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I have been thinking over the last few days about how I could create a high power pump-action pnuematic gun. Mostly I have been thinking about the valve, As there arent too many that would do the trick. I thought about having a hammer valve with high pressures, and a strong hammer. But I have also had the idea for a piston valve with a refill tank on the back. Basically its a co-ax launcher, but with a larger airtank behind the pilot. sliding he entire gun back would cause it to push in a check valve and allow more air into the piston. Any advice or other suggestions for valve types? I'm looking to get 5 shots per fill, at as much power I can get, with the gun bieng under .5M long.

Both those valves would work well for pump action, but I'm curious how you hope to achieve pump action in a co axial

Mag fed coaxs seem not to be popular but it really would be not to big of deal to use a tee fitting on pvc and extend a mag through.

Ok wait, how do I add an Image? I havent posted in so long.

[img]image%20URL[/img]

Wait, what happened to posting images directly to spudfiles? Is server hosting too expensive now or something?

Click on the button and it will give you the option of uploading images.

As to your design, I would shy away from pressurising for a secondary chamber, unless it's a regulated HPA source, because you'd get very inconsistent power. It would be a better idea to have a spring loaded ball valve and a momentary pilot. Here's how I would make it:

Yeah, That looks like it would work. Another thing I have thought about woud be a double barrelled launcher, with a seperate chamber for each barrel.

Also, any tips on how to make a hammer valve release more air per shot? a stronger hammer spring, of course, bu what other tweaks?

larger valve might do it to, but obviously only if you put in a heavier hammer/stronger spring

EvilFish wrote:Also, any tips on how to make a hammer valve release more air per shot? a stronger hammer spring, of course, bu what other tweaks?

A heavier striker (hammer) will increase dwell (the striker has momentum which must be cancelled out before the valve can begin to close), as will using a longer stem...this will open the valve further...increasing dwell, but not necessarily increasing flow rate.

Mods that increase dwell time can lead to hammer bounce...which wastes air.

Increasing port area through the valve and transfer port will increase flow. Smoothing passages will be of aid as well. Do some reading on Coanda.

Improving mass flow rate will improve flow. ie...unshroud the valve port. (but can also lead to hammer bounce...which wastes air)

It's a balancing act between variables.

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Re-sizing the photo to 640 X 480 usually works fine.

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