone i want to make my ball mill i have a 1/2 hp 1370 rpm motor and i want to spin a 8 inch jar what size of pulleys can i use? Link to comment Share on other sites More sharing options...
dagabu Posted November 23, 2012 Share Posted November 23, 2012 (edited) Its easiest to use an online calculator to get the rpms right. Its the first pulley on the motor that sets the from of the system since you can't power directly from the shaft. A 2" fixed pulley is a good place to start. A pulley rpm calculator found online makes easy work of the calculations. Remember to measure your drive rollers and jar to get the exact OD or you can easily under/over speed your mill. -dag Edited November 23, 2012 by dagabu Link to comment Share on other sites More sharing options...
Col Posted November 23, 2012 Share Posted November 23, 2012 (edited) Assuming your driven rollers are 3/4" outside diameter with the hose. A 2" pulley on the motor and a 4" pulley on the driven shaft will give you 65rpm on the jar. Note that it doesnt take losses into account but it`ll be somewhere in the ideal speed ballpark for that jar size. Edited November 23, 2012 by Col Link to comment Share on other sites More sharing options...
dagabu Posted November 23, 2012 Share Posted November 23, 2012 I have that calculation down for my 6" jar, are you sure that is for an 8" jar? Link to comment Share on other sites More sharing options...
Col Posted November 23, 2012 Share Posted November 23, 2012 (edited) I rounded it up to 200mm od and used 195mm for the jar id with 1/2" media to find the optimal and critical speeds (64.4rpm and 99rpm).A 150mm od jar on the same mill would run at 86.7rpm, assuming no losses I guess if the jar is made from pvc pipe, your 6" measurement could be geared to the id/nominal bore?It seems schedule 40 pvc pipe is 168mm od and 154mm id. With 3/8" media the optimal speed is around 72rpm, you`d get ~77rpm with a 2" + 4" pulley and 19mm od driveshafts.Now i`ve done all that.. you`re prolly using reducers on each end of the pipe which increase the diameter lol Edited November 23, 2012 by Col Link to comment Share on other sites More sharing options...
AlexPyro66 Posted November 23, 2012 Author Share Posted November 23, 2012 Thank you very much for your replies yes the od is 8 inches Link to comment Share on other sites More sharing options...
Bobosan Posted December 22, 2012 Share Posted December 22, 2012 Thread is a tad old but in case anyone wants a installable pulley/speed calculator, one is attached.RPM Calculator Setup.zip Link to comment Share on other sites More sharing options...
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