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GATE 2025 AG – Question 55

Farm Machinery · Machine Design · 2 marks · Numerical answer

A uniform solid round shaft transmits 25 kW at 540 rpm. Allowable shear stress is 35 MPa and maximum torque is 20% above mean torque. Neglect bending. Find minimum diameter in mm, to two decimals.

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Correct answer: 41.50 to 43.50

Explanation

Mean torque is $T_m=P/\omega=25000(60)/(2\pi540)=442.097$ N·m. Design torque is $T_{max}=1.2T_m=530.516$ N·m. For a solid circular shaft,$\tau_{max}=16T_{max}/(\pi d^3)$. Thus $d=[16(530.516)/(\pi35\times10^6)]^{1/3}=.0425795$ m, or **42.58 mm**.

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