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A steel shaft of length 1.5 m has to transmit 80 kW at 3000 rev/min. The allowable shear

stress is 80 MN/m² and the Modulus of Rigidity of steel, G, is 80 GN/m². The density of

steel is 7800 kg/m³.

a) Calculate the torque in the shaft.

b) For a solid shaft:

i) calculate the minimum allowable diameter,

(4 marks)

ii) and the angle of twist of one end relative to the other end when subjected to this

torque.

(2 marks)

(2 marks)

c) If a hollow shaft, where the ratio of outer to inner diameter is 2.25: 1, is considered,

i) calculate the minimum value of the outer diameter,

ii) and the angle of twist of one end relative to the other.

d) What is the ratio of the mass of the solid shaft to the mass of the hollow shaft?

(4 marks)

(2 marks)

(4 marks)

e) Discuss briefly why hollow drive shafts are often used in vehicles designed for competitive

motorsport but are rare on cars manufactured for the mass market.

(2 marks)

Fig: 1