Shrader valve screw on

[Sticky_Tape]

Hello I have a problem with a launcher I am making it is sort of a shell pneumatic and what I need is some attachment that can screw onto the shrader on the shell if I don't the piston in the shell will keep venting can sombody give the name of a attachment that can screw onto the shrader?

[Hawkeye]

A schrader seals itself. When you remove the pump, it won't leak. Many tires are left uncapped and hold pressure for long periods.

[Sticky_Tape]

Wait you don't understand. They shell that I am making has a low pilot camber volume and when you take off the pump a small amount of air comes out the same amout of air that would vent the piston I need a attachment that will stop that amount of air coming out of the shell when I take the pump off. What I am trying to say is I need the needle in the shrader not to be pushed in so that the air wont come out when I take the pump off.

[Maniac]

A ball valve!