ELECTRO-TECHNICAL
SERIES
REESE LIBRARY
__n__n__n__ rt,
UNIVERSITY OF CALIFORNIA.
^ecerceJ &CA. / ~, , 180 & .
'cessions No. &i 00 1- . CA/.s-.s- No.
BY THE SAME AUTHORS
Elementary Electro - Technical Series
COMPRISING
Alternating Electric Currents.
Electric Heating.
Electromagnetism.
Electricity in Electro-Therapeutics.
Electric Arc Lighting.
Electric Incandescent Lighting.
Electric Motors.
Electric Street Railways.
Electric Telephony.
Electric Telegraphy.
Cloth, Price per Volume, $1.00.
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Cloth, $2.50.
THE W. J. JOHNSTON COMPANY
253 BROADWAY, NEW YORK
ELEMENTARY ELECTRO-TECHNICAL SERIES
ELECTRIC STREET
RAILWAYS
BY
EDWIN J. HOUSTON, PH. D.
AND
A. E. KEffN^LLY, So. D.
NEW YORK
THE W. J. JOHNSTON COMPANY
253 BROADWAY
1896
VI PREFACE.
clear conception of its method of oper-
ation. The authors have prepared this
little volume of the Mectro- Technical Series
in the belief that these difficulties are ap-
parent rather than real that it is quite
possible for the general public to obtain a
fairly intimate knowledge of the leading
principles of electric traction without any
previous knowledge of electrotechnics.
It is a matter of nece'ssity rather than
choice, at the close of this nineteenth cen-
tury, when electric traction has become so
nearly universal, that a knowledge of the
main principles concerned should be gener-
ally accessible, without special training,
and more especially is this desirable on the
part of those, now an exceedingly exten-
sive class, w r ho are connected in some way
or other with such enterprises.
The authors present this book to the
general public hoping that it will meet the
need above referred to.
(UNIVERSITY
CONTENTS.
I. INTRODUCTION, .... 1
II. EARLY HISTORY OF THE ELECTRIC
RAILWAY, .... 8
III. ELEMENTARY ELECTRIC PRINCIPLES, 15
IV. THE MOTOR, 67
V. CARS AND CAR TRUCKS, . . 97
VI. ELECTRIC LIGHTING AND HEATING
OF CARS, ..... 134
VII. CONTROLLERS AND SWITCHES, . 154
VIII. TROLLEYS, 204
IX. TROLLEY LINE CONSTRUCTION, .- 219
X. TRACK CONSTRUCTION, . . . 242
iii
IV CONTENTS.
CHAPTER PAGE
XL ELECTEOLYSIS, .... 249
XII. SWITCHBOARDS, .... 262
XIII. GENERATORS AND POWER HOUSES, 279
XIV. OPERATION AND MAINTENANCE, . 297
XV. STORAGE BATTERY SYSTEM, . . 307
XVI. ELECTRIC LOCOMOTIVES, . . 323
ELECTRIC STREET RAIL-
WAYS.
CHAPTER I.
INT KODUCTION.
THE introduction of the electric street
railway naturally caused much wonder-
ment. There seemed at the first some-
thing weird in the possibility of propel-
ling a heavily loaded vehicle, from place to
place, without any apparent motive power,
and, even at the present time, there remains
no little astonishment in the mind of the
casual observer as to how the electric
agency can silently, yet surely, find its way
from a power house, in some remote corner
of a city, through an intricate maze of
2 ELECTRIC STREET RAILWAYS.
streets and turnings, and propel eacli car
as though the latter were under the guid-
ance of a familiar spirit. The wonder
grows, when it is pointed out that the
electric current not only has to find its
way from the power house over the
trolley wires to the cars, wherever these
may be, but has also to return to the
power house through the track and
ground.
It is, unfortunately, too true that the
real nature of electricity remains un-
known, even in this electric age. For this
reason, there has, perhaps, existed, in the
minds of the public, too marked an unwill-
ingness to attempt even to form ideas as
to the laws which control electric opera-
tions. But it should not be forgotten,
that although our knowledge of the exact
nature of electricity is imperfect, yet
INTRODUCTION. 3
our knowledge of the manner in which it
operates, that is of the laws which control
it, is surprisingly definite. Indeed, so far
as the laws which govern the flow of
electric currents through conducting paths
or circuits are concerned, our knowledge
is even more definite than of the laws
which control the flow of water or gas
through pipes. In fact, as we shall
subsequently see, a remarkable analogy
exists between the laws which govern the
flow of gross matter in the fluid state, that
is as liquids or gases, and the law T s which
govern the flmv of electricity.
It may be well, therefore, before pro-
ceeding further with the general discus-
sion of electric street railways, to outline
briefly the points of similarity between
the flow of liquids and the flow of elec-
tricity.
4 ELECTRIC STREET RAILWAYS.
Perhaps no better illustration could be
given, concerning some of the laws of
liquid flow, than that taken from the dis-
tribution of water through the mains and
pipes of a large city. Here, as is well
known, a supply of water is provided in
a reservoir, at a high level or pressure.
Pipes or mains connecting with this reser-
voir extend beneath the streets to all por-
tions of the city that are to be supplied
with water. No difficulty will be experi-
enced in understanding how, if no obstruc-
tion exists in the pipes, the water will
flow through them from the reservoir and
escape through any outlet at a lower level.
"
Let us now examine the network of
pipes connected with a reservoir in a
system of municipal water distribution.
It is evident that the object of such a
system is to supply the houses or other
INTRODUCTION. 5
buildings either with water, or with the
power the water is capable of exerting.
For this purpose two sets of pipes are
provided ; viz.,
(1) Those connected immediately with the
reservoir and intended to carry the water.
(2) Those connected to the consumers'
waste pipes.
The latter are connected intermediately
with the sew^er system, and ultimately
with the lake, river, or ocean into which
such sewer system discharges.
Between the reservoir and the river, it
is evident that the flow of water through
the pipes is due to gravity, the water find-
ing its way through the pipes in obedience
to the law of liquid levels. After the
river has been reached, and the water is
ultimately discharged into the ocean, thus
reaching its lowest level, some means must
6 ELECTRIC STREET RAILWAYS.
be provided for causing the water to rise
against the force of gravity and fill the
reservoir afresh. This energy is received
from the sun during the evaporation of
the water when it passes into vapor and
rises into the atmosphere. On the loss of
the heat so received the water again falls
under the influence of gravity, and returns
to the reservoir.
An analogy between the preceding
system of water distribution through the
pipes of a city, and a system of electric
distribution through the trolley wires, is
evident. Here, as we shall more fully see
in a subsequent chapter, an actual differ-
ence of electric level exists, whereby an
electric source, or generator, at the power
house, causes the electricity to flow
througl; all the conducting outgoing trol-
ley wires from the higher electric level
INTRODUCTION. 7
of the generator to the cars. In passing
through the cars, it may light and heat
them as well as drive their motors. On
leaving the cars it flows through the
ground back again to the generators in the
power house. In this latter part of its cir-
cuit or path, an analogy is to be found
between the discharge of the water to
the lower level of the ocean, prior to
its passage back again to the higher level
of the reservoir.
