A pop-pop boat (also known as a flash-steamer, hot-air-boat, or toc-toc after a German version from the 1920s [1] ) is a toy with a simple steam engine without moving parts, typically powered by a candle or vegetable oil burner. The name comes from the noise made by some versions of the boats.
Initially patented in 1891, the concept has undergone a number of changes and subsequent patents.
The engine consists of a boiler and one or more exhaust tubes, in which an oscillation of the water is established in the tubes to eject water out the exhaust tubes in pulses to propel the boat.
Credit for the first pop pop boat is usually given to a Frenchman named Thomas Piot. In 1891, Piot filed a patent application 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.[ citation needed ]
In 1915, an American named Charles J. McHugh filed a patent application 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 common over the years in 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.
McHugh filed for another patent in 1926. This was again a diaphragm engine design, refined so that it could be more easily fabricated commercially. [6] In 1934, Paul Jones filed a patent for another diaphragm design which could be produced industrially 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 such large numbers, pop pop boats continue to be produced. These toys have come in many varieties over the years. Some have been simple and inexpensive, while others have been much more ornate and artistic. As with many toys, pop pop boats are often sought by collectors, and the prices paid vary depending on rarity and design.
A pop pop boat is powered by a simple heat engine. This engine, sometimes referred to as a pulsating water engine, [1] consists of a boiler and one or more exhaust tubes. A heating element of some sort is placed under the boiler. Candles or small oil burners are commonly used. While a single exhaust tube may be used, two exhaust tubes are much more commonly used. This is because 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. The boiler and exhaust tubes are usually made out of metal, with tin or copper being common.
When heat is applied to the boiler, water in the boiler evaporates, producing steam. The expanding steam is suddenly pushed out of the boiler,[ dubious – discuss ] making a "pop" sound, and pushes some of the water out of the exhaust tube, propelling the boat forward. The boiler is now dry, and cannot, therefore, generate any more steam. The momentum of the column of water in the exhaust tube keeps it moving outward, so that the pressure inside the boiler drops below atmospheric pressure. In the case of a diaphragm type engine, the boiler also bulges inward at this point, also making a popping sound. The pressure outside the boiler now forces water back into the boiler.[ dubious – discuss ] This water then boils and the cycle repeats.[ dubious – discuss ] The popping noise is more pronounced when a diaphragm-type boiler is used: coil-type boilers are much quieter.
Any air in the boiler can act as a spring and support the oscillation of the water, but if too much air enters the boiler, the oscillation stops because all the water has been displaced, and no steam can be generated. Water contains some dissolved air, which can build up in the engine during operation. Therefore, engines must "burp" out air periodically in order to run for a long time. [8]
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. The internal-combustion analog of the pop pop boat engine is the valveless pulse jet.
Commercial pop pop boats have usually been made out of tinplate. The hull of the boat may be made out of any material that floats. Homemade pop pop boats are often made out of wood.
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 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.
The operation of the pop pop boat may seem surprising, since one might expect that if water is going in and out through the exhaust tube, the boat should merely shake back and forth. But while the water pushed out carries away with it momentum, which must be balanced (by Newton's third law) by an opposite momentum on the part of the boat, the water sucked in quickly impinges on the boiler tank and transfers its momentum to the boat. The initial reaction force on the boat (which would pull it backwards) is therefore cancelled by the pushing of the water when it hits the inside of the boiler. The result is that the inflow of water causes no appreciable force on the boat. [9]
Some authors have argued that the reason why the pop pop boat works is that the water being propelled out the back of the boat forms a narrow jet, while the water being drawn back in on the second half of the cycle is drawn in from all directions. [10] [11] This asymmetry may be seen as well in the way in which one blows out a candle: it is easy to extinguish a candle by blowing on it, since all of the air expelled is moving in a concentrated, directional jet. However, it is difficult to put out the flame by sucking in air, the air being sucked in coming from all directions. [3] This observation, though correct, may be misleading as an explanation of why the pop pop boat moves forward. The asymmetry of the shapes of the inflow and the outflow is a consequence of the viscosity of water, whereas the boat would be able to operate in an ideal fluid. [9] Furthermore, as they pass through the exhausts, the inflowing and the outflowing water carry the same momentum (in opposite directions), relative to the boat. The important difference is that the momentum of the outflow is expelled, whereas the momentum of the inflow is soon transferred to the boat. [9] The sucking/blowing asymmetry does make the boat more efficient, even if it's not the principle on which it operates.
