home made compressors.

Hello machine head

Yes, many have done exactly that years ago, when compressors were very expensive.

However, to purchase a new compressor unit, complete with regulator valve, air tank, electric motor, cord, plug, ready to go, is far cheaper than they used to be.

I'm talking about compressor units "Made in China", obtainable from your local discount store, and here in NZ, such a 2HP compressor is sold for NZ$99 = US$80 at "special sale times".

Alternatively, you may obtain from a scrapyard, an older commercial refrigeration compressor of the non-sealed unit type.

Whatever type of unity you use, please remember to keep up the special lubricating oil, or the compressor will mechanically "seize' very quickly.

You haven't advised your intended pressure, nor the volume of air or other gas per minute, so that's the best which may be done for you, until those are known.

Kind Regards....

Thanks Sparkie , you are right of course . The cost has gone down thanks to China etc.

I was curious to see how some of the ole boys would have actually done the nuts and bolts aspect of it as a garage project or as a money saving , build it yourself thing.

Im in Ontario Canada and have seen small oiless 3hp compressors going for less than $ 100.00 !

I have seen this done on Volkswagen air cooled flat 4 cyl. engines, Jeep 4 cyl engines, Buick 231V6 engines, and Ford V8s. 302, or 351 Windsor.

The way it is done is to replace the cylinder head on one bank with a new designed head. Air is drawn into the cylinder through a spring loaded check valve, from a new air inlet for that head. After being compressed, the air is forced out past another check valve, into a reservoir, where it is stored. The normal intake manifold is blocked to that head, and of course no exhaust manifold is needed on that head. The lifters and possibly the pushrods for that head are not needed, so they are held in place with retaining springs. I do not know if water circulates through the new head. The engine runs just fine on only one bank of cylinders. It is just a longer span between cylinder pulses. Last year I tried to find out if there was a conversion to do this to a 502 Chevy. I was not able to find one though. Hope that sheds some light on these engine-compressors.

If a more complex head design were manufactured, that used the existing cam lobes and valves, efficiency might be improved. Not sure. But these engines will run 4000 rpm.

Thanks Bob C ;

Just looking for info. and you have answered my question . The " new designed head " thing sounds like big bucks eh ?

Will go for the cheap China or Korean route.

Thanks to all .

The head was actually very simple All that it needed to do was seal the top of the engine block to prevent coolant losses and seal compression. A 3/4" thick steel plate with holes inline with the head bolt holes. Drill and tap two 1/2" pipe thread holes. one lets air in, one lets air out. Thread a check valve into the holes. Air filters and a connection to the reservoir. If you had a will, it would be an easy project.

Hmmm... now you have me going , i better check that will and start looking for some parts . Could be something to do to keep me out of trouble this winter .

Thanks bob c .

I built a small compressor from a Villiers Petrol engine about 25yrs back. I used a small electric motor to power it.

It was a single cyl 4 stroke motor from an old portable cement mixer. It was trial-&-error. I disconnected the pushrod to the inlet valve & replaced the valve spring with a weak one so the inlet would allow air to draw past it on every down stroke. The exhaust valve was disabled so it remained closed. I inserted a non-return valve into the spark plug hole for the air delivery.

I discovered that the max pressure was about 60-70psi. The combustion chamber in the head was the culprit. I needed to make the compression ratio as close to infinite as possible (ie piston compresses cyl volume down to nothing when at TDC). To achieve this I removed the head & filled the combusdtion chamber with epoxy filler. I trimmed a bit away so the inlet valve could move.

This worked well & would provide over 120psi. I connected it to a large tank, so the lack of size of the compressor was partially offset by the large capacity of the tank. The compressor was estimated at approx 2-3 cfm. The tank was an old 90kg LPG tank. I put in a relief valve & cut-out sw, & connected the compressor to the tank with nylon pressure hose held on with normal hose clamps. This way I figured I'd never have a catastrophic failure because the hose would blow off long before the structural strength of the tank was at risk. I used it up until a couple of years ago.

VW engines were used here a while back as medium capacity compressors, like a sandblasting compressor for hire. They used one side as the engine (2 cyl petrol), & the other side was converted to a 2 cyl compressor. A V or horiz opposed engine is ideal, as you have separate heads etc.

Cheers Tony

Now if you really want to go cheap, you can make your own reed valves to use with Bob's compressor design. A flat surface a hole, a way to thread fittings in and a set of stainless steel feeler gauges.

