Why Does a Lift Need a Counterweight?

Step 1 of 5

A lift car is far too heavy to just hoist.

An empty car already weighs about a tonne before anybody steps in, and a motor strong enough to lift that directly would be enormous.

Step 2 of 5

A second weight hangs on the other end.

The cable runs up over a wheel at the top and back down to a stack of steel blocks travelling in the same shaft as the car.

Step 3 of 5

The motor only lifts the imbalance.

With the two sides nearly matched, the motor is not fighting a tonne of steel. It only has to supply whatever small difference remains.

Step 4 of 5

It is matched to a half-full car.

The weight is chosen to balance the car plus about half its passengers, so the motor works gently whether the lift is empty or busy.

Step 5 of 5

Safety does not rely on the rope.

If the car ever moves too fast, a spinning governor trips and steel jaws clamp onto the guide rails, holding the car whatever the cable does.

Lift cars usually hang from six or more separate ropes, and each one alone is strong enough to hold the fully loaded car.