MINI troubles

[urgle the danish cow]

I have been trying to make a few mini co-axial piston valve guns and have not been succeeding very much. the problem i keep having is that the piston will seal but it wont pilot? i am using a schrader valve to fill and pilot and my pistons have all been machined nylon with rubber sealing faces. what am i doing wrong?

[streetfire]

maybe the air isn't getting past the piston so there is nothing to fire make a small cut in the piston to let air through

[urgle the danish cow]

maybe the air isn't getting past the piston so there is nothing to fire make a small cut in the piston to let air through

its under size, the tube inner diameter is .478 and my piston is .465

[Brian the brain]

That littlebit of blowby could be huge in comparison.
How big is the barrel?
If that takes up a large portion of the sealing face and you have blowby...

well.....
there's your problem..

If you are able to machine the pistons, why not add a floating O-ring that works like a checkvalve..

[urgle the danish cow]

That littlebit of blowby could be huge in comparison.
How big is the barrel?
If that takes up a large portion of the sealing face and you have blowby...

well.....
there's your problem..

If you are able to machine the pistons, why not add a floating O-ring that works like a checkvalve..

what do you mean? and the barrel is 6mm

[jackssmirkingrevenge]

do the math, here's an example: http://www.spudfiles.com/forums/viewtop ... tml#327579