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The steps of an escalator are powered by a rotating chain mechanism. Matt Bird / Getty ImagesEscalators rank among the largest and most costly machines that people use daily, yet they remain remarkably simple.
At its core, an escalator is essentially a variation of the conveyor belt. Two rotating chains drive a set of stairs in a continuous loop, efficiently transporting people short distances at a decent speed.
In this piece, we take a closer look at an escalator to understand how all the components come together. Although the mechanism is quite simple, the system ensuring the seamless movement of the steps is incredibly clever.
Initially, escalators were referred to by several different names, such as "travelling staircase," "inclined elevator," and "magic stairway." Around 1900, Charles Seeberger, the designer of the escalator's predecessor, coined the term that would eventually become the standard. He combined "elevator" with "scala," the Latin term for steps, to create the name "escalator."
Steppin' Out
The separate steps that make up an escalator.The foundation of an escalator consists of two chains, which loop around a set of gears. An electric motor drives the drive gears at the top, which in turn rotate the chains. A standard escalator is powered by a motor with 100 horsepower to rotate the gears. Both the motor and the chain system are encased in the truss, a sturdy metal framework that connects two floors.
Instead of transporting a flat surface like a conveyor belt, the chain loops propel a series of steps. The most fascinating part of an escalator is how these steps stay level as they move. As the chains operate, the steps remain horizontal. At the top and bottom of the escalator, the steps overlap, creating a smooth, flat surface for easier access and exit.
Each step on an escalator features two sets of wheels, which roll along separate tracks. The top set of wheels (near the step's upper part) is attached to the rotating chains, which are driven by the drive gear at the top. The other set of wheels simply glides along its track, following the first set.
The tracks are spaced to ensure each step remains level at all times. At both the top and bottom, the tracks align horizontally, flattening the stairway. Each step has grooves designed to fit seamlessly with the steps in front and behind it during this process of flattening.
In addition to rotating the primary chain loops, the electric motor in an escalator also powers the handrails. The handrail consists of a rubber conveyor belt that loops around a series of wheels. The belt is meticulously calibrated to match the speed of the steps, providing riders with stability as they move up or down the escalator.
While an escalator may not be as efficient as an elevator for transporting people up many stories, it excels in moving individuals over shorter distances. This is due to the escalator's high loading rate. Unlike an elevator, which requires you to wait for it to reach its destination and return before new passengers can board, an escalator continuously accommodates new riders as soon as there's space.
Escalators can travel anywhere from 90 to 180 feet per minute (27 to 55 meters per minute). A typical escalator moving at 145 feet (44 meters) per minute can transport over 10,000 people per hour, far surpassing the capacity of a regular elevator.
