WR-5

If an electric motor delivers a maximum 27 HP at 1725 RPM through the output motor shaft,
a) Size the solid motor shaft. Ignore the stress concentration created by the keyway;
b) Specify a nominal-sized parallel, square key so that it will fail should the load cause the motor to reach its maximum power capacity.
Specifications: Factor of safety for shaft: 1.6
Medium carbon steel for all components:

Ultimate normal stress: 90 ksi
Ultimate shear stress: 67 ksi
Yield normal stress: 60 ksi

Assume yield stress in shear equals 60% yield normal stress.
NOTE: See Machinery's Handbook, Industrial Press Inc. for nominal key sizes.
Hint: Do not include the factor of safety in design of the key. Why?

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