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First 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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First piston cannon

Unread postAuthor: TheLostOtter » Sun Aug 23, 2009 3:43 pm

I've been out of the tater launching world for a few years. Started with some tiny combustion cannons and then to a 1.5" ball valve pneumatic and then to a 1.5" sprinkler valve cannon. This summer I just got the itch to build something better than all those other ones so I decided to make a coaxial piston valve cannon.

Everything is SCH40 PVC:
2", 8' long barrel
4", 4' long chamber
Piston is a 3" ABS cap
Pilot valve is a 0.75" jar top sprinkler valve.

Not really much else to say because it's pretty basic and ugly, but here are some pics!

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The barrel extends to the edge of the pic, just hard to see because of the sun

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Piston sealed against the barrel. For a bumper I just coiled up some air compressor tubing and let that expand around the circumference. The piston weighs hardly anything so it works fine.

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Ugly barrel supports but they get the job done perfectly

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Im just using decal material (really thick sticker) to provide the seal with the barrel. I used a router on the the cap to get a perfect ramp shape so the air passing doesn't hit a blunt edge.

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There was a pretty small gap around the piston and it wouldnt fire so I had to mess around. A combination of decal sheet and electrical tape fixed that and it fits perfect now.

All in all I'm pretty impressed with it. I don't get any honking, piston opens basically instantly. I've only had it up to 100psi, my compressor only goes up to 120psi. As for muzzle velocity I have no idea. Only thing I can really say is that it splintered up a 2x6 I shot with a potato but that doesn't really come as a surprise.
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Unread postAuthor: maverik94 » Sun Aug 23, 2009 5:08 pm

Damage Pics Please! By the way, nice cannon.
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Current Project: None, I'm in Spudremission.
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Unread postAuthor: theBOOM » Sun Aug 23, 2009 8:27 pm

Good first cannon, i like the creativity that you used to attach the barrel to your chamber :) good job, and yes damage pics please! :twisted:
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Unread postAuthor: Crna Legija » Sun Aug 23, 2009 11:43 pm

Nice canon. i like the barrel support did you glue the bit of pipe on or just cram them in

and nice bike what it is it? looks really clean
i got a 07 crf 450
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Unread postAuthor: THUNDERLORD » Mon Aug 24, 2009 12:07 am

-_- wrote:....and nice bike what it is it? looks really clean
i got a 07 crf 450


Been looking for a on-road/off road bike sold for parts myself lately.

I want to chop the entire fork neck off (front end) and weld it to a chopper style frame.
With a street front tire (mounted to dirt bike spoked rim).
That way it will have the spoked front rim, disc brake, brake, speedometer and handlebar assembly.
The engine will be an aftermarket american v-twin harley style, it will be funny to see if I can use the VIN # off the street legeal dirt-bike (since the VIN is located on the tube connecting forks) and register it as that bike with differnt engine installed.

I might sell my Thunderhorse soon while building it. :(

On topic: cool cannon, good job! 8)
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Unread postAuthor: TheLostOtter » Mon Aug 24, 2009 12:16 am

Thanks guys, I'll try and get damage pics soon.

The barrel supports are glued in there, how well I'm not sure but they havent come loose yet.

The bike is a 07 RM250, I love it!
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Unread postAuthor: rna_duelers » Mon Aug 24, 2009 3:20 am

Nice cannon,I've got to say I've wanted to build a large coaxial like this but bever got round to it.

That 3" ABS is perfect as a piston,nice and light :D happy spudding.
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Unread postAuthor: covey12 » Thu Aug 27, 2009 9:33 pm

that is an incredible accomplishment for your first piston/coaxial gun to be that big power must be amazing, what do you use for ammo?
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Unread postAuthor: TheLostOtter » Thu Aug 27, 2009 9:42 pm

Right now I'm just shooting potatoes, I'm too scared to shoot anything solid because the area behind my house is only about 2-300 yards of sparsely wooded desert. The taters are good because they turn into mist once they hit anything.

I'm having a hell of a time getting this thing sealed. So far I have epoxied the top of the sprinkler valve3 times and I keep getting leaks. Never had this much trouble with the last one I did. I think I will just goop some sort of rubber sealant in there and then air it up so the pressure forces it into the hole/crack and then let it sit empty so it can dry.

The 4" cap is also damn hard to get sealed too and really hard to remove once it's tight.
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