why back in my day ..........
Before soda cans were all aluminum, they were the perfect size and configuration to make a tennis ball cannon, especially the ones with a pull tab.
We would cut the top and bottom out of about 6 cans. These were taped together with copious amounts of black tape to form a long barrel. One more can was taped to the bottom. The pull tab end up toward the barrel and the bottom .. well.. at the bottom. We then poked a small hole (just big enough for the tip of a lighter fluid can nozzle) into the bottom.
Now you shove a tennis ball down the throat of the contraption, its a tight fit, and squirt a little lighter fluid into the hole at the bottom. Give it a shake to vaporize it, then hold the bottom over a candle.
We had tennis balls going 2 blocks in the air.
