Mechanical Engineering - Machine Design - Discussion

Hollow shaft can bear more Shear Stress.

Please note that the two shafts have same length and weight, then you can conclude that the outer DIA of the Hollow Section will be bigger than Solid rod, the greater the DIA the Greater the Torsion Resistance (Power Transmitted).

Another Aspect the Polar moment of inertia, which is inversely probational with the Shear stress.

τ = Tp/J.
τ : Shear Stress.
T : Transmitted Torque.
P : Radial Distance to Shaft Center.
J : Polar moment of inertia.

From the torsion equation, we may answer this question. For identical length and weight the polar moment of inertia for the hollow shaft is less than that of a solid shaft, as a result, the shear stress for the hollow shaft is more than the solid shaft. That means the resisting force to torsion is more in a case of tthe hollow shaft, hence it is better compared to the solid shaft.

If two shafts of same weight and cross section then hollow shaft having more stength. If two shaft of same diameter then solid shaft having more strength and stiffness.

If two shaft are in equal weight then the cross-section of the hollow shaft remains the shear stress and transmitted torque.

The weight & Length of the shafts are identical means the hollow shaft diameter naturally going to increase hence the Hollo shaft will have the more torsional strength. Hence hollow shaft with the same weight will give move strength.