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3 inch piston valved huge cannon - totally nuts

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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3 inch piston valved huge cannon - totally nuts

Unread postAuthor: bl74 » Wed Jun 16, 2010 11:26 pm

Alright so this is my second pneumatic, the first one was a double 4 inch chamber dual 1 inch sprinkler valve gun but turned out to be way to big to transport or even shoot. So i decided to recycle some parts and put them towards a new better designed gun. I usually try to get the most power possible with what I have so i figured that i would need to learn how to build a piston valve. Well i researched a lot, asked some questions here, used ggdt and tried to make the best possible design where I could get the most power out of its size using the pipe I had. And finally i built it and holy crap its totally nuts. The thing is actually scary I think I ended up going overboard again. Its huge but manageable. I usually do shots at only 40 psi and it sends potatoes so fast they can barely be seen before they explode on something. Shooting rocks against a rock wall causes them to explode into nothing while tiny shards of rock can be heard slowly falling down on trees for a few seconds. At 50 psi potatoes are perfectly accurate and instantly disappear into the distance. The best part is that I could probably take it up to even 100 psi because I made sure to use all the right parts, but i'm afraid my piston will kill itself.

Barrel - 7.5 feet of 1.5 in pipe attached to 2 in. thread adapter to fit piston tee. recycled this from old gun

Chamber - 5 feet of 3 in pipe

Piston - 3 in tee with 2 in outlet. Decided to used 2 in instead of 1.5 in because I posted here and was told that a 1.5 in outlet would open faster in a 2 in tee, so i figured i might as well make use of my 3 in tee and scale it up to a 2 in outlet and get more flow. I could always make use of it and upgrade my barrel to 2 in since I made it removable.
The actual piston is made out of hot glue, an idea I got here. The sealing face is neoprene rubber and the bumper side is piece of basketball rubber attached to two layers of the foam used for mug warmers.

Pilot valve - 1 inch modified sprinkler valve also recycled from last. Also, the pilot end can be unscrewed for access to the piston. This turned out to be a good idea because my pistons all beat themselves to crap before I made a good one.



Here you can see the 2 in outlet pipe inside of the 3 in tee.

This is the final piston that should hopefully stay together. The first piston I made was out of a food can with tape around it. It quickly began to leak and got crushed up pretty good. I had no idea how intensely they get fired back. Then i made a hot glue piston which turned out like this after a few mods.

Here is the bumper that that I hope doesn't get killed. I needed the bumper to stop the piston before it slid out of the pipe into the pilot fitting so I attached a smaller pipe to the inside of the fitting sticking out a little. The first bumper was just 3 layers of the foam hitting against the pipe and it quickly got ruined because the end of the pipe chopped into the foam. Next I did the same thing but I improvised some crazy crap and dulled the end of the pipe by cutting up pieces of hose and screwing them on. This worked and seemed to do no damage until a 50 psi shot the other day when the piston got stuck. I opened it up and somehow the end up the pipe still cut a perfect circle into the foam. So finally I attached a piece of basketball rubber that shouldn't get chopped up.

Heres the sprinkler valve with the pilot end fitting and my bumper thing.

The thing is nuts over 8 feet long probably 9. I actually built it last summer but didn't upload it until now because the piston broke the other day and i had to take it apart to fix. Well thanks to the people on this site for helping and giving ideas especially jor2daje and his sweet diagram I based my valve off of - http://i715.photobucket.com/albums/ww152/jor2daje/mypistonvalve.jpg?t=1248468706 . The gun is awesome and works perfectly with no leaks. So gnarly
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Unread postAuthor: deathbyDWV » Wed Jun 16, 2010 11:49 pm

Very nice job. Posts like these make me want to take new pics of my howitzer and post them... It's more than a year old and is still a blast (literally) to shoot...

May I suggest modifying this "knocker" round for 1.5" pipe?
I shot one through 5 sheets of OSB at 60 psi... :twisted:
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Unread postAuthor: Technician1002 » Thu Jun 17, 2010 12:16 am

Very nice. A two inch port. This is in the same valve size as my apple cannon. Extra bumper is recommended. I found a long bumper can allow higher pressure shots with less damage to the valve. In my sig, see the bumper I use on the 2 inch piston in my ABS cannon. I call that one my apple cannon. The 2 inch barrel is too large for most spuds except bakers, so it is mostly used with fallen apples. I cut the center out of a dense foam football for the bumper.
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Last edited by Technician1002 on Thu Jun 17, 2010 10:15 am, edited 1 time in total.
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Unread postAuthor: Gun Freak » Thu Jun 17, 2010 9:25 am

Awsome cannon dude, VERY clean and you definitely did some research here, used all the right parts, although that hot glue piston must be really heavy... still, if it works, it works, great job 4/5
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