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What affects the Tone of the gun?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: ramses » Mon Feb 22, 2010 12:16 pm

jimmy101 wrote: Blow harder and the tone jumps (without pasing through intermediate frequencies) to twice the fundamental frequency.


excellent description, but in cylindrical bore closed pipe instruments, (like the clarinet) it overblows a 12th, rather than an octave. this is equivalent to 3x the fundamental. In a video I watched about flash powder, it was proven that the frequency decreases over distance. This is may or may not apply, since no part of the muzzle blast pressure wave is supersonic.
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thanks, and how about this...

Unread postAuthor: owmatooth » Sat Feb 27, 2010 9:40 am

Ok, I appreciate the replies, and wanted to throw out another observation-

My barrel is 24 inches, when I load a projectile, and push it down the barrel say 22 inches or so- I get a typical pop sound to it.

If I only push the projectile down 4 inches or so, I get a much deeper tone and only a mild decrease in distance...

but if I use a six inch barrell and push it down 4 inches I'm back to the same pop as the 24 inch barrel with the load all the way down. hmmm
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Unread postAuthor: jackssmirkingrevenge » Sat Feb 27, 2010 2:27 pm

It's certainly an unconventional specification you're looking at, is there any particular reason for it? I can understand wanting to suppress the shooting noise, but merely changing the tone is a bit weird :?
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Unread postAuthor: owmatooth » Sat Feb 27, 2010 2:56 pm

The end game is to bury the tube in a pirate cannon prop, for a boating pirate party in a few months. Actually launching projectiles is probably not going to be a major part, as the sound and effects will be the main part. I've been running it at 80psi with about a cup of water and no projectile and it does about what I'm looking for...

thanks all for the input
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Unread postAuthor: jimmy101 » Sat Feb 27, 2010 5:08 pm

If you haven't already seen it check out this instructable. I believe it is based on an old Popular Science article. Mostly for how to construct the outer shell so it actually looks like a 300 year old cannon. The guts (actual firing part) can be whatever you want.

A 1/4 cup or so of flower in the barrel will give a nice "smoke" cloud when fired.

Post a picture when you are done, sounds like a fun project.
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Re: thanks, and how about this...

Unread postAuthor: ramses » Sat Feb 27, 2010 9:44 pm

owmatooth wrote:Ok, I appreciate the replies, and wanted to throw out another observation-

My barrel is 24 inches, when I load a projectile, and push it down the barrel say 22 inches or so- I get a typical pop sound to it.

If I only push the projectile down 4 inches or so, I get a much deeper tone and only a mild decrease in distance...

but if I use a six inch barrell and push it down 4 inches I'm back to the same pop as the 24 inch barrel with the load all the way down. hmmm


weird... one would think that having it 4 inches in the barrel would cause shock heating of the air, raising the SOS and thus the pitch. I can only guess that without a projectile, you decrease the tendency for it to overblow. how id the transition to the larger diameter done? Could you post audio of each shot and a scale-ish drawing?
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