Lesson 2 of 8How lifts work
How a traction lift works.
Most passenger lifts are traction lifts: the car hangs from ropes that run over a grooved wheel, balanced by a counterweight. Here is how that arrangement moves the car, and why it works so well.
What traction means.
On a traction lift, the car and the counterweight hang from opposite ends of a set of steel ropes. The ropes pass over a grooved wheel, the traction sheave, which is turned by the machine. They are not fixed to the sheave or wound onto it. They grip its grooves by friction, in the same way a belt grips a pulley.
When the motor turns the sheave, friction carries the ropes with it. One side of the ropes rises and the other falls, so the car goes up as the counterweight comes down, and the other way round. That grip is called traction, and it gives the lift its name.
Because the ropes are not stored on a drum, the length of travel is not limited by the size of a drum. That is one reason traction lifts serve everything from three-storey blocks to the tallest towers.
Why the counterweight matters.
The counterweight is a steel frame filled with weights that runs on its own guide rails. It usually weighs as much as the empty car plus around 40 to 50 per cent of the rated load. There is no fixed figure: the designer chooses the balance for each lift. When the car is part loaded, the two sides are almost balanced, and the motor only has to move the difference.
This is what makes traction lifts efficient. An empty car is lighter than the counterweight, so going up the motor is mainly holding back the heavier side. A full car is heavier than the counterweight, so the motor works hardest lifting it and holds it back on the way down.
The counterweight also matters for safety. Traction depends on weight pressing the ropes into the grooves on both sides of the sheave, and the standard for new lifts, BS EN 81-20, sets limits in both directions:
- Enough grip: a car loaded to 125 per cent of its rated load must stay level at a floor without the ropes slipping.
- Not too much grip: if the car or the counterweight is stopped, for example because the counterweight has come to rest on its buffers in the pit, the machine must not keep lifting the other side into a dangerous position. Either the ropes slip on the sheave, or a safety device stops the machine.
1:1 and 2:1 roping.
The roping ratio describes how far the ropes move compared with the car. The two most common arrangements are shown below.
1:1 roping
2:1 roping
Describe these diagrams
Left, 1:1 roping: the ropes are fixed to the top of the car, run up over the traction sheave and down to the counterweight. When the sheave moves 1 metre of rope, the car moves 1 metre.
Right, 2:1 roping: the rope ends are fixed at the top of the shaft. The ropes run down around a pulley on the car, up over the traction sheave, down around a pulley on the counterweight and back up. When the sheave moves 2 metres of rope, the car moves 1 metre.
1:1 roping
The ropes are fixed to the top of the car, pass over the sheave and are fixed to the top of the counterweight. The car moves at the same speed as the ropes, and the ropes carry the full weight of the car and its load.
2:1 roping
The rope ends are fixed at the top of the shaft, and the ropes pass around pulleys on the car and the counterweight. The car moves at half the rope speed, and the load is shared between twice as many falls of rope. The machine can therefore be smaller and turn faster for the same lift, which is why 2:1 roping is common on machine room-less lifts.
Compensation
On a tall lift the ropes themselves are heavy. With the car at the bottom, most of their length hangs on the car side of the sheave; with the car at the top, most of it hangs on the counterweight side. Where that would upset the traction or overload the motor, compensation is fitted: chains, ropes or belts that hang in a loop between the bottom of the car and the bottom of the counterweight, so the weight on each side stays even.
BS EN 81-20 allows chains, ropes or belts up to a rated speed of 3.0 m/s. Faster lifts must use compensating ropes held taut by a tensioning pulley in the pit, and above 3.5 m/s they also need an anti-rebound device.
Geared and gearless machines.
The machine is the motor, the brake and the traction sheave. There are two main types.
| Geared machine | Gearless machine | |
|---|---|---|
| How it drives the sheave | The motor turns the sheave through a gearbox, usually a worm gear | The sheave is mounted on the motor, with no gearbox |
| Where you find it | Many older lifts and some goods lifts | Most modern traction lifts, including machine room-less lifts |
| Motor | A smaller motor running at high speed | A larger, slow-turning motor, often with permanent magnets |
| Maintenance points | Gearbox oil, gear wear and alignment | Bearings, brake and encoder, with no gearbox to service |
A geared machine uses a gearbox to turn a fast, compact motor into the slow, powerful rotation the sheave needs. A gearless machine does without the gearbox, which makes it quieter and more efficient but needs a motor that can turn slowly with a lot of torque.