The physics of the operation of the pop pop boat is similar to that of the Feynman sprinkler, a submerged sprinkler which is seen to turn weakly or not at all as water is sucked in through it. In both cases, the reaction force on the solid device caused by the sucking in of the fluid is balanced by the fluid impinging on the inside of the device. [9] [12]
The pop pop boat featured prominently in the 2008 Japanese animated fantasy film Ponyo . [13] Toy boats with a diaphragm type engine, like the one shown in the film, were produced and sold as a tie-in when the movie was released. [14]
A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be transformed by a connecting rod and crank into rotational force for work. The term "steam engine" is most commonly applied to reciprocating engines as just described, although some authorities have also referred to the steam turbine and devices such as Hero's aeolipile as "steam engines". The essential feature of steam engines is that they are external combustion engines, where the working fluid is separated from the combustion products. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle. In general usage, the term steam engine can refer to either complete steam plants, such as railway steam locomotives and portable engines, or may refer to the piston or turbine machinery alone, as in the beam engine and stationary steam engine.
A pulsejet engine is a type of jet engine in which combustion occurs in pulses. A pulsejet engine can be made with few or no moving parts, and is capable of running statically. The best known example is the Argus As 109-014 used to propel Nazi Germany's V-1 flying bomb.
A boiler is a closed vessel in which fluid is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central heating, boiler-based power generation, cooking, and sanitation.
A check valve, non-return valve, reflux valve, retention valve, foot valve, or one-way valve is a valve that normally allows fluid to flow through it in only one direction.
An aeolipile, aeolipyle, or eolipile, from the Greek "Αἰόλου πύλη," lit. 'Aeolus gate', also known as a Hero'sengine, is a simple, bladeless radial steam turbine which spins when the central water container is heated. Torque is produced by steam jets exiting the turbine. The Greek-Egyptian mathematician and engineer Hero of Alexandria described the device in the 1st century AD, and many sources give him the credit for its invention. However, Vitruvius was the first to describe this appliance in his De architectura.
An injector is a system of ducting and nozzles used to direct the flow of a high-pressure fluid in such a way that a lower pressure fluid is entrained in the jet and carried through a duct to a region of higher pressure. It is a fluid-dynamic pump with no moving parts except a valve to control inlet flow.
A fire-tube boiler is a type of boiler invented in 1828 by Mark Seguin, in which hot gases pass from a fire through one or more tubes running through a sealed container of water. The heat of the gases is transferred through the walls of the tubes by thermal conduction, heating the water and ultimately creating steam.
A smokebox is one of the major basic parts of a steam locomotive exhaust system. Smoke and hot gases pass from the firebox through tubes where they pass heat to the surrounding water in the boiler. The smoke then enters the smokebox, and is exhausted to the atmosphere through the chimney. Early locomotives had no smokebox and relied on a long chimney to provide natural draught for the fire but smokeboxes were soon included in the design for two specific reasons. Firstly and most importantly, the blast of exhaust steam from the cylinders, when directed upwards through an airtight smokebox with an appropriate design of exhaust nozzle, effectively draws hot gases through the boiler tubes and flues and, consequently, fresh combustion air into the firebox. Secondly, the smokebox provides a convenient collection point for ash and cinders ("char") drawn through the boiler tubes, which can be easily cleaned out at the end of a working day. Without a smokebox, all char must pass up the chimney or it will collect in the tubes and flues themselves, gradually blocking them.
