The math is different, depending on whether its single or two stage.
Single stage: First figure out the volume of each cylinder. This would
be as follows: (caution, this calls for the cylinder radius, which is
1/2 the bore)
radius X radius X 3.14159 X stroke (all numbers in inches)
Then multiply by the number of cylinders (usually 2) and the compressor
RPM. If you don't know the compressor RPM, measure the two pulley
diameters and calculate it as follows:
compressorRPM = (motorRPM X Motor pulley dia.) / Compressor pulley dia.
Anyway, this gives you the free air cim (cubic inches / minute). Divide
that number by 1728 to get the CFM free air. Multiply that number by
about 80% to get the CFM at designed pressure.
For two stage compressors, only calculate the volume of the large
cylinder. and go through the above as if it were a one cylinder
compressor.
These results are approximate! If you don't like my answer, just
remember that I am a low life slimy lurker! Flames to /dev/nul
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