electric to gas air compressor?
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  1. #1
    Join Date
    Mar 2010
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    sandusky ohio
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    27

    electric to gas air compressor?

    Anyone ever converted a electric air compressor to use a gas engine? I have an old one with a bad motor and would like to convert it to use one of the cheep honda clone engines that are out there. I think it would be a bonus to my mobile capabilities. Could you use a clutch like an auto AC system uses? What would you use to control the engine speed?
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  2. #2
    Join Date
    Jul 2010
    Location
    Georgia, USA
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    153

    Re: electric to gas air compressor?

    It depends on the size of the compressor. What size AC motor did it have? If less tha 2HP you might be OK with the 6.5HP gas engine from Harbor Freight - probably still on sale for $99.

    You really need a compressor with an unloader, which allows you to start the engine without the load of the compressor. I don't know if an electric clutch such as on car air condtioners could handle the load of a big air compressor. A little Google research on the HP required by car air conditioning compressors should give you that answer. A small gas engine simply may not have enough mass to have the inertia to start an air compressor without an unloader. That would almost be like turning a locked rotor. The only 'give' in the system would be the the belt(s) and that kind of torque load may shorten belt life.

    You want to run the gas engine at it's design speed (3000 - 3600 RPM) and adjust the pulley ratio to get the compressor speed right. Small gas engines don't make much power at lower-than-optimum speeds.

    On the other hand, If you have the parts - go for it. You might luck out and have a combination that works.

    Remember to post pictures and details when you get it working.

    John
    Last edited by papaof2; 10-02-2010 at 12:28 PM. Reason: spelling

  3. #3
    Join Date
    Aug 2008
    Location
    Sudbury, Ontario
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    741

    Re: electric to gas air compressor?

    Ditto on the unloader, simply put an electric compressor depends on the pressure switch to start/stop. A gas engine runs continuously, you need the unloader to bypass the valves in the compressor head so when the pressure switch reaches the high pressure set point the compressor stops compressing air until it reaches the low pressure set point at which time the unloader stops bypassing and allows the compressor to compress air normally. Otherwise you would end up blowing off air through the relief valve when the pressure reached set point. Also when the bypass is active, the motor doesn't work nearly as hard or consume as much fuel.

    I have a small compressor I intend to convert to gas someday (When my brother returns it) I have a separate head for this compressor that has the unloader built in..

    Clear as mud? Hope this helps.
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  4. #4
    Join Date
    Mar 2010
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    sandusky ohio
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    Re: electric to gas air compressor?

    Thanks guys I will get some pics and specs soon, its burried in the garage and deer season has started and duck season is less than 2 weeks away so it may take me a while. Its an old sears compressor and I THINK it is 2 hp. PS what does an unloader look like?
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  5. #5
    Join Date
    Oct 2006
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    5,241

    Re: electric to gas air compressor?

    To do this, basicly you need both a new gas motor and a new continuous-run pump with unloader head. All you'll be saving from your existing compressor is the tank. May as well just buy a new gas compressor. The end cost will be about the same and alot less hassle and you can sell your existing electric compressor to re-coup some money, or save it for use in the shop and keep the gas one on the truck.
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  6. #6
    Join Date
    Jan 2007
    Location
    Ogden, IA
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    441

    Re: electric to gas air compressor?

    You can get replacement unloaders for pretty reasonable on ebay. Despite the discouragement I think you can build one for pretty reasonable.

    I have an American IMC "Powrprofile" gas compressor and the unloader runs the throttle on the gas motor. When its reached enough pressure it also vents the compressor output to atmosphere. To answer your question it looks like a fancy brass valve with a throttle cable coming off it that runs to the gas engine.

  7. #7

    Re: electric to gas air compressor?

    I have run gas compressors off electric, and electric compressors off gas. You can use the "air conditioning" type clutch on the compressor to cut it in and out with a 12 volt source, or use an unloader as described. The clutch will be able to more than handle the load of a 10 horse or smaller compressor.
    With either, be sure to use a SAFETY VALVE between the compressor and tank to avoid catastrophic results.

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