Barrel Sealing Piston Cannon Problem

[spudkilla224]

Hello, I built a barrel sealing piston valve cannon, and it seals against the barrel fine, but when i turn the 1/4" ball valve to exhuast the air behind the piston, all the air comes out from the air chamber. i don't think my piston is moving backwards.

my piston is made from two 1.25" couplers with a rubber sealing face.
my piston slides back and forth very easily. it just doesn't open when i try to exhuast the air.

i was thinking about adding a bolt with a 2" diameter fender washer to catch the air coming from the airchamber to help push the piston back. do you think that would work?

EDIT: my barrel size is 2", but the sealing face pipe is 1.5"

how do u find pilot volume?

[Carlman]

need more specs mate like barrel size chamber vol and pilot vol.

usually u need a bigger pilot valve

[MrCrowley]

While a larger pilot valve would work, cutting down the pilot volume by filling the extra space with a larger bumper or making the piston a tighter fit will increase performance while maintaining the smaller pilot valve.

Though a larger pilot valve never hurt nobody.

Along with leaks, this is the most common piston problem on the site, there'll be heaps of similar topics to help you out as well.