First Piston Cannon

[frigaardj]

This is my first cannon showcasing post on SpudFiles, although I have made other cannons in the past. This is also my first piston valve cannon, and is built around a 2" (50mm) tee.

Here are the specs:
- 50cm long 50mm SCH40 PVC chamber (giving for a 1 litre chamber approx.)
- Piston built from layered wood around 1/4" threaded bar. Sealing face made from 3 layers of bicycle inner tube.
- Pilot valve is 1/2" ball valve, mounted alongside shcrader onto 3/8" tee.

So far I have only done a few low pressure shots (30-40 psi) for fear of the neighbour's wrath. Even with this pressure it delivers some good recoil and demolishes lemons. Sometime this weekend I'll go somewhere remote and launch off some 100+ psi shots.

And the photos:


Whole thing with barrel.


Taken looking into the tee, before assembly.


Detachable pilot end. (yellow is PTFE)


Piston, front end to the left. (white stuff is lithium grease that has unfortunately soaked into the wood).


Bayonet style breach loading - fast and effective.

TO DO:
- Fix slight leak on sealing face (very minor)
- Barrel support, and different bore barrels.
- Have fun.

Please post suggestions etc.


8)

[Lockednloaded]

Wow! Really clean first, congrats!

As far as suggestions go, you've got the major stuff covered. I do thing you should reduce the pilot volume by replacing the male adapter+cap with a threaded bushing. You should be able to improve performance that way and you could fit a more comfortable pilot valve as well

[jackssmirkingrevenge]

Not bad, not bad at all.

I like the bayonet mount, but the way you made it a tight fitting projectile could rip it off with relative ease.

You would also benefit from a lighter piston, once you're making it on a threaded rod why not use washers instead of wood?

[frigaardj]

Wow! Really clean first, congrats!

I do think you should reduce the pilot volume by replacing the male adapter+cap with a threaded bushing. You should be able to improve performance that way and you could fit a more comfortable pilot valve as well

Thanks

Actually I have filled up all of that pilot volume with compressed newspaper around a small section of pipe, topped off with hot glue:

I like the bayonet mount, but the way you made it a tight fitting projectile could rip it off with relative ease.

Although it looks fragile in the photo, it is actually pretty rigid and I would have a hard time snapping it, but I will make it more solid on future barrels.

[Gun Freak]

JSR, I think using washers would make it heavier, because you need at least 10 to hold the o-rings (maybe 12), and then nuts.

Nice job on the cannon, looks like it'll put a golf ball 200 yards easy.

[mattyzip77]

simple, nice, clean build! Nice work! Sanding drums work well as a piston incase you wanna change it! I like it!!!

[evanmcorleytv]

very nice, and clean!! Excellent build!! Any videos yet?

[frigaardj]

Nice job on the cannon, looks like it'll put a golf ball 200 yards easy.

At 50 psi it puts a lemon about 150 metres (165 yards), although I haven't tried higher pressures yet.

[youtube][/youtube]
This is a video testing a frozen lemon into chipboard at 50 psi, seems to work well. All the other holes are also frozen lemons at 40-50 psi. I can't think of what it'll do at 120 psi!