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Mini Coaxial Piston.

Discuss miniature cannons built from things such as pill bottles and pen caps.
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Mini Coaxial Piston.

Unread postAuthor: clemsonguy1125 » Sun Jan 17, 2010 6:56 pm

Im building a mini coaxial gun from 1/2 in copper. The barrels a piece of brake line. All I have left to do is epoxy it together and add the piston. My question is whats the best was to build the piston. Ive considered using epoxy or bondo but wasnt sure about the air leaking around the epoxy piston. Do i need to cut a groove in it, and what size if so. Also is there a way to make it serviceable without using fittings,would using screws work.
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Re: Mini Coaxial Piston.

Unread postAuthor: jackssmirkingrevenge » Sun Jan 17, 2010 10:06 pm

clemsonguy1125 wrote:I've considered using epoxy or bondo but wasn't sure about the air leaking around the epoxy piston. Do I need to cut a groove in it, and what size if so.


Works perfectly well for me, I've never needed to make an equalisation hole or groove because unless you put in an o-ring, the piston will never be 100% airtight.

Also is there a way to make it serviceable without using fittings, would using screws work


You could conceivable cast an epoxy plug with an o-ring for airtightness that is held in with screws.
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Unread postAuthor: theBOOM » Mon Jan 18, 2010 2:41 am

For convenience I would use hotglue for the piston its relatively light and not brittle at all and to attach a sealing face you just have to heat up and press the sealing face down...

Why not just get some 1/2" fittings, I think you're gonna have a hard time using screws as it will be hard to get a 100% seal unless you tap the screws in with the corresponding tap.... to much work IMO?
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Unread postAuthor: chinnerz » Mon Jan 18, 2010 3:16 am

indeed, hotglue is a good idea, however make it longer than half the ID of your chamber, or this may happen http://www.spudfiles.com/forums/something-bad-happened-help-needed-t20128.html
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Unread postAuthor: clemsonguy1125 » Mon Jan 18, 2010 12:29 pm

Well last night will looking for some hot glue sticks I found a marker cap thats slides easily and while looking through the chamber with a piston in it you cant see lite so I ll use that
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