Apart from hydraulic elevator, geared and gearless traction elevators with machine room (MR) / without machine room (MRL) are other common types.
Traction elevators are lifted by ropes, which pass over a wheel attached to an electric motor above the elevator shaft. They are used for mid and high-rise applications and have much higher travel speeds than hydraulic elevators. A counter weight makes the elevators more efficient by offsetting the weight of the car and occupants, so that the motor doesn't have to move as much weight.
Geared traction elevators have a gearbox that is attached to the motor, which drives the wheel that moves the ropes. Geared traction elevators are capable of travel speeds up to 500 feet per minute. The maximum travel distance for a geared traction elevator is around 250 feet.
Gearless traction elevators have the wheel attached directly to the motor. Gearless traction elevators are capable of speeds up to 2,000 feet per minute and they have a maximum travel distance of around 2,000 feet so they are the only choice for high-rise applications.
Geared traction elevators are middle of the road in terms of initial cost, ongoing maintenance costs, and energy consumption. While gearless traction elevators have a high initial cost, medium ongoing maintenance costs, and use energy a bit more efficiently than geared traction elevators.
It is important that traction elevator ropes and sheaves are checked for wear on a regular basis. As they wear, the traction between the sheave and the cables is reduced and the slippage becomes more regular, which reduces the efficiency and can become dangerous if left unchecked.
Traction elevators have height restrictions that are governed by the length and weight of the cables or ropes. New materials that are stronger and lighter, such as carbon fiber, will allow traction elevators to achieve new heights.
Machine-Room-Less Elevators are traction elevators that do not have a dedicated machine room above the elevator shaft. The machine sits in the override space and is accessed from the top of the elevator cab when maintenance or repairs are required. The control boxes are located in a control room that is adjacent to the elevator shaft on the highest landing and within around 150 feet of the machine.
Machine-room-less elevators have a maximum travel distance of up to 250 feet and can travel at speeds up to 500 feet-per-minute. MRL elevators are comparable to geared traction elevators in terms of initial and maintenance costs, but they have relatively low energy consumption compared to geared elevators.
Machine-room-less elevators are becoming the most popular choice for mid-rise buildings where the travel distance is up to 250 feet. They are energy efficient, require less space, and their operation and reliability are on par with gear-less traction elevators.
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