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mini tennis ball cannon

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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mini tennis ball cannon

Unread postAuthor: homedepotpro » Tue Jun 05, 2007 6:15 pm

I want to make a small sturdy hair spray combustion gun that is not too loud and easily shot inside a confined area. I also don't want too much power, maybe able to shot like 40-60 yards. The noise is the main issue, i don't want it to draw too much attention. My main question is what should the length of the barrel and diameter/length of the chamber be to accommodate these characteristics.

here is a rough idea that includes some of the components that i want:
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Unread postAuthor: hi » Tue Jun 05, 2007 6:32 pm

if you built it as a pneumatic it wouldnt be loud at all.

to answer your question, it would need a 3'' chamber about 1 foot long and a 2.5'' barrel about 2 1/2 feet long. thats how i would build it.
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Unread postAuthor: Arborman » Tue Jun 05, 2007 7:24 pm

pneumatics can soooo be very loud. thats relly only if you use a piston valve though.

you should consider a modded sprinkler valve pneumatic. i use mine in state parks where rules are tight and patrols are frequent. it is very quiet, and if you use a lower C:B ratio you will definently get what you want.

but then again, there is the whole compressor thing.
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Unread postAuthor: homedepotpro » Tue Jun 05, 2007 7:35 pm

yeah i want it to be portable and simple
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Unread postAuthor: experament-u2 » Tue Jun 05, 2007 10:27 pm

its being a while since iv made a combustion but dosnt a longer barrel help the noise problem a bit cause shorter ones are louder?
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Unread postAuthor: homedepotpro » Tue Jun 05, 2007 11:44 pm

i think short is louder because the gas expands more rapidly. That is why i want to know what the C:B ratio should be
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Unread postAuthor: hi » Tue Jun 05, 2007 11:54 pm

thats why hand guns are louder than rifles even though rifles fire larger rounds.
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Unread postAuthor: jimmy101 » Wed Jun 06, 2007 6:35 pm

For a 3"D chamber I would start with a chamber of ~6" length.
Chamber volume=42ci

Make a 2.5"D x ~24" barrel and see how it performs and how loud it is.
Barrel volume=118ci
So you will have a ~1:2.8 C:B ratio (0.35:1 as people would normally write it).


Shorten the barrel to increase performance, at the expense of more noise, unitl you get the performance you want.

Probably would be easier to get it quite if you use CO2 or propane in a simple pneumatic.
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Unread postAuthor: lukemc » Wed Jun 06, 2007 6:42 pm

you should do what jimmy said but with a shorter barrel and a silencer. they arnt perticulary hard to make but can be made just by drilling a bunch of holes from about 6" down to the muzzle then wraping carpet or foam around it and then some lager pvc over that
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Unread postAuthor: jimmy101 » Thu Jun 07, 2007 4:11 pm

If the ATF finds you with a silencer, even on a spudgun, they will ...

... and I don't think you'll be released after a day or two like Paris Hilton was.

(I assume HomeDepotPro is in the USofA)
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