Problem 303: Torsion

Problem 303:

                    A steel marine propeller shaft 14 in. in diameter and 18 ft long is used to transmit 5000 hp at 189 rpm. If G = 12 × 10⁶ psi, determine the maximum shearing stress.

Solution:

Given,

          Diameter, d = 14 in

          Length, L = 18 ft = 18 x 12 in

          Power, P = 5000 hp

          Frequency, f = 189 rpm

          G = 12 × 10⁶ psi

          Maximum shearing stress, τ_max =?

1 hp = 33,000 ft·lb/min = 396,000 lb·in/min

We know that, torque:

We also know that, Maximum shearing stress:

So, Maximum shearing stress =  3094.6 psi