Although we have thus traced the anal-
ogy between liquid flow and electric flow,
and have shown that the same general
laws apply to each, yet it must be remem-
bered that this is an analogy only ; and
that electricity is not believed to be a mate-
rial fluid. The analogy is, however, useful,
and will aid the student in forming practi-
cal conceptions of the electric circuit.
CHAPTER II.
EARLY HISTORY OF THE ELECTRIC RAILWAY.
THE broad idea of propelling vehicles
by means of the electric current appears to
have suggested itself to the minds of
inventors at an early date. As long ago as
1835, Thomas Davenport, of Vermont, con-
structed a working model of a car pro-
pelled by an electric motor of his own
invention. In 1838, Robert Davidson, of
Scotland, also produced an electrically pro-
pelled car. Both of these early cars
derived their propelling current from
voltaic batteries carried on the car.
The idea of taking the electric current
required for the propulsion of the car from
8
HISTORY. OF THE ELECTRIC RAILWAY. 9
conductors laid alongside the track was
not conceived until a somewhat later date ;
namely, in 1840, when Henry Pinkus
obtained letters patent in Great Britain for
a method of propelling carriages either on
railroads or on ordinary highways. This
patent discloses among other things, the
broad idea of taking electric current from
conductors, in contradistinction to employ-
ing batteries on the car.
Space will not permit us to enter in
detail on this portion of the early history
of the electric railway. It will suffice to
say, that in 1851, Professor Page of the
Smithsonian Institution devised an electric
locomotive which he ran on a track at the
rate of nineteen miles an hour. This
locomotive, like those of Davenport and
Davidson, carried the voltaic battery
required for its propulsion. About the
10 ELECTRIC STREET RAILWAYS.
same time Professor Moses G. Farmer also
devised an electrically propelled car.
All these early discoveries belong to the
type of ideas that are born too early to
come to fruition. Practically the only
electric source that was known at this date
was the voltaic battery, which is incapable
of commercially producing the powerful
electric currents required for the propul-
sion of street cars. It was not until the
dynamo-electric machine was perfected
that electric car propulsion became com-
mercially practicable.
The advent of the dynamo-electric
generator, therefore, marked the second era
in the history of electric railway develop-
ment. The low cost at which this elec-
tric source can furnish powerful currents
attracted the attention of inventors, who
HISTORY OF THE ELECTRIC RAILWAY. 11
long before had recognized the part elec-
tric! fcy was destined to play in electric
locomotion. Consequently, this era of the
history of the electric railway contains
many inventions.
It is not our intention to enter into any
discussion as to the claims of the various
inventors to priority in any of the more
salient features of the art of electric trac-
tion. We will content ourselves with a
brief account only of some of the work
accomplished at this time.
One of the pioneers at the beginning of
this era in the history of the electric rail-
way was George Green, who devised a
road on a plan similar to that of Farmer,
but containing many marked improve-
ments. Green, who was poor, experienced
difficulty in getting his patent interests
12 ELECTRIC STREET RAILWAYS.
attended to. Being placed in interferences
with, other applicants, a patent was not
issued to him until the last month of 1891,
although applied for as early as 1879.
Passing by a number of inventors who
devised electric locomotives of various
types, we come to the electric railway of
Siemens and Halske, which was put into
actual operation at the Industrial Exhibi-
tion of Berlin in 1879. As in all electric
railways belonging to this era, the motive
power was derived from dynamos located
at a central station. The current was
delivered to the motor by means of a slid-
ing contact under the locomotive, rubbing
against a rail placed midway between the
two track rails.
Very little was done in electric railways
in the United States, prior to 1883. It is
HISTORY OF THE ELECTRIC RAILWAY. 13
true that in 1880 some work was under-
taken by Edison which resulted in the
erection of an experimental track, and that
prior to this date ; namely, in May, 1879,
Stephen D. Field had done some experi-
mental work which he protected in the
United States Patent office by a caveat.
In the meantime inventors in other
countries had by no means been idle.
The honor of establishing the first com-
mercial electric street railway appears to
belong to Germany, where the Lichten-
feld line was put in operation in 1881.
Another road was opened at Portrush, in
the north of Ireland, in 1883, the dynamos
being in this case driven by water power.
Among early railways operated in the
United States was one constructed and
put in operation by Vanderpoele, at the
14 ELECTRIC STREET RAILWAYS.
Chicago State Fair during two months
in 1884. A short line, located on one
of the piers on Coney Island, N. Y., was
operated during the summer season of
1884. The year 1884 also saw the first
public electric street railway in operation
at Providence, R. L, and the first practical
trolley road was that in the suburbs of
Kansas City, Mo., in the same year.
The advantages possessed by electric
traction over ordinary methods, such for
example, as horse cars, are so great, that
while in 1884 the first electric road was
installed in the United States, there were,
in
1889, 50 roads with 100 miles of track.
1890, 200 " 1,200 "
1891, 275 " 2,250 "
1894, 606 " 7,470 "
1895 (July), 880 " 10,863 "
IVERSITY)
w .X
CHAPTER III.
ELEMENTARY ELECTRIC PRINCIPLES.
BEFORE proceeding to a consideration of
purely electrical matters it will be advis-
able to discuss briefly the general subjects
of work and activity. Suppose, for
example, that a street car is being drawn
at a steady rate of 5 miles an hour by
a horse along a level track. Then it is
evident that the horse has to do work in a
mechanical sense, in order to maintain the
motion. If the car could be so constructed
that there was absolutely no friction in its
journal bearings, and, moreover, if the road-
bed could be so constructed that there
were no inequalities in its metal surfaces,
15
16 ELECTRIC STKEET RAILWAYS.
and no friction between the wheels and
the rails, then no work would have to be
expended in maintaining a steady speed
on a level road; or, in other words, once
the car was set in motion, it would con-
tinue to run at the same rate for an indefi-
nite period. Under practical conditions,
however, as is well known, a certain
amount of friction necessarily occurs and
has to be overcome. The greater this
friction the greater will be the amount of
work which must be expended in order to
keep the car running. If the road instead
of being level is on a gradient, then it is
evident that an ascent of this gradient
necessitates the expenditure of work
against gravitational force, in addition to
the work expended in overcoming friction.
The heavier the car and the greater its
load ; i. e., the greater the number of pas-
sengers it carries, the greater will be the
ELEMENTARY ELECTRIC PRINCIPLES. 17
frictional work and also the gravitational
work.
