Building a compressor...

[Satashooter]

Hello all,

I'm looking for some input on an idea that popped up in passing conversation the other day.

We were on the subject of various tools, and a friend mentiond seeing years ago on a farm, an old boy had been tinkering with afew Ford 1.8 non turbo diesel lumps. He had a couple running on trollys and benches and was using them for a generator, and apprently in some fashion an air compressor... Friend seemed to think it was being used to power a blast pott as well!

This got me thinking... I'm a sprayer by trade and although my compressor does a decent enough job of supplying my air fed and a gun, it lacks abit with a DA, but I use an electric one anyway. I certainly wouldnt pass up more CFM's. The idea of being able to power a blast pot is appealing to say the least!

Has anyone ever come across this being done, with any engine?

I gave it some thought, and the only real problem I can see would be having to alter the valve timing slightly so the inlet and outlet valves opend at slightly different times. After all a diesel engine is built to run incredible compression, it seems totally feasable? If the size of the pistons in my pumps are anything to go by as well, the bottom end of an engine would really chuck out some CFMs. Further thinking... if this is possible, why not use a smaller diesel generator engine (with smaller pistons) for a 2nd stage as well? With abit of head scratching and working out, with the right ratios...

Anyone have any thoughts, or even doing this them selfs?

 

[grandads_shed]

i can not see why a engine would not work , just have to fit a one way valve where the sparkplugs go and shut off the exhaust valves.or remove all valves and fit reedvalves
you can change it from four stroke to 2stroke by changing the belt sprocket on the cam shaft to one the same size as the one on the crank shaft
then you just need a motor that will turn it, but if the engine is big enough then it could turn slower thus probably being quieter

 

[Bsmith]

You would need a different camshaft so, the inlet valves would open on induction and ignition stroke, and the exhaust valves open on compression and exhaust stroke? Interesting, am I right?

 

[Satashooter]

I thought this

I had a look at the Ford 1.8 non turbo lump, and they make 60hp. Compressors with 60hp behind are pretty heffty bits of kit to say the least

I'm not sure you would get a cam shaft off the shelf todo it, as if an engine ran this way it would go bang I think!

But yeh, the inlet valve would have to open right as the piston is dropping from TDC, then when at the bottom would have to close and the outlet open, and vice versa. Most engines have slight valve overlap, when both in and out are open.

 

[rtbcomp]

Assuming a 4 cylinder lump, remove the camshaft, fit weak inlet springs so they act as poppet valves, remove the injectors, connect cyls 1&4 and 2&3 together with a bit of pipe and a T-piece, connect in-line non return valves to the legs of the Ts for the outlet.

Block the oil feed to the camshaft so the crank still gets oil pressure.

 

[grandads_shed]

come to think of it the water cooling will make it quieter as well

 

[Satashooter]

Sounds like you've done this before

What are the results like?

 

[rtbcomp]

Only in my dreams - It's something I've been planning though.

 

[Satashooter]

I'm going to go for a delve at the shop on Monday as I'm sure theres a N/A 1.8 ford diesel lump sat at the back somewhere thats been collecting dust for years, going to see if I can get this running on a bench.

The idea of doing away with the head altogether, and instead, putting a sheet of heavy gauge steel on the surface grinder, and bolting this too the top and putting two check valves in opposite ways on each cylinder... but I think by doing this I'm going to cutt off water and oil circulation.

I had a qwick look and they do composite steel head gaskets for the engine

 

[Bsmith]

Think you would be better to modify the cylinder head with one way valves if that's the way your going as you may need the c/head recesses above the pistons and flat mild steel plate may be inclined to warp with the heat generated.

 

[rtbcomp]

You could just remove the camshaft and use 4 non-return valves in the external plumbing.

I would definitely keep the head, no point in doing the extra work.

 

[shenion]

I have seen B&S motors used as pumps. Remove valve tappets and put one way valves in the head.

You want to keep the compressed area as small as possible. Piping 2 cyls together then a check valve will reduce compression significantly. Put the check valves as close as possible to the head.

 

[rtbcomp]

I......
You want to keep the compressed area (Volume?*) as small as possible. Piping 2 cyls together then a check valve will reduce compression significantly. Put the check valves as close as possible to the head.

* my comment

Good point - that would cut down on dead volume.

You could use narrow bore pipes, but that would increase cylinder pressure and decrease flow. There would be an increase in temperature, but paradoxically that could lead to cooler air. The hot air in the cylinder would lose a lot of heat to the water jacket and the greater pressure drop could reduce the air temperature significantly.

Time for experiment.

 

[Fazerruss]

Does this plan involve using an electric motor to drive the engine?
Cause I wonder if it would be possible to use a 4 cyl engine with 2 cyl as pump and 2 as internal combustion engine to provide the power rotation.... all in one tidy lump?

