First piston cannon

[TheLostOtter]

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!


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


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.


Ugly barrel supports but they get the job done perfectly


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.


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.

[maverik94]

Damage Pics Please! By the way, nice cannon.

[theBOOM]

Good first cannon, i like the creativity that you used to attach the barrel to your chamber good job, and yes damage pics please!

[Crna Legija]

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

[THUNDERLORD]

....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)

[TheLostOtter]

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!

[rna_duelers]

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 happy spudding.

[covey12]

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?

[TheLostOtter]

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.