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The Drinking Bird

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The Drinking Bird and Thermodynamics 101

My stepson received a drinking bird as a stocking stuffer one Christmas, and it was the hit of the party. His Guitar Hero was abandoned in a corner for hours while our group huddled around the dinner table, mesmerized by the dip, dip, dipping bird. Though it looks like a toy, the drinking bird is actually a small, cleverly designed thermodynamic engine. When the head of the bird is moistened, it repeatedly tips over and seems to be drinking from a glass of water.

The drinking bird looks harmless, but there are a few safety concerns to keep in mind. The glass tube is filled with colored dichloromethane (also called methylene chloride) which can irritate the skin and lungs. Be sure to keep children and animals at a safe distance when the drinking bird is on display.

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Here's How the Drinking Bird Works

Courtesy of Wikipedia

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:

The water evaporates from the felt on the head.

Evaporation lowers the temperature of the glass head (heat of vaporization).

The temperature's drop causes some of the dichloromethane vapor in the head to condense.

The lower temperature and condensation together cause the pressure to drop in the head (ideal gas law).

The pressure differential between the head and base causes the liquid to be pushed up from the base.

As liquid flows into the head, the bird becomes top heavy and tips over during its oscillations.

When the bird tips over, the bottom end of the neck tube rises above the surface of the liquid.

A bubble of vapor rises up the tube through this gap, displacing liquid as it goes.

Liquid flows back to the bottom bulb, and vapor pressure equalizes between the top and bottom bulbs.

The weight of the liquid in the bottom bulb restores the bird to its vertical position.

The liquid in the bottom bulb is heated by ambient air, which is at a temperature slightly higher than the temperature of the bird's head.

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.

Created in 1945

The drinking bird was invented by Miles V. Sullivan in 1945. It was patented a year later. Sullivan was a Ph.D. inventor-scientist at Bell labs in Murray Hill, New Jersey.

I Could Sure Use a Drink!

What Do You Call the Drinking Bird?

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The Drinking Bird

It's a Small, Cleverly Designed Thermodynamic Engine

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Camden Mar 28, 2012 @ 7:48 am | delete

I had one of these as a kid - I didn't know you could still get them!

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A-Redneck Feb 26, 2011 @ 8:38 pm | delete

I didn't think that they still made these. Of course when I was a kid our family had one sitting on the kitchen window. I think everyone had one back then.

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AndyPo Nov 26, 2010 @ 9:55 am | delete

A classic. Very well explained too.

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Sylvestermouse Oct 13, 2010 @ 1:54 pm | delete

Great information! We love these little guys too, but I did giggle at the idea of abandoning Guitar Hero for it :)

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Flo Aug 14, 2010 @ 6:12 am | delete

You can get these birds here. They are great. http://www.noveltieswholesale.com/drinkbird.html
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