In order to estimate the amount of
work done in any particular case, as for
example, in the case above referred to of a
moving car, reference is had to certain
units of work. It is evident that when
the car is being pulled by a rope, the rope
is subjected to tension, such as might be
produced by a weight supported over a
pulley. The harder the horse pulls, the
greater will be the tension and the greater
the equivalent weight. Thus a horse may
readily exert a pull upon its traces of
400 pounds weight. The greater the dis-
tance through which the tension is ex-
erted, the greater will be the work done.
Thus if a tension of 400 pounds weight
be steadily exerted upon a car so as to
draw the latter through a distance of
18 ELECTRIC STREET RAILWAYS.
100 feet, then the work done will be 100
times as great as if the car were only
drawn under this tension through 1 foot;
and, generally, the amount of work, which
is performed by a tension or pull, is equal
to the tension multiplied by the distance
through which it has been exerted, so that
if the horse continues to exert a pull of
400 pounds so as to draw the car 100
feet, the horse will have expended on
the car an amount of work equal to
400 X 100 = 40,000 foot-pounds.
The foot-pound is not generally em-
ployed as the unit of work, e'xcept in
English-speaking countries, and, even in
such countries, scientific men generally
prefer the joule, a unit based on the
French system of weights and measures.
/TOO
A joule is of a foot-pound, approxi-
ELEMENTARY ELECTRIC PRINCIPLES. 19
mately ; or, one foot-pound may be taken
as equal to 1.355 joules. The foot-pound
is, consequently, roughly one-third greater
than the joule. If we multiply the
number of foot-pounds by 1.355, we
obtain the number of joules within a
degree of accuracy sufficient for all ordi-
nary purposes. For example, when a
man, weighing 150 pounds, raises himself
through a vertical distance of 100 feet, he
performs an amount of work equal to
100 x 150 = 15,000 foot-pounds in the
process. The same amount of work might
be expressed in joules instead of in foot-
pounds by multiplying the number of
foot-pounds by 1.355; or, 15,000 x
1.355 = 20,325 joules. Again, when the
horse raises a 25,000 pound car along a
gradient through a total vertical distance
of 100 feet, it thereby necessarily per-
forms an amount of work against gravi-
20 ELECTRIC STREET RAILWAYS.
tation, represented by 100 X 25,000
2,500,000 foot-pounds. This amount of
work might be expressed in joules by
multiplying by 1.355 = 3,387,500 joules.
A very important distinction must be
carefully kept in mind between work
expended in performing any operation,
and the rate at which that work is ex-
pended ; or, as it is usually called, the activ-
ity. For example, a man weighing 150
pounds may raise his weight through 100
feet, by ascending a flight of stairs, in 10
minutes, or in 1 minute. The amount
of work done against gravitation will in
either case be the same ; namely, 15,000
foot-pounds, or 20,325 joules, but it is evi-
dent that the effort which the man must
exert in the two cases, and the relative
degree of exhaustion which he will
undergo will be very different. Ascend-
ELEMENTARY ELECTRIC PRINCIPLES. 21
ing the flight in 10 minutes would be
walking upstairs at a leisurely rate, while
ascending it iu 1 minute would mean
running upstairs at nearly full speed.
The man is obviously ten times more
active in the second case than in the first ;
or, he expends energy ten times faster.
In other words, he works ten times as fast
in the second case as in the first. Conse-
quently, activity may be defined as the
rate-of-working.
The unit of activity generally employed
in English-speaking countries is that based
on the foot-pound, and is \X\zfoot-pound-per
second, so that unit activity is the rate
of expending 1 foot pound of work in 1
second. If, for example, a man raises his
weight of 1 50 pounds through -r^th of a
foot in each second of time, he expends an
22 ELECTKIC STREET RAILWAYS.
amount of work equal to 150 X - = 1
150
foot-pound in each second ; or, is working
at the unit rate, or with the unit activity.
As this rate of working would evidently
be a very small one, in dealing with large
machines it is more usual to employ a
unit called the horse-power, which is 550
foot-pounds in 1 second. Thus, when a
man weighing 150 pounds, raises his
weight through 100 feet in 1 minute or 60
seconds, he will perform 15,000 foot-pounds
in 60 seconds, or he will average a rate
of working of - = 250 foot-pounds
250 5 .
per second; or, == jths horse-power ;
or, will be working roughly at half the
rate of a standard horse. If, however, the
man ascends 100 feet in 10 minutes, he
performs 15,000 foot-pounds in 600 sec-
ELEMENTARY ELECTRIC PRINCIPLES. 23
onds; or, at an average rate of 25 foot-
pounds-per-second, that is his activity is
only -^ = Truths of one horse-power.
OOU
Where the joule is employed as the
unit of work, the international unit of
activity is the joule-per-second ; or, as it
is commonly called, the watt, after James
Watt. It is an interesting fact that James
Watt introduced the term horse-power in
connection with his early steam engine,
and, in accordance with international
usage, of naming practical units after the
names of distinguished scientists, Watt's
name has been selected in connection with
the international unit of activity. An
activity of 1 foot-pound per second is
an activity of 1.355 joules-per-second or
1.355 watts. Similarly, an activity of 1
horse-power, or 550 foot-pounds-per-sec-
OF THE
TJNI^ ERSITT
24 ELECTRIC STREET RAILWAYS.
ond, is an activity of 550 X 1.355 746
joules-per-second, or 746 watts. If we
multiply the number of horse-power
which are being developed in any machine
by 746, we obtain the activity of that
machine expressed in watts. As the rate
of 0.738 foot-pound -per-second is a very
small unit, being about 26 per cent, smaller
than the foot-pound per second, and
requiring, therefore, large numbers to
express large powers, in dealing with
engines, it is customary to use a deci-
mal multiple of this unit, so that the
practical international unit of activity
is the kilowatt, or 1,000 watts. Conse-
quently, the horse-power, being as above
746
mentioned 746 watts, is r-ths f
larger unit, or the kilowatt, and may be
taken as, approximately, 3/4ths of a kilo-
watt. A kilowatt will, therefore, be 4/3rds
ELEMENTARY ELECTRIC PRINCIPLES. 25
or 1 l/3rd horse-power, approximately.
When we speak of a dynamo or motor
as having a capacity of 100 kilowatts, (that
is to say of being capable of maintaining
an activity of 100 kilowatts, or 100,000
watts = 100,000 joules-per-second = 73,800
foot-pounds -per-second,) we mean an
activity of 1 1/3 x 100 = 133 horse-
power, approximately ; or, 134 horse-power
more nearly.
The problem which presents itself to
the street railway manager is that of
economically driving street cars by electric
power, and it is to be carefully remem-
bered that the same amount of power
must be exerted by the engines in the
power house as by horses drawing the
cars along the streets at the same rate. In
fact the engines in the power house will
have to work harder, or develop a greater
26 ELECTRIC STREET RAILWAYS.
activity than the horses, owing to the
necessary losses of power which inci-
dentally occur in transmission. If, for
example, we imagine that all the cars in
the streets of the city are travelling steadily
along at the same average rate as the pis-
tons of the engines in the power house, then
the pull exerted by the pistons will be
equal to the aggregate equivalent pull of
all the cars, increased by a certain amount
corresponding to losses in transmission.
