I still haven't managed to get a metal pengun to work so far, so I'm just gonna use my RAP pens (they're awesome, rifled and thick, but not brittle-they split like abs, rather than shattering like pvc.) until I can iron all the bugs out.. When I've got the plastic one working I'll nick some of dad's...

Cool. Instead of fiber glassing I'd recommend epoxying it and then tightly wrapping it in a braided fishing line such as spectra. Cool to see this piston working though.

Good idea. I know barrels can get in the way but I've been building mini's lately so it hasn't been much of a problem.

Ohh I was under the impression they were using the plans as payment or something like that :\ oh well..cool anyway

Awesome, lucky to get free work like that done.

Cool design also, which cad program did you use?

Wouldn't you be needing a pressure chamber for any real kind of power? It's probably best to just make a gasket and a locking mechanism to hold it shut. It'd be a fair bit simpler if it was built as a combustion.

Even if using a bv (and fan hopefully) still try to build it to have access to your chamber. In the how to section theres an advanced combustion guide which has good advice on fuel metering and an excel spreadsheet.

psycix wrote:Well then maybe its an oxygen cylinder used for welding or something like that.

That's oxy-acet with a blowtorch like attachment you're thinking about. MIG welders use a noble gas like neon or argon to prevent burning.

http://i266.photobucket.com/albums/ii259/nonicknameowns/CO2engine001.jpg Complete engine. http://i266.photobucket.com/albums/ii259/nonicknameowns/CO2engine002.jpg Rear of engine with cylinder removed. http://i266.photobucket.com/albums/ii259/nonicknameowns/CO2engine003.jpg Piston and crankshaft. ht...

Cool, good luck. For my year 9 metalwork project I machined an air/CO2 engine. I'll post some pics in a min..

I'd just reccomend a compressor, as long as it has a decent sized tank. If it's a good one it may have enough flow to power your gun even without a fully pressurised tank. And btw It's not very smart (like psy said) to use pure O2 in any cannon that has substantial friction...Or combustions

Similar to JSR's blow forward breech, except when fired his moved the bolt forward, allowing the burst of pressurised air through. I like yours though, but do a quick search for jsr's, it's pretty good. (most things he makes are..) EDIT: http://www.spudfiles.com/forums/6mm-semi-added-trigger-and-mag...

That's extremely common in spud guns. Old concept. still is a good idea though..

I made a pen gun similar to your second one (except shorter and from aluminium) but the piston didn't seal the barrel. I just got some stainless tubing so I'm making another today with a cast piston. I like it, quite honest how you show all your projects. Maybe you show try get some copper pipe from...

Cool gun 8) . You weren't covering the barrel during firing where you?