Without the tennis ball, you'd still get a heck of a bang! In my neighborhood, you'd see small groups of kids, all carrying these cannons around. It was a real fad and I wonder how older residents put up with it. That was near sea level in PA. When I moved to a mile high, I made one for the 4th and it wouldn't work. Due to the lighter fluid recipe being changed or the increased elevation is my guess.