It remains now to show how power can
be calculated and expressed in electric
units. In other words, if we require to
supply a certain activity in horse-power or
kilowatts to a moving car, we need to find
how to express this power in relation to
electric circuits, since the power must be
conveyed by the electric circuits from the
power house to the car. We will, there-
ELEMENTARY ELECTRIC PRINCIPLES. 27
fore, discuss the elementary principles of
electric circuits.
An electric circuit is a conducting path
provided for the passage of electricity. It
connects an electric source or generator,
with the devices to be operated by the
electric current. Such a circuit is said to
be made or closed when its path is com-
pleted, and is said to be broken or opened
when its path is interrupted at some point
or points. Thus, in the case of the elec-
tric car, an electric circuit exists between
the power house where the current is
generated, through the trolley wire and
track, to the motors of the car. When
such a circuit is closed, the current passes
through the car, and drives the motor or
motors. On the contrary, when the circuit
is opened by the motor man at the switch,
the current ceases to flow.
28 ELECTRIC STREET RAILWAYS.
Fig. 1, represents a simple electric cir-
cuit consisting of a generator G, a trolley
wire W W , a car with its trolley
Tj motors m m, and the track K K,
employed as a return conductor. What
passes through this circuit is an electric
flow, generally called an electric current.
W > W
FIG. 1. SIMPLE CAB CIRCUIT.
In order to obtain definite ideas concern-
ing an electric current, a unit of electric
current, or rate-of-flow, called an ampere, is
employed. It will be advisable, however,
before discussing the value of the ampere,
to consider certain other quantities which
are always intimately connected with
every electric circuit. Turning our atten-
ELEMENTARY ELECTRIC PRINCIPLES. 29
tion first to the generator G, it is necessary
to observe that the primary function of
the generator is not, as is ordinarily
believed, to produce electric current, but
to produce in the circuit a variety of force,
called electromotive force, which is gener-
ally abbreviated E. M. F. When the
generator is driven by an engine it will
supply an E. M. F. whether the electric
circuit is open or closed, that is to say,
whether an electric current can or cannot
flow in the circuit. In other words, the
generator, when running, always supplies
E. M. F., but no current can be sent
through the circuit until the circuit is
closed. This corresponds to the case of a
reservoir, which produces a water pressure
whether the water be escaping under that
pressure or not.
In Fig. 2, a rotary pump P, is supposed
30 ELECTRIC STREET RAILWAYS.
to be placed in a power house situated by
the side of a river K K, and provided with
a pipe by which it can draw water from the
river and send it through the pipe W W.
M is a water motor situated at some con-
w
K|
FIG. 2. SIMPLE WATER CIRCUIT.
venient point and connected with the
main pipe W W, by a small branch pipe,
in which is placed a valve V. When the
valve is closed, the motor M, is prevented
from running, since no water current
passes through it. The hydraulic circuit
W W, K J 7 may then be said to be broken
ELEMENTARY ELECTRIC PRINCIPLES. 31
or open. When, however, the valve V, is
opened, water passes through the motor
Mj and discharges into the river, thus clos-
ing the hydraulic circuit, and permitting a
water current to flow through the circuit.
It is evident that whether the valve F, be
opened or not, the generator or water
pump P, will develop, when running, a
pressure or watermotive force in the pipe
W W, but that no current or flow of water
can take place until the valve F, permits
it to do so, thus closing the circuit. Here
the watermotive force, produced by the
action of the pump whether the hydraulic
circuit be opened or closed, corresponds to
the electromotive force produced by the
generator whether the electric circuit be
opened or closed.
The pressure generated in the supply
pipe W W, by the pump P, might be
32 ELECTRIC STREET RAILWAYS.
expressed in pounds-per-square-inch ; or, as
the pressure produced by a column of
water a certain number of feet in height.
In the electric circuit the pressure pro-
duced by the action of the generator 6r, is
expressed in units of electromotive force,
called volts. In street-car systems the elec-
tric pressure produced by the generator is
almost invariably about 500 volts ; that is
to say, the pressure between the trolley
wires and the track is maintained, approxi-
mately, at 500 volts, while the pressure at
the power house between the terminals of
the generator 6r, may be somewhat in
excess of this, say 550 volts, in order to
make up for the loss of pressure occurring
in the circuit.
If a reservoir R, Fig. 3, filled with water
and maintained at a constant level L L, be
allowed to discharge steadily through two
ELEMENTARY ELECTRIC PRINCIPLES. 33
pipes, as indicated in Fig. 3, one pipe A !>,
being a long, narrow pipe, and the other
C D, being a short, wide pipe, it is evident
that a much greater flow of water will
take place in a given time through the
pipe O Dj than through the pipe A ,
since the water pressure at the openings A
I
FIG. 3. RESISTANCE OF WATER PIPES.
and Cj is the same ; namely, the height of
water in the reservoir. The difference in
the rat e-of -flow of water may be ascribed
to the different resistance offered by the
two pipes to the flow of water, the resist-
ance of the long, narrow pipe being com-
paratively great, and that of the short,
wide pipe being comparatively small.
34 ELECTRIC STREET RAILWAYS.
In the same way, Fig. 4, represents an
electric generator 6r, which, when running,
O / O'
acts the part of the reservoir in the pre-
ceding case, since it supplies a steady elec-
tric pressure between its terminals. If
two circuits are closed to this pressure, one
through a long, thin wire A A' B B, and
B 1
FIG. 4. RESISTANCE OP CONDUCTING WIRES.
the other, through a short, thick wire O C'
D 1 D, then the electric flow or current,
which will pass through these two circuits,
will be very different, a comparatively
small or feeble current passing through
the long, fine-wire circuit, and a compara-
tively strong, or heavy current, passing
through the short thick- wire circuit.
ELEMENTARY ELECTRIC PRINCIPLES. 35
This difference in flow or current be-
tween the two circuits may be ascribed to
a difference in what is called their electric
resistance. The electric resistance of a
long, thin- wire circuit is comparatively
great ; i. e., it offers a comparatively great
obstacle to the passage of electricity under
the pressure of the generator G ; while a
short, thick-wire circuit has a compara-
tively small electric resistance; i. e., it
offers a lesser obstacle to the passage of
electricity.
