Fire Extinguisher Paintball Gun

[mgmtrtms]

I was reading this idea http://www.rotteneggs.com/r3/show/se/176885.html, and thought it was great, basicly it was a paintball gun made from a fire extinguisher (fire extinguishers being illegal in my hometown of Australia). However, It would be very expensive, fire extinguishers are expensive, and getting them refilled could be auquard when theres a barrel attached to it. So I had this idea that you could refill it, with air, using an air compressor, instead of co2. I cant think of any reason why it wouldnt work. But how would you go about doing this? Any help would be highly appreciated.

[nbk2000]

An interesting idea, and good for those people living in really fucked up places where the sheeple are bleating for banning anything not toddler proof.

Improve your grammar in the future and you'll have a future here too. ;)

[zaibatsu]

Sorry, but fire extinguishers are illegal where you live? WTF? I wouldn't suggest refilling a fire extinguisher with air, I doubt it would be very good and you would have to go very high pressure to store enough volume of air. Unlike CO2 which is liquified in the cannister due to the pressure, and then changes state to gas when the pressure begins to drop, correct me if I'm wrong.

Also, a standard car tyre-type compressor won't reach high pressure, I think there is a limit around 250psi or something similar. Last time I looked RWS/Dianawerk/Daystate offered a compressor to refill PCP airgun cylinders to high pressures at around £400 in the UK. However, they don't remove much moisture from the air, and the last thing you want is rust on the inside of your steel cylinder.

Then, you'd have to consider a valve mechanism to withstand these pressure, not in itself too difficult but linking it up with a trigger and making it failsafe could be challenging.

Up to the job? Or a nice idea that isn't going to be of much use? I'll let you decide.

[Skean Dhu]

Why go through all of the trouble to use a Fire extinguisher ? You don't need 800PSI of CO2 to send a paintball 300+ FPS downrange. This handy program allows you to plug in the dimensions of your launcher and it spits out all of the theoretical fun facts.
http://www.thehalls-in-bfe.com/GGDT/index.html

After installing and meddling around a bit becuase I wanted to mess around in the program and I was feeling generous. I came up with these build specs for a paintball gun, that dosen't require high pressure CO2 gas to operate.
Parts list
-2" PVC pipe
-electronic sprinkler valve
-0.7" tubing
-air compressor
-neccesary fittings to put it together
-paintballs/ other .7" diameter objects
Barrel dimensions: 0.7" diam x 29" length
Resevior dimensions: 2" diam x 4" long
fill PSI: 40 PSI @70*f Muzzle velocity: 219 FPS Muzzle energy: 6.6 Ft*Lb
fill PSI: 70 PSI @70*f Muzzle velocity: 361 FPS Muzzle energy: 17.8 Ft*Lb
fill PSI: 100 PSI @70*f Muzzle velocity: 462FPS Muzzle energy: 29.3 Ft*Lb

These specs were tweaked for optimum performance. In case you decide to try your hand at this, I'll save you some trouble and give you some numbers.
paintballs weigh on average less than 3.5g I put in 4g to play it safe since I only looked at one site. In the calculation program unless you are using a specially made valve just use the 'generic' setting in the drop down menu.

After you make this launcher you may want to try your hand at a barrel sealing valve. But for just a simple paintball launcher to impress your freinds with and annoy birds, this will suffice. For optimum performance I would pneumatically modify the sprinkler valve so it can be tripped via a blowgun.

[Hirudinea]

Couldn't you buy/rent a bottle of CO2 to refill the fire extinguisher? Or failing that couldn't you jury rig a CO2 filler from an air pump, dry ice and a container for the dry ice?

[billybobjoe]

Or put the dry ice and let expansion do the rest. Are bandages and gauze banned in your area? I mean you COULD asphyxiate some one with them.

[ozboy]

CO2 fire extinguishers are NOT banned in OZ.

I think you're getting confused with the BCF (Bromochlorofluoromethane) (Yellow) fire extinguishers.

[FragmentedSanity]

I kinda thought he meant to say paintball guns were banned, they aren't illegal however - you just require a firearms licence, and all that goes with having said licence; Aussie gun laws have been covered in a few places here.

