A SELF-MOVING STAIRCASE
At the American Exhibition, held in the Crystal Palace in 1902, there
was shown a staircase which, on payment of a penny, transported any
sufficiently daring person from the ground-floor to the gallery above.
All that the experimenters had to do was to step boldly on, take hold
of the balustrade, which moved at an equal pace with the stairs, and
step off when the upper level was reached.
The "escalator" (Latin _scalae_ = flight of stairs) hails from the
United States, where it is proving a serious rival to the elevator. In
principle, it is a continuously working lift, the slow travel of which
is more than compensated by the fact that it is always available. The
ordinary elevator is very useful in a large business or commercial
house, where it saves the legs of people who, if they had to tramp up
flight after flight of stairs, would probably not spend so much money
as they would be ready to part with if their vertical travel from one
floor to another was entirely free of effort. But the ordinary lift is,
like a railway, intermittent. We all know what it means to stand at the
grille and watch the cage slide downwards on its journey of, perhaps,
four floors, when we want to go to a floor higher up. Rather than face
the delay we use our legs.
Theoretically, therefore, a large emporium should contain at least two
lifts. If the number be further increased, the would-be passenger will
have a still better chance of getting off at once. Thus at the station
of the Central London Railway we have to wait but a very few seconds
before a grille is thrown back and an attendant invites us to "Hurry up
there, please!"
Yet there is delay while the cage is being filled. The actual journey
occupies but a small fraction of the time which elapses between the
moment when the first passenger enters the lift at the one end of the
trip and the moment when the last person leaves it at the other end. In
a building where the lift stops every fifteen feet or so to take people
on or put them off, the waste of time is still more accentuated.
The escalator is always ready. You step on and are transported one
stage. A second staircase takes you on at once if you desire it. There
is no delay. Furthermore, the room occupied by a single escalator is
much less than that occupied by the number of lifts required to give
anything like an equally efficient service.
In large American stores, then, it is coming into favour, and also
on the Manhattan Elevated Railway of New York. When once the little
nervousness accompanying the first use has worn off, it eclipses the
lift. A writer in _Cassier's Magazine_ says: "In one large retail store
during the holiday season more than 6,000 persons per hour have been
carried upon the escalator for five hours of the day, and the aggregate
for an entire day is believed to be 50,000. In the same store on an
ordinary day the passengers alighting at the second floor from the
eight large lifts, which run from the basement to the fifth floor, were
counted, likewise the number at the escalator. This latter was found
to be 859 per cent. of the number delivered by the eight lifts. In
another establishment, in a very busy hour, the number taken from the
first floor by the escalator was four times the number taken from the
first floor by the fourteen lifts, which were running at their maximum
capacity. To the merchant this spells opportunity for business.
"The experience at the Twenty-third Street and Sixth Avenue station
of the Manhattan Elevated Railway in New York, during a recent
shut-down of the escalator, which has been in service for some time,
is interesting as showing the attitude of the public, of which many
millions have been carried by the installation during the several years
of its operation. The daily traffic receipts of this station for a
period beginning several weeks before the shut-down and extending as
many after, for the years 1903 and 1902, and receipts of the adjacent
stations for the same period were carefully plotted ... and the loss
area during the period of shut-down was determined. The loss area was
found to embrace 64,645 fares. It was, furthermore, daily a matter of
observation that numbers of people, finding that the escalator was not
running, refused to climb the stairs, and turned away from the station.
"In the case of a great store, the escalator may be constructed as
one continuous machine, with landings at each floor, and so arranged
that steps which carry passengers up may perform a like service in
carrying others down; or separate machines may be installed in various
locations affording the best opportunity for displaying merchandise to
the customer who may be proceeding from the lower to the upper floor.
In the case of a six-storey building so equipped with escalator service
in both directions, or in all ten escalator flights, it is obvious
that the facilities are equal to an impossible number of elevators;
and as facility of access has a direct bearing upon opportunities for
business, it may well be argued that the relative value, measured by
rent, of the main and upper floors is greatly changed."
