Power from Rubber Drives Odd Engine (Jul, 1939)
Power from Rubber Drives Odd Engine
A “rubber pendulum,” operating as a scientific curiosity at the National Bureau of Standards, demonstrates a novel way of making heat do work. Supported on knife edges, a pendulum bar topped by brass weights can rock as far from the vertical as the tension of rubber bands, restraining its , lower end, will permit. Warmth from a radiant heater makes the rubber exhibit its unusual property of contracting under heat, instead of expanding as most substances do, and the shrinking bands pull the pendulum upright. At this point a sheet-metal shield screens them from the heat, and they relax. The momentum of the pendulum carries it over to the other side, where the process is repeated, and it continues to swing back and forth. A steam engine, which likewise transforms heat into mechanical energy, simply uses another working substanceâ€”steamâ€”instead of rubber. In theory, a “heat engine” could employ any substance that expands or contracts with temperature changes.