I find the idea that fire extinguishers are banned in your hometown somewhat strange - I've never been one to claim our government was doing a great job or anything but not even politicians are silly enough to put a blanket ban on fire extinguishers. If on the other hand, by some leap of idiocy fire extinguishers were banned, why would you use an illegal item - ie already more difficult to acquire and a liability if discovered - to produce yet another illegal item (the "paintball gun").

Unless Ozboy was right and your talking about a certain type of fire extinguisher - the best way to make a fire extinguisher illegal would be to stick a barrel on it as suggested as you'd then be breaking firearms laws.

[Chris The Great]

A compressor from a fridge should charge the thing over 500psi without a problem. I think they can reach upwards of 750psi.

[Red Beret]

If you really want to use extinguishers to propell things, and are worried about getting them refilled, steal them.

I personally wouldn't go to so much effort, but it eleminates the problem of refilling. Do you want rapid fire? If not, consider a P.A.C.-Pressurised Air Cannon.

There are other methods of using compressed air to propel projectiles, but it all depends on whether or not you require portability and a practical item, to use and carry.

[brother john]

I was talking to a fellow at a welding supply store I do business with a while back about refilling an empty CO2 fire extinguisher [FE] that a neighbor gave me. I'm wanting to refill it myself as in the U.S. it is required to be hydrostatic tested each time they are refilled. Most tanks don't need tested but every 10 years or something like that. FE's are the only tanks I've heard of that get every time. I didn't see any problem with doing my own refill but wanted some advice from a professional. The two fellows there saw little danger in doing so either due to in the process I would have a certain amount of volume not being filled in the FE as I will be using a 50 Lb. cylinder as the source. It simply won't completely fill. Instead of 20 Lbs. on the fill I might only get 15 Lbs. which is fine with me.

The trick to achieve is a high-pressure hose with one end having the tank connection,which is easy, the other other end whatever it takes to connect to the extinguisher which could be a bugger. With two FE's that are the same you could rob the parts you need to make up the hard end. There's probably no problem with simply putting CO2 back in the same place it came out.In this case the barrel or where it attaches?

The fill is made by getting the two tanks situated with the source tank upside down or at least at like a 45* slope with the valve on the low end. The contents are a gas above a liquid. You want to transfer the liquid into your FE, not the gaseous part. Connect the two with the transfer hose, open both valves, and wait until you can't hear it anymore. Close the valves, diconnect the hose, go shoot paintballs.

Propane is transferred in the same manner. Also it is a gas above a liquid. I use a hydraulic hose from some machine to transfer it.

I have CO2 to use on my MIG welder.It's inexpensive and works just fine for welding steel.

Skean Dhu's idea with the air sounds pretty good. Compressed air is way easier to come by than CO2. You could try the air and if it doesn't have enough oomph then move on up to higher pressure.

One plus I can see for the CO2 is that it will take much longer to run out.

[nbk2000]

If you can unscrew the handle from the tank, you could simply pour a weighed amount of crushed dry ice into the tank, and screw the handle back in, letting it warm up to pressurize the tank.

No need for regulators or tanks. :)

Just make sure that the tank has been heated and purged with dried air to remove all traces of moisture from the tank before adding the dry ice.

[Skean Dhu]

After reading NBK's post I got curious as to how economical that would be for someone to do.

So after consulting the internet I came up with a few things that kind of surprised me. I was expecting it to be a rather pricey endeavour (in the long run ) for someone to continualy use dry ice to (re)fill a fire extinguisher. However from the few sites I looked at it looks to be a very economical method even in the long run.

When I had more time and money and spent both on paintball, it was considered a good deal to get CO2 for $0.08-0.10/ oz.
With dry Ice I was able to find it at $0.04/oz(5lb block) and $0.12/oz, the latter site having a minimum order size of 12lbs and a $15 service/delivery fee.

So aside from dry ice being more economical for the causual experimenter it seems to be (from my limited research into the topic) cheaper in the long run aswell. The initial setup costs for a CO2 rig is around $100, that gets you a 5lb tank of gas, and a regulator(those used for pressurizing kegs can be found for 30-50 dollars on ebay, which regulate down to 0-60psi). It also costs (according to the below site) around 10 bucks to fill a 5lb tank.
http://www.csd.net/~cgadd/aqua/diy_co2rig.htm
So basically, if you can locate a source for cheap dry ice and are able to screw the valve back onto the tank easily and quickly, it will save you some money to go the route NBK suggests.