piston help

[Model12]

I just finished my piston cannon and now that its done I have tried it and when you pump the pilot up when you start getting to any pressure air starts whistling out of the barrel. I know the piston is against the barrel and my sealing face is the rubber from an airsoft sticky target, its really rubbery sticky stuff, also its tacky which I thought would be good. But the air keeps coming out of the barrel so has anyone else had this problem and how do you fix it?

[jrrdw]

Seal the bolt holding the sealing face to the piston.

[Model12]

Never thought about that, would 5 minute Epoxy work?

[jrrdw]

Never thought about that, would 5 minute Epoxy work?

Yea, just take the bolt back out and smeer a bunch in the hole and shove the bolt back in and retighten. Allow to cure fully before retrying.

[th3p0p0]

ok look that stuff that you are trying to use as a sealing face is not going to work. Thats why its not working. try bike tube.

[SpudUke5]

Not only what the others said but what are you pumping it with?

You usually want something that pums quickly and has a decent air flow.

[Model12]

Okay first I just epoxied the sealing face, now I filled the hole with epoxy and put the bolt in and also smeared some around the washer on the front just to be sure. If this doesn't work Ill fill up every little part on the piston with epoxy. By the way I'm using a bike pump which I know is very lame but when I'm at my Dad's place I can use the brand new large compressor for my guns. But I have hope because a couple times when testing I have heard the piston slam back just a little.

[MrCrowley]

ok look that stuff that you are trying to use as a sealing face is not going to work. Thats why its not working. try bike tube.

Not necessarily.

Like Jrrdw said, epoxy the bolt on the sealing face. Also make sure your seat (barrel) is perfectly flat.

If that doesn't work, try another sealing face.

Hmm bike pump could be your problem as well.
Try not to get epoxy on the actual sealing face as well.

[Model12]

YES!!! The Epoxy just dried and I tried it and it worked! It still leaks bad but I can just slap on more epoxy, but I got a Piston gun to work! This is only my third potato gun ever so thats awesome

Nevermind it shot kleenex but not a marble, so the piston got more epoxy

[MaxuS]

My third gun was a copper piston spudgun, actuated by a 1/2" QEV.
What pressure have you had it up too so far?
And what is your piston made from, my one was a bolt piston..

[Model12]

my piston is an end cap with washers and bolts and such

[psycix]

I dont know up to what pressures you pump, but my piston gun leaks air UNTIL about 2 bar (30PSI)
The piston just hasnt got enough pressure on it yet to make a firm seal.
When I pump it higher it doesnt leak anymore.