Question about a mini coaxial piston gun. Plans posted.

[Kash munni]

Ok so I am making a mini coaxial piston gun and I have developed what looks like a plan. It will be totally portable like my other guns, having it's own pump attached. Here's the plan:

http://s288.photobucket.com/albums/ll19 ... rrifle.jpg

The ball valve will serve as the pilot valve.

My questions:
1. Will the needle work ok as a piston stopper at the relatively low pressures of a hand pump? If not then how should I stop the piston?
2. Will a piston valve work around those pressures? I don't really see why it wouldn't, but I would like assurance from you guys.
3. What are some things I can use as a piston for 1/2" SCH 40 pvc that I would probably have around? I will be looking, but if anyone knows any tricks, that would help alot.

Thanks

[brogdenlaxmiddie]

1. Will the needle work ok as a piston stopper at the relatively low pressures of a hand pump? If not then how should I stop the piston?
Use a bumper
2. Will a piston valve work around those pressures? I don't really see why it wouldn't, but I would like assurance from you guys.
It should work fine. Just keep a low pilot vol.
3. What are some things I can use as a piston for 1/2" SCH 40 pvc that I would probably have around? I will be looking, but if anyone knows any tricks, that would help alot.
No idea. Like you said though, just keep looking around.

[jr]

I like the design.... I have been considering a mini my self!

[Kash munni]

Thanks brogden. It will be a challenge to keep the pilot volume low while still having a a bumper in front of the needle... but i'm up to it. I hope to finsh it tomorrow after making a run to lowes for parts.

Also thanks jr. I love pneumatic guns but I hate having to have an external air source. That's why I always design my guns around a hand pump. Some day I'll make a big artillery style cannon... but for now I like the smallbore stuff. 8)

[jackssmirkingrevenge]

That needle will be bent out of shape by the first shot. For minis, remember - low volume, high pressure - invest in a shock pump.

[Kash munni]

If I see a decently priced bike pump at wal-mart today then I will look into it. Would there be any schrader valves at wal-mart? If not I think I have one on an old bike tire.

If I take that route, would drilling into the side of the PVC for the schrader make it unstable to use under pressure? I've heard warnings about putting holes into cylindrical pressure chambers before.