The Craftmans Shop > Backyard Ballistics

Spud Gun

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doubleboost:
Hi
Just a few pictures of a stainless spug gun i built a few years ago the propelant was hairspray the results devistating






Regards
John

Brass_Machine:
Holy crap John! I built a much milder version a few years ago for my nephew. Made with PVC and an electric start (from grill). I believe we used Axe deodorant spray for the propellant.

Very cool

Eric

raynerd:
That looks fantastic. I teach chemistry and one of the physics teachers built a pressurised spud gun, similar scale to the one shown in the picture. You compressed air in a chamber which had a stop valve to the barrel. Jammed a potatoe in the barrel and then released the valve. To use it in school (they used it to look at projectiles or something at A level!) we had to have it police checked and they found that it was way over the legal limits and was classed as a firearm.

I really want to say this next bit but I`m sure I could be wrong: He then went to shorten the barrel a little bit and for some reason this increased the power upto a critical point - would this be correct?

Chris

Bernd:
Chris,

I've played around with this stuff. Although I haven't read or seen any specks it does kind of make sense.

If you think about it you are using air to propell the potatoe as the air expands it loses it's potenial. Were as with gun powder the hot gases expand. So shorting the barrel would seem to make sense since you are freeing the potatoe of friction sooner. If you extended the pipe or made it longer the friction would eventually stop the potatoe.

Does that make any sense to you. It just seems logical.

Bernd

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