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Marble Cannon

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: noname » Wed Jul 05, 2006 9:25 pm

Mine is floating, but the ones in my valves use springs.
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Unread postAuthor: OwThatsMyEye » Wed Jul 05, 2006 11:36 pm

PVC Arsenal 17 wrote:Is it a better fit than 3/4 pvc? I might try it thanks.

we were talking about the diaphragm which is the valve that seals the barrel until the back of the gun is vented.

If you have a floating diaphragm, it seals by pushing against the barrel when air is put into the chamber from behind it at a fast rate.

A spring diaphragm is the same setup but uses a spring to help it seal so you don't waste air pressure to move it.

A fixed diaphragm is a sheet of rubber or neoprene that always seals against the barrel and just flexes in and out.

yea copper fits alot better that pvc. and know what the diaphragms are i was just confused about the co2 cannon you guys were talking about.
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Unread postAuthor: zeigs spud » Mon Sep 11, 2006 6:47 pm

Hey can u do me a favor and message me the details of how u built it what peices u used and i'm new to the air powerd guns so how u put the air in? i've seen bike punps but do u drill in the hole and put a bike valve thing there to keep the air from coming out? well if you could do that i weould really aperciate that?

p.s. why is it so bulky aroudn the barrel?
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Unread postAuthor: PVC Arsenal 17 » Mon Sep 11, 2006 6:55 pm

OK dude. His gun is called a coaxial. This means that a smaller pipe runs the length of a larger diameter one. Floating inside the larger pipe is a piston or a diaphragm that presses up against the inner pipe which is the barrel. When the gun is pressurized from behind, suction pulls the piston against the barrel and seals it. Meanwhile, air leaks by into the larger pipe. This is the "pressure chamber"

So... Now you have a sealed barrel inside a pressurized "shroud" To fire it, air from behind the piston is exhausted and the piston is pulled back due a strong suction. When it moves back, the seal with the barrel is broken and a new one is made behind it. The prevents the air in the chamber from exhausting as well. Instead it all rushes out through the inner pipe, propelling the projectile.

This is quite a common design that continues to prove itself through time. It is one of the powerful designs around and it can be made easily by the average builder. The "pipe within a pipe" concept makes it very compact and self contained.

Contrary to what most people say, I think this is the best design to build as a beginner. With experience you will get a nack for them and they will get better and better.

Basically what you need to look for is:

2" pipe
1/2" pipe
2" coupling
2" female adapter
2" x 1/2" slip bushing
2" x 1/2" threaded bushing
1/2" ball valve.
1/2" tee
1/2" x 1/8" bushing
1/8" tire valve
Rubber sheet


Glue the female adapter to one end of the 2" and the coupling to the other. Glue in the slip bushing to the coupling. Let all this dry. Cut out a sheet of rubber for diaphragm valve (rubber pipe cap) so it fits into female adapter. Thread in the bushing vertically with the rubber sitting on the inside over it. now, get a length of 1/2" pipe and slide it all the way through the 2" pipe via slip bushing till it firmly presses on the rubber sheet. mark it and glue. let it dry. Assemble the bushing, then tee, then tire valve, then ball vave. put PTFE tape on all threads. Fill it with the tire valve and fire by opening the ball valve.
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Last edited by PVC Arsenal 17 on Mon Sep 11, 2006 7:10 pm, edited 1 time in total.

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Unread postAuthor: zeigs spud » Mon Sep 11, 2006 7:03 pm

I'm sorry can some1 make a picture example of how that woorks on like ms paint (doesn't have to be good for me lol..)? srry i feal stupid now but yeah lol
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Unread postAuthor: PVC Arsenal 17 » Mon Sep 11, 2006 7:11 pm

look here under "quick exhaust cannon" great animated diagram http://www.xinventions.com/main/spud/ho ... tm#How%20a%
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Unread postAuthor: OwThatsMyEye » Tue Sep 12, 2006 3:57 pm

Thx for explaining that to him Arsenal. I wouldn't recomend that a coaxial be the first cannon that you make but you feel up to it than go for it. I see if i can make some plans for you but it may take awile.
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Unread postAuthor: zeigs spud » Tue Sep 12, 2006 4:00 pm

lol thanks. yea i don't think i will make that kind for a while. is there a power difrince if i don't have one like that?
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Unread postAuthor: MrCrowley » Tue Sep 12, 2006 4:56 pm

if you havnt built a combustion,do that,but if you like pneumatics(more powerfull)build a simple over-under cannon.
if you want more info go to spudwiki located at the top of the page in the blue area.i dont recomend starting with a coax but if you have some skill go for it. a coax with a 4" chamber and a 1.5" barrel is less powerfull then an over-under design with a 4" chamber and 1.5" barrel as in the coax the barrel takes up room in the chamber.
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Unread postAuthor: zeigs spud » Tue Sep 12, 2006 6:21 pm

lol this topic has turned into a help page for me lol srry bought that. but thanks. i've already started plans for a breechloading over under and a new kind of ammo for them. i'll probably post it all when i am done (the ammo mabey sooner). i just don't know what to use when i put the pipes together to hold them together.
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Unread postAuthor: noname » Tue Sep 12, 2006 6:46 pm

PVC primer and cement, what else? Elmers maybe? :lol:
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Unread postAuthor: zeigs spud » Tue Sep 12, 2006 9:14 pm

k well i'm new to this sowht kinda cement? rubber cement?
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Unread postAuthor: SpudStuff » Tue Sep 12, 2006 9:49 pm

zeigs spud wrote:k well i'm new and retarrrded to this sowht kinda forum? rubber cement? ?


I speak english not retard SO, learn to spell and ask a real question.
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Unread postAuthor: zeigs spud » Tue Sep 12, 2006 9:58 pm

dude i asked wht kinda cement not forum. where did u get that lol? anywho calm down god. if u don't wana answer then just don't. i think thats pretty simple.
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Unread postAuthor: SpudStuff » Tue Sep 12, 2006 10:17 pm

Sorry zeigs (can't even capitolize your own name) but you need to:
1. Learn to spell
2. Learn proper grammer.
3. Do research
4. Get your head out of your ass.
Now is that clear.
anywho calm down god.


You Got That Right :D
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