Author Topic: Small air compressor capability for powering simple engines.  (Read 1255 times)

Offline Gas_mantle

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Small air compressor capability for powering simple engines.
« on: January 07, 2016, 01:05:08 PM »
Hi all,

As a beginner I've made a few simple wobblers and well on the way to completing the 'Potty Mill' engine so I'm looking for something else fairly simple to build till I can buy a mill in a few weeks..

I'm thinking of making a simple single cylinder single acting engine but want to make something a little bigger than my previous models so I'm wondering what size of engine a simple air brush compressor might realistically be expected to power.

If I was to make something with say a 1" bore and stroke by my reckoning that's just under 13cc, my compressor can deliver 27ltr per min at up to 30psi - though I appreciate that's the makers claim and the reality might be a bit less. So at say 400rpm then engine would displace 400 x 13cc = just over 5 ltr per min.

Allowing for air loss and inefficiencies of machining I still seem to be well within the 27ltr per min capacity - is that a reasonable assumption or am I missing something ?

Anyone got any idea what the little airbrush compressors are capable of powering ?

Many thanks
Peter.


Offline philjoe5

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Re: Small air compressor capability for powering simple engines.
« Reply #1 on: January 07, 2016, 02:39:26 PM »
Peter,
I've powered a double acting mill engine with a 1.25" bore x 1.80" stroke with an airbrush compressor.  However, I could only do this after having many hours of running on this engine with larger compressors.  My point is, there is air flow to consider but also the engine's friction as well.

Good luck with your next engine

Cheers,
Phil
If you pick up a starving dog and make him prosperous, he will not bite you. This is the principal difference between a dog and a man.  - Mark Twain

Offline Gas_mantle

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Re: Small air compressor capability for powering simple engines.
« Reply #2 on: January 07, 2016, 03:00:11 PM »
Hi Phil,

Thanks for the reply, it's reassuring to know you were able to use a small compressor to power an engine much larger than I'm looking at making.

I reckon your engine is about 33cc compared to the 13cc I had in mind and taking account yours is double acting it would appear that all things being equal your engine needs over 4x the volume of air that mine would.

I'm hoping by that approximation even allowing for friction, machining inaccuracies etc I ought to have enough compressor capacity for a simple 1" bore x 1" stroke.

Peter.

Offline Thor

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Re: Small air compressor capability for powering simple engines.
« Reply #3 on: January 07, 2016, 05:20:48 PM »
Hi Peter,

 I think your compressor should be up to the task. I use a small airbrush compressor to run my wobblers, up to 16mm (5/8") bore and 19mm (3/4") stroke. I don't think my compressor would be suitable for the kind of engine you are talking about.

Thor

Offline Gas_mantle

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Re: Small air compressor capability for powering simple engines.
« Reply #4 on: January 08, 2016, 11:55:17 AM »
Thanks Thor,

I'll make the engine and see how it goes, the compressor is a stop gap till I can get a boiler so even if it's not gutsy enough I hope to get or make a boiler before too long .