Combustion Cannon

[kingvitamin]

Well now me and my brother recently made a combustion cannon. the barrel is 48in long and 2IN diameter and the chamber was 2 Ft long by 3in diameter, we used dwv abs pipe. It's work pretty well we fired a potato 300ft. Unfortunately our cannon is too powerful for potatos(as they disenigrate when fired). Does anyone have an idea for some better ammo?

 

Also does anyone have some plans that they would like to share with me? We want to make more cannons.

 

thanks

[aquaman]

One of my friends made a cannon like This. It works fine for potatoes.

 

Other ammo: Try different fruits, vegetables, balls (tennis?), or basically anything that'll fit and that you really don't need.

[justanotherpyro]

Combustions are by far cooler, but I really like my pneumatic. It was a bitch tomake but it is 100% reliable, and can shoot water and paintballs. But I am of course hooked to the air compressor.

 

A good, but dangerous ammo is a golf ball.

[kingvitamin]

Hey i was thinking for ignition instead of a bbq sparker perhaps i could drill a hole in the chamber. then place a bbq lighter in it, make sure it is a snug fit then place epoxy putty around the whole just in case. would this work?

[Swany]

Get some new potatos. I have yet to have a potato vaporise upon firing with 2 different launchers, and have achieved distances of over 100m with both.

 

Pneumatics appeal to be, for ballistics testing, and raw power.

 

Combustions only generate 25-35psi, wheras a good pneumatic could go to 150psi, though 100 is quite acceptable.

 

And yes, the ligher would work. I have made ignition systems out of old disposible camera flash units as well.

[aquaman]

Hey i was thinking for ignition instead of a bbq sparker perhaps i could drill a hole in the chamber. then place a bbq lighter in it, make sure it is a snug fit then place epoxy putty around the whole just in case. would this work?

Heck my friend and I just drilled a half inch hole in the chamber. To light it he plugged the hole (tape, finger) and then I sprayed the chamber with hair spray and screwed the cap on. He then would unplug the hole and I quickly lit a lighter and just place it over the hole. And then wooosh...thump, the potatoe would go like 200 yds.

 

So I know for a fact that you don't need electrical ignition. The electrial ignition tends to get all gumbed up and not work. My way it always ignites like 90% of the time. 10% of the time he did not have enough hair spray or he had too much of it the chamber.

[Swany]

Build a direct propane injection system. Use charles' law to calculate the correct PSI, and thus you never over/under fill the gun. Plus, it looks very sexy, in a very ugly way. I shall get a vid of it, since the camera is on the other side of the country.

[Mumbles]

My cannon is a bit bigger, but handles potatos just fine. Maybe you just have shitty potatoes. I do my best to get potatoes larger than the barrel. My barrel has a knife on the end to cut to size. For a better fit, the knife is not directly on the interior wall. It is put out a bit to compress the potato upon pushing into the barrel for a better seal. The barrel is 2" x 5', and the chamber is 4" x 20" I think. The chamber has a volume of 1.5x that of the barrel.

[justanotherpyro]

If you use pizo ignition propane is the way to go. Its way to easy to soak the contacts and make it malfunction. Do what swany said. It works great for a combustion design, and propane won't leak out of the chamber because its heavy.

 

The other route is a lantern ignitor that has a flick switch. A good way to use the lantern ignitor is to put it in the cap that screws off of the chamber. It takes more moisture for the flint to not work than it does for the pizo, so you can wait longer for your shot, and not have to rush it. Also, a personal favorite fuel is 50:50 diesel/gasoline in a fine mist glasses cleaner spray bottle.

[Pyrohawk]

I have always wanted to try pumping acetylene and pure oxygen into the chamber (oxy acetylene torch). But I have heard its to powerful and will blow apart the ordinary cannon. I once read a website about a guy who tried it with his PVC potatoe gun and it exploded in his face....

[justanotherpyro]

I have always wanted to try pumping acetylene and pure oxygen into the chamber (oxy acetylene torch). But I have heard its to powerful and will blow apart the ordinary cannon. I once read a website about a guy who tried it with his PVC potatoe gun and it exploded in his face....

Propane in a balloon makes a fireball. Oxy/Acetylene in a ballon goes off like a shotgun. Not recomended unless the cannon is made out of steel, which isn't recomended either. If a regular spudgun isn't cool enough, make a pneumatic pumpkin launcher.

[Swany]

Here is a closeup of my cannon injection system...

[thathad2hurtbad]

... Pnuematic Pumpkin Launcher.....

