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Hot glue piston

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Hot glue piston

Unread postAuthor: Mr.Russ » Thu Feb 01, 2007 7:50 pm

Last night I made myself a hot glue piston, and i cracked it ouf ot the pvc today...

Its for a 1" chamber, i have the chamber, the piston doesnt fit in it well? its really hard to get in and the valve is open. This is for a relatively small chamber aswell, about 15cm long.

I can get pictures soon.

I also made a wooden piston but that leaks around it ALOT.

Any ideas on other pistons i can make that will be a tight fit?

Thanks
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Unread postAuthor: Hotwired » Thu Feb 01, 2007 7:58 pm

Polymorph might work.

If you click my signature link (not the picture one) my cannon has a moulded grip made of it.

If you value your sanity however make BLOODY SURE it does not touch the plastic when its softened. It sticks like tar to anything made of plastic when its soft. Line it with foil or something.

When its hard its supposed to be like nylon. I guess thats about right.
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Unread postAuthor: Mr.Russ » Thu Feb 01, 2007 8:02 pm

okay, well i have decided on this:

instead of filling 1" offcut with glue, im going to cut a piece of 3/4" pvc and put some rubber on the end, then fill that with glue and use that as my piston. If it is to loose i will find an O ring or something else to make it tight.

pics when done

EDIT: it has dried, i put my barrel in with a fitting, and i blow into the end, the air goes past the piston but it goes out the barrel. wtf?
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Unread postAuthor: Mr.Russ » Thu Feb 01, 2007 10:20 pm

Bump

I know not to double post but nobody is helping.
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Unread postAuthor: MrCrowley » Thu Feb 01, 2007 10:30 pm

You blew into the end? No bloody wonder it doesn't work. You either need a bike pump and a workout and pump like crazy or you need a air compressor with a tank and regulate it to abouve 30psi and it should move.
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Unread postAuthor: Mr.Russ » Thu Feb 01, 2007 10:35 pm

nooooooo.... like i was imitating air being in there by having a constant blow through it, it leaks out the barrel with that low pressure of air, whats it gonna do with higher?

Or am i doing it all completely wrong
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Unread postAuthor: Hotwired » Thu Feb 01, 2007 10:45 pm

You need the piston to smack into the sealing face and seal, as you increase the pressure after that it just gets tighter and there should be no leakage at all.

Blowing into it to imitate pressure is going to do bugger all. You can't create the kind of pressure needed.

I use QEV's which are essentially ultralight commercial piston valves and they need 20psi to seal, before that they'll leak and hiss.
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Unread postAuthor: Mr.Russ » Thu Feb 01, 2007 11:34 pm

okay. so i need to charge it up with a higher amount of pressure. Is there a way that i can add a secondary chamber? I dont think this one will be big enough.

thanks
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Unread postAuthor: MrCrowley » Fri Feb 02, 2007 12:04 am

Cut it off make it bigger or add an extension to it. You just need a air compressor with a tank and the piston will easily seal,or you could add o-rings and do it with a bike pump.
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