Traction Elevator

Traction lifts are a simple system. A motor is attached to a sheave (a toothed pulley), with a rope or cable looped over it. The rope is attached at one end to the lift car, and on the other end to a counterweight.

When the lift is called to a floor, the motor turns the sheave. This motor can move in both directions – one moving the lift car up, the other moving it down. As the lift car rises, the counterweight lowers – and vice versa. The counterweight means there is less strain on the motor and the whole system, meaning that less power is required to move the lift car up or down. This is similar to a see-saw – if there is only one person on the see-saw it takes far more energy to get to the top, whereas the balance between two people make it easier.