Holy CRAP o.=.o.....and IDEA!! Automatic combustion.

[dragon finder]

Wow it's been a while sence I've been here o.=.O......if ANY of you remeber me XD hahaha.

Any who. I've had this idea on my mind for many years when I was fiddling around with pulse jet engines.

So what are the things needed for an automatic combustion gun?

1.) A way to vent the chamber quickly and introduce more air with oxygen into it.

2.) Injecting fuel into the chamber quickly and precisely.

3.) Reloading.

~~~~~~~~~~~~~~~~

2.) Well introducing the fuel into the chamber fast is no big problem. Using a fuel metering system with electronic valves to open and close at the right times. Or some sort of clock work thingy.

3.) Reloading is a bit trickier but I've seen a ton of different ideas and methods to reload, preferably one using a blow-back system

1.) The biggest problem is venting and recharging the chamber with fresh air. It could be done with some complex system of fans and blowers but it there would be significant lag time. SO! What I suggest is a Reed Valve.
~A reed valve works as a check valve. When there is a combustion in the chamber all the hot gasses escape through the barrel, creating a vaccuum in the chamber. This vacuumm will pull the reeds on the valve back and allow air to enter into it through the holes in the end cap or what ever you want. Then when pressure is normalized the reed valve will bend back to cover the holes and start all over again!.
~In pulse jets this happends thousands of times per second and will destroy the reeds in a matter of moments. Some of the hot gasses are pulled back down the barrel and, in a pulse jet, will ignite the constantly flowing fuel. Simply add the fuel metering system to prevent this chain reaction and use a circuit to deliver a spark after the fuel has been injected to fire again!

Thats my idea and it will be of more use to you guys than to me as of lately. I'll put up some images to help give you an idea but simply googling Pulse Jets and roaming around, you'll get the idea fast.

I hope this helped!! Please comment and tell me what you think....and say Hi XD

[Technician1002]

I've seen pulse jets.. Very noisy, very hot, and very inefficient. Loading something like a pulse jet where the acoustic wave refreshed the chamber air would be very difficult. Elsewhere I had some other thoughts on a full auto combustion, but it required powered venting/fueling as a proportioned mix on delivery. It would use a much slower repetition rate to permit gravity feeding gumballs for ammo. I'll have to hunt up links later.

The air and fuel are delivered at proportionate rates to the chamber and ignited. The backflash pressure interupts the fuel and air delivery so the source extinguishes the flow until the chamber returns to atm pressure where the process is repeated. Gravity fed ammo and a spark timer finishes the full auto design.

[Moonbogg]

Why not forget about chamber venting and just use O2?

[brogdenlaxmiddie]

Theres a couple of things I think you can work out Dragon, (btw I remember you) and I give you my full support. Of the automatic combustion ideas thrown around this site every now and then, yours looks the most promising to me. good luck man

[dragon finder]

Moonbogg: I'd use O2 but ONLY if I had a metal body. Using pure O2 and fuel could lead to detonation rather than just a fwoosh (cant spel deflaguration or what ever it is X3) I was thinking about it yes, and I'd prefure to do that but i'm still way to novice to pull that off.

Brogden: Thank you. I know it's just an idea but it's ment to be tweeked. Thats why I put my idea up after keeping it to myself for such a long time. I'm pretty damn sure it will work given the proper factors. Like using PVC sheet for the reed valve rather than metal.

Tech: I'm not making a pulse jet potato gun! XD nor am I suggesting it. I just want to use the reed valve to refill the chamber with air. Not make a thousand explosions in it per second. ^.=.^

ANY WHO. I probably won't use this but you guys and any one else reading this PLEASE use it or improve it. I'd love to see where it goes.

[jimmy101]

Do propane fired paintball guns and nailers use reed valves?

There are a number of propane powered combustion devices that can cycle fast enough to be considered automatics. Somebody has already figured out how to purge and recharge the chamber.

[sockdog]

how interesting.........i can see how it works but you will need a cooling system.........if pvc is used at all i think.........should be easy too make that though

i personally would love to make this but i lack the potato gun know how to pull it off

a similar but easier to built reed valve

----outer pipe--------
--inner pipe--
------bolt----(ball)--I
---------------
------------------------

o ring on the end of the inner pipe


and there's a perfectly reliable reed valve........no need for pvc at all

