| 摘要 |
A rotatable device having outwardly extending weighted arms of thermally expandable material is supported for rotation about an axis arranged at an angle to the vertical. The device is exposed to the sun or other source of radiant energy, causing the arms to expand lengthwise. A sun shield is provided over a portion of the area of movement of the arms so that when they move out of the shade of the shield, they expand lengthwise and whey they move into such shade, they contract. The resultant differential lengthening of the arms establishes an unbalance of moments of gravitational force in the arms to thereby apply a continuous torque to the assembly.
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