Hand Cranked Air Compressor

[Robert Hornby]

I would like to try and run a couple of small model engines on air. They work fine at home and need only about 6 psi. from my 240 volt compressor. However I have been asked to show them to my Probus group and give a talk about them and model making in general. It would be nice to have one running but taking an air compressor into our meeting venue would not be really satisfactory. So I was thinking if it would be possible to build a manual hand cranked one specific for the job. I have a 250mm dia. flywheel casting that I could use for the crank wheel.
Robert

[Edward]

Have you got a spare wheel in your car? that'd probably provide enough air to run it for a reasonable time and then you could just pump it up again

[Robert Hornby]

Thanks Edward, But taking a spare wheel into our meeting at the venue would not go down so very well, so I am still looking for ideas for a compressor.
Robert

[steamer]

You could get a compressed air tank from the auto parts store....that might be a better bet....I think you will be pumping for a Very long time with a hand crank...and it's a lot of work for just a demo.....do they have compressed air on the premises?....had to ask

[Brian Rupnow]

I have, in the past, used an ordinary hand operated tire pump to demo my small engines. You don't have any reserve of compressed air, but as long as you pump, the engines will run.---Brian

[jonesie]

i use a small airbrush compressor to run some of mine,maybe you can borrow one from someone ,they are nice and small. just a thought

[Robert Hornby]

Thanks guys for your ideas, I used to have an air brush compressor but it was quite noisy and would detract from the display. My wish to have a hand cranked compressor would also be something the kiddies could turn to get the model to work at the shows and itself would be a sort of model. I only need to generate around 6 or 7 psi. I have searched the internet for a compressor design without luck. I am assuming it only needs to be a cylinder with piston and two flap valves, one inlet and one outlet, or am I being too simplistic?
Robert

[crueby]

I like Brian's idea of a bicycle pump. Plenty of pressure, easy to operate.

[cnr6400]

Robert - in the very old days of hard hat divers hand driven air pumps were used. I have seen some in museums with 24" to 30" cranks on disks at each end, and 2 or 3 cylinders, also some with round-rimmed flywheels to be turned by hand. Later of course small engines and electric motors took over the duty. maybe a modern copy with kid-size cranks and lightweight aluminum cylinders and frame (for easier transportation) might do. Silicone rubber flap valves or thin stainless shim stock multi-leaf "petal" flap valves could be used. Just food for thought.

[steamer]

I like Brian's idea of a bicycle pump. Plenty of pressure, easy to operate.

Me too.    and perhaps an accumulator made from some PVC pipe fittings?....might smooth it out a bit....

Dave

[Charles Lamont]

An oscillating cylinder, or cylinders, would be OK for that sort of pressure. And no need for valves.

[MJM460]

Hi Robert, I wonder what pressure you could achieve with something like a fireside bellows/ small version of a blacksmiths bellows.  Leather flap valves, and flexible sides, or neoprene or similar, plywood construction, long handles to help with the necessary force.  You don’t need much volume.

Alternatively, a hand pump for pumping those hypalon inflatable dingy’s.  About three inches diameter, but like a car tyre pump, easy to get your weight over the handle so you can get the required pressure, which might just work.  (You could try Whitworths if you are near one of their Sydney outlets, or mail order from them.)

The main issue is that even 5 psi, the required force builds quickly as you increase the cross section area of a piston.

MJM460

[Daggers]

Hi,
Just been out in the garden spraying the roses using a hand pressurised garden spray. The one i have is quite large, might be worth a try?

[steamer]

Hi,
Just been out in the garden spraying the roses using a hand pressurised garden spray. The one i have is quite large, might be worth a try?

Brilliant idea!

[cheepo45]

I rigged up a garden sprayer for running my engines - it worked pretty well.
 Scott