Need some help with metal cannon

SPUDKILLER · Fri Mar 02, 2007 3:02 pm

I was in the junkyard and came across a tank that used to be used for a fire extinguishing system. the tank is about 3ft with a 9in diam. i was thinking of just building a combustion cannon out of it. but was wondering what would be a good way to insulate the wires for whatever ignition system i use. i cant think of anything that would melt or burn up when i ignite it. I will post pics of this thing as soon as i can. there is a tag on it that says it is usually pressurized to 360psi, tested to 720psi. I have taken the valve off of the top of the tank and it is empty on the inside.

any ideas

Pete Zaria · Fri Mar 02, 2007 4:04 pm

Welcome to the forums.

Browser around, there are quite a few nice guns made from fire extinguisher tanks here. I know McCrowley made a nice one...

Personally, I'd be thinking about a hybrid. How experienced with spudguns and/or real guns are you? Don't attempt a hybrid if you don't already have experience with both combustion and pneumatic guns - but if you do, a big fire extinguisher tank is a perfect hybrid combustion chamber.

Your only real problem will be figuring out how to get the wires for the ignition, and the fuel meter pipe, into the chamber without drilling/tapping holes. Attaching a 4-way T fitting to the front of the chamber could accomplish this.

As to worrying about the wires melting, it shouldn't be a problem. The chamber is only heated for a few fractions of a second. I'm using regular 18g shielded speaker wire for my spark strip in my combustion gun, and it holds up fine. Lamp cord would work fine, too.

Let us know if you have any specific questions or problems we can help you with.

Peace,
Pete Zaria.

Check out my YouTube SpudGun Channel! · Sat Mar 03, 2007 1:18 am

Pete Zaria wrote: Browser around, there are quite a few nice guns made from fire extinguisher tanks here. I know MrCrowley made a nice one...

Thanks for that Pete, Only this would be on a larger scale. As long as you have a welder and you know what you doing it is possible to make a metered combustion out of this tank.

Killjoy · Sat Mar 03, 2007 1:26 am

Damn your lucky to find somethin like that. um...i dont want to be a killjoy (no pun intended), but if you do make it a combustion, the barrel would need to be...oh say...50 feet long for a 1.2 to 1 chmaber to barrel ratio. I would personnally suggest a pneumatic considering the tank is made for decently high pressures.

killagorrila99 · Sat Mar 03, 2007 2:12 am

SPUDKILLER wrote:the tank is about 3ft with a 9in diam.

DDT To da fricken max! lol. But since its rated that high, Aim for ddt. Should be good.

EDIT: 30 seconds of searching found this http://www.spudfiles.com/forums/viewtopic.php?t=1573&

spudthug · Sat Mar 03, 2007 8:13 am

1. welcome to spudfiles
2. where is this junkyard...lol j/k
3. make it a pneumatic!!@#@#!$!
4. combustion in a fire extinguisher is a waste...
5. a 720 psi pneumatic!!!!!!!!!
6. dont ever pass this up you could put a hole through a board with a paintball
7. welcome again

jjjd · Sat Mar 03, 2007 10:30 am

Yeah i woudl probably make it a hybrid or a pnematic, making it just a combustion would be a very big waste. to insulate im not really sure, sound hard

LGM · Sat Mar 03, 2007 10:43 am

Definetly go for hybrid, with a chamber that big you could launch some very large objects at high speeds. Or smaller objects at even better speeds.

SPUDKILLER · Sat Mar 03, 2007 10:45 am

i have definitely been thinking about a pneumatic. the valve that was on top just screwed off, so there is threads inside the top of the tank. i was going to go to lowes and see if it has the same thread pitch as a piece of galvanized pipe. if so the maybe i can work up a adapter type deal where i can switch out barrels when i want. so who wants to see what a golf ball does at about 300psi.....

SPUDKILLER · Sat Mar 03, 2007 10:55 am

i was thinking about how to do a pneumatic, all i would need for the tank itself would be something like a schrader valve to pressurize the tank. the the usual fittings, ball valve or something of that nature. i just feel that it would be safer than doing a combustion gun. the only thing is i dont have air compressor to fill the tank with. so if i wanted to go to my buddies house and shoot it then that means i wouln't be able to because i dont have an air tank. i was thinking of buying a small compressor that i could carry with me.

loganphyve · Sat Mar 03, 2007 11:14 am

I am currently building a pneumatic with on-board air. I'm sure you'll find a solution.

BTW spudkiller... Instead of repeat posts, you can edit your originals to save space.

Loganphyve
ÜberComputer Studios LTD.
"Seamless Technology Integration"

Matheusilla · Sat Mar 03, 2007 11:20 am

one of my favorite pneumatic tanks is a small extinguisher tank. It's a small kitchen model, says it's tested to 300psi, ubelievabl if you saw how thick the walls are (alumminum on top of that). The thread pitch on mine was just a little bigger than npt threads, so I steel epoxied a piece of galv. 1/2" in as far as I could put it. Since I never pump over 120-150psi so I feel safe about my connection. However, you may wanna do something different to be safer.

willarddaniels · Sat Mar 03, 2007 12:41 pm

Use a spark plug and make it a hybrid.
Weld a reinforcing plate on the bottom, drill and tap a hole for the spark plug and fuel/oxy/air supplies through this. If you can't, I'm sure you can find a shop that will for 40-50 bucks (maybe free if you haggle well and promise to provide spectacular demonstrations upon completion).
A machine shop can easily make an adapter/nipple that will match your tank's threads on one end and be npt on the other. This will probably cost the 40-50 clams. Possibly get it done at the same shop.
Good luck