Golfball Cannon
A quick video showing my pneumatic golfball cannon, attached is a basic diagram of how the valve was created. There are several instructables that show similar construction.
http://i715.photobucket.com/albums/ww152/jor2daje/mypistonvalve.jpg?t=1248468706
http://i715.photobucket.com/albums/ww152/jor2daje/mypistonvalve.jpg?t=1248468706