Electric resistance is usually measured
in terms of a unit of resistance called the
ohm, after Dr. Ohm of Berlin, who first
pointed out the laws regulating the flow
of electricity in conducting circuits. The
amount of resistance ; i. e., the number of
ohms in a given uniform conductor, such as
a copper wire, depends upon the length of
! "UNIVERSITY
36 ELECTRIC STREET RAILWAYS.
the wire, upon its area of cross-section and
upon its physical condition. The longer
and narrower a wire, the greater will be
its electric resistance. In the same way,
the longer and narrower a pipe, the
greater its water resistance; on the con-
trary, the shorter a wire and the greater its
area of cross-section, the smaller will be
its resistance. An ordinary copper trolley
wire, which is No. 0, American Wire
Gauge, with a diameter of 0.325", has a
resistance per mile of, approximately, half
an ohm, so that 2 miles of this wire
would have a resistance of, approximately,
1 ohm, and 1 foot of the wire would
have a resistance of J x =
ohm, approximately. If the trolley wire
instead of being No. gauge were No.
0000, which is a wire about twice as heavy
as No. 0, having a diameter of 0.46", it
ELEMENTARY ELECTRIC PRINCIPLES. 37
would have only half the resistance of No.
0, and, therefore, approximately, l/4th ohm
per mile.
In Fig. 5, five copper wires, having dif-
ferent lengths and areas of cross-sec-
B 10
A 10
O 10
FIG. 5. RESISTANCE OF WIRES.
tion, are diagrammatically represented.
A, represents a trolley wire 1 mile long
and 0.325" in diameter, having, there-
fore, a resistance of approximately 0.5
ohm. 13, is a wire 2 miles long of the
38 ELECTRIC STREET RAILWAYS.
same cross-section, and, therefore, offer-
ing 1.0 ohm. C) is a wire half a mile
long of the same cross-section, and,
therefore, offering a resistance of, approxi
mately, 0.25 ohm. _/>, is a wire 1 mile
long, but having a cross-section, as repre-
sented on the left hand side, say twice that
of any of the wires, A, B, or C. It will,
therefore, have half the resistance of A, or
05 *
- = 0.25 ohm. E, is a wire 0.65" in
2i
diameter, having, therefore, four times the
cross-section of A, and being 2 miles in
length. If the wire were of the same cross-
section as A, it would have 0.5 x 2 = 1
ohm, but being four times as heavy, its
resistance will be one-quarter of this, or
-^- = 0.25 ohm. Consequently, C, D,
and E^ have all the same resistance,
although their dimensions are so different.
ELEMENTARY ELECTRIC PRINCIPLES. 39
If, therefore, the cross-section and
length of any copper wire be known, we
can determine what its resistance will be,
assuming that the conducting power of the
substance of the wire is the same as that
of the trolley wire we have selected as our
standard. The resistance will be directly
proportional to the length, and inversely
proportional to the area of cross-section ;
or, in other words, if the length be doubled
the resistance will be doubled, while if
the area of cross-section be doubled the
resistance will be halved.
We have hitherto considered copper
wires only in estimating the resistance oi
a circuit. When any other conducting
material, such as iron, is employed, the
resistance of a wire having a given length
and cross-section will be materially dif-
ferent. Thus, an iron wire has, approxi-
40 ELECTRIC STREET RAILWAYS.
mately, 6 1/2 times as mucli resistance as
a wire of copper of equal dimensions.
Iron trolley wires are, therefore, never
used, for the reason that it would be nec-
essary to employ a wire having about 6 1/2
times the cross-section of ordinary trolley
wire to have the same conductance ; i. e.,
ability to conduct electric current. Iron,
however, enters into street railway circuits
in the form of the tracks, which, as we
have seen, form a portion of the return
circuit to the power house.
The dimensions of a wire which has a
resistance of 1 ohm will necessarily vary
with the character of the material of which
the wire is composed. Thus, in copper, its
length might be approximately 2 miles, if
its diameter was that of a trolley wire,
0.325"; or, its length might be only 1
foot, if of No. 40 American Wire Gauge,
ELEMENTARY ELECTRIC PRINCIPLES. 41
having a diameter of 0.003145" ; if of iron,
a length of about 900 feet of trolley wire ;
and, roughly, 2 inches of No. 40 wire
would have a resistance of 1 ohm. In
all cases the exact resistance would de-
pend upon the degree of purity of the
metal, as well as upon its physical condi-
tion ; that is to say, upon its hardness,
and temperature. Since mercury is a
metal, which is fluid at ordinary tem-
peratures, and can be readily obtained in a
nearly homogeneous and pure condition,
the ohm has been practically defined as
the resistance of a column of mercury
1.063 metres in length, and 1 square
millimetre in cross-section, at the temper-
ature of melting ice.
It is evident from what we have said
that the quantity of water which flows, in
any given time, through the pipe referred
42 ELECTKIC STREET RAILWAYS.
to in connection with Fig. 3, will depend
both on the pressure or head of water in
the reservoir, as well as upon the -resist-
ance which the pipe offers to the now. In
the case of the electric circuit the same
rule applies, that is to say, the quantity of
electricity which passes or flows in an elec-
tric circuit, depends not only upon the
electric pressure in the circuit which
causes the flow, but also upon the resis-
tance of the circuit which opposes it.
In the case of the electric circuit the
electric current is related to the E. M. F.
and to the resistance in accordance with a
law generally known as Ohm's law. This
law may be expressed as follows :
The current strength in amperes flowing
through a circuit, varies directly with the
pressure or E. M. F., and inversely with
ELEMENTARY ELECTRIC PRINCIPLES. 43
the resistance ; so that if we divide the
number of volts in the E. M. F. by the
number of ohms in the resistance, we obtain
the current strength in amperes; or, con-
volts
cisely, amperes = -r .
ohms
Thus, if a circuit contains an E. M. F. of
10 volts, and a resistance of 5 ohms, the
current in the circuit would be -~- 2
amperes.
We have seen, in connection with Fig. 3,
that the quantity of water which flows per
second through the water pipe from the
reservoir, depends both on the pressure at
the reservoir, and on the resistance of the
pipe. This, however, is only true when no
obstacle to the flow of the water exists save
the resistance of the pipe itself. If, for
example, instead of permitting the water
44
ELECTRIC STREET RAILWAYS.
to escape freely from the open end of the
pipe it be first caused to pass through, and
actuate, a water motor, then the condi-
tions of flow will be profoundly modified,
much less water flowing through the pipe
in the second case than in the first. If, for
FIG. 6. HYDRAULIC GRADIENT.
example, as in Fig. 6, the reservoir H, is
capable of discharging by the pipe A k',
either through the faucet &', into the air,
or through the faucet ?, after passing
through the motor M, the flow in the two
cases will be very different. In the first
ft/tU/L ~
case thej)ressure at the reservoir will be
that due to the height of the water A A',
say 50 feet, while the pressure at the dis-
ELEMENTARY ELECTRIC PRINCIPLES. 45
charge point, will simply be that of the
external air, or a column of feet. In
other words in discharging through the
pipe the water pressure suffers a drop as
represented by the dotted line A k', and
the pressure at the intermediate points is
indicated by the points V, c , d', e', f, g', li.
