Gere & Goodno — Torsion: Problem 3.7-1

3.7-1 A generator shaft in a small hydroelectric plant turns at 120 rpm and delivers 38 kW (see figure). (a) If the diameter of the shaft is \( d = 75 \text{ mm} \), what is the maximum shear \( \tau_{\text{max}} \) in the shaft? (b) If the shear stress is limited to 28 MPa, what is the minimum permissible diameter \( d_{\text{min}} \) of the shaft?