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c))motion solar wheel toys

Some solar wheel toys do not rely on gas expansion or liquid pumping. Instead, the solar toy is decorated with a number of black plastic strips along the perimeter- like a ferris wheel. These strips are bilayers made of two plastics with different expansion coefficients. When heated by the sun or even a table lamp, the difference in thermal expansion causes the strip to "bow" (note the strips near the lamp are more curved than those shaded by the wheel). Since they bow away from the center of rotation, the center of mass is moves toward the lamp, and the wheel - now unbalanced- rotates in response.

There is more information on these plastic strips, named c))motion, at talusfurniture. While the material was originally designed to solve common environmental and energy problems, it can also be used in toys. Two movies demonstrating solar wheel toys are the multi- armed "anemone" and the two-bladed "scoop".

In addition to the c))motion-based solar wheels, even simple rubber bands can form the basis for a rotating toy. In the early 1970's Paul B. Archibald invented a number of such devices. As described by C.L. Stong in the April 1971 Scientific American article, Some Delightful Engines Driven By the Heating of Rubber Bands, the first example was a pendulum.

Rubber stretches when heated. Every time the pendulum swings behind the "shadow vane" the rubber shrinks back towards its original length and gives the pendulum a "kick" by slightly lifting the center of mass (this is known as a "parametric amplifier"). While a very inefficient use of the incident radiation, the pendulum loses very little energy on each cycle, so the toy oscillates freely. Note, unlike the c))motion design, the rubber band engine is not self-starting and must be "primed" by first setting the pedulum swinging.

The second rubber band engine looks like a horizontal "bicycle wheel" where the metal spokes are replaced by rubber bands. The central axis is off-set, like a camshaft in an automobile. A heated plate stretches the nearby rubber bands, allowing the opposite bands to tug on the camshaft, causing the wheel to rotate. The next set of rubber bands rotate in above the hot plate, and the cycle continues.

Contact Greg Blonder by email here. Copyright Genuine Ideas, LLC.