If, however, the faucet &', be closed, and
that at I, be opened, thereby establishing
communication through the water motor
M, the motor will commence to operate,
and in so doing will develop a back pres-
sure, or counter watermotive force, which
opposes the flow of water and acts like a
resistance. The pressure at Jc', under these
circumstances, instead of being feet, w r ill
rise to & 2 , and the drop of pressure, which
has taken place in the tube A ~k ', will have
diminished from A A' to If L, with a cor-
respondingly reduced flow of water through
the pipe.
/^ ^ OF THE
TJNIVERSITTT,
46
ELECTKIC STREET RAILWAYS.
Similarly, if the electric circuit repre-
sented in Fig. 2, be so modified as in Fig.
7, that it may be closed either at c c, di-
rectly back through the track, or at If,
FIG. 7. ELECTRIC GRADIENT.
through an electric motor J/J the electric
flow or current in amperes will be very
different in the two cases. If the circuit
be closed through the track wire at c c,
the pressure, at A, will be say 500 volts,
as represented by the dotted line A a, and
supposing the length A H, to be 1 mile
of trolley wire, then neglecting, for con-
ELEMENTARY ELECTRIC PRINCIPLES. 47
venience, the resistance of the track and
generator, the resistance of the circuit will
be 0.5 ohm, and the current strength in
the circuit 500 volts + 0.5 ohm = 1,000
amperes.
If, however, the circuit be closed through
the motor M, the latter will be actuated by
the current and will be set into rotation,
whereby a back pressure, or Counter electro-
motive force, usually abbreviated C. E.
M. F., will be set up in the motor,
of say, 450 volts, as represented by the
dotted line H li ; so that the effective
pressure or E. M. F. which drives the
current through the circuit, will be re-
duced to hh' - 500 450 = 50 volts,
and the current strength, neglecting the
resistance of the generator motor and
track, will be, 50 volts -=- 0.5 ohm = 100
amperes.
48 ELECTRIC STKKET RAILWAYS.
A flow of water is sometimes rated as
being a certain quantity of water ; i. e., a
certain number of cubic feet or gallons per
second. In the same way the electric flow
may be rated as being a certain quantity
of electricity passing through the circuit
per second. The unit of electric quantity
is called the coulomb, and has been so
chosen that a flow of 1 coulomb per sec-
ond is called an ampere. Consequently, a
flow or current of 1 ampere, maintained in
a circuit for 1 minute, represents a total
flow of 60 coulombs of electricity, and,
maintained for one hour, a total flow of
3,600 coulombs.
When an E. M. F. acts on a broken or
open circuit, it is unable to send any
current through the circuit, and will,
therefore, do no work. Thus, when the
generator at the power house is driven
ELEMENTARY ELECTRIC PRINCIPLES. 49
by an engine and supplies an E. M. F.
of 500 volts to the trolley system con-
nected with it, no current will pass
through the generator if there be no cars
on the line, assuming that the wires are
properly insulated. Under these circum-
stances the generator will not be supply-
ing any power, and the engine will have
no work to do except to drive the genera-
tor against its friction. In fact, except
that the generator armature is magnetized,
it behaves like a mere wheel of copper
and iron, so supported on an axis in bear-
ings, that it might be rotated with a very
small expenditure of power. When, how-
ever, the circuit of the generator is closed
by the connection of the cars with the
trolley wire, so that a current is trans-
mitted through the circuit or circuits
under the pressure of 500 volts, the
generator does work at a rate which will
50 ELECTRIC STREET RAILWAYS.
depend upon the amount of current sup-
plied, the greater the current strength in
amperes delivered to the trolley system,
and distributed to the cars, the greater
will be the activity which the generator
has to supply, and the greater will be the
activity which the engine must supply to
drive it, so that when the load conies on
the system by the operation of the cars,
the generator which previously required
say 20 horse-power only to revolve it,
may now require the engine to supply 500
horse-power, which activity will be trans-
formed into electric activity in the circuit.
If we multiply the pressure in volts by
the current strength in amperes which is
being supplied by that pressure, we obtain
the activity supplied in watts. Thus, if
a generator supplying 550 volts at its
terminals to a trolley system delivers a
current strength of 50 amperes through
ELEMENTARY ELECTRIC PRINCIPLES. 51
the circuit containing its armature, trolley,
street-car motor, and track, then the ac-
tivity supplied by the generator at its ter-
minals will be 550 volts X 50 amperes =
27,500 watts = 27.5 kilowatts (usually ab-
breviated KW) = 36.85 HP = 27,500
joules-per-second = 20,268 foot-pound s-per-
second. The engine would have to supply
more power than this to the genera-
tor, since it would have to make up
for the loss of power in the generator
owing to its mechanical and electrical fric-
tions, but if the generator had an efficiency
of 90 per cent., that is to say, if its output
was 90 per cent, of its intake, then the
activity which the engine would have
to supply to the generator would be
= 30>555 watts = 3(X555
KW = 40.94 HP 30,555 joules-per-
second = 22,517 foot-pounds-per-second.
52 ELECTRIC STREET RAILWAYS.
Just as the total amount of work ex-
pended by water escaping from a reser-
voir, is equal, in foot-pounds, to the
number of pounds of water multiplied by
the number of feet through which it falls,
so the total amount of work expended by
electricity in flowing through a conductor
or circuit is equal, in joules, to the number
of coulombs of electricity multiplied by
the number of volts difference of electric
level, or pressure, under which it passes.
Thus a current of 50 amperes flowing
under a pressure of 550 volts, represents a
flow of 50 coulombs-per-second under that
pressure and an amount of work equal to
50 x 550 = 27,500 joules in each second,
or, in one hour of 3,600 seconds, a total
work of 3,600 X 27,500 = 99,000,000
joules. But Ave have seen that the ac-
tivity in this circuit is 27,500 watts, and
this activity maintained for an hour will
ELEMENTARY ELECTRIC PRINCIPLES. 53
require an expenditure of 27,500 watt-
hours, or 27.5 kilowatt-hours. A watt-
liour is, therefore, a quantity of work equal
to 3,600 joules, or 2,657 foot-pounds, while
a Jdlowatt-kowr, the unit of work usually
employed with large electric machines, will
be 1,000 times as much, or 3,600,000
joules = 2,657,000 foot-pounds.
If a pressure of 550 volts is maintained
steadily at the generator terminals, under
all conditions of load, the pressure at the
trolley of the single car we have con-
sidered, will be less than 500 volts by an
amount which will depend upon the size
and number of the conductors in the net-
work supplying it, and upon the length of
those conductors, or the distance of the
car from the power house. Thus, if the
car be 1 mile from the power house, and
if the track have, for simplicity, a negligi-
54 ELECTRIC STREET RAILWAYS.
ble resistance, while the single trolley wire
supplying the car has a resistance of 0.5
ohm per mile, then the resistance between
the generator and the car will be 0.5
ohm, and the drop in this length of con-
ductor will be 50 amperes X 0.5 ohm =
25 volts, so that the pressure at the termi-
nals of the car motor as determined by
a voltmeter, or instrument for measuring
the number of volts, would be 550 25 =
525 volts, and when the car was operating,
the voltmeter, if connected between the
trolley wire and the track at the car,
would show this pressure, while as soon as
the car was disconnected by opening the
switch, the pressure between the trolley
wire and the track would immediately
rise to 550 volts, assuming no other car or
leakage current to exist over the system.
