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.5" and 1.5" Piston Valve Cannons

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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.5" and 1.5" Piston Valve Cannons

Unread postAuthor: Trauts » Fri Feb 28, 2014 8:09 pm

Hello all! I've been chipping away at these cannons for a while and they're finally operational. I decided to stay away from pvc for my first cannons due to all the stories I hear about them failing, especially with pistons, plus all threaded fittings means it's much much easier to make modifications. Although they are both functional I still want to make changes and touch ups before a showcase post. I pretty much built them at the same time, as they are virtually the same design (piston valves) just different sizes. All critique welcome!

This is the 1.5" cannon. Barrel is not screwed in in the photo (1.5" sdr21 sleeved in sch80 pvc). First dry fire at only 50 psi was surprisingly loud, and it sounds really efficient. I plan on reducing the chamber size and adding barrel support.

2014-02-28 19.58.21.jpg
GB cannon


Piston needs a minor fix as it seems I've got metal on metal near the sealing face so there's a tiny leak from that.

2014-02-28 19.29.40.jpg
Piston for the 1.5" cannon


The filling and pilot station works well, although I would like to make it a bit more aesthetically pleasing. Some elbows might help for it to be more "in-line" but any recommendations would be great. Uses a standard modded sprinkler valve as a pilot.

2014-02-28 19.27.17.jpg
Pilot/filling area


Here's the smaller cannon. It's got a .5" copper barrel, great for marbles, batteries and homemade darts. Will probably be ordering some ball bearings as well.

2014-02-28 20.00.54.jpg
.5" cannon


The qev is probably overkill for the pilot, but with the length of hose I have I figured I'd be losing efficiency with just a blow gun pilot.

2014-02-28 20.01.16.jpg
Filling/pilot/piston housing


As for changes to the .5" one I'd like to make a body for it, or at least somewhat of a clean looking housing. I also plan on making a breach for it but I have struggled to find many good breaches for .5" copper barrels.

Got some dry fire videos of both. Nice to see a little bit of kick in both the cannons. Would love to do some damage videos asap but probably can't for a while - I'm in a pretty dense city atm :(

https://www.youtube.com/watch?v=o_kT5nDEIeE

https://www.youtube.com/watch?v=JNAhZQ7PgPQ
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Last edited by Trauts on Sun Mar 02, 2014 12:34 pm, edited 1 time in total.

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Re: .5" and 1.5" Piston Valve Cannons

Unread postAuthor: jackssmirkingrevenge » Sun Mar 02, 2014 8:56 am

looking good, we're going to be needing some damage videos :D
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Re: .5" and 1.5" Piston Valve Cannons

Unread postAuthor: Trauts » Mon Mar 03, 2014 4:34 pm

It seems like the sprinkler valve top is leaking as I get past 50psi, a result of a weak top and cheap epoxy. I'm thinking one of two options...

1-lather on the rest of the epoxy I have over the top of the valve

Probably worth trying even if it is a waste of epoxy

2-move the qev from the smaller cannon to the bigger one

I have a 2"x1/4" reducing bushing kicking around so I could keep the pilot volume for the qev pretty small, but would I be losing too much efficiency in doing so?

Eliminating the sprinkler valve would up the max pressure for the set-up, but I'm mostly wondering if my qev solution will work, and at the same time I'd probably have to totally change the smaller cannon to be blow gun operated.

Thanks!!!
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Re: .5" and 1.5" Piston Valve Cannons

Unread postAuthor: jackssmirkingrevenge » Mon Mar 03, 2014 4:50 pm

Trauts wrote:I'm mostly wondering if my qev solution will work


Short answer is yes, you have an o-ringed piston so a super high flow pilot is not critical.
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