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Psycix's first pneumatic. (coaxial piston)

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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Psycix's first pneumatic. (coaxial piston)

Unread postAuthor: psycix » Thu Jan 08, 2009 6:45 am

This is my first try at a pneumatic, its a coaxial piston valve launcher.
I built this about one year ago as an experiment just to see if I could build a piston valve and to orientate me in the world of pneumatics.
I thought it was about time to post it as I just passed 2000 posts but didnt post even one pneumatic yet. :)

It worked out very well. Sealing and pilotting worked fine from the first shot and never needed tweaking.
The only fail was that I fired it without a bumper for the first time when I tested whether it would seal. The piston endcap broke. Luckily I didn't glue the piston yet.


Specifications:
Chamber: 50mm pipe
Barrel: 25mm ID (32mm pipe)
Length:Both Barrel and chamber pipes are exactly one meter long.
Piston: Two sanded down 40mm endcaps on a piece of 40mm pipe, with inner bike tire bolted on. There is also some extra tire between the bolt and the washer to prevent leaking along the bolt.
Bumper: some sort of sturdy foam I found.
Pilot valve: 12mm ID ball valve
Fill valve: schrader


I usually breech-load it by screwing off the end cap and pulling out the piston. I primarily did the screw cap to make the piston is serviceable as many people need to tweak their first piston valve alot before they can get it to seal and pilot. Fortunately I only had to fix it once, because I was to exited to place a bumper before I tested the seal.


A much more powerful pneumatic is coming up soon, I just need to fix my higher pressure source...
Let me know what you think.
And now for the pictures:
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Attachments
damg pic.JPG
I shot this metal ball with a wadding.
It split the board and left a beautiful imprint.
piston crack.JPG
The piston before it was glued, after the first shot before I installed the bumper.
I replaced the broken endcap and installed a bumper.
breech-end.JPG
Looking down the chamber.
back end - bumper + piston.JPG
The finished piston and the screw-on cap with bumper.
muzzle.JPG
I like the look of this. No barrel sticking out.
back overview.JPG
The rear of the gun along with some ammo.
overview (sorry no foot).JPG
The gun along with the pump I used. I didnt have a compressor back then.
The outside is plain, simple and smooth. Its just one big stick with a valve on the end.
Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

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Unread postAuthor: SP00K » Thu Jan 08, 2009 7:22 am

Hmmmm, that's really interesting. And it gives me an idea.....
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Unread postAuthor: psycix » Thu Jan 08, 2009 9:06 am

SP00K wrote:Hmmmm, that's really interesting. And it gives me an idea.....

Care to share what specifically is interesting? :)
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Unread postAuthor: starman » Thu Jan 08, 2009 10:47 am

Neat little coax psycix! In my mind, a really practical shooter, although I don't believe I would try to breech load it each time. Just install a ball stop at the breech end of the barrel (may be tough now) and drop the ammo in.

You should have posted it sooner. Congrats on the 2k.
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Unread postAuthor: LikimysCrotchus5 » Thu Jan 08, 2009 3:28 pm

Well it is about time. It looks nice with clean construction.

What kind of pressure do you use this at?
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 08, 2009 6:26 pm

That broken endcap must have been exciting :?

Very nice effort, and yay for European grey plastic :D
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Unread postAuthor: SP00K » Thu Jan 08, 2009 6:47 pm

Oh, tssh. I forgot to post that. I wrote that post up just before school as the bell rang.

Yeah, I have a pretty centered idea about what coaxs usually look like I I never thought about making the barrel flush. Specifically, I think they always look like someone giving you the middle finger. Lol.

I thinks it pretty good looking too. :)
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Unread postAuthor: psycix » Thu Jan 08, 2009 9:02 pm

Its not the best PVC but its the best in the local harware stores. There is no rating but I googled the codes on the side of the pipe and found some safety sheets. I have used it up to 6 bar, can't go much higher. Yeah, crappy pipe, I know.

But I dont really care about the pressure or power of this gun as it was not made to be powerful. It was made to step into pneumatics and the only thing that was important to me was that I made a fine working piston valve.
Dont worry, my future pneumatics which are made to be powerful do have proper piping. Steel and aluminum are my favorite materials now. No more shitty plastic.

I am not using the gun anymore though. Its lying under my bed, being nothing more then "my first pneumatic". :)

JSR wrote:That broken endcap must have been exciting

I mean that I was exited that the gun was almost done so I tested it to see if it would seal and the fired a blank shot. I was even more exited as the valve sealed and pilotted just as it should. Discovering a broken endcap was a bit "WTF".
I figured that it wouldnt break on only 1.5 bar.
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Unread postAuthor: jackssmirkingrevenge » Fri Jan 09, 2009 1:24 am

psycix wrote:I figured that it wouldnt break on only 1.5 bar.


wanker :D
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