In a gear train, how does increasing gear reduction affect torque and speed?

• A. Increases torque, decreases speed.
• B. Increases torque, increases speed.
• C. Decreases torque, increases speed.
• D. Decreases torque, decreases speed.

Answer: (A)

Increasing gear reduction increases the ratio between input and output gears, which changes how torque and speed relate. In an ideal gear train, output speed equals input speed divided by the reduction ratio, while output torque equals input torque multiplied by the reduction ratio. So as you raise the reduction, the output turns more slowly but with greater torque. In real gears, some power is lost to friction and inefficiencies, so the torque gain is a bit less than the ideal product, but the overall trend remains: more torque at lower speed. This is the trade-off gear reductions provide.