semi auto combustion

[taranathicus]

I want to make a semi and eventually fully auto combustion spud gun, simply because its something i really havent seen before. from personal experience i know a breech loading bolt action combustion will work. i have been thinking about a fuel injection system from a car, a compressor to blow the chamber in between shots, and starter coil ignition system. for the semi auto part i think its going ot be mostly electrical rather than compression powered as it is in most guns. im thinking i would have to pre cut potato bits for it, but i already do that for my other gun anyways and its not so bad. a gravity fed clip. steel barrel like my last gun. pvc everything else. i was going to use a liquid fuel, of a type to be decided as of this point. i have a design in my head right now for this, but i was wondering about other people's ideas, i have access to a lot of electrical hardware. i have a welder and i can use it. so give me some ideas if you would.

[Jakal444]

Sounds interesting...How many cannons have you built so far?

Rambo knows a lot about auto combustions.

[Shrimphead]

Why don't you go with a pre-manufactured ammo to save time, such as golfballs, tennis balls, or paintballs if you wanted that small of a caliber?

[taranathicus]

well so far ive made but one gun, and it worked really well, thats where im going to add the fuel injection and air clearing of the barrel to test. it currently works with bolt action breech loading. and as the the ammo question, its a spud gun, i mean its gotta shoot spuds, whats more impressive a fully auto tennis gun or a fully auto spud gun. i want this thing to be able to cure irish famines!

[Rambo]

After many shots(with no ammo, just for fun) I was wondering why the auto comb. is a little louder then a normal spudgun with the same volume.I think that because it uses air that was compresed miliseconds ago, it is still cold>more O2 molecules per sqare inch.

[FiveseveN]

Indeed, it works like a pulsejet (only with much longer wavelenght), and because of inertia, the gasses are compressed slightly just before ignition.
If we took the Reynst pulsejet design and add a long intake/exhaust (barrel) to it, (of course, not too long, or it will choke the flame) we get Rambo's auto combustion. It should work with any fuel as long as we keep the mixture under control.

[Jakal444]

You have a good idea but I think that maybe you should build at least one or two more cannons just to get a bit more experience, but thats just my opinion. I'm quite sure no-one on this forum wants you to accidentaly blow yourself up.

It will be difficult to fire spuds semi or full auto, they make good ammo but if you want a semi auto you can easily come up with a proper loading system for some other ammo. If your dead set on potatoes you can make frozen potato slugs.

[taranathicus]

The thought of frozen round shad crossed my mind, i know that ill have to make them a uniform size to make them work. also this may be the first spudgun ive made, but its certainly not the first bit of pyro ive played with. and ive never been patient when it comes to these things.

The idea of using a pulsejet with a really long wavelength(for a pulsejet) had occoured to me, its just that they get really really hot and well, i just have visions of cooked spuds flying with a sizzling sound out of a red hot metal barrel. i like it.

Ill try to get round to designing what im have in my head for this in cad and ill post some pictures of it. i have a four barreled anti aircraft gun style weapon with 4 combustion chambers 4 barrels. that would have 4 clips and shoot about 10-30 rounds per barrel then be out.

how many rapid shots can pvc take?

what sort of heat should i watch out for?

[Rambo]

My coke bottle auto combustion starts to melt after 3-4 shots.