The humble Pop-Pop boat has fascinated everyone from children to physicists for over a hundred years.
Otherwise known as flash-steamers, hot-air-boats, toc-tocs or more accurately a Pulsating Water Engine (P.W.E.), the pop-pop boat originated in an 1891 British patent for the coil type water pulse engines by an inventor named Thomas Piot.The popularity of the boats spread quickly, however, and they were soon being manufactured in many countries.
In early publications, mention is made of a series of boats made in the early 20th century by the German toy makers Ernst Planck. In 1916 a US patent was granted to Charles McHugh for the diaphragm type engine. The German name for the boat, toc-toc, originated as a product brand name for a diaphragm-boilered boat in the late 1920's, while they have also been called put-put, phut-phut, and pouet-pouet boats elsewhere.
There are two types of pop-pop engines. One is a copper tube coiled in the middle with both ends protruding from the rear of the boat. The other has two tubes connected to a boiler with a diaphragm that improves thrust and produces a popping sound.
The coil type boats are powered by a basic boiler comprising a thin coiled copper tube. The coils in the middle of the tube are positioned over a flame, which heats the water in the coils. The end of the tubes protrude from the back of the boat into the water. When the water boils, the expansion of the steam pushes the water out the tube at the back of the boat as a jet of steam, and the boat moves forward. After expansion, the steam cools to create a partial vacuum, sucking water back into the tubes to allow the cycle to begin again. It's that simple.
The diaphragm type engine is a slightly more sophisticated version which substitutes the coil with a shallow chamber with a flexible diaphragm for the coil. The flexing of the diaphragm gives a little more impulse to the escaping steam, as well as making a louder pop.
Pop Pop boat instructions
Place the candle into the fuel pan or pour a small amount of olive oil into the pan. Thread a wick through the holder and place it into the pan.
Prime the engine with water. Squirt water into a jet using the straw or syringe provided. Do this until water comes out the other jet.
Place the boat on the water trying not to let any water escape from the jets. Light the wick and carefully place the fuel pan beneath the water boiling pan.
After a little while, the boiler will heat up enough to create steam from the water inside. As the boiler gets hotter, the boat will get faster.
Pop-Pop boat troubleshooting
Most problems with pop pop boats are due to either no water in the boiler, improper heating of the boiler, or a clogged water tube. Using the straw or syringe provided, flush water through the tubes and place the boat in a tub of water without letting any water out of the tubes.
The Fuel Cells (candles) need up to 2 minutes before the candle generates enough heat to get the boat moving. If you are using olive oil, make sure the wick is not too short or too long. The proper length of the wick should be about 5 mm above the oil, the same goes for the candles. Other types of fuels either do not work well or will over heat the boiler causing damage to it.