Make one and show it to us!

Then Ill be happy for the rest of my life....

[Douchermann]

Lol, a stoicheometric mix of oxygen and acetylene will detonate, just like a stoicheometric mixture of hydrogen and oxygen.

 

I have had a couple potato cannons before. My first one was a basic design, but the seal around the grill sparker eventually started leaking and the flame slowly at away at the PVC where the sparker. After a while, the hole was too lose and the sparker popped out every time you shot it so I trashed it. My other one was a bit different, it had a 75 degree elbow joint on it with a 2inch threaded cap in which the sparker was placed. This was so you could just replace that little part if something happened to the sparker.

I left this out one cold night and it tipped over. When PVC is cold it is very fragile, so the barrel shattered when it hit the ground. My third one, which I havn't finished, has the same design as the last, but this time the barrel is threaded on. This way, if that breaks it can be replaced and plus you could put bigger barrels on for like toilet paper, or smaller barrles for grapes (those hurt when they come out of a combustion cannon, but nothing more than a powerful paintball gun). I hope this has given ideas to some people. If you want pictures, I'll post a pic of my newest gun, but its not finished yet (I keep forgetting to buy a sparker at menards).

[Mephistos Minion]

Get a steel pipe same ID as your barrel, fill with molten parrafin. When its set, heat the outside of the pipe for a bit to melt the very outer part of the parafin slug inside, push it out and cut it into sections slightly longer than your pipe ID. Makes for some really good ammo.

[FrankRizzo]

I'm partial to attaching wads of 000 steel wool to the back of potatoes... makes for a nice tracer-type effect as it burns.

[Swany]

I agree with that.

 

H2/O2 mixes can detonate, and when they do they produce about 10x the pressure they would if they simply deflagrated.

 

I found a place where I can get cylinders of H2C2, H2, and O2. Hooray.

 

Here are some detonation pressures of gasses in bar. 1 bar = 14.5037738 pounds per square inch. Convert it yourselves, fools:

Hydrogen:Oxygen 6:1=101.4

Hydrogen:Oxygen 2:1=106.9

Propane:Oxygen stoich=132.7

Butane:Oxygen stoich=190

Ethylene:Oxygen stoich=202.6

Acetylene:Oxygen 1:1=276

 

H2/O2 is suprisingly low, compared to the hydrocarbons.

 

Someone else did the calculations, I found them on my computer. I forgot from whence they came, however.

 

EDIT: where found is referrring to a saved document regarding this.

[Karl]

Here is a closeup of my cannon injection system...

Propane Cannon, Drool!

 

 

I have my old spud-gun sitting next to me, hasn't been fired for about two years due to me not finding a reliable igniton source. It's short & stubby and does the part but im looking at upgrading. Can anyone tell me how i can adapt it to take propane from those Camping Stove cylinders? Where do you find the valve?

 

Karl

[Ozzy]

I've made ice slugs, i took a piece of my barrel "2inch" cut it about 4/5 inches long cleaned up the edges so its nice and smooth then put a piece of saran wrap around the bottom of your mold pull tight put rubber band on and set on plate the fill with water and freeze

[Swany]

I epoxied mine in, it was an old torch. However, ideally, you could thread a torch end, or you can get valves for about 8$ a pop, I forget where, but your major hardware stores should have them

[Tweetybird88]

for ammo, you can wrap the potatoe in duct tape. That should work alot better from my expiriences.

[TiB]

Hey i was thinking for ignition instead of a bbq sparker perhaps i could drill a hole in the chamber. then place a bbq lighter in it, make sure it is a snug fit then place epoxy putty around the whole just in case. would this work?

Depending on the power of the thing, that could turn into a projectile and seriously harm you. The best way to light a combustion potato cannon is to take two threaded screws, screw them into the middle of the combustion chamber from either side and put them a few thousandths of an inch apart. then connect the barbecue sparker ends to the screws. Saves wear on the BBQ lighter and much easier, the threads hold the screws in place.

 

Edit: Oh my bad didn't realize this was a year old.

[bombboy218]

A realiable ignition source is a 1,000,000 volte stun gun i got it on ebay for 35$ shipped a lower voltage would work great but make sure the wires are very heavely gauge because mine mellted through the wire and arked to my finger i fainted from the shock i see why people use them for self defense

 

put a 2 screws about an inch and a half to 2 inches apart and it makes a very hot long spark

 

oops didnt know it was 2 years old

Edited January 28, 2008 by bombboy218