ELECTRICAL EQUIPMENT OF CARS
In determining the electrical equipment of the trains, the company has
aimed to secure an organization of motors and control apparatus easily
adequate to operate trains in both local and express service at the
highest speeds compatible with safety to the traveling public. For
each of the two classes of service the limiting safe speed is fixed by
the distance between stations at which the trains stop, by curves, and
by grades. Except in a few places, for example where the East Side
branch passes under the Harlem River, the tracks are so nearly level
that the consideration of grade does not materially affect
determination of the limiting speed. While the majority of the curves
are of large radius, the safe limiting speed, particularly for the
express service, is necessarily considerably less than it would be on
straight tracks.
The average speed of express trains between City Hall and 145th Street
on the West Side will approximate 25 miles an hour, including stops.
The maximum speed of trains will be 45 miles per hour. The average
speed of local and express trains will exceed the speed made by the
trains on any elevated railroad.
To attain these speeds without exceeding maximum safe limiting speeds
between stops, the equipment provided will accelerate trains carrying
maximum load at a rate of 1.25 miles per hour per second in starting
from stations on level track. To obtain the same acceleration by
locomotives, a draw-bar pull of 44,000 pounds would be necessary--a
pull equivalent to the maximum effect of six steam locomotives such as
were used recently upon the Manhattan Elevated Railway in New York,
and equivalent to the pull which can be exerted by two passenger
locomotives of the latest Pennsylvania Railroad type. Two of these
latter would weigh about 250 net tons. By the use of the multiple unit
system of electrical control, equivalent results in respect to rate of
acceleration and speed are attained, the total addition to train
weight aggregating but 55 net tons.
If the locomotive principle of train operation were adopted,
therefore, it is obvious that it would be necessary to employ a lower
rate of acceleration for express trains. This could be attained
without very material sacrifice of average speed, since the average
distance between express stations is nearly two miles. In the case of
local trains, however, which average nearly three stops per mile, no
considerable reduction in the acceleration is possible without a
material reduction in average speed. The weight of a local train
exceeds the weight of five trail cars, similarly loaded, by 33 net
tons, and equivalent adhesion and acceleration would require
locomotives having not less than 80 net tons effective upon drivers.
[Sidenote: _Switching_]
The multiple unit system adopted possesses material advantages over a
locomotive system in respect to switching at terminals. Some of the
express trains in rush hours will comprise eight cars, but at certain
times during the day and night when the number of people requiring
transportation is less than during the morning and evening, and were
locomotives used an enormous amount of switching, coupling and
uncoupling would be involved by the comparative frequent changes of
train lengths. In an eight-car multiple-unit express train, the first,
third, fifth, sixth, and eighth cars will be motor cars, while the
second, fourth, and seventh will be trail cars. An eight-car train can
be reduced, therefore, to a six-car train by uncoupling two cars from
either end, to a five-car train by uncoupling three cars from the rear
end, or to a three-car train by uncoupling five cars from either end.
In each case a motor car will remain at each end of the reduced train.
In like manner, a five-car local train may be reduced to three cars,
still leaving a motor car at each end by uncoupling two cars from
either end, since in the normal five-car local train the first, third,
and fifth cars will be motor cars.
[Illustration: 200 H. P. RAILWAY MOTOR]
[Sidenote: _Motors_]
The motors are of the direct current series type and are rated 200
horse power each. They have been especially designed for the subway
service in line with specifications prepared by engineers of the
Interborough Company, and will operate at an average effective
potential of 570 volts. They are supplied by two manufacturers and
differ in respect to important features of design and construction,
but both are believed to be thoroughly adequate for the intended
service.
[Illustration: 200 H. P. RAILWAY MOTOR]
The photographs on this page illustrate motors of each make. The
weight of one make complete, with gear and gear case, is 5,900 pounds.
The corresponding weight of the other is 5,750 pounds. The ratio of
gear reduction used with one motor is 19 to 63, and with the other
motor 20 to 63.
[Illustration: 200 H. P. RAILWAY MOTOR]
[Sidenote: _Motor
Control_]
By the system of motor control adopted for the trains, the power
delivered to the various motors throughout the train is simultaneously
controlled and regulated by the motorman at the head of the train.
