Compressed Air Foamer

Build a homemade water gun or water balloon launcher and tell us about it.
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superpants
Posts: 5
Joined: Mon Mar 29, 2010 4:45 pm

Compressed Air Foamer

Post by superpants » Mon Mar 29, 2010 4:57 pm

Greetings one and all!
I have recently come across the forum after it was picked up on the Make Magazine blog. It seems like a fascinating place, and I’m sure I will be getting inspiration from some of your projects.

Over the years I have made all sorts of projects, many involving water and foam, but haven’t got round to writing many of them up. One of the latest that I have been working on, and had its first public outing at the recent UK Maker Faire has been a Compressed Air Foam System (CAFS). Although not a pure water weapon, it does however project wet foam a reasonable distance.

For the complete details, I have a write-up on my website http://www.superpants.net, however the key details are as follows;

The system uses a soda keg (Cornelius keg) to hold a water and bubble-bath solution. The system is connected to a compressor, through a regulator to force the fluid out of the cylinder. This fluid is mixed with air in a tee-piece and discharged through a ball valve and a hose.

The brief description belies the many hours playing around with it and re-building it to get it to work successfully, but it does. A jet of foam with a consistency of shaving foam is projected at least 5 metres, and a nice snowy effect is achieved if pointed up.

I have a number of other projects on the go, so hopefully will be able to contribute these when they get finished.

Hope you find this interesting!

Image
http://www.flickr.com/photos/mrsuperpan ... 241766760/

Image
http://www.flickr.com/photos/mrsuperpan ... 241766760/

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C-A_99
Posts: 1502
Joined: Tue Aug 01, 2006 11:09 pm

Re: Compressed Air Foamer

Post by C-A_99 » Mon Mar 29, 2010 8:09 pm

Interesting project. From the looks of the pictures, it seems that it can also shoot water, though the design probably isn't ideal for it. (Judging by the lower diameter hose used)

What type of air source do you usually use? It also seems that you can get more range from the foam by using higher diameter tubes to allow for more flow, then channeling it into a nozzle. However, at the viscosity of foam, this probably doesn't work that way. (however, foam also seems to be less suceptible to air resistance breakup, meaning that when launched at the same velocity of water, given the same nozzle, it should go farther. The issue seems to be the viscosity of the foam making it difficult to launch at higher velocities)

Good luck with your projects and welcome to Super Soaker Central. Thanks for sharing.

superpants
Posts: 5
Joined: Mon Mar 29, 2010 4:45 pm

Re: Compressed Air Foamer

Post by superpants » Mon Mar 29, 2010 8:38 pm

It could indeed shoot water succesfully, although it's a bit overcomplicated for that! As the water to foam expansion ratio is quite high (estimated to be about 30:1), it needs a lot of air, at 2-3 bar pressure. I threrefore use a workshop air compressor to supply the air, which doesn't make it very portable. Given a bit of time i will probably try and build a portable system, but it will need a much smaller reservoir.

The final solution has taken quite a lot of experimentation. Key to this seems to be the bore of the delivery tube, relative to the bore of the pipework of the main system and the nozzle. If any of these are of significantly different bores, the foam doesn't form properly- It isn't possible to fit a small nozzle to larger bore tube without seriously imparing the foam generation. I have also tried using a trigger operated nozzle on the end, and failed to get any good flow either. I think i will be able to get this to work when I have gathered some fittings together that allow a pass through the valve with no change in bore.

I will have to try some experiments to look at the relative distances between water and foam- it will be interseting to try out. Wind does however affect the foam quite a lot- tends to break up the stream.

Thanks for the welcome

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zeda.beta
Posts: 683
Joined: Sun May 03, 2009 10:49 pm

Re: Compressed Air Foamer

Post by zeda.beta » Tue Apr 06, 2010 11:28 pm

First off, welcome, and was this forum really posted about in the Makezine blog? Second, what pressures are you operating at, because the stream looks pretty powerful, not to mention very coherent for something that is made out of foam.
-Zed
I reject your reality and substitute my own.
Quack damn you.

superpants
Posts: 5
Joined: Mon Mar 29, 2010 4:45 pm

Re: Compressed Air Foamer

Post by superpants » Wed Apr 07, 2010 11:20 am

The whole system is running at 2-3 Bar, so is exiting the nozzle at this sort of pressure. It is pretty coherent as the expansion ratio of the foam is quite low (estimated at about 30), meaning you get a dense, wet foam, not like normal bubble bath.

The post on the makezine blog is here:
http://blog.makezine.com/archive/2010/0 ... oaker.html

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