Both use a brake that is applied by springs and held off by an electric current. It holds the car still whenever it stops, and if the power fails, the springs apply it automatically.
On a lift built to BS EN 81-20, the brake must be able to stop the car on its own when it is travelling down at full speed with 25 per cent more than its rated load. Its mechanical parts are fitted in two sets, so if one set fails, the other can still slow, stop and hold the car.
Ropes and belts.
Most traction lifts hang from round steel wire ropes. Some newer lifts use flat coated steel belts instead, which can bend around smaller sheaves. Either way, the law requires more than one.
The law
Under the Lifts Regulations 2016, a lift whose car is suspended by ropes or chains must have at least two independent ropes or chains, each with its own anchorage.
In practice traction lifts often have three or more ropes, sized with a large safety margin. Our lesson on lift ropes explains how they are made, how they wear and when they are replaced.
Traction or hydraulic?
The main alternative is a hydraulic lift, which is pushed up by a ram driven by oil under pressure and lowers under its own weight. Hydraulic lifts suit low-rise buildings and heavy loads over short distances. Traction lifts suit most passenger lifts, and they are the only practical choice for taller buildings.
Our hydraulic lifts page compares the two side by side, including travel, speed, energy use and space.
What engineers check on a traction lift.
Because a traction lift depends on the grip between the ropes and the sheave, engineers pay close attention to everything that affects it.
- Ropes: broken wires, wear, corrosion, stretch and lubrication.
- Rope tension: ropes carrying unequal loads wear the sheave grooves unevenly, so tensions are checked and equalised.
- Sheave grooves: worn grooves change how the ropes sit and grip, and can lead to slipping.
- Brake: it must hold the car reliably, so its condition and adjustment are checked at every visit.
- Counterweight: its guide shoes, buffers and the clearance above and below it.
Engineer’s note
Uneven rope tension is easy to miss and expensive to ignore. A rope that carries more than its share wears faster and wears its groove deeper, which in turn makes the tension more uneven. Checking and equalising tension is part of a proper maintenance visit. See what a maintenance visit includes.
Check your understanding.
Three quick questions on this lesson. Choose an answer to check it, or open the answer below each question.
-
What moves the ropes on a traction lift?
Show the answer
B. Friction between the ropes and the grooves of the sheave. The ropes sit in grooves around the traction sheave. Friction between the two means that turning the sheave moves the ropes, raising one side and lowering the other.
-
On a lift with 2:1 roping, how far does the car move when the sheave moves 2 metres of rope?
Show the answer
B. 1 metre. With 2:1 roping the ropes pass around pulleys on the car and counterweight, so the car moves half as far, and half as fast, as the ropes.
-
What does the counterweight balance?
Show the answer
B. The car and part of its rated load. The counterweight weighs as much as the car plus part of the rated load. The motor then only has to move the difference between the two sides.
Sources.
The primary sources for this lesson. We checked them when the lesson was last updated on 18 October 2026. How we research and check our lessons.
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Related reading
Not sure what kind of lift you have?
Talk to an engineer. We can tell you how your lift is roped and driven, and what that means for its maintenance.
Common questions.
Quick answers to common questions about this topic.
What is a traction lift?
A traction lift is a lift whose car hangs from steel ropes or coated steel belts that run over a grooved sheave turned by an electric motor. Friction between the ropes and the sheave moves the car, and a counterweight on the other side of the sheave balances it.
What does 2:1 roping mean?
It means the ropes move twice as far as the car. The rope ends are fixed at the top of the shaft and the ropes pass around pulleys on the car and the counterweight, so the car travels at half the rope speed and each rope carries half the load.
Why do traction lifts have a counterweight?
The counterweight balances the car and part of its rated load, so the motor only has to move the difference in weight between the two sides. That saves energy and reduces wear. It also keeps enough weight on the ropes for them to grip the sheave.
Is a traction lift better than a hydraulic lift?
Neither is better in every building. Traction lifts suit most passenger lifts and taller buildings. Hydraulic lifts suit low-rise buildings and heavy loads over short distances. Our hydraulic lifts page compares the two.