This is Version 1.0 of the Semi-Automatic Pneumatic Tennis Ball Air Cannon.
We built this first version of the semi-automatic style with the hopper all inline because we this configuration allowed for fewer connecting pieces.
You can see the magazine hopper feeding into the Y tube and then into the barrel. All 3 pieces are made with 2.5 inch schedule 40 PVC pipe.
The air canister at the back is made with 4 inch schedule 40 PVC with a rounded cap at one end, and a 4 inch to 1 inch reducer at the other. The reducer feeds into the 1 inch ball ball valve.
A single hole was drilled into the air reservoir / shock tank to accommodate a quick release air hose fitting. This configuration hooks directly into an air compressor with 100 psi (pounds per square inch) air output.
With the roughly 3 feet long barrel the tennis balls were flying almost 300 feet (100 yards). With a 7 foot barrel (which is unwieldy to say the least, but we wanted to test) the balls flew over 600 feet and outside the neighborhood, never to be seen again.
p.s. My GAWD my garage is a mess!!! 😀