1. Problem 1
3.4-7 Four gears are attached to a circular shaft and transmit the torques shown in the
figure. The allowable shear stress in the shaft is 10,000 psi.
(a) What is the required diameter d of the shaft if it has a solid cross section? R// d=1.78 in
(b) What is the required outside diameter d if the shaft is hollow with an inside diameter of
1.0 in.? R// d=1.83 in
Problem 2
3.7-9 A motor delivers 275 hp at 1000 rpm to the end of a shaft (see figure). The gears at B
and C take out 125 and 150 hp, respectively. Determine the required diameter d of the shaft
if the allowable shear stress is 7500 psi and the angle of twist between the motor and gear C
is limited to 1.5°. (Assume G = 11.5E6 psi, L1 = 6 ft, and L2 = 4 ft.) R// d=2.75 in
2. Problem 3
3.8-12 The composite shaft shown in the figure is manufactured by shrink-fitting a steel
sleeve over a brass core so that the two parts act as a single solid bar in torsion. The outer
diameters of the two parts are d1 _ 40 mm for the brass core and d2 _ 50 mm for the steel
sleeve. The shear moduli of elasticity are Gb _ 36 GPa for the brass and Gs _ 80 GPa for
the steel. Assuming that the allowable shear stresses in the brass and steel are tb _ 48 MPa
and ts _ 80 MPa, respectively, determine the maximum permissible torque Tmax that may
be applied to the shaft. R// T=1520 Nm
