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new cannon design please asist.

Unread postPosted: Mon Jul 20, 2009 1:02 am
Author: SSGT Sultana
new spud cannon im deciding to make. consists of two small fire extingisher tanks which go to above 250psi each. two 3/4" nipples from these hook up to 3/4" 90 degree bends to 3/4" tee joint, which then goes to 3/4" tank valve then to the barrel. all of this allows for customisation and ease of use. all parts are pressure tested and galvonised. thinking about making size different but 3/4"will keep lots of pressure, and this also allows for barrel change going off the tank valve. pressure is the key issue as the fire extinguishers are the second smallest available but they hold high pressure. this design also allows for combustion and pnematic, when its made pics will be posted. just asking for advice on the sizes of fittings and anything else you can tell me will be great and you can also email me.

Unread postPosted: Mon Jul 20, 2009 1:19 am
Author: glass_05
loose the ball valve and get a modded sprinkler valve
and why not bump up to 1inch and instead of 3/4?

Unread postPosted: Mon Jul 20, 2009 1:23 am
Author: SSGT Sultana
yeah sounds good. 3/4" was first thought because its cheaper and provides more pressure. thanks

Unread postPosted: Mon Jul 20, 2009 1:25 am
Author: glass_05
i guess it really all depends what you are shooting out of it. if you dont need a 1 inch barrel then stick with the 3/4 and get a 3/4 sprinkler valve.

Unread postPosted: Mon Jul 20, 2009 1:28 am
Author: SSGT Sultana
gonna shoot a whole range of stuff. thats why i designed it so its fully customisable (the benefits of threaded parts hey). probably out of smaller barrels big marbles and shaped potatoes. heavier stuff who knows.

Unread postPosted: Mon Jul 20, 2009 2:36 am
Author: MrCrowley
I built this for my first cannon, fairly similar:
http://www.spudfiles.com/forums/viewtop ... html#56422

You'll have to get the fire extinguisher tanks welded like I did, only cost $20NZD for me. If you're using a ballvalve i'd recommend taking it to higher pressures, around 350-400psi, because ball valves are pretty slow opening valves. Meaning you get poor performance compared to a faster opening valve such as a QEV, Sprinkler valve or Piston Valve. But a sprinkler valve can only handle about 125psi.

You'll also want a much longer barrel than you have in the picture. How do you plan on getting 250psi by the way? Just curious.

Unread postPosted: Mon Jul 20, 2009 2:41 am
Author: SSGT Sultana
air compressor. plus my dad is a licensed pressure vessel welder so no prob there. previous spud cannons ive made worked fine with tank valve, and cos i wont have to by one makes it all easier but im open to options. and the picture is just a basic diagram overview not a detailed plan (obviously ).

Unread postPosted: Mon Jul 20, 2009 9:01 am
Author: Moonbogg
Have you considered making a hybrid? Just a thought.

Unread postPosted: Mon Jul 20, 2009 12:24 pm
Author: qwerty
are you sure hes that experienced yet to make hybrids when he dosent even understand about a CB ratio although you never know he could be some milatry superman spudgun god who's made a 50 inch 50000 psi piston cannon 8) :twisted: :shock:

Unread postPosted: Mon Jul 20, 2009 7:48 pm
Author: Mateo
although you never know he could be some milatry superman spudgun god who's made a 50 inch 50000 psi piston cannon


haha is that even possible?

and if your doin high pressure tanks and galvanized fittings then why would you use a plastic sprinkler valve that probably wouldnt be able to hold the same amount of pressure? id just make a spring assisted ball valve and use high pressures.

or you could build a metal piston or qev but from the looks of your design you want it to be pretty simple?

Unread postPosted: Mon Jul 20, 2009 8:09 pm
Author: SSGT Sultana
yeah simplicity and adaptability is main feature. yeah spring assited ball valve is what im doing, seems simple and can withstand the pressure. i also want this thing to last as well, sick of pvc its to weak.

Unread postPosted: Mon Jul 20, 2009 8:13 pm
Author: SSGT Sultana
also i dont want the fire extingishers weldied to gether although to make it transportable it loses it adapatabilty. i might also wanna have this with only one bottle or mabey three so it keeps my options open.

Unread postPosted: Mon Jul 20, 2009 8:47 pm
Author: MrCrowley
also i dont want the fire extingishers weldied to gether

If they're not welded, they'd be epoxied. As far as i'm aware you can't get normal threaded fittings (NPT) that will work with fire extinguisher threads.

and if your doin high pressure tanks and galvanized fittings then why would you use a plastic sprinkler valve that probably wouldnt be able to hold the same amount of pressure?

Are you referring to my cannon or what I said about fast opening valves?

If you were talking about my cannon, it was my first cannon. The sprinkler valve would be better than a ball valve and I only had means of reaching 115psi anyway. :)

I never told him, in fact I told him not to, use a sprinkler valve with this cannon unless he was limited to 125psi.

Sorry if I misinterpreted what you said.