The amount of drop which will be pro-
duced over a given length of conductor
ELEMENTARY ELECTRIC PRINCIPLES. 55
will depend entirely upon the current
strength, so that if we double the current
strength we double the drop.
The activity which the motor will
receive at its terminals will be the current
strength in amperes, (which is the same
all through the circuit when only one car
is employed,) multiplied by the pressure at
its terminals. Thus, in the preceding case,
the pressure being 525 volts at the motor
terminals between trolley and track, while
the current strength is 50 amperes, the
activity absorbed by the motor will be
525 volts X 50 amperes = 26.25 KW, or
1.25 KW less than that supplied by the
generator to the line. This activity of
1.25 KW is expended in the line as heat,
uniformly distributed through its sub-
stance ; for, the drop being 25 volts, and
the current strength 50 amperes, the activ-
56 ELECTRIC STREET RAILWAYS.
ity expended in this conductor will be 25
volts X 50 amperes 1,250 watts, == 1.25
KW expended entirely as heat.
Of the 26.25 KW delivered to the
motor, only a certain fraction will be use-
fully employed in driving the car, the
remainder being uselessly expended in
heating the motor. If the efficiency of
the motor be 80 per cent., then the activity
usefully expended in the preceding case
QA
will be 26.25 X = 21 KW = 28.14
HP = 21,000 joules-per-second 15,480
foot-pounds-per-second. This activity will
be supplied to the shaft of the motor.
Assuming at present that no power is
wasted in gears, then this activity will be
available for propelling the car. For
example, if the car friction were very
small, and its total weight, including
ELEMENTAEY ELECTRIC PRINCIPLES. 57
passengers was 30,000 pounds, then the
activity supplied would be capable of lift-
ing 30,000 pounds through a distance of
15.480
t Q ..Q,. = 0.516 toot-per-second. With a
1 per cent, grade this would represent a
speed of 51.6 feet-per-second, or 35.2 miles-
per-hour, and with a 10 per cent, grade
it would represent a speed of 5.16 feet
per second, or 3.52 miles-per-hour.
It is evident, therefore, that the activity
which can be communicated to a moving
car for a given activity supplied at the
driving shaft of the engines, depends upon
the efficiency of the generator, the effi-
ciency of the motor, and the efficiency of
the line conductor, including under this
term, the track.
The efficiency of a motor or generator is
58 ELECTRIC STREET EAILWAYS.
the ratio of the output to the intake. The
efficiency of a line conductor or circuit
may also be regarded as the ratio of the
output to the intake, the intake being
measured at the generator terminals and
the output at the motor terminals. The
efficiency of a generator or a motor usually
increases with the load up to full load or
nearly full load, so that, under ordinary
circumstances the more work we can get
the motor or generator to do, within the
limits of its capacity, the greater the propor-
tion of useful work delivered, to the work
received, although the loss of work will
be absolutely greater. Thus, a street car
motor, whose maximum activity is rated
at 15 KW (approximately 20 HP) would
require, perhaps, 2 KW to run it when
entirely free from all load or disconnected
from its gears ; i. e., when doing no use-
ful work, so that its efficiency would be
ELEMENTARY ELECTRIC PRINCIPLES. 59
= o. When fully loaded, however, it
might waste 3 KW and deliver 15 KW,
so that its intake would be 18 KW, and
15
its efficiency y^- =0.833 = 8 3. 3 per cent.
Its efficiency may, therefore, increase from
to 83.3 per cent, from no load to full
load, although the actual loss of activity
in it would increase in the same range
from 2 KW to 3 KW. The same princi-
ples apply to a generator, and for this
reason it is always more economical to
operate generators at a fair proportion of
their full load.
In the case of the line conductor or con-
ductors, including . track conductors, the
case is different. The efficiency is always
less as the load increases. Thus, if we
supply a current strength of 1 ampere
over a circuit of trollev conductor and
60 ELECTRIC STREET RAILWAYS.
track, having a total resistance of 1 ohm,
then the drop in this circuit will be
1 ampere X 1 ohm 1 volt, and if the
pressure at the motor be kept at 500 volts,
the pressure at the generator will have to
be adjusted to 501 volts ; or, if the pressure
at the generator be kept at 500 volts, the
pressure at the motor terminals will, with
a current of 1 ampere, automatically be-
come 499 volts. If, however, 2 amperes
be supplied through the same circuit,
the drop will double, or will become 2
volts, and the pressure at the generator
will be 502 volts, if that at the motor is
500. In the former case the efficiency of
the line circuit will be r ; in the latter
case it will be - . Similarly, if the cur-
rent strength be increased to 100 amperes,
the drop will increase to 100 volts, and
ELEMENTARY ELECTRIC PRINCIPLES. 61
with 500 volts at the generator there will
be 400 volts left at the motor, making the
400
efficiency r = 0.8 == 80 per cent. It is
evident, therefore, that the efficiency of the
line continuously decreases with the load.
It is clear from the preceding that if
a trolley wire were very long, say 15
miles, so that its resistance was 7.5 ohms,
then the current strength of 50 amperes
passing through the circuit to operate the
car motor at the extreme distance from
the power house would produce a drop of
50 amperes x 7.5 ohms = 375 volts, leaving
only 175 volts pressure at the motor when
550 volts was the pressure at the generator
terminals, and assuming no resistance in
the ground-return circuit. The activity
delivered by the generator would be 550
volts x 50 amperes = 37.5 KW. The
62 ELECTRIC STREET RAILWAYS.
activity available at the motor terminals
would only be 175 volts X 50 amperes =
8.75 KW, so that the efficiency of the line
O ^7 K
would only be ^ = 0.319 = 31.9 per
cent., while the available speed of the car
would be correspondingly reduced. In
other words, owing to the great length of
conductor, and resistance in the circuit, a
large percentage of the activity would be
expended in heating a long length of wire,
instead of driving the car.
