Converting a small engine into air compressor

[avz]

Hi all
Let's hope that I would'nt considered to be too weird. I would like to ask if anybody had turned a small engine into an air compressor pump (head). I would like to build my own compressor and since I have the tank and several electric motors (so I can choose the right one) I need the air pump. any ideas will be thanked.

 

[alchemysa]

I recently discovered it wasn't even worth repairing a compressor let alone building one. You need more than a pump. You'll need gauges, fittings, auto-shut-off switch, etc etc.

 

[vpd66]

I've tossed this idea around quite a bit in the past and still think about it. My thoughts would be you'd get much better performance and volume from a small car engine (4cylinder). After all, I've never heard of anyone complain of having too big or too much air volume from a compressor. The right way to convert an engine would be to use an overhead valve engine and just fabricate a flat plate cylinder head with 2 pipe fittings welded over each cyinder. Then build 2 manifolds that connect the pipe fittings over the cylinders. One for exhaust and one for intake. The key is that you will need to have check valves in the manifolds so when the piston goes down the intake check valve is open and when the piston comes up the intake valve is closed and the exhaust valve it open. I've yet to see any check valves available that would fit the bill, but I don't think it would be all that hard to fabricate some. Just my ideas.

 

[BHD]

not worth the hassle simply stated,

yes one could get a "spark plug pump" and screw it in to the spark plug hole and have a compressor, but the valves in the motor will only allow it to pump on one out of two strokes,

and to convert the valves to work on ever stoke is not impossible, (one needs to take the lifter out of the exhaust valve and then put very very light springs in the intake so it will open on it own when there is suction, (a spark plug pump was some what normal on the old 1940 to the 1960 or so, it was check valve that was threaded to the same as a spark plug and one could take one plug out of there motor and screw it in and have a emergency air compressor, I do not know if you can buy them new or not any more, Ebay would most likely be your best bet,

but one can buy a pancake air compressor for $100 and my guess is by the time you get all the things round up and make it safe, (pop off safety valve) pressure switch, pulleys, check valves, mounts and time you can buy one cheaper than make one, and the efficiency of it will be much better,

you would at least be better off at least buying the pump,

here is a Google search for air compressors under $150, many under $75,
air compressor - Google Search

the other factor is most check valves are not desigend to handle the heat that is created by a compressor head, air compressors use reed vales or disk valves normaly, and I think you would have spring and seat/seal failues if used much,

 

[NormL]

Hi all
Let's hope that I would'nt considered to be too weird. I would like to ask if anybody had turned a small engine into an air compressor pump (head). I would like to build my own compressor and since I have the tank and several electric motors (so I can choose the right one) I need the air pump. any ideas will be thanked.

Over the years I have made air compressors using automotive air-conditioner pumps. The ones I used came out of older Chrysler Corp. vehicles. They had 2 cylinder pumps back then and I even used them for my mobile shop back in the day. You have to remove a restictor on the intake side and if you are not using the electric clutch, just spotweld around the edge of it in three places to have it engaged full time. I'm guessing aftermarket single cylinder units would also work but i never tried any of those (always had easy access to the chryco stuff).

This setup supplied enough volume for light use of air tools and painting but not so much for air grinders and high volume uses such as raising a tubeless tire onto the bead.

 

[zonta223]

One of the most common mobile air compressors used to be the old volkswagon beetle engine. the front 2 cylinders were left as normal car engine configeration.
The rear 2 cylinders had the exhaust valve pushrods and rockers removed.....and non return valves fitted into the spark plug holes.
neat compact unit...electric start.no pulleys or gears required.
No pressure switches etc the air tank only fitted with twin safety blow off valves. produced enough air to run full sized jack hammers etc..............but may be to big for what you want.

 

[kelloggguy]

It might be possible to do, but why try when you can buy a brand new Kellogg 5HP pump for under $500, and a Saylor Beall design for under $400? Slightly less than double for a 10HP model.

 

[BHD]

here is a picture of a little compressor I made, it uses a regular pump,

it uses what is called a unloader valve, (which is different than a pop off valve) the pop off will just dump air out of the tank down to a safe level, not nessarly at a minimal level it may be 100 or it could be 20 before it re seats,

the unloader is like a pressure switch but only dumps the air out of the compressor head, not the tank, there are number of different configurations for different valve types and so on, some work by holding a valve in the head open and some just dump the air coming out of the head, the second type is usually used on smaller pumps, if your compressor is stop starting very rapidly then a unloader is a good choice over a pressure switch or if you have a gas engine operating the pump,

 

[Snaker]

I grew up using an old lawn mower engine for a pump. It didn't have a tank at all. The hose came from the sparkplug hole and if I remember right, the exhaust was blocked off completely. It was good for filling tires and that was about it. We had to hurry with it and as soon as we unhooked the air chuck we had to unplug the power cord because the belt would start to slip. I think it was only good for 60-70 psi. One of the problems with that setup is that you need a "like new" engine to get the higher compression psi and that will cost you these days. A worn out engine will be a worn out compressor.

I also would have to believe that setup wouldn't be all that effiencient with electricity and that can add up also.

 

[mainegoatman]

Hi all
I would like to ask if anybody had turned a small engine into an air compressor pump (head). I would like to build my own compressor and since I have the tank and several electric motors (so I can choose the right one) I need the air pump. any ideas will be thanked.

Yes I did this when I was 14 years old, more or less out of boredom and just because I like to tinker around with stuff. (I'm now 58 - my dad thought I was crazy)

I took an old lawn mower engine, remove the camshaft, ground off a lobe, drilled and tapped the shaft 180 degrees and threaded a bolt in, reground the bolt head to resemble the opposite cam lobe. This made each up stroke of the piston compress air. My dad had this thing that you could screw into a spark plug hole to pump up a tire etc. (on a multi cylinder engine) I don't know if you can still buy these things.

