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My First Pneumatic Cannon

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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My First Pneumatic Cannon

Unread postAuthor: nyharley » Wed Sep 30, 2009 9:09 pm

I have just built my first Pneumatic Cannon. It is just a regular spud cannon, but I am curious to know how you guys a loading these? With my combustion guns, I have the end cap removed when I am stuffing a spud down the barrel and it slides down nice and easy. On the pneumatic gun if I try to stuff a spud it creates pressure and won't go in. Luckily I have a detachable style barrel, but I do not want to remove the barrel every time I load a spud. Is there some type of pressure release I need to install for this? I am using a sprinkler valve actuated with 3 9volts in series, and fill the tank with a standard shrader valve.
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Unread postAuthor: mark.f » Wed Sep 30, 2009 9:16 pm

You could thread a drain-cock into the male adapter going into the sprinkler valve if it really bugs you.
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Unread postAuthor: cannon monkey » Wed Sep 30, 2009 9:25 pm

maybe a picture so i have an idea what ur say...but i got one using a sprinkler valve ( 1 inch) and 2 inch barrel.... what i did was



1 inch thread close nipple....to 1 inch threaded to 2 inch bell reducer... 2 inch of 2 inch pipe then male threads ( 2 inch)

on the barrel... i got 2 inch female threads then the 2 inch pipe
if u ask i will post pictures some where

i did this so i could take the barrel off to load no problems
dont need anything stick down to push my water balloons in all the way
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Unread postAuthor: nyharley » Wed Sep 30, 2009 9:40 pm

My barrel is also removable with a threaded coupler. Right now I am using the gun as a potato launcher, the barrel is filed at the tip so that it cuts the potatoes when you stuff them in the barrel. When doing this it creates pressure and the potato will not slide down the barrel. I can remove the barrel and load it, but that seems to be a drag. If I had some way to bleed the air with a valve when I am muzzle loading the gun I would be all set.

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Unread postAuthor: Technician1002 » Wed Sep 30, 2009 9:40 pm

A very small bleed hole at the breech of the barrel will fix the loading problem. Drill a small 1/8th inch hole in the coupling near the sprinkler valve to let out the trapped air when loading. During firing the short duration prevents much air from escaping the small hole. My QDV cannons don't have a shaft seal, so they bleed off through the center of the piston out the trigger rod. I have very little air leak past it as it is under pressure during the shot for less than 20 ms. This ability to load tight sealing projectiles is one of the reasons I like my apple cannon over a traditional piston cannon.

Edit, now that I see your picture a small hole can be located right in the breech threaded fitting through the double wall of the fitting and barrel. It would be directly cross from the pressure gauge. I would not weaken the smaller pipe by drilling it. If you change your mind only the barrel would need repair or replacing.
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Attachments
Valve Assy.jpg
Apple Cannon valve is a spool valve with a hole through the center. It permits barrel bleeding of pressure when loading tight fitting apples.

Valve is in the ABS test cannon posted elsewhere.
Last edited by Technician1002 on Wed Sep 30, 2009 9:45 pm, edited 2 times in total.
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Unread postAuthor: cannon monkey » Wed Sep 30, 2009 9:42 pm

do wat tech says or tiny ball valve :D
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Unread postAuthor: nyharley » Wed Sep 30, 2009 9:50 pm

Tech, thanks for the info. I definitely would only do it in the barrel just in case I change my mind... Thanks!
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Unread postAuthor: psycix » Thu Oct 01, 2009 5:10 am

You have a lot of dead space there man! Shorten that pipe between the elbow and the barrel.
Or, when you go changing anyway: take the upper elbow off and replace it with a T-piece, the same size as the barrel. Make a threaded plug in the back of the T, and you can load stuff from behind.
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Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

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Unread postAuthor: K8TOW » Thu Oct 01, 2009 9:00 am

you might also try using a camlocks (http://www.americanonsite.com/american/ ... kdisc.html ) or (http://www.hosexpress.com/camandgroove/ezbosslock.htm ).i just did a google and came up with these 2 websites.i will be buying them for my pneumatic gun.i have 3 different barrells.1/2",11/2"and a 2 ".i use them to shoot antennas into trees.
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