Or maybe it’s a Drinking Happy Bird (the packaging was a bit unclear). It is a glass bird, long neck, head and beak covered with some kind of fuzzy material, on a sort of hinge (there is a better word, I can’t think of it right now). You set it on a surface next to a water glass (and it can be a pretty short water glass), dunk the bird’s head in the water, and let go. it rocks up, and slowly begins rocking, making wider and wider arcs until the bird’s beak dips into the water again, at which point the arc it makes becomes much shorter and the pendulum action quicker, again slowly progressing until the bird once again dunks its beak…and so on, until the water is empty.
Really it’s almost like a perpetual motion machine. Except that periodically somebody has to bring it water.
So how does it work? What is making this thing rock?
It’s a thermometer; when the fluid inside fills the column, it overbalances; this causes part of it to enter the water, cooling it and causing the fluid in the column to go back down, restoring the original state of balance. It requires a warm room and a cold glass of water, so it isn’t really perpetual motion; it’s (inefficiently) exploiting the movement of heat from a warm medium to a colder one.
The link that Dragwyr suggests that it’s methylene chloride. When I worked in a machine shop we used to use a hypodermic syringe full of methylene chloride to glue large pieces of Plexiglas together. After machining a few slabs of inch-thick plastic to fit together in some way, we would put them together and inject the stuff at the edge of the joint, where it would wick in and instantly weld the plastic together. Quite impressive in its speed.
I once read an internet account by a guy who studied the dipping bird toy to determine just how much work (in the physics sense) it accomplishes as a heat pump. He rigged one to lift a paperclip, gradually, via a winch, so that each time the head bobbed it would incrementally, if almost imperceptibly, spool up the paperclip.
He calculated, IIRC, that one dipping bird generates the equivalent of one nano-horsepower or one millionth of a watt. NB: these calculations might have been rounded off. Theoretically, and assuming superconductor-like efficiencies in electrical microcurrent transmissions, this suggests that a power plant of 60,000,000 dipping birds all a-bobbing could power a standard 60-watt incandescent light bulb. (The mind boggles.)
Unfortunately, my Google-fu wasn’t good enough to locate this paper.
This set of reminiscences (a BIG pdf) about Enrico Fermi includes a talk by his daughter Nella that has her description of his particular fascination with the toy:
Also, some heat of the room will move directly into the cool water until the room and water are in thermal equilibrium…at which point the dipping bird won’t be dipping no more! - Jinx
I couldn’t resist returning to this thread, much as a dog returns to its own vomit.
The mad-monk scientist, engineer, whatever whose investigation into the work potential of the dipping bird is one Don Rathjen. And although I still haven’t found his own account of his experiment, I did manage to find a very nice write-up of same by one D.R. Watson, complete with a schematic drawing by Rathjen of the bird-powered “engine,” for the benefit of those of you who are considering making a dipping-bird-based attempt to live off of the electrical grid.
These guys should hold a convention or something. I can see it now. They’ll all be wearing blue top hats and red clown shoes…
