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03-02ChapGere.0014 - A-PDF Split DEMO Purchase from...

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Problem 3.7-2 A motor drives a shaft at 12 Hz and delivers 20 kW of power (see figure). (a) If the shaft has a diameter of 30 mm, what is the maximum shear stress max in the shaft? (b) If the maximum allowable shear stress is 40 MPa, what is the minimum permissible diameter d min of the shaft? Solution 3.7-2 Motor-driven shaft SECTION 3.7 Transmission of Power 217 d 12 Hz 20 kW f 12 Hz P 20 kW 20,000 N m/s T ORQUE P 2 f T P watts f Hz s 1 T Newton meters (a) M AXIMUM SHEAR STRESS max d 30 mm T P 2 f 20,000 W 2 (12 Hz) 265.3 N . m (b) M INIMUM DIAMETER d min allow 40 MPa d min 0.0323 m 32.3 mm 33.78 10 6 m 3 d 3 16 T t allow 16(265.3 N . m) (40 MPa) 50.0 MPa t max 16 T d 3 16(265.3 N . m) (0.030 m) 3 Problem 3.7-3 The propeller shaft of a large ship has outside diameter 18 in. and inside diameter 12 in., as shown in the figure. The shaft is rated for a maximum shear stress of 4500 psi. (a) If the shaft is turning at 100 rpm, what is the maximum horsepower that can be transmitted without exceeding the
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