Valve thing

[Doc j]

Hi.
New to forum.
Haha... Fresh meat...
Spent bit time reviewing stuff.
Sorta broken links, referring to Xyz. "blow forward, pics no longer valid sorta been challenge.
Any how been interesting.
Maybe wat came up with already been done.
Any how have come up with a semi auto valve concept.
Based on maintaining a nozzle seal to projectile.
Piston valve, nozle normally in closed position (retracted).off 3 way N. O. Valve. front of piston pilot.
Rear would be fed from tee from 3 way input.
Chamber is filled by pushback action opening one way valve.
Exhausting pilot, retracts nozle and piston.
And Closes of chamber fill.
Think merrit is if nozzle slightly short stroked by its too long, theory would still mean that creates good seat on projectile, the piston can still pop off feeding air through nozzle.
Few pics to follow.
Question, ya Rekon she a goer?.
Thinkin might not need piston shaft spring.?.

[keks2033]

[squib]

I used a feed/fire mechanism sorta kinda like that on a proof of concept BB MG. I went with a more modular approach. I used a chamber, piston, nozzle and spring assembly but released propellant air with a separate mechanism. Mine fed propellant air upstream of the piston/nozzle assembly with a return spring on the opposite side. When the propellant air pulses into the chamber the larger diameter of the piston (compared with the nozzle bore) uses the pulse to shove the piston/nozzle assembly forward, firing the BB in the breech and cutting off the magazine at the same time. The return spring then resets the P/N assembly and allows the next BB into the breech. I found the return spring did not need to be particularly strong. It is super- simple (no valves) and highly reliable. It worked flawlessly on my proof of concept. I know you wouldn't think a piston with a hole in it would do much, but when the air expands into the chamber a bit faster than the nozzle can release it, it will delay the pressure long enough to work just fine.
You've got some good things going on there. Fabrication and assembly are always the stickers.
BTW, I'm pretty fresh too. Hooray for fresh meat!
Good luck!

[Doc j]

OK.
So you saying too much going on in valve?.
Ditch the chamber feed, one way valve feed by nozzle / piston retraction.
Control with a valve that I dunno?. make it 2 position 4 way. Normal open.
Feed chamber be open then block.
Feed Piston, open then exhaust.

[squib]

Yes, there is a good bit going on there. I think (just my opinion) it might be better to try it with a bit of separation of function as it will be easier to troubleshoot. Propellant air/gas pulses can be delivered many different ways; hammer valve, piston valve, sprinkler valve etc. You've included an integral piston type valve to provide the propellant pulse if I grasp the concept correctly. I think that will work just fine, but you my find things will develop faster if you separate the functions initially for proving the idea. In this way, if you hit a snag developing one component or the other you only need to scrap the part that needs more attention instead of the whole shebang.
As for myself, I often find proceeding in this way helps me understand the mechanics of how it all works together (which can be difficult to predict at times) and this understanding will be valuable in the move toward integration.

Best of luck!