This is accomplished by means of a system of electric circuits
comprising essentially a small drum controller and an organization of
actuating circuits conveying small currents which energize electric
magnets placed beneath the cars, and so open and close the main power
circuits which supply energy to the motors. A controller is mounted
upon the platform at each end of each motor car, and the entire train
may be operated from any one of the points, the motorman normally
taking his post on the front platform of the first car. The switches
which open and close the power circuits through motors and rheostats
are called contactors, each comprising a magnetic blow-out switch and
the electro magnet which controls the movements of the switch. By
these contactors the usual series-multiple control of direct-current
motors is effected. The primary or control circuits regulate the
movement, not only of the contactors but also of the reverser, by
means of which the direction of the current supplied to motors may be
reversed at the will of the motorman.
[Illustration: APPARATUS UNDER COMPOSITE MOTOR CAR]
The photograph on this page shows the complete control wiring and
motor equipment of a motor car as seen beneath the car. In wiring the
cars unusual precautions have been adopted to guard against risk of
fire. As elsewhere described in this publication, the floors of all
motor cars are protected by sheet steel and a material composed of
asbestos and silicate of soda, which possesses great heat-resisting
properties. In addition to this, all of the important power wires
beneath the car are placed in conduits of fireproof material, of which
asbestos is the principal constituent. Furthermore, the vulcanized
rubber insulation of the wires themselves is covered with a special
braid of asbestos, and in order to diminish the amount of combustible
insulating material, the highest grade of vulcanized rubber has been
used, and the thickness of the insulation correspondingly reduced. It
is confidently believed that the woodwork of the car body proper
cannot be seriously endangered by an accident to the electric
apparatus beneath the car. Insulation is necessarily combustible, and
in burning evolves much smoke; occasional accidents to the apparatus,
notwithstanding every possible precaution, will sometimes happen; and
in the subway the flash even of an absolutely insignificant fuse may
be clearly visible and cause alarm. The public traveling in the subway
should remember that even very severe short-circuits and extremely
bright flashes beneath the car involve absolutely no danger to
passengers who remain inside the car.
The photograph on page 120 illustrates the control wiring of the
new steel motorcars. The method of assembling the apparatus differs
materially from that adopted in wiring the outfit of cars first
ordered, and, as the result of greater compactness which has been
attained, the aggregate length of the wiring has been reduced
one-third.
The quality and thickness of the insulation is the same as in the case
of the earlier cars, but the use of asbestos conduits is abandoned
and iron pipe substituted. In every respect it is believed that the
design and workmanship employed in mounting and wiring the motors and
control equipments under these steel cars is unequaled elsewhere in
similar work up to the present time.
[Illustration: APPARATUS UNDER STEEL MOTOR CAR]
The motors and car wiring are protected by a carefully planned system
of fuses, the function of which is to melt and open the circuits, so
cutting off power in case of failure of insulation.
Express trains and local trains alike are provided with a bus line,
which interconnects the electrical supply to all cars and prevents
interruption of the delivery of current to motors in case the
collector shoes attached to any given car should momentarily fail to
make contact with the third rail. At certain cross-overs this operates
to prevent extinguishing the lamps in successive cars as the train
passes from one track to another. The controller is so constructed
that when the train is in motion the motorman is compelled to keep his
hand upon it, otherwise the power is automatically cut off and the
brakes are applied. This important safety device, which, in case a
motorman be suddenly incapacitated at his post, will promptly stop the
train, is a recent invention and is first introduced in practical
service upon trains of the Interborough Company.
[Sidenote: _Heating
and
Lighting_]
All cars are heated and lighted by electricity. The heaters are placed
beneath the seats, and special precautions have been taken to insure
uniform distribution of the heat. The wiring for heaters and lights
has been practically safe-guarded to avoid, so far as possible, all
risk of short-circuit or fire, the wire used for the heater circuits
being carried upon porcelain insulators from all woodwork by large
clearances, while the wiring for lights is carried in metallic
conduit. All lamp sockets are specially designed to prevent
possibility of fire and are separated from the woodwork of the car by
air spaces and by asbestos.
[Illustration: (FIRE ALARM)]
The interior of each car is lighted by twenty-six 10-candle power
lamps, in addition to four lamps provided for platforms and markers.
The lamps for lighting the interior are carefully located, with a view
to securing uniform and effective illumination.