Hi Joaquin!
May i suggest the program called GGDT (gas gun design tool)? I'm sure you'll find it if you look around, should be on the spudwiki as well.

Its a program for just this purpose, fiddle around with it until you find the power you're satisfied with.

http://www.kjell.com/sortiment/el/elekt ... oar-p89414

Maybe that is what you want?

Fan va nice!

I also wonder what sort of compressor and chambers are used? And how is the breech is designed?

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I was thinking that it would be useless cause there would be pressure behind the piston pushing it forward, as opposed to all of Technician's cannons, where there is no pressure back there. All it would accomplish would be a longer trigger pull. There would indeed be pressure behind the piston (if ...

Nice gun!

Don't bother pumping above 3 bar or so, before you´ve opened that ball valve the dart will be long gone.

I made something similar a while ago , although It stopped the marbles from rolling down into the breech when the bolt moved back. As Crna Legija said, the movement of the bolt will probably be to fast for it to cycle properly. Skip the spring and let the air from refilling do the job, that way you ...

That system + piston hybrid might be the way to go. Maybe like this, although I think I put the check valve wrong. But the idea is almost like daccels. http://www.spudfiles.com/forums/fueling-with-pump-t21538.html And the reg could be this: http://www.spudfiles.com/forums/precise-propane-regulator-...

As with all these kinds of valves it can be really hard to get it to oscillate properly, there is a chance the bolt will slide back and reach an equilibrium where it don't close the inlet properly, and it sits still just hissing. Reminds me of this http://www.spudfiles.com/forums/gb-semi-t7899.html ...

Call some manufacturer of BBQ. They should have some info, maybe even sell spare parts.

Or use a drive circuit for an ignition coil.

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I'm thinking a hammer housed in a tube with a weak spring. When fully extended, the spring should not have enough force to open the valve, but with some momentum, it can open the valve for just a moment.

That's how Brian did it I think. Use it.

http://www.spudfiles.com/forums/old-sha ... 17827.html

Maybe you could try something like Brian? This sort of hammer should be pretty simple, just add some latch to hold it down.

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I agree with you Poland_Spud, and I think the reg issue is correct. One advantage is with the pump design would be that it delivers mixtures that could be ignited even with the residue and COX that's left from the previous deflagration, even without venting and even with some initial pressure (maybe...

Well, it says "epoxi paste" on the can..

Nice to see some response to this. :) The compression heating I also think is overrated (although I appreciate all your warnings and take them seriously) and the static ignition problem I also think is easy to overcome by remove the potential difference between the two moving parts. EDIT: But yeah, ...