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The ever-popular "first cannon" topic.

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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The ever-popular "first cannon" topic.

Unread postAuthor: paaiyan » Wed Dec 27, 2006 10:40 pm

Here's the specs. Keep in mind this is my first so it is rather simplistic. My total cannon length is about 8 1/2 feet. The chamber is 2 feet of 3-inch PVC with a female thread adapter and screw in cap on the rear. The front of the chamber has an adapter that drops it down to the 6 feet of 2-inch barrel. I did the calculations for the chamber to barrel volume ratio at the .8/1 ratio I found elsewhere on here. I can always cut down the barrel later should the need arise. Oh, and yes I did use SCH 40 PVC. I'm not entirely stupid.

It's all inline and I'm probably going to use Static Guard for fuel. Anyone got any ballpark ideas for how far I should be able to send a tater? I'll post pics of it once it's been completed, probably tomorrow.

Addendum: And as for the ignition system, I have two alligator clips attatched to the screw in cap that extend several inches into the chamber. they have heavy wires running through two holes in the cap sealed with epoxy. There'll be a thin wire strung between them. It resembles a model rocket ignitor, remote ignition. Basically just run a lot of current through the thin wire and heat it up a lot. If that can ignite the solid state fuel of a rocket I don't see any reason it wouldn't ignite volatile liquids.
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Unread postAuthor: sergeantspud2 » Wed Dec 27, 2006 11:23 pm

Im not sure on the distance, but your ignition system may become trouble some later on. Not everytime your going to have the right fuel mixture in the chamber so you igniter wont do anything and you'll just have to put in another ignitor untill you get the right mixture. I can maybe see this as a useful remote ignition if you had metered propane but with Static Gaurd it is going to be a challenge getting it to light. Just warning you because at first you may think its only 50cents each, well that adds up VERY quickly as Ive learned with my 12 gram pnumatic. They get expensive very quick.

Nice cannon specs I see you researched before building unlike I did on my first. :? Sounds like you have a good solid cannon.
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:D Always rely on Murphy's Laws :D
4.If you have enough grease & a big enough hammer, you can put anything... anywhere
3.If all else fails, hit it with a big hammer
2.Matter will be damaged in direct proportion to its value
1.If anything simply cannot go wrong, it will anyway
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Unread postAuthor: paaiyan » Wed Dec 27, 2006 11:25 pm

So, wait, i totally missed something. What's costing me 50 cents? Anyway, the way its rigged I can convert it to a piezo-electric spark system in about half a minute.
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Unread postAuthor: Insomniac » Wed Dec 27, 2006 11:27 pm

Well, does the wire melt each time and you need to replace it?? If so it will get really annoying.
I think sergentspud thinks that your using actuall model rocket ignotors, and not a piece of wire.
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Unread postAuthor: paaiyan » Wed Dec 27, 2006 11:33 pm

Oh no no no. I'm just using thin wires. and I've experimented with my mechanism a bit and found that one of the most effective filaments is actually a thin strip of the foil wrapper from a Hershey bar. The foil heats up enough to light the paper aflame and sometimes even lights the foil itself. I'll probably just cut strips with an exacto knife ro something. Sounds like a pain in the butt but whatever. Won't take but 10 seconds. I figure that if it's getting hot enough to light the aluminum on fire, it'll light Static Guard. Just take a couple tries to figure out how long of a spray to use and I'll be set.
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Unread postAuthor: sergeantspud2 » Thu Dec 28, 2006 12:00 am

Oh yeah my bad I thought you were going to use a rocket ignitor each time.
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:D Always rely on Murphy's Laws :D
4.If you have enough grease & a big enough hammer, you can put anything... anywhere
3.If all else fails, hit it with a big hammer
2.Matter will be damaged in direct proportion to its value
1.If anything simply cannot go wrong, it will anyway
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