From Wikipedia, the Free Encyclopedia s20

Putt Putt boat

Source http://www.spacetin.com/navigation_bars/Boats.html http://www.poppopboats.co.uk/

From Wikipedia, the free encyclopedia

A pop-pop boat is a toy with a very simple heat engine without moving parts, powered by a candle or oil burner. The name comes from the noise the boats make. Other names are putt-putt boat, crazy boat, flash-steamer, hot-air-boat, pulsating water engine boat. Around the world they may be called Can-Can-boot, Knatterboot, toc-toc, Puf-Puf boat, Poof Poof craft, Phut-Phut, or Pouet-Pouet.[1]

 Construction

Commercial pop pop boats have usually been made out of tin. The hull of the boat may be made out of any material that floats. Homemade pop pop boats are often made out of wood.

The boat's engine consists of a boiler and one or more exhaust tubes. While a single exhaust tube may be used, two exhaust tubes are much more commonly used. This is due to the fact that the boiler and the exhaust tubes have to be filled with water, and using two tubes allows water to be injected into one tube while air inside the engine escapes through the other tube. It is more difficult to remove the air and completely fill single exhaust tube types. The boiler and exhaust tubes are usually made out of metal, with tin or copper being common.

Boiler designs vary. Simple metal containers in the shape of a box or cylinder are common. A more efficient boiler can be made by using a metal pan whose top is a slightly concave diaphragm made out of a very thin, springy metal. Many pop pop boats have used a single tube of metal, which is formed into a coil in its center and left straight on both ends to form the exhausts. The coil in this version functions as the boiler.

A heating element of some sort is placed under the boiler. Candles or small oil burners are commonly used. History

The diaphragm type pop pop design. Coil type pop pop design.

Credit for the first pop pop boat is usually given to a Frenchman named Thomas Piot. In 1891, Piot filed a patent in the UK for a simple pop pop boat using a small boiler and two exhaust tubes.[2][3]. A 1975 article by Basil Harley mentions a similar boat seen in a French journal from 1880, indicating that this type of toy may have existed for many years prior to Piot's patent.

In 1915, an American named Charles J McHugh filed a patent for the diaphragm type of engine, which was an improvement to Piot's design.[4]

In 1920, William Purcell filed a patent for the coiled tube type of engine.[5] This type of engine has been very popular over the years with homemade pop pop boats, due to its simplicity of construction. The Cub Scout book (published by the Boy Scouts of America) contained a project called a "Jet Boat" for many years. This project used a coil type of engine based on Purcell's design which was placed in a wooden hull. Many commercial pop pop boats have also used this type of engine, due to its low cost.

Charles McHugh filed another patent in 1926. This was also for a diaphragm type of engine. This version refined the design so that it could be more easily produced commercially.[6]

In 1934, Paul Jones filed a patent for another diaphragm design. This was another refinement designed to improve commercial production. Jones' version of the engine could be easily produced from simple stamped parts.[7]

Many pop pop boats produced in the 1920s had a single exhaust pipe. Designs using two exhaust pipes are easier to fill, and have been much more common over the years.

Pop pop boats were popular for many years, especially in the 1940s and 1950s. Pop pop boats declined in popularity along with other tin toys in the latter half of the 20th century as plastic toys took over much of the market. While they are no longer produced in as large of numbers, pop pop boats continue to be produced today.

Pop pop boats have been produced in many varieties over the years. Some have been very simple and inexpensive, while others have been much more ornate and artistic. As with many toys, these boats are often sought by collectors, and the prices paid vary depending on the boat's rarity and design. Principle of operation

Pop-pop engine with a candle, a heating tank and two pipes (small arrows located at the end of the two pipes try to schematize the circulation of water).

A pop pop boat is powered by a very simple heat engine. This engine consists of a small boiler, which is connected to an exhaust tube. When heat is applied to the boiler, water in the boiler flashes into steam. The expanding steam pushes out the slug of water in the exhaust tube, propelling the boat forwards by a pulse of water. The steam bubble then condenses, creating a vacuum which draws water back in through the exhaust tube. The cooled water that is brought back into the boiler is then heated and flashed into steam, and the cycle keeps repeating. This constant flashing and cooling cycle of the engine creates the distinctive "pop pop" noise for which the boat is named. This noise is more pronounced when a diaphragm type boiler is used. Coil type boilers are much more quiet.

The operation of a pop pop boat is often poorly understood, because many people mistakenly assume that if water is only going in and out through the exhaust tube then the boat should only shake back and forth. The key principle is that the water being propelled out the back of the boat is directional, but the water being drawn back in on the second half of the cycle is not a directional jet, but instead is drawn in from all directions equally. This asymmetry is what propels the boat forward.[8][9]

The same principle can be demonstrated by blowing out a candle. It is easy to extinguish a candle by blowing on it, since all of the air being expelled is moving in one direction, being concentrated. However, it is difficult to put out the flame by sucking in air, since the air being sucked in comes from all directions, and not just the direction of the candle. [10]

An internal combustion version would be a valveless pulse jet which works on the same principle, only the working fluid is air, even though it is not a liquid.

Note that in pop pop boats with two exhaust tubes, the water is expelled from both tubes during the first phase of the cycle, and drawn in from both tubes during the second phase of the cycle. The water does not circulate in through one tube and out through the other.