Experimental Evaluation of the Deceleration of Aluminum Cylinders Rotating in a Magnetic Field and Comments on Magnetic Damping of a Flywheel Control

An experimental investigation has been made to determine the magnetic deceleration of a closed-end cylinder rotating in a magnetic field by use of opposed ball and socket air bearing support. The theories of smythe and Hooper were compared with the experimental data for aluminum cylinders with fineness ratios of 9:1, 4:1, and 2:l and a wall thickness of 0.254 centimeter and one cylinder with a fineness ratio of 6:1 and a wall thickness of 0.508 centimeter. A method is outlined by which the magnetic damping coefficient for the spinning motion of a body of revolution may be determined experimentally. The theory of Smythe for a thin-walled cylinder predicts values greater than experimental results for fineness ratios of less than 6:l. Hooper's theory is in agreement with the experimental results through-out the range of fineness ratios tested. A utilization of the magnetic damping to prevent overspeeding of a flywheel used in a satellite orientation system is discussed.