The Drinking Happy Bird
(Dippy Bird)
and his Pleasing Pet Plastic Palm "Pinkie"
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Chaos Glossary
Dippy Bird Data
Dippy Bird and the Carnot Cycle
Dippy Bird 6 MB Movie
Physics of the Dippy Bird (B. Houghton's peripatetic web site preserved)
The physics page has a number of references about the Dippy Bird
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This animation of the Dippy Bird is anatomically correct for a repeated cycle, but it does NOT exhibit the chaotic cycling of the true Bird. For that, you need the Bird itself or the MOVIE!
You can convert one of these gizmos to run without water. Remove the tail feather, paint the bulb very thinly with a flat back paint (careful not to add too much mass!) and place in the sun (window sill: outside may be too windy). I have a simple sneaky way to determine the difference in temperature on this version also. Be careful not to "cook" the bird, as it only has a narrow temperature range for stable operation. Play around with shading the bulb...
The Behavior of the Drinking Happy Bird is recorded at this link [CLICK HERE]. This is a SIX (6) MB movie. Don't play it unless you have serious bandwidth on your browser and a really hot wire for a connection. The Bird's behavior is caught between the cold of the head bulb and the relative warmth of the bottom bulb ( a difference in temperature of about 4 degrees Kelvin). I refuse to divulge the simple method to determine this...
The Bird is chaotic in the sense that its dippy behavior is regular but not predictable. There are several ways in which data sets reflecting the dippiness of the Bird can be recorded.
You may get a Bird. Parental supervision required as it is easy to break! Edmund Scientifics (www.edsci.com) has them for sale.
Caveat: These Birds are not toys!
They are made of glass filled with a fluid (methylene chloride), a gas phase (freon, a chlorofluorocarbon) and a really penetrating dye. Take care of your Bird by keeping it in a place where it will be protected from strong sunlight and will not tip over. Furthermore, you should use distilled water in its dipping cup to avoid mineral stalactites developing on its lower bulb. Try not to get fingerprints on it, because that will interfere with its temperature exchanges.
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FROM THE MOVIE! In full color! The Drinking Bird in various stages of its dipping cycle
FAR RIGHT: Behind vertical rest, because momentum of the recovery swing has moved the bird past resting position.
MIDDLE: Beginning of a HEAT EXCHANGE packet or bubble of freon gas. The blue fluid can be seen around the freon bubble (note it extends clear to the bulb under the green feather of the tail).
FAR LEFT: The finished heat exchange of a packet of warm freon to the evaporatively cooled head end.
The heat exchange occurs in two thirds of a second (20 frames at 29.95 frames per second), too fast for the transferred packet of freon vapor to come to equilibrium with its surroundings. This is analogous to the adiabatic heating of a packet of air at the ground on the afternoon of a humid sunny day. The packet of heated air rises too quickly to come to equilibrium with surrounding air. When it reaches cool air aloft, the moisture in the packet condenses and starts to form a cloud. The bases of clouds mark a boundary between air masses.
For the bird, the equilibration presumably occurs during the smaller dips between reset dips and may well be reflected in their number and frequency.
Counter-Intuitive Department for gases on the move...
Question: Is a packet of dry air heavier or lighter than the same packet (same number of molecules of gas) of wet air?
Answer: Consider a group of 12 "air" molecules (OK, I know that the gases are molecular nitrogen at 28 g/mole and molecular oxygen at 32 g/mole), so we will simplify this by assuming an average molecular weight of "air" molecules of 29 grams per mole. We have also decided to use the same fraction (12) of a gram molecular weight, which is Avogadro's Number or 6.02 x 1023 thingies in a mole of anything. Then that packet of dry air weighs 12 x 29 or 348 units. If we substitute 4 water molecules for 4 of the "air" molecules keeping the NUMBER of entities the same, they weigh 18 g/mole. So the arithmetic is (8 x 29) + (4 x 18) = (232) + (72) = 304 units for the whole "wet" packet! This is lighter than a neighboring packet of 12 "air" molecules that has no water molecules. Wowie! No wonder those lighter wet packets of humid air on a summer afternoon scoot aloft to make cumulus, which then may nimbus...
OK, what does this cute analogy have to do with the Bird? One of its working criteria is that the working fluid should not evaporate significantly into the gas phase. Or that the gas phase should not be soluble in the liquid phase, so volumes inside the Bird system react mainly to temperature differences (the freon does not become "wet" with methylene chloride molecules) and changes in packet mass are insignificant.