This timeline of heat engine technology describes how heat engines have been known since antiquity but have been made into increasingly useful devices since the 17th century as a better understanding of the processes involved was gained. A heat engine is any system that converts heat to mechanical energy, which can then be used to do mechanical work.They continue to be developed today.
A Feynman sprinkler, also referred to as a Feynman inverse sprinkler or reverse sprinkler, is a sprinkler-like device which is submerged in a tank and made to suck in the surrounding fluid. The question of how such a device would turn was the subject of an intense and remarkably long-lived debate. The device generally remains steady with no rotation, though with sufficiently low friction and high rate of inflow, it has been seen to turn weakly in the opposite direction of a conventional sprinkler.
Economizers, or economisers (UK), are mechanical devices intended to reduce energy consumption, or to perform useful function such as preheating a fluid. The term economizer is used for other purposes as well. Boiler, power plant, heating, refrigeration, ventilating, and air conditioning (HVAC) may all use economizers. In simple terms, an economizer is a heat exchanger.
The hot-bulb engine, also known as a semi-diesel or Akroyd engine, is a type of internal combustion engine in which fuel ignites by coming in contact with a red-hot metal surface inside a bulb, followed by the introduction of air (oxygen) compressed into the hot-bulb chamber by the rising piston. There is some ignition when the fuel is introduced, but it quickly uses up the available oxygen in the bulb. Vigorous ignition takes place only when sufficient oxygen is supplied to the hot-bulb chamber on the compression stroke of the engine.
A flash boiler is a type of water-tube boiler. The tubes are close together and water is pumped through them. A flash boiler differs from the type of monotube steam generator in which the tube is permanently filled with water. In a flash boiler, the tube is kept so hot that the water feed is quickly flashed into steam and superheated. Flash boilers had some use in automobiles in the 19th century and this use continued into the early 20th century.
A boiler or steam generator is a device used to create steam by applying heat energy to water. Although the definitions are somewhat flexible, it can be said that older steam generators were commonly termed boilers and worked at low to medium pressure but, at pressures above this, it is more usual to speak of a steam generator.
A shell or flued boiler is an early and relatively simple form of boiler used to make steam, usually for the purpose of driving a steam engine. The design marked a transitional stage in boiler development, between the early haystack boilers and the later multi-tube fire-tube boilers. A flued boiler is characterized by a large cylindrical boiler shell forming a tank of water, traversed by one or more large flues containing the furnace. These boilers appeared around the start of the 19th century and some forms remain in service today. Although mostly used for static steam plants, some were used in early steam vehicles, railway locomotives and ships.
A naphtha launch, sometimes called a "vapor launch", was a small motor launch, powered by a naphtha engine. They were a particularly American design, brought into being by a local law that made it impractical to use a steam launch for private use.
A vertical boiler with horizontal fire-tubes is a type of small vertical boiler, used to generate steam for small machinery. It is characterised by having many narrow fire-tubes, running horizontally.
Three-drum boilers are a class of water-tube boiler used to generate steam, typically to power ships. They are compact and of high evaporative power, factors that encourage this use. Other boiler designs may be more efficient, although bulkier, and so the three-drum pattern was rare as a land-based stationary boiler.
The Chaplin's patent distilling apparatus with Steam pump for circulating water attached was an early design of an evaporator, a device for producing fresh water on board ship by distillation of seawater. An example of this apparatus has been recovered from the wreck of SS Xantho (1872), an auxiliary steamship used in Australia to transport passengers and trade goods before ultimately sinking in Port Gregory, Western Australia in 1872. It is purported that the Alexander Chaplin distiller from the Xantho wreck is the only known surviving example of a Chaplin distilling apparatus on board a vessel of this period.
The Reed water tube boiler was a type of water tube boiler developed by J. W. Reed, manager of the engine works at Palmers Shipbuilding and Iron Company of Jarrow, England, where it was manufactured from 1893 to 1905. At this time, Palmers was a vertically integrated business: in its shipyard at Jarrow, using iron ore from its own mine in North Yorkshire, it produced the iron and steel needed for its ships, and engines and boilers of its own design.