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my first spud gun

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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my first spud gun

Unread postAuthor: 94celica » Tue Sep 25, 2007 7:54 pm

hi im new here, well yesterday i made a potato gun, it has a 4in I.D. chamber that is 20in long and the barrel is 2in I.D and is 20in long, is this good
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Unread postAuthor: spudgunnerwryyyyy » Tue Sep 25, 2007 8:01 pm

Your barrel could be like three feet long and with that change the gun would have better performance.
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Unread postAuthor: Fnord » Tue Sep 25, 2007 8:01 pm

I would put a longer barrel on it. It will be extremely loud with a 20" barrel, and with a chamber that size you could extend it up to about 8 feet if you want to get the most power possible.

Consider putting an 80mm computer case fan in the chamber. It will increase preformace.
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Unread postAuthor: 94celica » Tue Sep 25, 2007 8:33 pm

well i want to shorten the chamber, i also have a 40in barrel, how much should i shorten the chamber, yes it is loud
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Unread postAuthor: LikimysCrotchus5 » Tue Sep 25, 2007 10:53 pm

It would be better if you posted pics
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Unread postAuthor: jimmy101 » Wed Sep 26, 2007 11:20 am

Read up on "CB Ratio" on the Spud wiki;
http://www.spudfiles.com/spud_wiki/inde ... rrel_ratio

For a generic combustion spudgun you want the chamber volume to be 50% to 100% of the barrel volume, that is, a CB ratio in the range of 0.5 to 1.0.

For the original chamber volume, a 2" ID barrel should be 40 to 80 inches long for optimal performance.

If you cut the chamber length in half then the barrel length should be cut in half as well, giving a barrel 20 to 40 inches long.
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