![]() My model 230 compressor has a 3-1/2″ bore and 3″ stroke, whereas the slightly larger and current model 240 has a 4″ bore and a 3″ stroke. Luckily the current QR-25 brochure listed the cfm output of the 240 compressor as well as a suggested motor size and rpm range. ![]() Knowing that a model 240 compressor can produce 23.5 cfm (cubic feet per minute) of air flow at 100psi at its maximum speed of 900rpm, I made an educated guess that my 230 compressor was able to produce right around 20 cfm of air volume at 100psi. 100 psi, (pounds per square inch) is the limit and rating of Quincy’s entire line of single stage compressors. When higher air pressure is required, a two stage compressor must be used. One of the first things I noted was the relatively slow charge time of the 30 gallon compressor tank. I determined that the compressor was spinning well below its rated speed. The 3 horsepower motor was turning the compressor at just 565rpm. This resulted in a net volume output of just 10.8 cfm. I measured the current draw of the motor and checked it against the nameplate rating of the motor. The motor was drawing 18.6 amps at 100psi, just over the rating of the motor. I traced the high amperage motor draw to three things, thick old oil in the compressor, misaligned belts, and wires incapable of supporting a motor of this size. I was able to get the running amperage of the motor to be 14.2 amps, well underneath the 18 amp rating of the motor. I purchased a larger diameter pulley for the motor (6-1/4″ instead of 5-1/8″) which bumped the speed of the compressor up to 680rpm and output to 14.3cfm. The increased compressor speed increased the load on the motor to 16.2 amps, just under the 18 amp rating of the motor. The next step was to remove the pistons from the compressor. ![]() In order to do so, you have to remove the inspection cover on the side of the compressor, and remove the lock nuts on the end of the connecting rod caps. I took this opportunity to clean out all of the old oil and sludge from the inside of the compressor. Quincy uses a mesh screen to keep any large contaminants out of the oil pump. Removing the connecting rod caps is easier said then done.
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