When a larger gear drives a smaller gear, the smaller gear rotates faster but with reduced torque. This can be used in hoisting machinery when higher rotational speed of the drive sheave is needed, though most elevator drives prioritize torque for lifting heavy loads.
When a smaller gear drives a larger gear, the larger gear rotates more slowly but delivers greater torque. Geared traction elevators commonly use this setup to provide the necessary force to lift the elevator car safely.
An idler gear is placed between driving and driven gears to maintain or reverse rotation direction without changing the overall gear ratio. In elevator machinery, idler gears may be used to achieve compact layouts while ensuring the sheave turns correctly.
A sequence of multiple gears in series reduces input speed and multiplies torque through each stage of reduction. This arrangement is the basis of geared traction machines, converting the high-speed motor output into the controlled speed and torque needed at the drive sheave.
Gearless traction elevators have the motor directly coupled to the drive sheave, eliminating reduction gears. This design allows for higher travel speeds and smoother operation, making it ideal for very tall buildings.