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Coaxial Piston 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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Coaxial Piston Cannon

Unread postAuthor: nz_cannons » Wed Sep 05, 2007 12:56 am

I made this cannon recently, as more of a prototype for a larger version.

The chamber is about 75mm diameter(internal) and the barrel is 25mm.
Chamber length is about 800mm and the barrel 1300mm.

I take it up to 110psi usually.

Constructed mainly out of pressure rated PVC pipe, and black "Hanson" pipe fittings for the exhaust and filling area.

I made some darts to shoot out of it, these consisted of a short length of wooden dowel with a bolt in one end for weight, then a smaller diameter length attached to the other end for stability, they work extremely well, flying nice and straight.

Checking with google earth flight distance is round 270m.

Did make one cock-up though. While assembling the reducer fittings, one of them glued in at an angle, meaning the barrel points at an angle now, oh well still works. My mistake, will take more care next time huh.

Keep reading about "bumpers" behind the piston on many posts, this has no such thing, it just slams into the edge of the reducer fitting that screws into the back. The compressed air coming in when filling it up then pushes it back up against the barrel. Hasn't suffed any damage at all, is this normal?

First Post.
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Attachments
cannon full.jpg
Full view of the cannon, rear of chamber is exhausted by opening the ball valve.
inside.jpg
View of the inside, I just rungied up a centering device and hotglued it to the barrel, nothing fancy but it doesn't move and works well.
piston 1.jpg
The piston is completely homemade. Made out of two sheets of (don't know exactly what its called but its like plastic MDF/fiberboard, lightweight and easy to cut) stuck together and turned to the right size on a homemade lathe with a file. Homemade lathe is an electric hand drill held in a vice, works good as. The sealing material is some rubber cut from a truck tire inner tube. Theres a bolt through the middle to hold it all together. Lubricated with synthetic grease. It hasnt broken and seals well around the barrel
filling app.jpg
The filling device is pretty straight forward. Just a ball valve, tire valve and a reducer/increaser fitting that screws into the end of the cannon.
cock-up.jpg
This is a pic of the bent barrel I was talking about.
bent barrel.jpg
Hmm, brings down the look of the whole project..
damage1.jpg
Shooting into 30mm thick plank.
damage2.jpg
Back of plank.
ammo.jpg
This is what I was firing. Similer to the dart but with no tail.
Last edited by nz_cannons on Thu Sep 06, 2007 3:45 am, edited 1 time in total.

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Unread postAuthor: MrCrowley » Wed Sep 05, 2007 1:06 am

Very nice, that's one huge Hanson fitting :P
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Unread postAuthor: jackssmirkingrevenge » Wed Sep 05, 2007 1:54 am

Welcome to the forum, nice to see "newbies" with a decent cannon already under their belt :) Shame about the bent barrel but the damage shots speak for themselves, if it works it works :D
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Last edited by jackssmirkingrevenge on Wed Sep 05, 2007 1:55 am, edited 1 time in total.
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Unread postAuthor: Mitchza89 » Wed Sep 05, 2007 1:54 am

Gorgeous looking gun there mate. Job well done. Great damage pics too. Keep up the top work
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Unread postAuthor: spud yeti » Wed Sep 05, 2007 8:59 am

Good job. Thats a really great looking cannon (oh well about the barrel :wink: ).
I guess the only other thing you could do is give it the good old sprayjob...
Nice work
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really good quote/phrase here
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Unread postAuthor: thespeedycicada » Wed Sep 05, 2007 3:57 pm

nice gun too bad the barrels bent.Time for paint! you know i just noticed how much some coaxials (particulary this one) look like combustions.
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Unread postAuthor: phonut » Wed Sep 05, 2007 5:10 pm

Hi nz_cannons. Those are some nice damage shots.
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