SpudFiles

Hi everybody, i'm building a piston valve air cannon. I was just wondering if there is a certain pilot chamber to air chamber ratio that is perfered when making these. Thanks

yodabeast14 wrote:Hi everybody, i'm building a piston valve air cannon. I was just wondering if there is a certain pilot chamber to air chamber ratio that is perfered when making these. Thanks

The pilot chamber should be as small as possible. The piston doesn't need to travel more than 25% of the barrel diameter to allow full flow, thoughi n practice 50% is a better idea to account for piston bounce - so if you have a 1 inch barrel, the piston only needs to move 1/2". Keeping this distance to a minimum also keeps the piston from accelerating too much and reduces stress on the launcher from the impact.

Valve opening speed is key to performance, and the faster the pilot chamber empties, the faster the piston will open. It stands to reason that for a given pilot valve, a smaller pilot chamber will empty faster. If you drill the same hole in a 1 gallon bucket and a 2 gallon bucket full of water, the first one will empty around twice as fast.

The 25% applies to a coaxial valve where air can enter the valve seat from 360 degrees to be clear. If the piston is in a T with air entry from just one side, you will want a larger opening for full unrestricted flow.

Since they need o-rings, chamber sealing valves tend to be less common than barrel sealing valves so I assumed OP meant to make the latter.

Plenty of barrel sealing T and X valves JSR - I've got a arsenal of them!

I know you know that just helping the OP

mobile chernobyl wrote:Plenty of barrel sealing T and X valves JSR - I've got a arsenal of them!

I think you built your way out of the "typical spudder" category a long time ago