Home made air compressor...

[Spanner88]

Hi all,

Firstly hello to everyone, I came across this forum in my search for information on home made compressors, there seems to be afew threads that have toyed with the idea, and some even briefly mention a rather interesting idea, making a compressor from an old v8 engine...

Its this that interests me the most...

for a long time I've wanted the equipment to sand blast with, a big enough setup to blast parts of car bodies (like wheel arches and floor pans) and motorbike frames with...

Making a home made blast pot seems straight forward, using an old propane tank, some black iron fittings/pipe, leaver valves and a regulator.

But the problem it all boils down too is the high CFM's required to get the pot to function really well and use a decent sized blasting nozzel, hydrovane compressors are lots of £'s and I don't think I've ever managed to find a cheap pump going secondhand, theres afew hydrovanes from time to time, but never a piston pump, not anything above 30CFM

a diesel towable compressor is going to cost at least £1,000 and its going to be an old one at that

So I've got on to the idea of making a compressor using two 4 cylinder engines

I have lying around, pulled from an old 1998 ford transit a very simple mechanical 2.5 diesel engine (only has 1 live wire for the fuel solenoid besides the starter circuit electrics wise) so would be really simple to run up on a bench or stand...

I'm wondering why I cant get my hands on a simple 4 cylinder engine made from cast iron (something like a ford pinto) and some how stop the exhaust valves opening (maybe grind the cam lobes down with an angle grinder, then thread non return valves into the spark plug openings...

mount up the correct sized sprockets to the flywheels of the two engines and link the two together with a chain

using some 10mm or 15mm copper tube make up some kind of outlet manifold from the non return valves, send it into a pilot unloading valve of some kind (ive found these really easy to find on their own for petrol compressors with a built in engine throttle control)

http://www.ebay.co.uk/itm/GAS-AIR-C...913228?hash=item415059714c:g:aZgAAOSw~gRV6ErI

If these compressors based on old V8 engines put some out seriously high cfm's (so I've read)

This should work rather well?

What do people think to the idea? How many cfm's would a 2.0 4 cylinder car engine make?

 

[the snooper]

Should work but to what degree on a pinto all you need to do is remove the rockers for the exhaust valves you just need take sure pinto rotates the right way so that the cam belt tension is not on the tensioner

 

[Spanner88]

Solves that problem removing the rocker... simple

So you mean, you would make sure the direction the engine runs in are both the same?

Would their be an easy way of working out what CFM it would produce?

What gearing would you use? 1rpm of the diesel engine would equal, the same or more from the the pump engine?

 

[LewisT]

just a thought but wouldnt a dohc engine be better you could alter the exhaust cam timing to get compression on each revolution

 

[Gareth J]

*cough*
http://www.mig-welding.co.uk/forum/threads/giant-broomwade-compressor-15hp-3phase.62514/

Any use to you? Can do just the compressor without the tank, motor & ancillaires for £75. It's pretty big and should be good for a home blast setup.

 

[the snooper]

just a thought but wouldnt a dohc engine be better you could alter the exhaust cam timing to get compression on each revolution

The only other way is to get rid of camshaft remove inlet valves and seal the valve stem holes then fit reed valves on the inlets

 

[Seadog]

Would their be an easy way of working out what CFM it would produce?

One cc = 0.0000353147 cubic feet

The throughput can be worked out from the formula - cfm = rpm x engine capacity x 0.0000353147

For a 1400cc engine running at 1000 rpm the throughput would be 49.5 cfm

 

[rtbcomp]

Remove the camshaft(s) and plumb in-line non-return valves in the spark plug holes.

On a 4 cylinder engine join the two outer pots together and the two inner pots together and you'll only need 4 NRVs, (2 in, 2 out).

You'll have to make sure you can drive the oil pump. An old fashioned side-cam engine would be the best, then you could just remove the rockers. Block the oil feed to them.

If you join the pots as above and fit weaker springs to the inlet valves you can use the existing inlet manifold and air filter, then you'd just need 2 NRVs.

 

[dobbslc]

I removed a rocker from a 2.0 pinto once, it wasn't intentional though!
If you use one make sure the oil spray bar is removed and cleaned, they can get blocked apparently.......

PS: they can be "refitted" by loosening the adjuster off and tapping them back into place, saves taking the cam out

 

[brightspark]

your either on a 3mm jet running between 14cfm and 28cfm or next size up is a 6mm jet running @80 to 90 cfm

 

[normspanners]

The only other way is to get rid of camshaft remove inlet valves and seal the valve stem holes then fit reed valves on the inlets

or VERY soft inlet springs and let the compression close the inlets then can do away with the cam belt, run the oil pressure from the drive engine and a gravity feed back loop pipe from the compressor sump and then the engine can be coupled flywheel to flywheel
after all the speed would be around only 1500rpm I guess?

 

[dannyp]

you'd need a motor with the valves square onto the pistons for that i'd think. so if it ever did touch it wouldn't matter but if they were angeld valves it'd be clatter thump bang

i recon it might be as easy to make a head plate with reed valves for both inlet and outlet. as you want to remove as much combustion chamber capacity as possible idealy as that'll increse efficency. id let the oil pump in the engine being used as a ompressor lubricate it, mat also need to bodger someting up to deal with the coolat tho

 

[rtbcomp]

^^ The exhaust valves would be permanently closed (use NRVs in the plug holes to exhaust) and the inlet valves would only be 'sucked' open on the downstroke.

I do like the idea of a flat head plate though. You could fit fins to the pate for cooling.

I suppose you could use a diesel engine and exhaust through the injector holes.

 

[dannyp]

if doctoring the cyl head id be very tempted to use the same engine as compressor and drive. cyl s running as engine 2 cyls running as pump ? be easyer i thinks

 

[rtbcomp]

^^ I reckon you'd get too much heat into the air.

 

[Spanner88]

replies are really good guys, have clearly come to the right place

given me alot to think about, really appreciated!

 

[normspanners]

you'd need a motor with the valves square onto the pistons for that i'd think. so if it ever did touch it wouldn't matter but if they were angeld valves it'd be clatter thump bang

the 2.0 pinto was a freewheeling engine thats why I suggested that method

id let the oil pump in the engine being used as a ompressor lubricate it,

you cant then couple them flywheel to flywheel. Which is easier and you can de coup[le by using the standard clutch. Also the oil pump in the pinto drives off the cam belt .

 

[normspanners]

^^ I reckon you'd get too much heat into the air.

Yep seperate small rad with no stat IMO

 

[DrDeAtH]

Make manifolds, each with non return valves in for each port, ensuring they flow the correct way.
Remove the valves from the head and block the valve guides off. Leave the spark plugs in.
That way, you will have a low resistance compressor pump in effect.

You just need to work out what to drive it with.. And do the cfm calcs

 

[dannyp]

how hard would it be to bolt an oil flooded screw compressor air end to your transit engine ?