[LanceM]

I have a new/old or old/new depending upon how you look at it compressor in the shop. I replaced the compressor 5-10 years ago with a Quincy QTS-3 keeping the tank and 3 hp motor. Doing some looking at the paperwork this compressor should be able to produce 9.6 scfm @ 90 psi, I don't think I'm getting that currently and I'm thinking of uping to a 5 HP and some different pulleys to spin things a little faster. (Recovery is slow and so is pump up in general)

So I guess my question is will spinning the compressor faster give me a higher cfm output? reason says it should, but with increased wear, which isn't a consern, if it blows in a year or two I'll have my excuse to go get a good 2 stage BTW, I figure I'm spinning the compressor around 800 rpm now with the current pulley ratio, I'm thinking of going for say 1200-1400 rpm... What ya think?

Lance

[willys36@aol.com]

Not a good idea to spin those faster than the factory designed them in the long term for the reasons you mentioned. However if you don't mind replacing it in the foreseeable future, it will definitely put out more air by spinning faster.

[LanceM]

That's part of my problem I guess is that since this is a make up of miss matched parts I don't really know what it was suppose to run speed wise and the current set up was a guess. What I might do is go to a 5 hp for the starting torque and raise my turn on trip point. Then step up the pulley size in increments till it can keep up with me. Make it last as long as it can with the least cost in. I figure this compressor dosen't owe me a dime, so if it goes it goes, no regrets.

[oldred]

Lance-No doubt about it if you spin it faster it will produce more air. But like Willys said it is not a good idea to spin too fast. Your motor speed is probably 3450 so you can measure the pulleys and get an idea of how fast you are now but heat build-up will limit how much faster you can go. One thing you do have in your favor is that Quincy as those darn things are just about indestructible! If you can, I would suggest some sort of extra cooling such as a small electric fan and monitor the heat for a while to see if you have a problem before it gets serious. Good luck!

[Huskinhano]

First, I'd so some research by calling uincy to see what rpm the compressor should be running. Spinning it faster may increase air pressure alright but not to to much for capacity. What will happen, you'll have more mechanical friction causing heat. Heat by itself will create more pressure without more volume IIRC, this is "Charle's" law for gases which states that a proportional increase in heat will cause a proportinal increase in pressure. Try this test. get a plastic bottle with a cap, empty of course. Put the lid on it at room temperature. Now heat that sealed container. You'll see the bottle expand. If you loosen the id, you'll hear the air escape. Does this mean that there is more air, no. Just more pressur with the same volum of air. Concersely, it you cool it such as putting it in the frig, you'll see the container colapse.

[oldred]

Huski-That is nonsense, Sure you will increase volume if you increase the RPM.- RPM x displacement = volume. Of course delivered air depends on the pressure at delivery but if you spin the pump faster you WILL produce more air. The bottle test you mention dosnt mean a darn thing since you are not adding more air only expanding the air already present by heating it. Pressure is a function of Resistance and can be any given value at any volume. Now you try this test, spin a compressor pump slowly by hand and note the small amount of air delivered and then spin it at full speed with the motor. Does it now produce more air? Of course it does! Now if you continue to increase speed it would produce air volume proportionally until the darn thing comes apart from excess speed.