The vertical drive shaft in Figure P2.31 is 20 mm in diameter, 650 mm long, andmade of

Chapter 7, Problem 7.15

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The vertical drive shaft in Figure P2.31 is 20 mm in diameter, 650 mm long, and made of steel. The motor to which it is attached at the top is equivalent to a steel flywheel 300 mm in diameter and 25 mm thick. When the vertical shaft is rotating at 3000 rpm, the propeller strikes a heavy obstruction, bringing it to a virtually instantaneous stop. Assume that the short horizontal propeller shaft and the bevel gears have negligible flexibility. Calculate the elastic torsional shear stress in the vertical shaft. (Since this stress far exceeds any possible torsional elastic strength, a shear pin or slipping clutch would be used to protect the shaft and associated costly parts.)