Air Pump Power

[Pat Cooke 2Participant @patcooke2]

I am a total newbie at this but I am at my happiest building things whether it be remote controlled planes or boats, models etc. etc.

Have now decided to try my hand at these type of models and have a couple of questions which I hope someone will understand and help with.

Can you change live steam to air pump power and if so how easy would it be please. If this can be done what pump would I need.

[Pat Cooke 2Participant @patcooke2]

[JasonBModerator @jasonb]

Yes very easy, just connect an air supoply and away you go, add a bit of oil for lubrication.

Pump would depend on size of model from a small aquarium pump to several HP compressor

[Pat Cooke 2Participant @patcooke2]

That's brilliant thanks, I was beginning to think I was looking for the impossible and having tried several shops was ready to give up. Will now go and investigate aquarium pumps.

[Speedy Builder5Participant @speedybuilder5]

Hold on a mo. How big/ type (loco, stationary,marine, single, double, triple etc) is your engine ? An aquarium pump would only drive a very small engine – perhaps something like a small Mamod model.

[Pat Cooke 2Participant @patcooke2]

This is a totally new exercise for me so at the moment I do not have an engine until I build/acquire one but was probably thinking along the lines of a Mamod. Is there some sort of chart which would show me sizes that I would need pumpwise please.

[Neil WyattModerator @neilwyatt]

There's no chart, but as a rule of thumb bear in mind the same volume of air needs to run through both pump and engine, so the bit that does the pumping needs to be of a similar size to the engine cylinder for them to run at similar speeds.

Aquarium pump – very small engines

Diaphragm pump – should handle engines of about 3/4" bore 1" stroke easily.

Over ~1" bore – probably need a proper compressor with air reservoir.

Very often volume of air matters more than pressure that cheap '150 psi' tyre pump from the garage won't shift enough air for anything bigger than a tiny engine, while a HVLP pump may well turn a largish model, albeit slowly.

Don't expect air-powered engines to do much of a job of work, just to show off their operation.

[Pat Cooke 2Participant @patcooke2]

Thanks that is very helpful

[Paul LousickParticipant @paullousick59116]

Hi Pat,

An aquarium pump may not be large enough. They only supply a small volume of air at low pressure. You may need something a bit bigger like an airbrush compressor or larger. An alternative is a small steam generator as described in a previous MEW post about making a simple boiler. http://www.model-engineer.co.uk/forums/postings.asp?th=109271

As a guide, a 6 or 8 cfm air compressor will run a 3" Fowler traction engine for a couple of minutes with a tank of air at 60 psi then slow to a few rpm as the pressure falls. We have also used a big petrol powered compressor (used to operate jack hammers) to move a full size 12 ton traction engine under air.

Paul

[Ian S CParticipant @iansc]

I'v tried an aquarium pump on my smallest wobbler (steam engine), and it does not work, the pump is a small diaphragm type in a box about 3" x 2" x 1 1/2", the motor has a 3 mm / 1/8" bore, and a 8 mm/ 5/16" stroke (can't remember if I built it metric or imperial, maybe it was both. I have a small (medical) diaphragm compressor that produces 30 psi, I'v had that running two motors, one a single cylinder with a 5 mm bore and 1/2" stroke, the other a V twin with 1/4" bore, and 1/2" stroke. It would probably run one of the smaller Stuart Turner engines.

Ian S C

[Pat Cooke 2Participant @patcooke2]

Thank you for all your help and suggestions, I have just been to see a guy who runs a tool shop (really old school type) and have come home with an old medical compression similar to the modern nebulisers, am currently trying to make it work and see what happens with that.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Pat Cooke 2 on 21/09/2015 13:40:23:

Thank you for all your help and suggestions, I have just been to see a guy who runs a tool shop (really old school type) and have come home with an old medical compression similar to the modern nebulisers, am currently trying to make it work and see what happens with that.

.

Pat,

My wild guess is that will be a Charles Austen pump

… they were very helpful when I last dealt with them.

MichaelG.

[Author]

Posts