| Drinking bird | |
|---|---|
Drinking Bird about to dip its beak in the water |
|
| Classification | Heat engines |
| Application | Toy, Scientific demonstration |
| Fuel Source | Heat transfer |
| Components | Bulbs, Tube, Axle, Support |
| Inventor | Miles V. Sullivan |
| Invented | 1945 |
Drinking birds, also known as dippy birds and dipping birds,[1] are toy heat engines that mimic the motions of a bird drinking from a fountain or other water source. They are sometimes incorrectly considered examples of a perpetual motion device.
Contents |
A drinking bird consists of two glass bulbs joined by a glass tube (the bird's neck). The tube extends nearly all the way into the bottom bulb, and attaches to the top bulb but does not extend into it. The space inside the bird contains a fluid, usually colored. The fluid is typically dichloromethane, also known as methylene chloride. Formerly trichloromonofluoromethane was used.
Air is removed from the apparatus during manufacture, so the space inside the body is filled by vapor evaporated from the fluid. The upper bulb has a "beak" attached which, along with the head, is covered in a felt-like material. The bird is typically decorated with paper eyes, a plastic top hat, and one or more tail feathers. The whole setup pivots on an adjustable crosspiece attached to the neck.
Despite the drinking bird's appearance and classification as a toy, some safety considerations apply. Early models were often filled with highly flammable substances. The fluid in later versions is nonflammable. Dichloromethane can irritate the skin on contact, and the lungs if inhaled; it is a mutagen and teratogen, and potentially a carcinogen. The intact toy is leakproof and completely safe, but if broken hazardous dichloromethane is released. Dichloromethane evaporates quickly; good ventilation after a spill will dilute and disperse the vapor.
The drinking bird is an interesting exhibition of several physical laws and is therefore a staple of basic chemistry and physics education. These include:
The drinking bird is a heat engine that exploits a temperature differential to convert heat energy to a pressure differential within the device, and perform mechanical work. Like all heat engines, the drinking bird works through a thermodynamic cycle. The initial state of the system is a bird with a wet head oriented vertically with an initial oscillation on its pivot.
The process operates as follows:[2]
If a glass of water is placed so that the beak dips into it on its descent, the bird will continue to absorb water and the cycle will continue as long as there is enough water in the glass to keep the head wet. However, the bird will continue to dip even without a source of water, as long as the head is wet, or as long as a temperature differential is maintained between the head and body. This differential can be generated without evaporative cooling in the head—for instance, a heat source directed at the bottom bulb will create a pressure differential between top and bottom that will drive the engine. The ultimate source of energy is the temperature gradient between the toy and the surrounding environment—the toy is not a perpetual motion machine.
An analysis[3] showed that the evaporative heat flux driving a small bird was about 1⁄2 W, whereas the mechanical power expressed in bird's motion was about 1⁄20,000 W. The system efficiency is about 0.01%. More practically, about 1⁄1,000,000 W can be extracted from the bird, either with a coil/magnet or a ratchet used to winch paperclips.
A 'dunking bird of the second kind' was introduced [4], which, while similar to the original drinking bird, is not a heat engine, and will operate without a temperature difference, instead extracting free energy directly from the evaporation of water.
Such a bird works as follows: It is balanced such that, when dry, it tips into a head down position. The bird is placed next to a water source such that this position brings its beak into contact with water. Water is then lifted into the beak by capillary action (the authors used a triangular sponge) and carried past the fulcrum. When enough water has been raised, the bird tips into a head up position. With the beak out of the water, eventually enough water evaporate from the sponge for the head to tip down again.
The drinking bird was invented by Miles V. Sullivan and co-developed by George H. Shackley in 1945 and patented in 1946. He was a Ph.D. inventor-scientist at Bell Labs in Murray Hill, NJ, USA. U.S. Patent 2,402,463. The patent was titled "Activated Amusement Device." [5]
The drinking bird has been used in many fictional contexts to automatically press buttons. In The Simpsons episode "King-Size Homer", Homer used one to repeatedly press a key on a computer keyboard. Two of them were used in the 1990 film Darkman to set off explosions. Drinking birds have appeared as part of a Rube Goldberg machine in the film Pee-wee's Big Adventure[6] and the Family Guy episode "8 Simple Rules for Buying My Teenage Daughter".
Drinking birds have been featured as plot elements in the 1951 Merrie Melodies cartoon Putty Tat Trouble and the 1968 science fiction thriller The Power. They have also had minor appearances in several movies and TV shows, including the Woody Allen movie Sleeper, the 1979 science fiction film "Alien", the 2008 film "Max Payne", the 2010 film "Megamind", and episodes of the American TV shows The Simpsons and Mad Men.
Among video games, the drinking bird appeared as the "dunkin' dragon" in the Sierra game Quest for Glory I (1989), in the Gremlin Interactive game Normality (1996), and as a "water bird" furniture item in the Animal Crossing games (1999).