# compressor speed question



## kjbllc (Jan 16, 2012)

I have a divilbliss 230 about a 1957, the motor just went up. It was a 1725 rpm, and the new one I got is a 3450. The compressor says 300 rpm minimum, but does not say what the max speed is. It is a double belt pulley, I am thinking there is a minimum size sheave that I can get and still get the resistance I need to turn the compressor. I did some calculations ( well i went on line and got some formulas and worked them out) and a 4" sheave looks like it will give about 540 rpms. Is this too fast for the old girl? 

its a 3 hp. 
here is the formula I used
Grpm = Mrpm (Md / Gd)
Where:
Grpm = RPM of Grinder (mill)
Gd = Diameter of Grinder (mill) sheave
Mrpm = RPM of motor
Md = Diameter of Motor sheave

my compressor pulley is 19 in across which I calculated ( i hope ) at 59.69 or 60" around
any help would be appreciated, I have to use a new pulley as the old one is about 1" in diameter and the new motor is 5/8" . thanks for any help


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## rhenning (Jul 23, 2011)

Put a pulley 1/2 the size of the original pulley on the 1725 motor and it will run exactly like it did stock with the new 3450 motor. If the original pulley was 8 inches then a 4 inch pulley would be right. If the original was 6 inches was then a 3 inch would be right. I would the guess the original manufacturer was running the compressor at the best speed. Roger


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## Ironmower (Sep 19, 2010)

Exactly, Roger!


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