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Anything wrong with a 2" chamber?

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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Anything wrong with a 2" chamber?

Unread postAuthor: Binder17 » Thu Jul 05, 2007 12:22 pm

I have designed a spudgun that has a 2" X 6" chamber and .75" X 48" barrel. I will use metered fuel and fire with a bbq sparker. I not going to bother putting a fan in it. Is this worth building and will it shoot?
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Unread postAuthor: hi » Thu Jul 05, 2007 12:25 pm

i have a cannon with a 2x18'' chamber and a 3' barrel, it gets about 250 feet with a tater.

te one you designed has a barrel that is way to big, you need the barrel to be no more than about 15 inches.
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Unread postAuthor: Binder17 » Thu Jul 05, 2007 12:29 pm

So don't worry about the ratio?
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Unread postAuthor: rednecktatertosser » Thu Jul 05, 2007 12:33 pm

hi wrote:i have a cannon with a 2x18'' chamber and a 3' barrel, it gets about 250 feet with a tater.

te one you designed has a barrel that is way to big, you need the barrel to be no more than about 15 inches.


Hi you know his barrel is 3/4" not 1-1/2" right? cause a 15"x3/4" barrel would be about right.

@Binder- you should really consider a fan, they really boost performance, but in the end its up to you.
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Unread postAuthor: hi » Thu Jul 05, 2007 12:47 pm

no, what i mean is that i made a cannon with a 1.5'' barrel. it has nothing to do with his.

i know that 15 inches is about right because thats what i said, reread my post redneck.....

edit- yes worry about the ratios, a chamber that is 2'' diameter and 6'' long needs a 3/4'' barrel that is about 15 inches long.

if it was 48'' it wouldn't leave the barrel.
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Unread postAuthor: rednecktatertosser » Thu Jul 05, 2007 12:52 pm

OOPs i thougt the original post said 2'x6" nevermind, your right.
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Unread postAuthor: psycix » Thu Jul 05, 2007 1:12 pm

why wouldnt it leave the barrel with 48"?
The ratio is about 0,95 then, on 15" the ratio would be like 3.
And hey, if the barrel is too long, just take some off :)
U can always make it shorter.

(btw Chamber fan will boost performance alot + luxury of vending chamber)
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Unread postAuthor: WOW!! » Thu Jul 05, 2007 1:30 pm

I made one that is 2''x6'' with a 1'' barrel. It works really good. Shoots 175+ feet. Single electrodes and a BBQ ignitor. Nothing fancy just something to use around the shop and for the little kids to use.
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Unread postAuthor: Binder17 » Thu Jul 05, 2007 1:39 pm

I'm just going to put some pennies in the chamber to shake around and mix the fuel and air. It is not worth wiring a fan in it.
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Unread postAuthor: psycix » Thu Jul 05, 2007 3:25 pm

That will do too.

Just wondering to be sure:
Do pennies spark?
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Unread postAuthor: hi » Thu Jul 05, 2007 3:28 pm

pennies would probaably spark, they are mostly copper.


I made one that is 2''x6'' with a 1'' barrel. It works really good. Shoots 175+ feet.


are you sure do dont mean 1'?

anyway, a 2x6'' chamber cant provide enough power for a 48'' barrel, its just to big. even wth oxygen and mapp gas (dont even think about trying it) it wouldnt be enough.

you need a 15 to 18 inch barrel tops, no more than that. it simply wont work. try it and see.
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Unread postAuthor: Jumpin Jehosaphat » Thu Jul 05, 2007 3:51 pm

Using sch 40 PVC the ID of a 2" pipe is 2.049, so the volume of 6" of that would be about 19.784 cubic inches. The ID of 3/4" PVC is 0.810" so the volume of 48" of that would be about 24.734 cubic inches.
The C:B ratio of the cannon described in the first post would be 0.7999:1
The dimensions given in the first post are perfect! You could stand to make the barrel an inch or two longer, but I wouldn't.
Hi, I agree it doesn't seem like this should work, but the barrel is less than half the diameter of the chamber he is using, this makes a huge difference when calculating the volumes.
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Unread postAuthor: Binder17 » Thu Jul 05, 2007 4:02 pm

So the .8:1 ratio I used is right and the specs I came out with are right?
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Unread postAuthor: noname » Thu Jul 05, 2007 4:10 pm

I knew something was missing...
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Last edited by noname on Thu Jul 05, 2007 5:57 pm, edited 1 time in total.
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Unread postAuthor: Binder17 » Thu Jul 05, 2007 4:25 pm

Volume is pi*r^2*l

His math was perfect. Double check your formulas.
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