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First cannon

Built a combustion cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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First cannon

Unread postAuthor: paaiyan » Fri Feb 09, 2007 12:22 am

OK granted, it's extremely simple and a beginner design, but it's my first try at this. No I haven't tested it yet, working on finding a remote location as I'm not entirely sure what the powers going to be like. I'll put up more pics once I get it painted, right now you can still see the pvc glue and all.

Edit: The ignition system is something of my own design. I'll get a couple of pictures of how i did it tomorrow and post them. I think it's kinda cool myself but that's just me.
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It's just a couple inches shy of 10 feet long. The chamber is 2 1/2 feet of 4-inch pvc and the rest is 2-inch. I'll be using Static Guard as fuel, if anyone can give me a rough estimate about how far it may shoot I'd appreciate the input.
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Unread postAuthor: frankrede » Fri Feb 09, 2007 2:49 am

Wow thats pretty massive, you might want to consider installing a chamber fan. A rough estimate on range would be well over 100 yards, maybe twice that.
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Unread postAuthor: Insomniac » Fri Feb 09, 2007 5:15 am

That thing is a BEAST!!!!!
The C:B ratio doesn't look very good, it would probably be a good idea to cut some of the barrel off. But thats just me, I could be wrong.

Anyways, very nice gun!
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Unread postAuthor: paaiyan » Fri Feb 09, 2007 8:41 am

Well as for the C:B ratio, I really don't remember what I used because I'm just cool like that, but I did use the one that gave me the most barrel. That way's safer because you can always cut some off should the need arise. It's a pain in the butt to add more.
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Unread postAuthor: jrrdw » Fri Feb 09, 2007 9:03 am

I'll guess at the range with that set up -- 75 yards tops. If the barrel was 1" in diameter, i'de guess 200/250 yards. It seems that when rule of thumb is followed, 200 yards seems to be the standered distance for most of common combustions.
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Unread postAuthor: paaiyan » Fri Feb 09, 2007 9:26 am

Alright I realized I have 3-inch on the chamber instead of 4. Redid the math and my C:B ratio is look just about .8:1. I remember looking around for a bit to see what everyone thought was good and that seemed to be pretty well accepted. And it's apparently only 8.5 feet long, I was assuming that the ceiling in my garage was the same 10 feet as in my house. Yes I know, I should know all this stuff but I actually built it a couple months ago and had since forgotten the specs.
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Unread postAuthor: fom » Fri Feb 09, 2007 6:21 pm

LOL

a .8:1 ratio would be best for propane/mapp gas but since you using static guard cut some of the barrel off, I dont know how much, someone smarter than me should know.

Edit: I just remeber a 1.5:1 ratio is best for aresols.
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Unread postAuthor: SpudBlaster15 » Fri Feb 09, 2007 10:15 pm

A 1:1 ratio is ideal for an aerosol based combustion, because with a non-stoichiometric mix as is commonly encountered with the "spray and pray" method, much less energy is produced (obviously) per given chamber volume measurment. That said,

V=pir^2h
V=pi(1.5^2)(30)
V=212in^3

You will want a barrel with a volume of (roughly) 212in^3, so, using 2 inch pipe, a barrel of 68" fits the bill.

V=pi(1^2)(68 )
V=213.6in^3

You would be much better off with a 4" diameter chamber that is 17" in length. The flame front burns in a spherical manner, and the less contact it has with the chamber walls (a short, fat chamber), the less heat energy it loses to the walls. Burn time is also greatly reduced. You may want to try multiple, evenly spaced spark gaps to increases burn rate and decrease energy loss.
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