# Gasoline Powered Air Compressor Set-up



## cathead (May 1, 2015)

Well, a big air compressor showed up at the scrap heap.  It had no electric motor and it had been
banged about but was basically in one piece.  I installed a lawn tractor engine with a starter-
generator on it.  A battery rack was installed so it could be started and the battery charged.  
The interesting part was the air pressure switch.  Most pressure switches open up when 
the cut off pressure is reached.  I put the pressure switch in series with the points to stop 
the engine when up to 175 lbs.  It didn't stop to my amazement!!  Then I added a shorting pole
on the control switch to short out the points at pressure.  That worked just fine. Possibly one of
you have a better idea.  The ultimate would be to also to have the compressor start
automatically but would need some special controls for that I suppose.  Again, maybe
one of you may know about this.  For now, it compresses to 175 lbs in 5 minutes and shuts off. 
It will be great for remote use.  Next, maybe a trailer for it?



Here's a couple photos.  The control is a little hard to see but if you look closely at the control,
you can see the added copper grounding pole that shorts the points to ground when at pressure.  

I don't know what this thing weighs but has an 80 gallon tank and a bit top heavy so looking at
my options in moving it about with wheels....


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## Patrick (May 1, 2015)

Now that's using your head for more than just a hat rack, I think you did OK getting this put together. Anytime someone can save a piece of equipment from being scraped out is a good thing. Hope you get some good use from it.
Regards


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## cathead (May 1, 2015)

I hope to use it to start a bit diesel engine I have.      73, de KB0MM


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## brino (May 1, 2015)

Great idea. Would be perfect for remote off-grid use.

Be sure the tank is safe!

-brino


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## kvt (May 1, 2015)

I have that type of compressor,   What it actually needs is a piece that hooks to the throttle,   When it reaches pressure, it opens the valve, and that applies pressure to the piece that hooks to the throttle causing it to throttle down.   At the same time it applies pressure to the bypass on the compressor so that it will not pump an longer.   Thus at idle it is just the motor running and spinning the pump.   Once it reaches the low pressure setting on the valve,   IT then shuts the pressure off to the throttle which speeds the motor back up, and also releases the pressure on the bypass so that the pump will come back on line.   Mine is like a 1966 model, and is somewhere else so I cannot get a picture of it at this time.,   But the valve system goes between the tank and the output of the compressor.   If I remember correctly there is a spring that hods the throttle open until the pressure switch pushes the throttle closed.    Hope this helps.


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## cathead (May 1, 2015)

kvt said:


> I have that type of compressor,   What it actually needs is a piece that hooks to the throttle,   When it reaches pressure, it opens the valve, and that applies pressure to the piece that hooks to the throttle causing it to throttle down.   At the same time it applies pressure to the bypass on the compressor so that it will not pump an longer.   Thus at idle it is just the motor running and spinning the pump.   Once it reaches the low pressure setting on the valve,   IT then shuts the pressure off to the throttle which speeds the motor back up, and also releases the pressure on the bypass so that the pump will come back on line.   Mine is like a 1966 model, and is somewhere else so I cannot get a picture of it at this time.,   But the valve system goes between the tank and the output of the compressor.   If I remember correctly there is a spring that hods the throttle open until the pressure switch pushes the throttle closed.    Hope this helps.



Thanks KVT for the good information.  I can see building a spring loaded piston to control the throttle.  I will sleep on it and see what brain has come up with in the morning.


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## Strtspdlx (May 1, 2015)

For starting can you use a pressure switch that applies ground and hook up a starter solenoid that's constantly hot. When the pressure switch closes it applies ground to solenoid thus cranking the motor? It should start as the switch grounding the points should be open allowing them to produce spark. You could probably put the pressure switch inline with the pump output line or preferably after a water separator. It's just a matter of finding a switch of the right fittings and the correct on pressure. If you can find an adjustable one that would probably be best. 

Edit: thinking about it now unless that switch is momentary it'll keep cranking till its up to pressure which is not what you want. 

Regards-Carlo


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## sinebar (May 1, 2015)

How about adding a either a centrifugal or electric clutch?


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## RJSakowski (May 1, 2015)

How about an automotive a/c clutch?  That, in combination with a solenoid setup as described by KVT to throttle back the engine should work.  An auto-start system would be more complicated but highly desirable for times when your air use is minimal.  I have a Sanborne 2 hp oiless compressor that I keep in my basement shop.  It was advertised to be quiet operation but is one of the noisiest pieces of equipment I own.  To control noise and maintain household tranquility, I charge up the tank and shut the compressor off.  I get about three to ten days of shop use before having to recharge.
For an auto-start, how about using one pole of the cutout switch with a centrifugal switch to break the start circuit?  You could use the back emf on the starter motor to disengage the starter, running it and the centrifugal switch through a latching relay similar to some of the E stop circuits used.


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## mzayd3 (May 1, 2015)

I bet the voltage off the distributor for the spark is insanely high and there is not enough distance between the contacts of the switch to extinguish the arc.  


Sent from my iPhone using Tapatalk


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## kvt (May 1, 2015)

Ok, for a start circuit,   Does the motor have a charge circuit on it.   Most of the lawn tractors etc did.   
One you would need an on off switch  (You do not want it starting when not needed. why waste the gas)
two you would need a switch in the pressure line, that would close a circuit when it was low pressure. thus applying pos to a start solenoid, 
three you would need a relay hook to the charging circuit,   (thus as soon as it started it would power up and undo the power to a positive side of a start relay. thus breaking the power between the pressure switch and the start solenoid,
four   a starter solenoid from something like a lawn tractor or old ford product.   (pos in,  pos out,  and pos from the start position on the ignition switch,   It got ground from the frame of the solenoid)
Good fine stand wire,  The vibration on the compressor will cause normal hard wires to break.  
(oh by the way your battery may not last long mounted on the compressor like that,   To much vibration for some batteries)
 Hope this helps. or at least gives you something to think about.


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