Using a tea-light candle for heat, this little feller slowly putt-putts around. The can is still in one piece. I cut the opening so that the fold-out parts form the rider and the handlebars. Eighth-inch brass tubing is coiled over the candle. To operate, I just fill the tubing with tap water and then cap the ends with my fingers while submerging them to keep the tubing filled. I then light the candle. The heat expands the water, which pushes the boat forward. Colder water rushes in, and the process repeats, resulting in a vibrating putt-putt locomotion.