Although recently brought back to some degree of interest after, appearing in Hayao Miyasaki’s “Ponyo,” these tin toy boats have been chugging around the world for over a century.
Of course it depends on who you ask, but the “Pon Pon Maru” was officially credited to a Frenchman named Thomas Piot in 1891, and was later improved by American Charles J McHugh in 1915. The basis of the design contains no moving parts and is powered by a simple steam-engine-like propulsion system. The more common examples are made up of a small, disc-like diaphragm made of tin or copper with two pipes leading from it into the water. After water is forced into the diaphragm through one of the pipes, a heating element (usually a candle) is placed under it. Once the water heats to a vapor it is expelled out of both pipes and propels the boat forward. The vacuum created in the diaphragm from the exhausted steam then pulls water back up into the diaphragm, and the process is repeated again. This action is what gives the boat its trademark sound as it zips along the water.
Whether you call it a “Pop Pop Boat,” “Putt Putt,” “Knatterboot,” or the Japanese equivalent “Pon Pon Maru,” the simply designed toy craft is great physics powered fun!