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gas powered air compressor

16036 Views 27 Replies 14 Participants Last post by  biscuit
it's funny. the other day i was thinking i would like to build a gas powered air compressor. i figured i could use any electric one with a belt. and low and behold i found one on the side of the road. i figured the elec motor was bad. i brought it home, plugged it in and it works fine. went thru about 4 cycles of filling it with air and using a blow gun to empty it. it's a sears/craftsman 1hp. but i already have an elec one. so i am gonna sacrifice this one to build a gas one. now the search is on for a sideshaft engine. does anyone have any suggestions on what equipment i might find that has one? i live in the northeast. so we have all kinds of equipment kicking around at times.
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You can convert a small electric compressor to gas by just changing the electric motor to the gas engine and using an electric clutch on the engine.

You need a gas engine with a good governor and a throttle you can set to maintain the engine speed.

Wire the existing pressure switch to engage and disengage the electric clutch the same way it started and stopped the electric motor.
The pressure line coming out of the compressor to the tank already has a pressure unloader valve in it so the electric motor didn't start under pressure.

The disadvantage is the gas engine has to run at a higher RPM all the time whereas the Granger valve allows the engine to idle when not driving the compressor.

I've seen the Amish redo small compressors this way and they work good for small jobs.
You want an unloader. $60 at Grainger. It has a built in pressure valve.

It has a port for engine control so you hook a small piece of tubing to it and buy the smallest air cylinder you can. If you have a lathe, you can make one. 1/2" dia and 1" throw is enough. Hook it to the throttle because when you reach pressure, the engine port will go active and you'll throttle back. When need pressure, she'll throttle up again. :trink39:

PS: Looking at Grainger on the same page, I see they have the engine control solenoid too. $20 is kinda expensive for that.

25 years ago I built the same thing. I used an old 1.5 hp cast iron Briggs, a little 1 lunger and a semi truck air tank. It was a cool little unit and with the flywheel weight it had, it would idle right down but when it needed pressure, it was a puff of black smoke and a roar.
I think most snow thrower engines lack any sort of air filtration. Something to keep in mind.
it even came with the centrifugal clutch that i can use on something else
Why not keep the centrifugal clutch on the engine for your compressor? If you do that then all you need to do is install an electric pressure switch and a solenoid on the engine throttle. Set the switch and solenoid to raise the throttle from idle to full throttle when pressure drops below about 90 psi and to turn off at about 125 psi.

The pressure switch and solenoid should cost you less than the fancy valve and the centrifugal clutch provides slippage to reduce the abrupt engagement that an electric clutch causes when it kicks in.

Rolair compressors use a simple diverter valve to unload the compressor if you insist on building your own. A centrifugal clutch is going to have a hard time starting a loaded compressor. If you have all the pieces laying around this would be a good learning experience, but if you're doing it to save money, you'ld be better off buying a used Emglo or Rolair with the gas engine. Avoid the cheap imports, there isn't much life built into them and all you'll end up with some day is a spare engine.
A centrifugal clutch is going to have a hard time starting a loaded compressor.
I'd say that this is entirely dependent on the gear ratio driving it. In any case the centrifugal clutch would have the advantage of a cushioned engagement over an electric clutch.

Most air compressors can be plumbed up in such a manner that when the pressure reaches the maximum desired setting,a valve sends some of the compressed air to the
intake valve on the pump and holds it open,allowing the pump tp "frewheel" without producing any pressure,until enough pressure drop occours and the valve closes and allows the pump to "pump" again by letting the intake valve work normally..

I have seen the old car A/C compressors (the "log" style ones,or York & Tecumseh 2 cyl ones),converted to air compressors by using a gas engine to power them,but you'll need a battery & charging system to get power to engauge the 12V clutch to engauge..we had a truck at the junkyard we put a 4 cyl air pump on its 390 Ford engine we got from a compressor that someone scrapped after the tank rotted thru..used all the original plumbing but it had no valving to shut down the air pump when it reached its maximum--we just let it run with the safety blow off valve open--it wasn't too often it "popped" off anyway,with two of us using air impact guns or sandblasting with had a manual idler "clutch" you had to engauge to tighten the belt under the hood to operate the pump..was very crude,but it worked good...
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never made the compressor. couldn't find a pulley that would fit. plus re-routing the air intakes was a nightmare. so i gave the engine to my buddy (already said that)and went back to focus on my Craftsman 11hp rider. did the pulley swap and a few other mods. then last night i pulled the tires off the rims and welded them to some S-10 rims. gonna put some meaty snow tires on them and run them on the tractor. was thinkin about finding a harley engine and putting it on the craftsman. and vids or in depth pic of this bein done?
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