are one of the largest, most expensive machines people use on
a regular basis, but they're also one of the simplest. At its
most basic level, an escalator is just a simple variation on
the conveyer belt. A pair of rotating chain loops pull a
series of stairs in a constant cycle, moving a lot of people a
short distance at a good speed.
The steps of an escalator ride on a rotating
In this edition of HowStuffWorks,
we'll look inside an escalator to find out exactly how these
elements fit together. While it is exceedingly simple, the
system that keeps all the steps moving in perfect synchrony is
really quite brilliant.
of an escalator is a pair of chains, looped around two pairs
motor turns the drive gears at the top, which
rotate the chain loops. A typical escalator uses a 100 horsepower
motor to rotate the gears. The motor and chain system are
housed inside the truss, a metal structure extending
between two floors.
What's in a
Name?Early escalators were
known by a variety of names, including "travelling
staircase," "inclined elevator" and "magic stairway."
Around 1900, Charles Seeberger, who designed the
forerunner of the modern escalator, came up with the
name that finally stuck. His term "escalator" is a
combination of "elevator" and "scala," the Latin word
Instead of moving a flat surface, as in a conveyer belt,
the chain loops move a series of steps. The coolest
thing about an escalator is the way these steps move. As the
chains move, the steps always stay level. At the top and
bottom of the escalator, the steps collapse on each other,
creating a flat platform. This makes it easier to get on and
off the escalator. In the diagram below, you can see how the
escalator does all of this.
Each step in the escalator has two sets of wheels,
which roll along two separate tracks. The upper set (the
wheels near the top of the step) are connected to the rotating
chains, and so are pulled by the drive gear at the top of the
escalator. The other set of wheels simply glides along its
track, following behind the first set.
The individual steps from an
The tracks are spaced apart in such a way that each
step will always remain level. At the top and bottom of the
escalator, the tracks level off to a horizontal position,
flattening the stairway. Each step has a series of grooves in
it, so it will fit together with the steps behind it and in
front of it during this flattening.
addition to rotating the main chain loops, the electric motor
in an escalator also moves the handrails. A handrail is
simply a rubber conveyer belt that is looped around a series
of wheels. This belt is precisely configured so that it moves
at exactly the same speed as the steps, to give riders some
SpeedEscalator speeds vary
from about 90 feet per minute to 180 feet per minute (27
to 55 meters per minute). An escalator moving 145 feet
(44 m) per minute can carry more than 10,000 people an
hour -- many more people than a standard
The escalator system isn't nearly as good as an elevator at
lifting people dozens of stories, but it is much better at
moving people a short distance. This is because of the
escalator's high loading rate. Once an elevator is
filled up, you have to wait for it to reach its floor and
return before anybody else can get on. On an escalator, as
soon as you load one person on, there's space for another.
To learn more about escalators, check out the links on the
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