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Coaxial Not Firing

Posted: Mon Dec 14, 2009 1:06 am
by FreakyShotGlass
Its been a while but I decided to finally make another cannon. But I have a problem the piston seals and pressure builds but when it comes time to fire all the pressure is released through the pilot valve which is a 20mm sprinkler valve. Is this because the piston is not tight enough and it will be back to the workshop to make a better one or is there something else at play?

Re: Coaxial Not Firing

Posted: Mon Dec 14, 2009 1:23 am
by jackssmirkingrevenge
FreakyShotGlass wrote:Is this because the piston is not tight enough
Probably ;)

Posted: Mon Dec 14, 2009 2:18 am
by Gippeto
Yup...the leading cause of "failure to actuate".

A distant second is likely surface area differential.

Posted: Mon Dec 14, 2009 2:52 am
by FreakyShotGlass
Ok I have it going now with a very tight piston but now it won't hold over 40 psi, past that it just leaks out of the barrel.

Posted: Mon Dec 14, 2009 3:28 am
by Willdebeers
You don't want it to tight, but not too loose. For the easy option, wrap it in tape until there is no play, but you can push it with your little finger.

Posted: Mon Dec 14, 2009 7:38 am
by Demon
To make the piston the more leak proof for cheap is to wrap around some very thin tape.