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The Harley Davidson Tribute 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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Unread postAuthor: Slugfoot » Tue Dec 05, 2006 9:15 pm

Beautiful cannon......ruined. :lol: :lol:
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Unread postAuthor: schmanman » Tue Dec 05, 2006 9:24 pm

wow, I really like it. nice paint job. ha, my uncle rides Harley's too. he has a roadmaster with tons of stuff on it.

drac, you saved the cam-locks and stuff, right? It looks like a nice cannon you made, but the chamber design is a bit odd. but then again, trial and error like that is how spud guns became this advanced. :wink:
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Unread postAuthor: MikeNice » Wed Dec 06, 2006 12:43 am

Chamber is 4 x18 barrel is 2 x 48. I know if you do the math it comes nowhere near the golden 1.5:1 C:B ratio, but I have experimented with longer barrels and it just doesn't see to shoot as well. This is a way kick ass powerful gun, I've blown holes in at least 1/2" plywood with a gun of the exact same measurements using a potato and Right Guard (before they ruined it). The sizes I used for it work extremely well. I've also messed around with ignition point placement and have found no advantage to placing them across from each other in a line. You may know something I don't TaTer, but this is working pretty good for me. I'll dig up the pic of the plywood sign I blasted and put it up here. I'm glad ya'll dig the gun. Hey Slugfoot . . . "Beautiful cannon......ruined. " ?????? I think I missed it.
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Unread postAuthor: SpudBlaster15 » Wed Dec 06, 2006 12:56 am

Your ratio is approximately 1.5:1. That said, the 1.5:1 ratio is FAR from optimal for a fixed chamber size. Doubling the barrel length would result in a huge increase in power, unless you are using a crappy propellant such as hairspray.

You are probably misinterpreting the reduction in noise output that a longer barrel provides as a reduction in muzzle velocity. Most people believe that if their gun makes a loud noise it is "powerful". Inefficiency is not something you should deliberatly seek.
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Unread postAuthor: MikeNice » Wed Dec 06, 2006 8:38 am

When I was expeimenting barrel lengths I was doing hangtime tests. I built a wood stand that held it prety close to vertical. Although I wasn't using metered propane to get a perfectly consistant fuel load, and I WAS using potatos which may have varied a few ounces, overall, the 48" barrel had consistantly longer hangtimes than the 50", 52", 54", 56", and 62" barrels that I was testing. (I had to look back at my notes for those) Obviously the fact that I wasn't using a measurable fuel load or consistantly weighted projectiles may have caused some variation in the results but overall I've been pretty satisfied with the conclusion of the 48" barrel working the best with my guns. Believe me if a diferent barrel did better I would have used that length. I was going for max power without having to step into metered propane. "Inefficiency is not something you should deliberatly seek." I couldn't agree with you more. These measurements do pretty well and I wouldn't say it's loud as hell, but it's pretty loud. Someday I'll get around to putting all the results on a spreadsheet and I'll post them somewhere.
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Unread postAuthor: SpudBlaster15 » Wed Dec 06, 2006 6:49 pm

Were you using a chamber fan to properly mix the fuel before the shot? Obviously, the "ideal" C:B ratio assumes that all (or most) of the energy that is available is released, and without a chamber fan, only a portion of the fuel actually reacts.
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Unread postAuthor: MikeNice » Wed Dec 06, 2006 10:01 pm

No, I've never used a chamber fan but I do use dual ignition to hopefully ignite as much as possible. I've had plans for a long time to build a metered propane, stun gun powered, gun with a chamber fan. I've been pretty content with the simplicity / power of the guns I have built so far though so I'm in no real rush with those.
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Unread postAuthor: SpudBlaster15 » Wed Dec 06, 2006 11:26 pm

An additional spark gap really doesnt make much of a difference if the air and fuel are not mixed properly.

That said, what kind of hang times were you achieving in your tests?
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Unread postAuthor: MikeNice » Sun Dec 10, 2006 3:44 pm

Depending on the barrel I was getting a lot of 10-12's with the occasional 13-14 throwing my averages off. The 48" barrel averaged mid 12's. What do you power a chamber fan with? I'm starting to really think about putting one in since you say it makes that big of a difference. Maybe I'll get out one of these weekends and do some hang time tests with and without a chamber fan . . . .
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Unread postAuthor: King_TaTer » Sun Dec 10, 2006 3:54 pm

well considering fans run on electricity you should use a battery. but I do think that it is sweet you got up to 14 secs of hang time...pretty sweet. also if you want to find out the ideal C:B ratio for certian porjectiles visit this site

http://www.burntlatke.com/
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Unread postAuthor: SpudBlaster15 » Sun Dec 10, 2006 4:20 pm

If you use a PC fan, run it off of a 9 volt battery wired to two AAs in series to deliver a total of 12 volts. However, I suggest a camping fan instead. Those only require two AAs in series, and spin several times faster than a PC fan.
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