Tank less Compressor

[Ian UsmarParticipant @ianusmar79339]

So I have been watching some You tube videos that show people testing model steam engines using compressed air, I have found one called a "Clarke Jumbo Compressor" which seem to not have any resevior / tank. Would this be able to power the engines or do I need a certain PSI to run the engines?

Regards

Uzzy

[Ian UsmarParticipant @ianusmar79339]

Clarke Jumbo Air Compressor

[Dave HalfordParticipant @davehalford22513]

Here

Mostly used on constant bleed spray guns.

It would depend on the capacity of the engine/s

[SillyOldDufferModerator @sillyoldduffer]

A particular engine needs a certain pressure to turn, plus whatever volume of air is needed to keep it going.

Most compressors have no problem producing pressure, but volume is more difficult. A reservoir is the easiest way to provide volume – a whacking big tank full of air.

The amount of air consumed depends on the volume of the cylinder times rpm, doubled if the piston is double acting, and allowing for the pressure. Not difficult for a small engine to need a few cubic feet of air per minute, so the jumbo pump on it's own will probably struggle. The pressure / volume ratio doesn't match the engine. Adding a reservoir and regulator that reduces the output pressure to suit the engine fixes it. The regulator could be quite small.

Not keen on home-made pressure vessels myself. I've driven a engine with a car foot pump hooked up via a plastic lemonade bottle. Reasonably safe because the amount of energy I can store in the bottle is small. Doing the same with an electric pump is dodgy, because it could squeeze a lot of energy in before the bottle bursts. Easier and much safer to buy a commercial compressor with built-in reservoir and regulator.

Finding air pumps for engines is bit tricky. The type based on fans shift plenty of volume but the pressure is too low. Electric Tyre pumps are high-pressure low-volume. Workshop compressors can do pressure and volume but are big, noisy and expensive. Quiet inexpensive air pumps producing enough pressure and volume to run a small engine seem thin on the ground.

Dave

Edited By SillyOldDuffer on 11/01/2022 17:50:54

[Mike PooleParticipant @mikepoole82104]

A 2 litre pop bottle with dry ice and hot water produces a spectacular bang, good luck if you find any of the bottle pieces.

Mike

[Clive FosterParticipant @clivefoster55965]

A bit worrying to see that the Jumbo needs a spring in the regulator changed to reduce the pressure sufficiently to be safe with the spraygun supplied. Who reads the instructions for something that simple. Plug it in and go is the normal expectation for this sort of complete kit.

Changing it to increase pressure might be marginally acceptable.

Makes you wonder about how well thought out the whole kit and caboodle is and how much attention was paid to details like specifications.

The old Binks-Bullows hydrovane type compressors made for their continuous air guns would probably make the best fist of driving an engine when running without a tank.30 or 40 psi depending on which model. High build quality so they last for a very long time unless you forget to keep the oil topped up. But still not a lot of air in objective terms. About enough to keep up with a Bjur Spraymist unit.

Concerning reservoirs. 50 ft of air hose on a reel works pretty well at the sort of draw rate a small engine has.

Clive

[JasonBModerator @jasonb]

Without knowing what the engines are and what you intend to do with them it is almost impossible to say what would suit.

The smaller the capacity of an engine then the less volume of air needed so a small airbrush size compressor with no tank may be fine for something upto 20mm bore x 20mm stroke but if you have a large 50mm x 50mm engine then it's capacity will be more than the compressors displacement.

Linked to this is the speed you want to run at, the slower the engine the less volume of air it will need per minute so that 50x 50 may tick over on a mid size compressor if you just want it to run at 60rpm but the compressor will not keep up if you want to run at 600rpm

lastly comes what you want to do with the engine, I generally just like to run mine for display and turn the compressor down until the needle is hardly off the stop so 5psi (o.3bar) at the most. If on the other hand you want it to drive say a generator or pump then depending on teh load they put on the engine you will need to increase pressure so that cheap comp that has a FAD (free air delivery) of 2cfm at 20psi may only have half that at 50psi

One other thing to consider with no storage tank is that teh compressor will be running all the time and the cheap ones are often very noisy so that thought of relaxing and watching your latest creation ticking over will be shattered by the deafening noise of the compressor.

Anyway who needs a compressor

[Ian UsmarParticipant @ianusmar79339]

So the question on the engine is that its one my grandfather made ( Many years ago) I believe its similiar to a Stuart 10V, the fact is that my late uncle was going to try and make them from something clear as an executive toy means its in bits and needs to be re assembled but I will need something to run it. I noticed another thread that someone used the steam cleaner !!

Your thoughts Gentlemen.

[Howard LewisParticipant @howardlewis46836]

A reservoir, as its name, provides a reserve of air when the engine runs, so that the compressor does bot run constantly.

Some compressors are not intended for am 100% duty cycle, and will fail if used in that manner.

Direct drive compressors are noisier than belt driven machines because they are running faster and producing pressure pulses more frequently.

An engine will require a certain minimum pressure to enable it to run. What volume of air will depend upon:

The swept volume of the engine

The speed at which the engine is running

Leakages within the engine.(There will be some )

For a ,given size / length of leak path, the leakage will depend upon the pressure and the time that the path is open. So a slow running, leaky engine might require a greater volume of air than the same engine running at high speed.

Howard

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