I had a reed valve break when pulling an all nighter to get ready for something, old age don't remember what, the next morning. I'm thinking it was the 18 thousandths feeler gauge that was sacrificed for the cause. Of course Chinese check valves are probably pretty cheap.

A friend of mine actually converted a lawnmower engine to run on steam as a project for a class he was taking. I don't remember the specifics however, I believe they had locked the stock valves open and had created some sort of flapper valve control by an external pushrod connected to an eccentric attached to the crankshaft. A little time with a pencil and I'm sure you could work out the details . Get a small 2 cylinder engine, convert one cylinder to be a steam engine and the other to be the compressor, grabb the wife's pressure cooker, and you will have the ultimate Rube Goldberg air compressor. A plus to this is you may be able to recoup part of your investment by selling tickets to watch it run.

Not that it matters, but those Chinese lie like rugs (baby teeth in a 16-year-old gymnast?) if you ever see a loaded 3 hp compressor pluged into 110 V outlet you'd better check the circuit breaker it's welded shut.

PS off-topic did anyone else have trouble with the site last night. Has anyone accessed the site using sea monkey

And if you put the onions in the pressure cooker, they will cook faster.

Actually you can use a small 4 cyl diesel and no head mod at all...and since the compression on diesel is around 400psi you will have all the pressure you need...all you need to do is filter the air in use or disconsct the injector on that cyl and there you have it.

Have fun,

Roger

I've done this also but with a twist. I made mine a vaccum pump. I used check vavles to redirect the pressures.

Machine Head:

Try this site out, http://opensourcemachine.org/

and check attached pdf. This is a very old compressor setup but if you are interested in learning about the actual nuts and bolts of compressor design. Here's a good start.

UFG

For those interested, check valves are used on the air brake systems of heavy duty trucks. These valves are threaded on both ends, making fabrications easy. They are available in sizes 1/4, 3/8, and 1/2" pipe thread. Bendix and Midland are two manufacturers of them.

I worked with a fellow that built 2, back to back 6 cyl buick engines. One drove the other which had been modified into a compressor.

I vaguely remember him mentioning that he milled the compressor (engine) head down for more compression.

He sand blasted tractors on the side. He said this setup could run his sand blaster direct, without a tank.

I have also seen information on the net about converting a VW air cooled engine. 2 cyl drive and 2 cyl compress.

The first engine that I had seen modified that way was the VW. I wonder how a 6v53, 6v71, or a 6v92 would do as a high volume, high pressure air compressor?

Obviously the project has to do with getting the right valve timing to make the engine operate like a compressor. Think about the typical compressor cycle vs. the typical 4 stroke cycle vs. the typical 2 stroke cycle. This will help you choose your base motor. I like the ideas of the tricks mentioned in the above posts with existing 4 stroke engine valves -or- going to a one way valve arrangement (more like many compressors).

I am aware of a commercial application where a Detroit diesel engine (2 stroke) was modified where three cylinders (I think) were converted to operate as a compressor and the remaining three continued to operate as a diesel engine that ran the compressor. If memory serves me correctly this was a high volume low pressure application. If this is just a garage project for fun why not start with a two cylinder engine so it doesn't need an external power source.

Just a little playing around on paper would show you what the resultant pressure at a given RPM would be. Remember on the compression stroke to have the outlet valve open so you are just pushing against the pressure in the accumulation tank and not going to 90 psi just to let it vent to 40 psi when the valve opens to the tank (as the system pumps up).

Closest I can recall is before the CFC issue, my uncle took the compressor off a throw-away refrigerator and converted it to run on air. Real simple and it did work will for light shop work (no impact wrenches, etc.)

all the suggestions i read sound good,

I'll add one more, change the cam,

downstroke opens intake valve up stroke opens exhaust valve

There is a big difference between 'engine valves' and the 'compressor valves':

Engine valves open when you want to... During Compression stroke, when piston goes up, both valves (suction and discharge) are closed. At another instant, during Exhaust stroke, suction valve is closed and discharge valve is opened. This is achieved by 'cams'.

Compressor Valves open automatically when the they need to... During discharge stroke, the discharge valve will start to open only after a brief time, when the chamber pressure rises marginally more than the discharge header pressure. Same way, the suction valve opens only when the chamber pressure falls just below the atmospheric pressure. This take brief time (short movement of piston) for the locked volume (clearance volume) of gas at discharge pressure to expand just below the atmospheric pressure.

Thanks to all , for your help and info.

They make little pieces that take the place of your spark plug that you can run to an air tank for temporary uses, like inflating a flat tire, they're only for gasoline engines though, if thats what you are looking for: Google them, you'll find them