A two‑stage gear reduction drives a conveyor that must deliver a torque of $250$ N·m at $30$ rpm. Stage 1 consists of a driver gear with 25 teeth driving a 75‑tooth gear. Stage 2 uses the driven gear of stage 1 (on the same shaft) as the driver, which has 30 teeth and drives a 90‑tooth gear. Each stage has an efficiency of $85$ %. Determine:

(a) the required motor speed (rpm) and torque (N·m) assuming the motor runs at the speed of the first driver gear;

(b) the motor power (kW) needed.

Question

A two‑stage gear reduction drives a conveyor that must deliver a torque of $250$ N·m at $30$ rpm. Stage 1 consists of a driver gear with 25 teeth driving a 75‑tooth gear. Stage 2 uses the driven gear of stage 1 (on the same shaft) as the driver, which has 30 teeth and drives a 90‑tooth gear. Each stage has an efficiency of $85$ %. Determine:

(a) the required motor speed (rpm) and torque (N·m) assuming the motor runs at the speed of the first driver gear;

(b) the motor power (kW) needed.

Accepted Answer

Motor speed = 270 rpm; motor torque ≈ 3115 N·m; motor power ≈ 88.1 kW.

City Guilds Model Questions Vol1 2019 Engineering Question 33

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