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Air compressor

R/C Submarine modelers

Postby ThierryC » Wed Mar 17, 2004 10:55 am

Hi all

I am looking for the smallest possible air compressor. A car tyre air compressor is too big for the sub I have, so I need something even smaller and compact and that can produce at least 100psi of pressure. Would any of you have an idea of where could I find something like that ?
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Postby safrole » Wed Mar 17, 2004 12:03 pm

Here you go. Get out your wallet.

http://www.micropump.com/products/pumps/piston/

It probably doesn't have enough flow rate to do you any good, but maybe they can get you something more suitable, but I think the piston is the way you want to go. The diaphragm pumps seem to be lower pressure, but here is a link anyway.

http://www.sensidyne.com/oem/oemproduct.htm

You have piqued my interest. Are you inclined to share any more details on what you're doing? I'm especially interested if it has to do with your earlier post re: the gas/electric propulsion system.
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Postby Sub culture » Wed Mar 17, 2004 3:43 pm

safrole wrote:Here you go. Get out your wallet.

http://www.micropump.com/products/pumps/piston/

It probably doesn't have enough flow rate to do you any good, but maybe they can get you something more suitable, but I think the piston is the way you want to go. The diaphragm pumps seem to be lower pressure, but here is a link anyway.

http://www.sensidyne.com/oem/oemproduct.htm

You have piqued my interest. Are you inclined to share any more details on what you're doing? I'm especially interested if it has to do with your earlier post re: the gas/electric propulsion system.

Those diaphragm pumps look excellent, and parallel what I was developing myself, although I only require low pressure(8-12 psi) for a recirculating air system.

Running diaphragm pumps in series is one way of achieving higher pressures, this is how they do it in the gas bottleing industry I believe.

To be honest achieving 100 psi from a small piston pump will not be easy, it will require very fine machining which never comes cheap.


Either that or DIY...do you have a lathe?

Andy
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Postby raalst » Wed Mar 17, 2004 4:52 pm

maybe (just maybe) you should consider LEGO pneumatics
That stuff comes with able, small, smooth running pistons.
which are used to pump air.
a servo can be converted to provide the motorisation
(although it would be slow).
Image

my 2 cents...

this pump can create a pressure of 2 bar, i believe, but I have no clue how that relates to 100 Psi.




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Postby safrole » Wed Mar 17, 2004 6:02 pm

Maybe a tiny 2-stroke glow motor with an electric motor to drive it? You're essentially using the fine machining and reed valves as a high-sealing pump.

The Dutch believe legos can be used for anything, but I'm not too sure. :)

(just kidding)
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Postby safrole » Wed Mar 17, 2004 6:03 pm

2 bar is about 30psi
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Postby KOEZE » Fri Mar 19, 2004 4:20 am

Maybe a tiny 2-stroke glow motor with an electric motor to drive it? You're essentially using the fine machining and reed valves as a high-sealing pump.

2 Stroke can't work. A 4 stroke may work. They have intake and outlet valves needed to build up pressure. A 2 stroke gets its air/fuel mixture from the oil pan.
But then you'll get about the same size as a car tire compressor.
You may want to consider a steam engine instead of lego as it doesn't rely on plastics (reducing max pressure). Also a pneumatic cylinder may do the trick. With these options friction and the heating of air being compressed may cause problems with the seals.

On the other hand. I don't know how much air you need but you could use a geared pump to pump fluid into a pressure vessel compressing the air in there. Use the air and pump out the fluid to allow new air in. This way seals and leakage are less important but you are restricted to the max pressure that can be supplied by such a pump and very little volume.

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Postby Sub culture » Fri Mar 19, 2004 6:15 am

KOEZE wrote:
Maybe a tiny 2-stroke glow motor with an electric motor to drive it? You're essentially using the fine machining and reed valves as a high-sealing pump.

2 Stroke can't work. A 4 stroke may work. They have intake and outlet valves needed to build up pressure. A 2 stroke gets its air/fuel mixture from the oil pan.
But then you'll get about the same size as a car tire compressor.
You may want to consider a steam engine instead of lego as it doesn't rely on plastics (reducing max pressure). Also a pneumatic cylinder may do the trick. With these options friction and the heating of air being compressed may cause problems with the seals.

On the other hand. I don't know how much air you need but you could use a geared pump to pump fluid into a pressure vessel compressing the air in there. Use the air and pump out the fluid to allow new air in. This way seals and leakage are less important but you are restricted to the max pressure that can be supplied by such a pump and very little volume.

EJK

A 2-stroke engine will work. Nick Burge succesfully converted a small Cox glow engine for his HMS Acrylic over a decade ago.

The glow plug was replaced with a small one way valve for the compressors exhaust and the air inlet was the standard air and fuel vent at the base of the cylinder. Simple and cheap if you have an old glow engine lying around that won't start anymore!

However, you will be lucky to achieve the pressure you require for your application. Most piston compressors can RELIABLY get up to around 40-50 PSI, beyond that you will struggle.

Plus you need to consider displacement. If you have a lot of water to move you will need to pump a lot of air, so you will likely need multiple cylinders. A large single cylinder would do the same job, but will produce quite a bit of vibration.

A twin horizontally opposed design would be a good compromise. Craycraft (nee OTW) used to produce such a compressor for their compressed air WTC/module systems, although I don't think these are available any longer.

The Lego system doesn't look like it will last IMHO.

May I ask why you are looking for such high pressures?

Andy
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Want to dive your boat in crystal clear water? Then you had better Dive-in- http://www.diveintomodelsubmarines.co.uk
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