I failed to mention all the air powered baseball firing cannons I built when my son was in Little League. The kids were at first squeamish standing at the plate facing a booming cannon on the mound firing knuckle balls at them, but they got used to it. I never did hit any of them. What was most popular was using it for fly ball practice. I had a mobile compressor I put together from an old York car AC compressor belted to a 12V 1/3 hp motor. I could fire them as fast as they were returned to me, no matter how many were being fired. I just had to regulate the pressure so they would stay in the field. I still have the last one I built. I clocked the balls up to 103mph @ 40psi. I stopped there.