converting a old air compressor

[farmall 55a case]

I would like to convert this compressor to gas powered! I have a Briggs 5hp side shaft engine. The compressor is a Curtis and says to run at 350 rpm as a min. And is a 35 gallon tank. What all would I need to do this and is it worth the effort? I have no money in tank or motor, so I don't mind spending a little to make it work! Thanks! And any info will be greatly appreciated!

 

[davesl708]

First you need to have a mount that will accept the gas engine. You will need to do the math to determine the hp needed and what size sheaves to drive the compressor at the optimum rpm while the engine runs at its optimum rpm.
The sheave on the compressor should stay the same and the engine sheave should be sized to match the needed rpms.

 

[Bird]

Of course you'd have to have some kind of gear reduction to go with that Briggs. Personally, my opinion is that it would not be worth the effort. But since I've never done that, I could be wrong. I've always owned electric compressors.

 

[George2615]

When the compressor is running on electric, it reaches desired pressure and a pressure switch shuts it off. You'll have to figure a way the shut the gas powered motor down at desired pressure or it will just keep building till the safety blows off.

 

[BHD]

basically you need an unloader designed for a gas powered air compressor, New Pilot Discharge Unloader Valve Check Valve for gas air compressor 95-125 psi - Air Compressor Accessories - Amazon.com

there are number of unloaders out there,

here is the compressor I set up, had one compressor that the tank rotted out, and one that the pump went to pieces, to this is what I come up with, after this picture was taken I added a centrifugal clutch that I could grease, it helps the engine start easer, and I also added the throttle on it so it idles down when up to pressure,

 

[hosspuller]

Check the tank carefully... Inspect it internally. Would be a shame to put in a lot of time & money, then find the tank is a leaker...

 

[farmall 55a case]

Thanks for all the info and tips! I was thinking about putting a electric clutch off of a mower to allow the engine to free wheel after it reaches max psi. Would need a air over electric switch to control it tho! Has anyone ever tried to do that? I would have a electric source from the trucks battery. Or would this just make it more complicated?

 

[Egon]

As mentioned!

You could also set up a unloader valve prior to a check valve on the tank inlet.

 

[BHD]

there were many who used the a old AC pump with the electric clutch and a pressure switch for air compressors under the hood of there pickups, many used a square tube welded up as a rear bumper for an air tank.

the problem is many AC clutches take a taper shaft,
but riding lawn mowers many times use a electric clutch for there mower drive,

but the unloader valve just dumps the air instead of feeding it to the tank, and with the centrifugal clutch and the throttle control the pump stops or nearly stops when filled,

 

[Sprinklerman]

Dont forget a pressure relief valve .

 

[muddstopper]

If you use the pressure switch that is already on the electric compressor, and wire it 12v instead of 110, then you could use a electric mower clutch on your gas engine. Nothing to it. The big problem would be to get the hp and gear ratio correct. Most mowers use a straight shaft, not tapered so finding a horizonal engine should be easy enough. Now the kicker is that the engine is going to continue to run, even when the clutch is not engaged and making air. Probably not a big problem since you would most likely just be using the compressor for a few minutes at a time.

 

[farmall 55a case]

Well here it is should work for what I want it for. I used a old tiller motor that is a 6.5 Briggs, found a twin cylinder pump at a yard sale and ordered a IR pressure kick down bull whip, and mounted it all up! Hardest part was getting it to idle down and rev to the max rpm. It builds up to 120 psi pretty quickly. It will come in handy for fixing flat tires and blowing of balers! No more running back to the shop!! Of course I had to put my farms name on it and a IH logo! All in all I have about 200 dollars in it.

 

[PILOON]

Here is a KISS method for the unloader problem.
It works because I did it with a rig that I set up that was electric.
I placed a check valve between the compressor and the cut off switch.
That way the tank is always under pressure even with no pressure back to the compressor.
Next I caused a slow leak between the check valve and compressor. It was a very tiny hole, just enough to bleed off the remaining pressure but not large enough to slow down the tank fill.*
With a gas engine it would need to run all the time and a pressure switch could be rewired (needing voltage) to control an electric clutch much as they commonly sell for go carts.
If the engine used is of sufficient HP they generally have 12 volt outputs so there is the electrics for the clutch.

*even a loose fitting will prove that method.

Go cart clutches (they fit straight shafts and available in many sizes)

 

[jwmorris]

The go kart clutches I have seen all work from centrifugal force, like a chainsaw.

Any car with an AC compressor on it would have an electric clutch though.

All compressors have check valves in between the compressor and tank. On electric ones they are so there is no head pressure on the compressor to have to over come when it kicks back on (the hissing sound you hear when the compressor shuts off is the bleeding of the line).

On gas compressors they are there to not stall the engine at idle and let compressed air bypas the tank until internal pressure falls enough to throttle up the engine and shutoff the bypass.