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PostPosted: Mon Mar 21, 2005 6:27 pm
by Drew Rowland
This is my first pneumatic, and a bit of an upgrade from my old super-ghetto combustion (it didn't even have a BBQ lighter, it had a touch-hole[:p]) The name stands for Pneumatically Actuated Potato Accelorator, and as a plus is spanish for potato (right?)
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As you can probably tell, this is a piston coaxial, with a 6" chamber. It is exausted by a modded sprinkler valve. Here's the back end:
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I'm not sure if this has been done before, but I put the sprinkler valve inside the cannon both to protect it and to prevent leaks: there isn't any pressure diffrential. Here's the inside of the back plug:
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I had turned a step into the female coupler so that there was more than just the glue holding it in there, and it was extremly lucky that the fittings I used allowed it to sit even with the edge of the sprinkler valve.
Its got a spudtech 5'x1.5" rifled barrel and yes I know the C:B is all out of whack but thats b/c I intend to add barrel extentions later.
It's only been a few hours since I finished gluing it so I've only taken it to about 40psi, but its still plenty powerful, I get 13 second hang-times for a vertical shot at 40psi. The piston I'm using is a nylon disc from a cutting board turned to the correct diameter bolted to a 3"x1.5" reducer which fits almost perfectly in the 4" pipe that the piston travels in. (It took some sanding)
Here's another pic of the plug:
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Let me know what you think, and PCGUY you can put it on spudfiles if you like.

PostPosted: Mon Mar 21, 2005 6:35 pm
by utcpyro
That thing is crazy... And this is your first pnumatic gun?!


PostPosted: Mon Mar 21, 2005 6:38 pm
by Drew Rowland
Well I decided I'd like to start big and get bigger, but I'm affraid my next cannon won't come any time soon: I blew all my money on parts for this gun.

PostPosted: Mon Mar 21, 2005 6:47 pm
by Longshot
looks well thought out. Pretty sweet. To hone performance i'd fell in the dead area around the sprinkler valve with some expanding foam, or something to reduce exhausting volume.

PostPosted: Mon Mar 21, 2005 7:12 pm
by buzzboy
Is that sch. 80 or conduit(sp)

PostPosted: Mon Mar 21, 2005 7:19 pm
by Drew Rowland
Everything is SCH40 except for the plug, which is SCH80. USplatics sells SCH40 pipe in both grey and white.

PostPosted: Mon Mar 21, 2005 8:43 pm
is that a pressure gauge I see on the back coupling of the chamber in the first pic?

sweet cannon. Nicely planned out. i'm getting a real itching to build a piston cannon.....

PostPosted: Mon Mar 21, 2005 8:51 pm
by Drew Rowland
Yeah that's a 0-160 psi gauge mounted in the double-thick plastic in the back. It makes it much easier to shoot consistantly and not run the compessor obssesively long.

PostPosted: Mon Mar 21, 2005 9:17 pm
by OJHSPyro89
This is something you dont see too often...
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Very nice work. I love the whole hidden fittings things. At first i thought you where exhausting froma blowgun. Nice work man. I wanna see some more of ur stuff.

PostPosted: Mon Mar 21, 2005 9:21 pm
by Longshot
it sure makes that 1.5" barrel look tiny as all get out. I love this gun. I hope you have a video camera.