I rigged up a motor to it and it worked.

If I would do this again I would build up the cam with weld instead of a bolt head.

Yes this was very primitive, but that's the general idea if one would refine it.

It would be a fun project if you have the time but I'm thinking it would be easier to find a used air pump at a yard sale or something.

I also know people who have convert auto air conditioner compressors into air compressors on there trucks using the engine to drive it. The only problem with doing that is you must devise a way to add oil to the air intake and then filter it out)

 

[smiley]

NormL has the right idea. Just find an auto air conditioning compressor and hook a motor to it for the easiest fairly high volume one. I have about 3 of them right now in various places. One is a York, one Japanese and the other was off a 69 Ford econoline. That one I've been using with a pancake tank and it keeps up with the power nailer.
I've long considered using an auto engine for large volume like sandblasting, jackhammer etc. and have a Mopar 225 slant six set aside for the purpose, to run on 4 compress on 2. The Advantage of the slant 6 is the fact that the intake and exhaust manifolds all have individual tubes to each cylinder so would be easy to cut off and fabricate whatever necessary. As BHD mentioned, weak springs on the exhaust valves will allow them to suck in air on the downstroke so there are no wasted strokes. And BHD, that's a neat looking rig you've got there.
AVZ give it a try and keep us posted.
Smiley

 

[pat32rf]

I started to do this with an old 2 stroke lawn mower but it was going to cost too much for the valves.
I do know of a couple of people who have used old sealed units out of refridgerators. They were both told that it wouldn't work, so they did it, then addeda 20lb propane tank for a resevoir. Small, quiet units for under their workbenches....
I have an old V-4 refridgeration unit that I have been using for about 25 years now. 2hp motor gives me 100psi. Two 100lb propane tanks (hydrostated to 300psi) give loads of storage.....

 

[avz]

Hi
Thanks for the input. I'm glad to know that it can be done and so I'll follow your guidance and try to do it. I'll report progress when achieved. if you have more info and/or advise - please let me (us) know.

 

[mainegoatman]

NormL has the right idea. Just find an auto air conditioning compressor

Smiley, Have you had any problems with lubricating the auto air compressor? The reason I ask is because it's my understanding that the refrigerant has lubricating qualities, so if you replace it with air it gets pretty dry in there and they can overheat/burn up.

I know a lot of guys with 4WD vehicles, myself included, who deflate their tires to around 18psi when going out in sand dunes, the desert etc. for extra traction, so most of us have some kind of portable air tank or compressor they carry with them to re-inflate the tires.

Some jeep guys have converted their AC pump to pump air into a small on board tank. They work good, but they put an inline air tool oiler between the air filter and pump inlet.

 

[Jason14j]

Volvo made an AC compressor that had an oil reservoir like a lawnmower engine, search the off road / jeep sites...Runs off the truck engine and has a clutch. Makes good volume and pressure, no oil in the lines

 

[NormL]

Smiley, Have you had any problems with lubricating the auto air compressor? The reason I ask is because it's my understanding that the refrigerant has lubricating qualities, so if you replace it with air it gets pretty dry in there and they can overheat/burn up.

The twin cylinder compressors off Chryco vehicles have a sump for the lubricating oil and do not run dry. If you don't remove the restrictor in the intake the oil in the sump will be sucked out and then it will run dry and seize in no time! Ask me how I know.

 

[RPW]

Yes I made one from an old B&S motor. This was before I new how to weld but I took the cam to a local welding shop (this was a few years ago) and had them build up additional cam lobes to operate the valves on each stroke. Closed off the sparkplug hole and used the intake and exhaust ports as needed. It wasn't the best compressor but it worked.

 

[pickstock]

best one i saw was a VW beetle engine, there was a company doing it but i saw some done at home.

IMHO this is the best option for most things, 2 cylinders were conventional and an engine, the 2 others were the compressor. If you want more air just rev the engine more.

 

[smiley]

Smiley, Have you had any problems with lubricating the auto air compressor? The reason I ask is because it's my understanding that the refrigerant has lubricating qualities, so if you replace it with air it gets pretty dry in there and they can overheat/burn up.

I know a lot of guys with 4WD vehicles, myself included, who deflate their tires to around 18psi when going out in sand dunes, the desert etc. for extra traction, so most of us have some kind of portable air tank or compressor they carry with them to re-inflate the tires.

Some jeep guys have converted their AC pump to pump air into a small on board tank. They work good, but they put an inline air tool oiler between the air filter and pump inlet.

I was in Canada most of last week and just catching up.
The econoline pump has been in use for about 10 years and all I ever did was dump a couple ounces of motor oil down the intake side. The Japanese one (Sanyo maybe?? -- it's in Fla) gets used only a few times each winter so I can't comment about it's longevity. I put oil in this one also the same way. The Yorks have their own oil reservoir and here is a link to a good diagram and discussion on them.
On Board Air

Here's another link discussing the points you mention. They say using motor oil in it won't work because the compressor will seize. Unless your life or a long hike is depending on it, what's the difference if it does seize? They're cheap enough to just replace it and go for another 10 years. Besides that it probably oils my air tools and nailers at the same time. Might not do tires much good but I use it for that too.
On Board Air

I should say for safetys sake, be sure and put a pressure relief valve on. Mine stuck and was at 220 pounds when I realized something wasn't right and before I could shut it down, it blew a rubber hose.

 

[mainegoatman]

Here's another link discussing the points you mention.
On Board Air

Thanks for the info & link. I have wanted to add an on board compressor to my FJ Cruiser, but there is no room under the hood so I carry around a portable 12Volt one which works pretty good but slow

I wonder if anyone has added a York compressor to a tractor engine?