by LukeSkyRocket » Mon Jan 01, 2007 10:51 am
There was a similar discussion on spudfiles, (I think that's where it was) about using something like a carburator to inject fuel into the breach of a pneumatic's barrel, along with a stun-gun spark to keep it ignited. The idea of mixing the fuel into the air in the pneumatic tank came up, and was rejected because of the possibility of the flame flashing back into the chamber and blowing the gun up.
I think spuzi said this, but if you ignite the fuel-air mix in the barrel-breach/small-chamber/whatever, the expansion will probably stop the flow from the tank, since there will be higher pressure where the ignition is. Or at least if it doesn't stop the flow, it will slow it. And that could allow the flame from to travel back to the tank. So then the tank would need to be able to hold full pressure. So then you might as well go with galfisk's valved hybrid. I don't care if his design requires lathe work, it's still awesome.
(A little bit of background: Galfisk's valve is a barrel-sealing piston valve. The ignition of the mix in the chamber causes a pressure rise in the gas on the chamber side of the piston, but the pilot volume doesn't ignite, and so the pressure remains lower. This has the same effect as venting the pilot area a bit: triggers the piston. So the piston starts to open, and as it does it causes a valve in the pilot area to actually vent the pilot. Then it's all downhill.)
I have a thought: could one make a hybrid valve like Galfisk's, but leave out the valve that vents the pilot area? This would likely mean that as the pressure in the chamber dropped during the shot, the valve would start to come closed prematurely, harming preformance. However, that all depends on what happens to the pressure; it may stay high enough for the shot to be successfully completed. I've had thoughts about a coax built like that.