Full auto gun - almost finished

Harness the power of precision mixtures of pressurized flammable vapor. Safety first! These are advanced potato guns - not for the beginner.
Tshylea
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Fri Dec 22, 2006 9:50 pm

Alright I'm almost finished my full auto gun. I'm putting this in the hybrid section because it is technically a hybrid, although I don't plan on ever taking it past a 1x mix.

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It will be firing either golf balls, or if I don't feel like spending all that money on buying golf balls that I might not get back, I will inject water into ping pong balls and then freeze them. Any other ammo suggestions would be appreciated though.

The concept is based on the piston driven blowback system of an AK-47. The piston on the bottom will be compressed when the gun is fired, thus re-loading and re-setting everything. I didn't draw all the connections and switches into the picture, because it would just make everything much more confusing, but basically when the piston on the barrel is compressed, it does 4 things:

1) It opens the breech.
2) It spins the hopper. The picture isn't too clear, but right above the breech are 2 disks. The top one has a bunch of holes cut in it, and the bottom only has one hole in it; directly above the breech. The bottom disk is fixed, but the top disk spins. Every time it spins, a new ball drops into a hole in the top disk and rests on the bottom one. When the top disk spins enough, the hole in the top disk and bottom disk will line up, and the ball will drop down into the breech. There is a whole system of rods and some springs driving it and aligning it, but that is the basic idea, and I'm not artistic enough to draw it out.
3) It turns the stun gun off. I'm not sure how many gaps it will have, or how exactly I will set that up, and the drawing is just an illustration to show that there will be more than one gap.
4) It turns the 3-way solenoid (that's what the "3-W" stands for btw) from filling the metering pipe to the chamber.

Now when the piston is compressed, it does all of this stuff, then when the spring pushes it back, it does pretty much the opposite. It closes the breech, it doesn't do anything to the hopper, but it turns the stun gun on, and turns the solenoid valve to fill the metering pipe.

That assembly just after the chamber is my design for a no burst disk hybrid. It isn't there because the chamber will be a higher pressure than the barrel, but because the ping pong balls don't fit perfectly in my 1 1/2" pipe, so I need to keep the propane from leaking out, and the air from simply pushing the balls down the barrel until they fall out, and having the crappiest, most overly complicated pneumatic ever built. Basically it works because when the pressure in the chamber exceeds the very small force of the spring, the first piston is pushed up, and pulls the barrel sealing second piston up as well, opening up the chamber to the barrel. Any suggestions on this would be great, as I have never built this kind of system before. Let me know if you have any other ideas as to how I could stop the propane and air from leaking out.

The compressed air is constantly being injected, but at a fairly slow rate. The rate of injection will determine the rate of fire. I'll have to experiment with rates of fire, because although the air controls it, the rate of fire is limited by the springs, and the propane. Depending on how fast the solenoid valve that I get will open and close, I should be able to go fairly fast, but then the springs will be a big factor. If they are too stiff, the combustion won't be able to completely compress the pistons, and if they are too soft, they won't be able to return the pistons to the proper position fast enough to get that machine gun effect.

Oh and there will be a chamber fan, or possibly two, constantly running, just incase the movement of the propane and the compressed air isn't enough to get a good mix in the short amount of time before the stun gun is turned back on. I would like to blame the terrible picture of the fan on the dieing batteries in my mouse.

I think that's about it for explaining how it works. I'll go and take some pictures of what I have finished right now and come back and post them. I just need to get the valve, the stun gun and the quick connects for my grandpa's air compressor. Oh and the no-burst-disk system needs to be made and installed, and then everything hooked up with rods and wires and whatnot.

Any suggestions are more than welcome, but please no "There is no way that will work" posts. If you don't think it will work, I don't want to hear about it unless you can tell me exactly why you think it won't work, and give me at least some sort of idea of what you think I would need to do to improve it.

