Compute the outside diameter of the shaft:
A hollow shaft of diameter ratio is 0.4 is needed to transit 600 kW at 120 rpm. The maximum torque being 20% greater than the mean torque. The shear stress is restricted to 60 N/mm^{2} and the lowest of 0.01 radians per unit length. Compute the outside diameter of the shaft. Take G = 0.8 × 105 N/mm^{2}.
Solution
d_{i} / d_{o} = 0.4
di = 0.4 d_{o}
R = d_{o}/ 2
P = 600 kN, N = 120 rpm, P = 2π NT /60
600 × 10^{3} =( 2π× 120T )/60
∴ T = 47.7 × 10^{3 }N-m
T_{max} = 1.2 T = 1.2 × 47.7 × 10^{3 } = 57.3 × 10^{3} N-m
τ_{max} = 60 N/mm^{2} = 60 × 106 N/m^{2}
T_{max } = τ_{max} × Z P
⇒ 57.3 × 10^{3 } = 60 × 10^{6 } × 0.19
∴ do = 0.17 m
T_{max} / J = G θ/ l
∴ do = 0.165 m
∴ do = 0.17 m = 170 mm