Hollow vs. Solid Shaft

Course subject(s) 3. Torsion

An engineer is asked to size a 3 m long aluminum shaft designed to transmit a torque of 1200 Nm. The engineer has the following two design constraints and two design options:

Design Constraints:

  • Maximum allowable shear stress within the shaft = 40 MPa
  • Maximum allowable twist = 0.75 deg/m
  • G = 78 GPa

Design Options:

  • Solid circular shaft cross-section of diameter d
  • Hollow circular shaft with outer diameter d2 and wall thickness of 10% d2


  1. Which shaft design will be more weight efficient and why?
  2. What is the minimum diameter, d, of the solid shaft?
  3. What is the minimum outer diameter, d2, of the hollow shaft?
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