Oh and just to answer the "why would you do this?" question before it is asked, think about that for a minute. You are on a website devoted to turning plumbing parts into devices that will make veggetables fly through the air. The "why would you do this?" argument stopped being valid the second you registered on this forum.
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Bluetooth
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Fri Dec 22, 2006 9:56 pm

OMG.................................................................. Thats forking amazing (jaw drops in amazement) Do you mean you've almost finished designing it or building it? If I was you I'd forget the hybrid part and hook it up to CO2.
Tshylea
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Fri Dec 22, 2006 10:04 pm

I'm almost finished building it. Give me a few minutes to upload the pictures.
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judgment_arms
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Fri Dec 22, 2006 10:12 pm

Vary interesting, I’m still trying to understand every thing.
My question is, does it work, more specifically; do the gasses from firing produce enough pressure to cycle the action? The pressures generated by a firearm are in the thousands; well most hybrids don’t even go past 500psi. It’s puzzling that the pressure generated by a combustion would be enough to even move the piston let alone cycle the action.
Another question: in the picture the gas tube is the same diameter as the barrel and you’re shooting a round projectile, with the gas tube being bellow the barrel, as in the picture, wouldn’t the round just drop in to the gas tube.
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iknowmy3tables
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Fri Dec 22, 2006 10:22 pm

:shock: wow its actually gas operated (its technically not blowback), hybrid and automatic.OMG congrats professer supercrazyinsanelybriliantcoolhowthefdidyoudothat. just make sure you actually finish it soon
Tshylea
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Fri Dec 22, 2006 10:26 pm

Well I'm not sure if it will work. I'm hoping it will, but the pressure generated could be a big problem. I'm trying to get around this by having everything well lubed and having as many things driven electronically as possible. The only real difficult thing to move is the breech cover. I guess the only way to find out is to test it.

The picture is misleading, but the barrel is 1 1/2" and everything else is 1 1/4". The chamber is 3" and the portion that holds the barrel up is blocked off.

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The clear tape holding the hopper on is only temporary. The entire gun was in about 7 pieces, so I just threw everything together to get a picture.
The propane bottle is only there to hold it up, and I know it looks like it sags a bit in the middle, but again, that's because it isn't all glued together. I'm probably going to add the chamber sealing pistons tomorrow.
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judgment_arms
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Fri Dec 22, 2006 10:36 pm

Interesting, you’ve obviously done your homework. Me and my dad came up with a loading mechanism similar to that but for a pneumatic MG I was designing, decided it would be too impractical. Nice work, I hope it works.
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Fri Dec 22, 2006 10:50 pm

Watch that DWV ABS, especially in a "hybrid." It will eventually blow off and you'll have to rebuild the whole thing.
Tshylea
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Fri Dec 22, 2006 10:58 pm

I'm never gonna take it over a 1x mix, so I figure I should be alright. I've got a couple other combustion guns made from DWV ABS and I've put hundreds of rounds through them with no problems.
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Mon Jan 08, 2007 9:35 am

I know this is a bit old but I got the perfect sugestion for the loading mechnism, what you're would work better than this is a complete Carousel loader and all you got to do is add pipes on top of each hole instead, the system was once used on old crank powered gatling guns
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judgment_arms
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Mon Jan 08, 2007 11:40 am

It’s not that old. But the carousel loader is impractical as you can only have so many rounds or the disk would be huge. I think the Gatling gun you’re talking about was the “police” model that shot .38 special, I believe, which is a rather small caliber compared to the ball he’s using. As a completely irrelevant side note: the .38 special is the same caliber as a 9mm, .357, the only difference being that the .38 special brass is as long as the entire 9mm cartridge, and it also has a heavier bullet, the two bullets travel at about the same velocity but the .38 has more energy. So anybody care to tell me why the police use 9mm? yes that was random but…
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iknowmy3tables
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Mon Jan 08, 2007 8:05 pm

Oh I see more energy is needed to rotate the mag, oh well it was just for more simplicity in the feeding, but I'm sure the feeding system I'm talking about was for cranking mgs
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