Micro Pneumatic Coaxial

[PVC Arsenal 17]

It's finally done! Here is my micro pnematic cannon. It's only a foot long but pretty powerful. The main chamber is 2 3/4 inch cleanouts and a 3/4 inch coupling. A length of 3/4 pipe runs inside from end to end. The front end is made of copper and brass fittings with a brass barrel. There is a Presta valve threaded into a cap and JB Welded. The Presta is great because it's really small and doubles as the trigger. You just push the knob on the back to fire. The diaphragm was punched out of a rubber sink stopper using a sharpened 3/4 copper sleeve. My primary ammo is bb's but k'nex rods make for some devastating little spears. Hope you guys like it!

Here is a video a test fire but I don't know why there is no sound:
http://media.putfile.com/DSCN0736-75

[Holland_Charley]

Very very nice,

how far does it shoots?

greets

[Benny]

nice, try using micro stefans as ammo.

[PVC Arsenal 17]

Thanks for the compliments.

With K'nex rods it can shoot maybe a bit over 50 feet but bb's go out of sight. It's pretty powerful for being so small.

[PVC Arsenal 17]

I found a new ammo! Q-tips! They are perfect, I would never have though they can punch through carboard they way they do in this cannon.

[noname]

the diaphram doesnt have to seal against the chamber walls does it?
Its just the the barrel it has to seal against?

[Darkside 6ix]

looks pretty cool. i like it alot. me myself are saving up money to build a mini hybrid for a rainy day. minis are my favorite

[PVC Arsenal 17]

The diaphragm must seal against the barrel. That is very important. It does not have to seal against the chamber walls and it should actually be a little smaller than the walls in diameter so it has room to flex in and out. In must also seal against the fitting screwed in behind it, in this case a 3/4 inch nipple. If it doesn't seal well against it, the air in the main chamber can leak out the back when fired, causing less air to go out the barrel where it is supposed to. I covered my diaphragm in a little dap of hand soap so it seals better.


This actually isn't my smallest micro pneumatic, I made some with an orange pill can and a pen tube for a barrel. The diaphragm was piece of inner tube and it rested against a bottle cap that was glued in with a big hole drilled through it. The can's cap was also glued and had a tire valve in it. It actually worked until the glue stopped holding. Here is a simple little diagram I made of it a while ago.