 

[striker]

I think this used to be done with vw air cooled engines. 2 cylinders driving 2 cylinders pumping air. Massive cfm if I remember correctly.

 

[Satashooter]

I never thought the mild steel would warp, very good point!

Lowering the compression as it were, like mentiond, was a consideration... thats why taking the head off and replacing it with flat steel plate and having check valves directly next to the top of the cylinder was a consideration, but like you say it might warp and what not. Needless to say they would be flush with the plate, because other wise the pistons would come up and smack the bottom of the check valve.

And I plan to run it with a 1.8 N/A diesel lump (rather than a motor) I don't even know if a motor would manage it!? Would have to be a hell of a motor... Imagin the force required for the power unit, when this thing starts up and it already has, say 120psi of presure inside and its topping back up, driving 4 pistons almost 3.6" in diameter... this is why I'm wondering if its worth combing a small diesel generator engine to form a "2nd stage" setup with smaller pistons.

So one lump to power, then fashion two differnt sizes pullys on the flywheel, then power going to the bigger engine for 1st stage, and the other going to the smaller engine for 2nd stage. Then a masterpiece of check valves and pipework in some such order compression loss is kept down. I say flywheel and not crank because chances are a viscous fan is going to have to be used behind the rad to keep the thing cool... same with the 1st stage lump, not sure if the cooling systems could be combined into one, but otherwise its going to over heat as its not in a car moving forward...

I don't think the power unit will have to be doing a crazy amount of RPMS, as the gearing to the 1st and 2nd stage engines can be changed to suit... but the displacment relating between 1st and 2nd stages is going to take some scratching to work out thats for sure, so will the pully sizes.

After doing some more research, this has been done using V8's in america. One bank runs as an engine, the other as the compressor... clever! unfortunatly the fuel consumption is terrible with it being a petrol v8 tank.

I've found some old tractors that have some clever workings, with take offs on the front for pneumatic tools and you can run it off the engine their really old mind, it seems like the old Hotrodders in the US have been going mad on this for years, and why not to be honest... when a compressor that struggles to power a full sized DA costs the thick end of a grand new...

 

[KemppiFrog]

http://www.mig-welding.co.uk/forum/showthread.php?t=39815

This project went on the back burner and the gates were done by 'other methods'. But now I am being pushed by a decorator to get it finished, so watch this space.
KF

 

[rtbcomp]

Another reason for joining the cylinders.

Leave the valve gear in place, when No1 is on the induction stroke No4 is on the power stroke, so 1 & 4 get filled with air via No 1 inlet valve.

When No 1 is on the compression stroke No 4 is on exhaust, so the air from 1 & 4 gets pushed out via No 4 exhaust.

The roles are reversed when No 1 is on the power stroke, same applies to 2 & 3.

Shenion's point about excess volume is valid, but given the volume of the cylinders maybe the volume of any pipework doesn't matter too much?

 

[Satashooter]

Kemppifrog - interesting you've chosen to use the ford 1.8 as well but a turbo version. Is this for the same reason as my thinking, that its incredibly simple? I beleive the only electrics the motor has is a fuel solenoid, the rest are pickups for sensors. intrigued your using the turbo version though, do you think it will be turning enough RPM's when running to make use of the turbo?

I've got a little bit of exsperince with marine engines in pleasure craft (mainly sports cruisers around 30ft) and they have alot of problems (most used their boats inland) that the turbo never come on too boost because of river speed limits, and the turbos kept seizing up after a season. I'm also thinking along the lines that the N/A chucks out 60hp as is, which seems more than enough for a compressor.

You pointed something very interesting out though... thats the ratio in relation to the oil pump, I never thought of that! But cant get my head around how the pump ratio would be changed, providing the rotating asembly is still turning with the pump? So it wouldnt matter what speed or gearing is being put into the Renault bottom end?

 

[KemppiFrog]

Not complicated about the 1.8TD, It is what I had spare. I expect the turbo will be spinning at 2000rpm, but little boost.
Not quit sure about your take on the oil pump. The Renault needs to turn the same way as normal for it's oil pump to pressurise the oil system. If I had run it from the flywheel end (first choice) the pump would have sucked, not blown, as it would be going against it's normal rotation.

RTB's comments are good too. I did think about having the inlet and exhaust both from the plug holes with two NRVs in the adapters. But was concerned that the inflow would be slow due to the small bore size, so elected to use the inlets to fill. I do have a few spare hours this coming week, so will buckle down and get the details sorted.
I am a fan of simple systems and ,as said, the only electrical connection is the stop solenoid. The heater plugs and cold start also need power, but easy to sort. My Renault Espace is the same technology, which is why I keep it, rather than get the eye-watering bills from more modern stuff. Two keys for my mates Kangoo= €350....
KF