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Aluminum mini-mini combustion spudgun idea

Discuss miniature cannons built from things such as pill bottles and pen caps.
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Aluminum mini-mini combustion spudgun idea

Unread postAuthor: 88pathoffroad » Tue Dec 08, 2009 11:33 pm

I scored some nice limited-edition anodized aluminum 7-11 Slurpee straws recently with the thought that I'd like to try to use one to make a nice all-aluminum mini spudgun. I have an aluminum cable TV fitting with o-ringed caps I'd like to use for the combustion chamber. I'm going to sand and polish the chamber and leave the barrel anodized (I scored red, gold and purple).

After calculating the volume of the barrel and the chamber I chose, it comes out to about 1.3:1. I used mm to measure because trying to calculate volumes with fractions of inches gave me a headache... ;)

Barrel: 9mm x 255mm
Chamber: 15mm x 70mm

My math's not off, is it?

All told, the whole thing will measure 12.5 inches long (or 32 cm). Butane fuel, lighter ignition via externally mounted sparker with small wires epoxied into holes drilled in the chamber. I'll use epoxy to seal the barrel to the chamber after drilling the cap to the outer diameter of the barrel for a snug fit. Maybe I could slide an o-ring on the barrel inside and out before epoxying? Hmmm. Probably not all that much pressure in a chamber so small, but it'd be nice to not get burnt by venting exhaust through a small opening...

Thoughts? :D
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Re: Aluminum mini-mini combustion spudgun idea

Unread postAuthor: jackssmirkingrevenge » Wed Dec 09, 2009 12:32 am

88pathoffroad wrote:I used mm to measure because trying to calculate volumes with fractions of inches gave me a headache... ;)


gooooooo metric system! :D

Since you're using an aluminium body, make sure your ignition points are well insulated.
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Unread postAuthor: starman » Wed Dec 09, 2009 7:50 am

Your fuel/air mix will be difficult to get right because of the small chamber space. If you want consistent shots from it, you should think about using something along the lines of a hypodermic syringe to meter the fuel.

Yeah what Jack said...what are you using for ignition?
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