Edit: How is it the reed valve will fully vent the chamber? How to make enough of a vaccume without hindering performance greatly? hmm....

Edit: ya'd need a long barrel & proportional chamber(or perhaps smaller than proportional chamber) so incoming o2 is seperate from outgoing flames of the last shot

another Edit: the c:b would have to be 1 or less :1 wich is normal cb anyway

[jimmy101]

Edit: How is it the reed valve will fully vent the chamber? How to make enough of a vaccume without hindering performance greatly? hmm....

You might be able to take advantage of the momentum of the combustion gases. Once the round uncorks the barrel the gases not only are still expanding but they also have momentum. Not a lot, but perhaps enough to suck in fresh air from the breech end as the spent gases continue out the muzzle because of their momentum.

[THUNDERLORD]

Not powerful enough to do this
More info here, IDK how good the plans are, but if you scroll down, click helicopter, read about the inventor, he seems pretty cool. Something about he wanted to build an aerial motorcycle...I like the jet tip rotor concept for CO2 jetpack/ jetpack variation myself.
Those other ones (OP) seem like...Bullet size. 8)
(Although the Gluhareff ones sort of do too).

[dragon finder]

well it will vent the chamber enough IF it is made properly, A pulse jet vents and recharges thousands of times per second. IF we are lucky we could get maybe ONE round per second or round about. I know it will work but it will take alot of testing and tweeking before we can find out the proper reed material, size, hole size, reed thickness, how many reeds on the valve and so on.

[THUNDERLORD]

I am more interested in a gas assist vent (similar to gas bolt assist in firearms).
A simple port (probably a "T") near muzzle,
and a piston inside, so as the projectile is about to exit, (and propellant has done it's work),
some propellant gasses drive the piston back,
which strikes/presses a check valve (or lever to one), venting the chamber...
proper timing as well, since the projectile will have exited when the piston rod opened the simple vent valve.
I think it has potential.
Won't be long until I start tinkering on one. 8)

[Spain707]

First post.

I joined to discuss ideas I have for an automatic propane cannon.

this is very similar to what thunderlord was saying

Blow-back in its correct usage cannot work in a potato gun. The slide is actuated by the casing which is being propelled backward. Potato guns have no cased ammunition.

A gas operated system would work and that is what I am working on.

Essentially the action of the gun will be made of a 2.5" tee with a 2.5" coupler fitted to one end without a nipple. In the center of the tee would be a segment of 2.5" pipe just long enough to cover the top inlet of the tee effectively rendering the tee a coupler. At the final inlet of the tee would be the barrel. Between the back of the tee and the pipe segment there would be a spring sized to fit in the tee holding the pipe segment in the closed position.

Down the barrel there would be a 4 way that would redirect gas from the barrel to the tee (think ar-15/ak-47). the pipe segment would have 2 bolts coming out of the sides protruding through 2 slits cut into the side of the tee. The gas channels would have a piston at the ends actuating the pipe segment via the bolts. When the pressure subsides, the spring returns the segment to the closed position. When the segment was open, an other tennis ball would drop into the chamber (gun chamber not potato gun chamber). I would wire the system with some home made switches to control the gas metering system and a spark cut off as to prevent premature ignition.

It would all run off one button.

there are a lot more ideas to be put into this gun but this is just talking about the actual feeding of ammunition.

tell me what you think and I will try to get a more clear diagram up/.

[Hubb]

This has been discussed. I don't think it's been done, though.
http://www.spudfiles.com/forums/carv-valve-t17908.html

Personally, I think a carburetor system will be the way to go on a auto-combustion/hybrid, but that's just me.

[jackssmirkingrevenge]

Personally, I think a carburetor system will be the way to go on a auto-combustion/hybrid, but that's just me.

I'm with you there. Any reciprocating piston internal combustion engine is a full auto hybrid, only the projectile happens to be connected to the launcher and comes back every time you fire the damn thing. Must be an Aussie invention

[smiley_666]

Must be an Aussie invention

OI!

Personally, I think a carburetor system will be the way to go on a auto-combustion/hybrid, but that's just me.

if i were to try this id use a 'tesla valve', the top bit in the picture. its an aerodynamic one way valve. id shorten it and place between the carby and chamber and it should work . maybe put a fan infront of the carby to get some more air flow.