Just joined + My propane WIP

[ozoncqp]

Awesome man, really awesome.
Cleary the pump action thing to add freash air works. But woulnd't a just 40mm fan in the back of the chamber be better? I'm not trying to sound like a smartass, but the fan would/should be able to clear out the chamber between the shot and the reload, right?
I'm just thinking theoretical here.
I still like it tho! Makes me wanna go and rip my old boss from all his cyllinders recon he got a 120cm one

[Moonbogg]

Impressive! I like it. It looks like a mechanical beast of destruction. Very good looking design. Looks like something the Terminator might use if he was into extreme tennis. Any idea on range?

[psycix]

Looks cool!

Does it have a chamber fan?

[chenslee]

You guys have to stop razzing me about the fan!

I'm not going to put a fan in it. I'll switch over to CO2 before I do that.

The air cylinder on the bottom pumps air and fuel. I originally intended it to only need to be pumped once, but that didn't work out. On the forward stroke it pumps air, and on the backward stroke it pumps air and fuel. If I used a fan, I'd have to leave the bolt open. I can feed a ball and then pump air and fuel in regardless of if the bolt was open or closed, how long the bolt was open or closed, or if there was a ball in the chamber. The three full pumps I'm using now is working fairly consistently over multiple shots.

What I didn't count on was having to pump it as much as I am. The solution is to put a bigger cylinder with more volume per pump, but because each stroke opens 3 check valves with a cracking pressure between 2.5 and 5 psi, a larger cylinder would be that much harder to operate.

I think there is another solution (NOT A FAN ) but I'm keeping that to myself until I prove that it works. That and it's another $50 in parts.

[psycix]

I recommend the fan not for venting, but for more power due to better mixing of the fuel and induced turbulence.

Is your air and fuel entering through the back? Note that all burnt gases need to get driven out of the chamber, and not mix with the fresh air.

[chenslee]

Air and fuel are being forced through an orifice in the rear. This seems to sufficiency mix them.

I also seem to be getting decent second, third, fourth, etc. shot combustion without a fan.

I'm going to try this next

[Mongloid]

I made you some new plans that should help out.

[starman]

Humm OK Mongloid, that was a little off-the-wall.

Re: fan Chenslee. They do improve things and aren't at all difficult to incorporate. I know you've heard all this before....but... If your tennis balls are fitting tightly, that may be compensating some for a somewhat slower chamber burn.

[chenslee]

double ewe tee eff.

[inonickname]

Hey..at least he isn't grave digging....

(I kind of loled at the air/wind in the chamber).

Rather than pre charged supplies of a fuel/oxidizer why not just have a pressurized fuel and use a venturi to mix and purge the chamber? Unless you already are..

[chenslee]

Air and fuel get pushed through a very small orifice at the same time. I think that orifices are a special case of venturi, it certainly trades pressure for velocity.

This is a diagram of my CURRENT SETUP. Filling and emptying of the metering tank is controlled with pressure from the air pump.

[chenslee]

Last night I finally put the new springs on and tested it with the bernzomatic nozzle jammed in the back. It feeds great and shoots but not consistently. It's not bad considering I'm not even metering the propane anymore.

[Technician1002]

Air and fuel get pushed through a very small orifice at the same time. I think that orifices are a special case of venturi, it certainly trades pressure for velocity.

This is a diagram of my CURRENT SETUP. Filling and emptying of the metering tank is controlled with pressure from the air pump.

I like this set up. It's similar to one I was toying with earlier. The only change is instead of using a metering chamber, both air and fuel would go through metering jets. The propane regulator instead of being adjusted by a spring under tension, the propane regulator would work on the pumped air pressure. Heavy stroke high delivery pressure of both. Light stroke light delivery pressure of both. The mix would be uniform and the volume would be metered by the pump displacement.

The only modification to the propane regulator would be the removal of the spring and feeding the pump air pressure in it's place.

[chenslee]

I like this set up. It's similar to one I was toying with earlier. The only change is instead of using a metering chamber, both air and fuel would go through metering jets. The propane regulator instead of being adjusted by a spring under tension, the propane regulator would work on the pumped air pressure. Heavy stroke high delivery pressure of both. Light stroke light delivery pressure of both. The mix would be uniform and the volume would be metered by the pump displacement.

The only modification to the propane regulator would be the removal of the spring and feeding the pump air pressure in it's place.

I like that idea, like rising rate fuel pressure regulator on turbocharged cars. More pressure=more fuel.

Also: NO METERING

[youtube][/youtube]

[Mongloid]

You must have put a fan in it.