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My 3" piston, 2" porting GB 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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My 3" piston, 2" porting GB cannon

Unread postAuthor: kablooie » Fri Feb 29, 2008 12:06 am

This is my most recent creation, a 3" piston, 2" porting Golf Ball cannon. It is a lot of fun (and very loud), will shoot a golf ball out of sight at 40 psi. Here are some stats in a handy little list:
-3" piston
-2" porting
-1.5" golf ball barrel (sleeved in 2" sch. 80)
-1" sprinkler valve pilot
-Drain plug rubber thing as sealing face
-Peanut butter jar piston (with duct tape and filled with foam and hot glue)
-The enormous pilot volume is greatly reduced by the large piston and a big section of pool noodle acting as a bumper
-Filled via schrader/bike pump or bulk CO2 once i get safety valve.

This cannon is my very first piston valve cannon, and I experienced many setbacks (gluing modded bushings sucks) and it took forever for me to get the valve to seal. One piece of advice is to not use bike innertube if it has small seams (raised lines or indents) and to sand the sealing part of the barrel as flat and smooth as possible (finishing with fine grain sandpaper worked for me, without it sealing was impossible).

Do I need a barrel support? I take the barrel on and off constantly to transport the cannon or to use different barrels. I know i need paint, but paint is not an option because I do not want to freak out neighbors by carrying what looks like a dangerous weapon around (not that it isn't).

Pics:
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Attachments
Bumper Seat.jpg
This is where the Pool noodle bumper sits, the hole in the foam lines up with the outlet of the fitting.
Bumper.jpg
This is a pool noodle bumper/pilot volume reducer, it is reinforced by washers on either side. It has a hole through the middle for airflow.
Bumper.jpg (19.18 KiB) Viewed 1557 times
PIlot assembly.jpg
This is the pilot fill/exhaust assembly, I figure the 1" sprinkler will make up for any extra pilot volume.
Vavle and Pilot.jpg
This is the Valve and Pilot assembly pretty much self explanatory.
Piston cannon final.jpg
This the whole beast. Loud, powerful, and lots of fun.
Piston Inside.jpg
This is the piston when it was still unfinished, I have since filled it with expanding foam and made other minor improvments
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Unread postAuthor: kablooie » Fri Feb 29, 2008 1:37 am

Bump. Am I allowed to do this? some feedback would be nice though. Thanks!
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Unread postAuthor: Hubb » Fri Feb 29, 2008 1:40 am

Here's some feedback (for my 1000th post :D ).

It looks great. Pilot volume may be a little excessive, but it looks great. Paint it and take some damage shots and you're good to go.
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Unread postAuthor: kablooie » Fri Feb 29, 2008 1:47 am

Hey, thanks for responding. The pilot volume is a little bit extreme but I believe I have put enough stuff in the pilot area to make a little more feasible, and the 1" sprinkler works admirably to get the rest out. Damage shots are not likely, and neither is paint sadly because my parents will only tolerate so much destruction and my neighbors are probably already wondering what i am doing with cannons in my yard. Congrats on the 1000th post! (only 964 left for me!)
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Unread postAuthor: jackssmirkingrevenge » Fri Feb 29, 2008 2:03 am

Looking good, personally I would have made the chamber a bit larger and eliminated the tee before the sprinkler by filling directly through the sprinkler.
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Unread postAuthor: feral_patriot » Fri Feb 29, 2008 2:53 am

Bbbbingo! 8)
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Re: My 3" piston, 2" porting GB cannon

Unread postAuthor: Carlman » Fri Feb 29, 2008 6:08 am

kablooie wrote:...I know i need paint, but paint is not an option because I do not want to freak out neighbors by carrying what looks like a dangerous weapon around (not that it isn't)...


you could paint it fluoro... :D , im sure they wont think a bright green painted bit of pvc is dangerous lol

yea nice cannon mate but as JSR saud remove the fill T and install the schrader in the bottom of the sprinkler valve

EDIT: your tee is glued in so for your next one work on your pilot volume
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Re: My 3" piston, 2" porting GB cannon

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Unread postAuthor: bigbob12345 » Fri Feb 29, 2008 8:21 am

Nice gun though as others have mentioned there is an unnessary amount of pilot volume.
You could have made the chamber longer which would make it look better
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Unread postAuthor: Fnord » Fri Feb 29, 2008 11:27 am

You do realize that pool noodles shrink in a compressed air environment right?
Take the volume of the foam in cubic inches and divide it by how many BAR you're putting into the gun and that's about how big it will be when the gun is pressurized.

But other than that it looks good. I'm guessing it looks a lot bigger in person than in the pics. (that's what she said!)
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Unread postAuthor: STHORNE » Fri Feb 29, 2008 12:57 pm

Very nice job on the gb cannon kablooie. I like the neatness of the gun.

Job well done!
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Congrats! Bout time you hit 1,000 eh?
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Unread postAuthor: brother361 » Fri Feb 29, 2008 2:35 pm

wow that tee is pretty good but i think the chamber should be longer for more power or are you restrictaded because of a bike pump or somethin
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Unread postAuthor: explsvcookie257 » Fri Feb 29, 2008 4:39 pm

hey i no this is random but im making a piston valve just like yours and was wondering is the brand of peanut butter skippy because i found some in my house and it fit perfectly in the 3" pipe but of course you would need duct tape and how well does the piston seal like the part with duct tape?
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Unread postAuthor: jrrdw » Fri Feb 29, 2008 4:57 pm

Don't worry about the pilot volume, a fast moving piston needs the extra braking room! :wink: I'd worry more about the pool noodle holding up hit after hit after hit. I think it will stay squished after awhile. Good build for a first piston valve.
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Unread postAuthor: brother361 » Fri Feb 29, 2008 4:57 pm

i can tell u now duct tape wont rele work very good ur better off makin a expoxy piston or somthing like that it just would be easier
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Unread postAuthor: MrCrowley » Fri Feb 29, 2008 5:07 pm

Duct tape can work, it's been done before. Some guy even managed to make a chamber sealing piston with duct tape. I would think duct tape would be fine on pistons up to 2", the higher you go, more chance of it jamming IMO.
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