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5 Foot Coax

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: Fish8myb8 » Wed Mar 24, 2010 8:27 pm

so a flat sealing face is that important, huh? I'll make sure to sand mine down very flat and smooth and have neoprene on the piston.

How's this for a first design?
1/2" inch barrel inside 2" pipe. Kept in place by 2 2" to 1/2" reducers, with a 1/2" tee at the end for a 1/8" schrader and 1/4" trigger to be threaded into endcaps.
Piston will probably be molded inside the pipe itself with epoxy (Thanks JSR :wink: )after it has been lubed.

Image :wink:
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Unread postAuthor: clemsonguy1125 » Wed Mar 24, 2010 8:37 pm

Looks good, is it servicable and Id upgrade to a 1/4 inch or 1/2 inch ball valve, or even a sprinkler valve, and for a barrel support I cut up a 11/2 in to 1/2in bushing then sanded it down. For the piston I used a 11/4 coupler but molding hot glue sounds good. How long is it? Its a great start though.
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Unread postAuthor: Fish8myb8 » Wed Mar 24, 2010 8:46 pm

Thanks :D
It's not serviceable if I were to solvent weld all the pvc parts to each other, but I could solvent weld the barrel inside the 2" to 1/2" reducer to the left, and bolt /screw the chamber 2" pipe to the reducer so it were serviceable. Might be leaky though. I do have a spare QEV laying around, and a 1/2" ball valve, would that be good in place of a sprinkler valve? I don't really care what it looks like. Just want to get the concept to work. I'll go to Lowes soon and see how that coupler fits into the pipe. Sounds like a great idea to use a coupler as a piston!! thanks so much

dimensions: the 2" chamber is 10" long, 1/2" pipe goes into it 8 inches. Don't know any other dimensions I could give, just regular pipe fittings. The length of pipe between the backstop on the piston, the 2" to 1/2" and 1/2" tee is minimal, just enough to get both ends of it fully into the fittings it holds together
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Last edited by Fish8myb8 on Wed Mar 24, 2010 8:53 pm, edited 1 time in total.
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Unread postAuthor: clemsonguy1125 » Wed Mar 24, 2010 8:51 pm

I really suggest you make it serviceable as I adjusted all my piston valves as least 20 times each, its only about 3 buck worth of fittings and are well worth it, a 1/2 ball qev would work great.Good Luck
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Unread postAuthor: Fish8myb8 » Wed Mar 24, 2010 8:56 pm

Alright that should really help then.
Thanks for the suggestions and help, wouldn't get this far without it.
I already have parts for a fullmetal 1 shot 3/4" QEV gun shipping in, so I'll start this coax after that's done and played with. I just wanted a gun that I can play around with and be sure it works in between designing and tweeking other stuff in between. Cuz my other launcher blew up at 110 psi from a DWV end cap.
Thanks again :)
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Unread postAuthor: clemsonguy1125 » Wed Mar 24, 2010 9:03 pm

Cool if you have a 3/4 qev why not try to make it semiautomatic, I know you want a simple gun but you can always adjust it later :wink:
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Unread postAuthor: Mtrhd0024 » Wed Mar 24, 2010 9:15 pm

Fish8myb8:

In order to get the piston to seal, you need to make sure the barrel is DEAD square inside the tank, (cut it with a chop saw or a mitre box if you've got one) and make sure the piston face is flat. Sand the edge of the barrel smooth with 600, and then 1000 wet and dry sand paper until it is perfectly smooth. I cut my gasket out of rubber sheet I bought at Ace hardware. Doing everything above, my piston sealed first time no problem!

You can check out my thread (8ft coaxial golfball cannon) to see closeup pictures of my cannon. The piston design i used worked really well. I experimented with molding glues, and it really didn't work out that well. But mine was on a larger scale, small scale might work ok!
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Unread postAuthor: deathbyDWV » Wed Mar 24, 2010 10:18 pm

Looks good. Next you should make an even bigger one!

Like this...
http://www.spudfiles.com/forums/sneek-peek-of-my-first-pistion-valve-gun-4-coaxil-t20100.html

...or mine... (but i wont put a link cuz it doesn't seem right :? )

What are you using for a sealing face?

I suggest making some darts...
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Unread postAuthor: clemsonguy1125 » Thu Mar 25, 2010 2:53 pm

Mtrhd0024, I just used factory cut pipe so I know its perfectly square, funny enough mine worked perfect first time and I used the same rubber sheet you did, then I decided to try to make it better but I messed it up so I am rebuilding it
Deathbydwv-Ill make some darts as soon as I get the new piston working
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Unread postAuthor: Fish8myb8 » Thu Mar 25, 2010 6:30 pm

Yeah I always leave the factory cut end on one side of the pipe in case I ever have to use that end as the barrel sealing side. But I'll remember sandpaper for the future. Have any of you made Copper coaxs yet? is it a bit(if any) harder than PVC?
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Unread postAuthor: clemsonguy1125 » Thu Mar 25, 2010 7:02 pm

Ive attempted to make a mini copper coax but failed because it wasnt serviceable, if you make it serviceable you shouldnt have any problems, just make sure you know how to use epoxy or solder
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Unread postAuthor: Fish8myb8 » Thu Mar 25, 2010 7:29 pm

alright sounds easy enough. i would try to make a semi QEV gun, but I'd need pretty high pressures for that. I can only get to 120 with my current pump, and a shock pump will only give me 2 or 3 shots, after all that pumping.
I'll just stick to the 1 shot for now.
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Unread postAuthor: clemsonguy1125 » Thu Mar 25, 2010 7:41 pm

Or if you have a compresser you could use that but most dont go above 150, or you could go with regulated HPA
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Unread postAuthor: Fish8myb8 » Thu Mar 25, 2010 7:47 pm

Regulator setups seem expensive and pumps are too. I wanted to try c02 or some paintball canisters but they were too expensive for what they offer. I'll get quite a bit of money on by birthday, then I'll be looking more into compressors and regulator setups
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Unread postAuthor: clemsonguy1125 » Thu Mar 25, 2010 8:10 pm

Im with you there, right now im looking into a propane fill setup
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