Each step in a staircase has two parts--the "tread" or horizontal
board on which the foot is placed, and the vertical "riser" which acts
both as a support to the tread above and also prevents the foot from
slipping under the tread. In the escalator each tread is attached
rigidly to its riser, and the two together form an independent unit.
For the convenience of passengers in stepping on or off at the upper
and lower landings, the treads in these places are all in the same
horizontal plane. As they approach the incline the risers gradually
appear, and the treads separate vertically. At the top of the incline
the process is gradually reversed, the risers disappearing until the
treads once more form a horizontal belt.
The means of effecting this change is most ingenious. Each tread and
its riser is carried on a couple of vertical triangular brackets, one
at each side of the staircase. The base of the bracket is uppermost, to
engage with the tread, and its apex has a hole through which passes a
transverse bar, which in its central part forms a pin in the link-chain
by which power is transmitted to the escalator. Naturally, the step
would tip over. This is prevented by a yoke attached to each end of the
bar, at right angles to it and parallel to the tread. The yoke has at
each extremity a small wheel running on its own rail--there being two
rails for each side of the staircase.
Since step, brackets, bar, and yoke are all rigidly joined together,
the step is unable to leave the horizontal, but its relation to the
steps above and below is determined by the arrangement of the rails on
which the yoke wheels run. When these are in the same plane, all the
yokes, and consequently the treads, will also be in the same plane.
But at the incline, where the inner rail gradually sinks lower than
its fellow, the front wheel of one tread is lower than the front wheel
of the next, and the risers appear. It may be added that, owing to the
double track at each side of the staircase, the back wheel of one tread
does not interfere with the front wheel of that below; and that on the
level they come abreast without jostling, as the yoke is bent.
The chain, of which the step-bars form pins, travels under the centre
of the staircase. It is made up of links eighteen inches long, having,
in addition to the bars, a number of steel cross-pins 1-1/2 inches in
diameter, their axes three inches apart, so that the chain as a whole
has a three-inch "pitch." The hubs of the links are bushed with bronze,
and have a graphite "inlay," which makes them self-lubricating. Every
joint is turned to within 1/1,000 inch of absolute accuracy.
The tracks are of steel and hardwood, insulated from the ironwork which
supports them by sheets of rubber. The wheels are so constructed as to
be practically noiseless, so that as a whole the escalator works very
quietly.
"It has been observed," says the authority already quoted, "that
beginners take pains to step upon a single tread, and that after a
little experience no attention whatever is given to the footing, owing
to the facility of adapting oneself to the situation. The upper landing
is somewhat longer, thereby affording an interval for stepping off at
either side of sufficient duration to meet the requirements of the
aged and infirm. The sole function of the travelling landing is to
provide a time interval to meet the requirements of the slowest-acting
passenger, and not of the alert. The terminal of the exit landing, be
it top or bottom (for the escalator operates equally well for either
ascent or descent), is a barrier, called the shunt, of which the lower
member travels horizontally in a plane oblique to the direction of
movement of the steps, and at a speed proportionately greater, thereby
imparting a right-angle resultant to the person or obstacle on the step
which may come in contact with the shunt. By reason of this resultant
motion, the person or obstacle is gently pushed off the end of the
step upon the floor, without shock or injury in the slightest degree.
The motion of the escalator is so smooth and constant that it does not
interpose the least obstacle to the free movement of the passenger, who
may walk in either direction or assume any attitude to the same degree
as upon a stationary staircase."
At Cleveland, U.S.A., there has been erected a rolling roadway,
consisting of an inclined endless belt and platform made of planks
eight feet long, placed transversely across the roadway. The timbers
are fastened together in trucks of two planks each, adjoining trucks
being joined by heavy links to form a moving roadway, which runs on
4,000 small wheels. At each end the roadway, which is continuous,
passes round enormous rollers. Its total length is 420 feet, and the
rise 65 feet. Four electric motors placed at regular intervals along
its length, and all controlled by one man at the head of the incline,
drive it at three miles an hour. It can accommodate six wagons at a
time.