The same condition of line efficiency
would be produced by a number of cars
over a shorter length of circuit. Thus,
o
reverting to the case of a single mile of
trolley wire, if a bunch of five trolley cars
should start together from the distant end
of the line towards the power house, each
taking 50 amperes of current strength, the
ELEMENTARY ELECTRIC PRINCIPLES. 63
total current strength supplied to the
bunch would be 250 amperes, and the
drop in the line would be 250 amperes
X 0.5 ohm = 125 volts, making the pres-
sure at the bunch 425 volts. The line
efficiency, under these conditions would
425
be ^-r 0.772 = 77.2 per cent. Conse-
o50
sequently, when the distance to whicli cars
have to be run is great, or, when the
number of cars and the current strength
to be collectively supplied are great, the
amount of copper employed to supply the
system must be increased so as to reduce
the effective conductor resistance. If, for
example, we double the area of cross-sec-
tion of the trolley wire, and, therefore, its
weight per mile, we halve the resistance of
the conductor per mile and, consequently,
halve the drop, excluding track resistance,
and, therefore halve the drop which will
64 ELECTRIC STREET RAILWAYS.
occur at any given distance with any given
load.
There is, however, an obvious limit to
the size of trolley wire which can he prac-
tically employed. In fact, trolley wires
are almost always constructed of No. 0,
A. W. G. They are supplemented, how-
ever, in practice, by what are called
feeders; i. e., feeding conductors which
are separate from the trolley wires, but
which lead from the generator in the
power house and connect with the trolley
wire at suitable distances along the track.
Thus in Fig. 8, Gr, is the generator, and
C, a car at a certain distance along the
track. & f\, a Ft, G F* G F* four
separate feeders connecting with the trolley
wire at different distances. As shown in
the diagram, the current strength required
to supply the car, is probably supplied
ELEMENTARY ELECTRIC PRINCIPLES. 65
in a large measure by feeder G F^ so that
the feeders G F 2 , G ^ and G F 4j are
comparatively idle. Consequently, the drop
of the feeder G F^ will be comparatively
FIG. 8. FEEDER SYSTEM.
great with reference to that of the other
feeders. F^ F%, F& and F^ are called feed-
ing points.
In practice it is usual to so arrange the
feeders and the distances between feeding
points, that when all the cars are being
66 ELECTRIC STREET RAILWAYS.
operated at average distances, the drop
shall nowhere be in excess of 50 volts, and,
therefore, that with 550 volts at the gene-
rator terminals the pressure shall not be
lower than 500 volts at any point on the
line.
OF THE
-TIVERSITT
CHAPTER IV.
THE MOTOR.
As is well known, the power which pro-
pels a trolley car is obtained from the
electric current transmitted through the
circuit, by the intervention of an electric
motor or motors, there being usually two
motors placed on the truck of an ordinary
street car. Fig. 9, shows the general con-
struction of a truck with two motors J/J
M, in place, one geared to the axle of each
pair of wheels. Reserving for description
in Chapter V. the different methods
adopted for the mounting or hanging of
a motor, as well as the details in the
construction of the car truck, we will now
00 ELECTRIC STREET RAILWAYS.
proceed to the general description of the
motor, its construction and operation.
Fig. 10 shows a form of electric motor
in extended use. Here the motor is coin-
FIG. 9. CAR TRUCK WITH MOTORS IN PLACE.
pletely enclosed in a cast-steel frame F, F,
F, made in two halves, fitted together, as
shown. Since the motor runs within a few
inches of the surface of the street, and is,
therefore, exposed to dust, mud and water,
it becomes absolutely necessary not only to
^provide it with a casing, but also to make
this casing practically air and water tight.
The main shaft of the motor is seen pro-
THE MOTOR.
69
jecting through its bearing at A y and this
bearing is lubricated by the grease box O.
FIG. 10. FORM OF ELECTRIC MOTOR.
The armature shaft is connected with the
axle of the wheels on which the truck
rests, by gear ivheels enclosed in the gear
cover 6r, G. The gears are inserted in
70 ELECTRIC STREET RAILWAYS.
order to reduce the speed of the car as
well as to increase the effective pull of
the motor, as will be more clearly pointed
out subsequently. The main axle passes
through the bearing B, lubricated by the
grease box C'. The motor is supported
on the truck by the lugs Z', L'. Access
to the working parts of the motor is had
by the lid L, L, L, while a more nearly
complete inspection can be obtained by
unscrewing two bolts, one of which is seen
at B, and throwing back the upper half of
the motor upon hinges H, H. The insu-
lated cables K, K, pass through holes in
the castings and supply electric current to
the motor. This particular motor is called
a Gr. E. 800 motor, the number 800 repre-
senting that it is capable of exerting on
the car a push of 800 Ibs. weight at the
main axle, when supplied with the full cur-
rent strength, and mounted on 33" wheels
THE MOTOR. 71
on level rails. Two such motors when sup-
plied with full current strength, therefore,
give a push of 1,600 Ibs. weight to a car.
Fig. 11, shows the same motor with the
upper half thrown back on its hinges, thus
permitting an inspection of the parts of
the motor. Here, as in all this class of
electric motors, the essential parts consist
of an armature or rotating part A A, with
a commutator at M M, upon which rest
the brushes (7, (7, which carry the current
from the trolley line into and out of the
armature. The armature rotates between
four poles, of which one is shown in the
upper lid at P, surrounded by a magnetiz-
ing coil of wire W. The armature shaft
has a pinion N, secured to one of its ex-
tremities, which engages with a gear-wheel
on the main axle of the truck, which axle
passes through the bearings JB, B.
72 ELECTRIC STREET RAILWAYS.
The armature of one of the electric
motors above described consists essentially
of three parts ; namely, the armature
FIG. 11. MOTOR OF FIG. 10 OPENED.
core, mounted on its shaft, the armature
windings or coils, which are placed on
the armature, and the commutator. The
THE MOTOR.
73
general appearance presented by an arma-
ture core, mounted on its shaft, is shown
in Fig. 12. Here, as will be seen from an
FIG. 12. UNWOUND ARMATURE.
inspection of the figure, the core consists
of a cylindrical body made of soft iron,
If the armature core be made from a
74 ELECTRIC STREET RAILWAYS.
solid mass of iron, it has been found by ex-
perience that during the changes in mag-
netization to which it is subjected, when it
rotates, deleterious electric currents called
eddy currents, are generated in it. These
currents cannot be employed in the ex-
ternal circuit. ; they merely serve to heat
the armature core and so prevent the effi-
cient operation of the motor. By adopt-
ing the simple expedient of laminating the
core ; that is, of forming it of thin sheets
of iron, laid side by side, this difficulty is
avoided. The armature core shown in
Fig. 12, is laminated, that is, formed of
discs or rings clamped together and sup-
ported at right angles to the axis of the
shaft. The edges of the cylindrical iron
core thus formed are provided, circuni-
ferentially, with a series of longitudinal
grooves or recesses, as shown. These are
intended for the reception of the insulated
THE MOTOR. 75
copper conductors that carry the electric
current.
In placing the insulated copper wire on
the armature core, care is necessary to ob-
tain a symmetrical disposition of the wires.
One method of arranging the conductors
on the core is shown in Fig. 13, which
represents an armature in the process of
winding. Armatures for motors are made
in a variety of forms of which, perhaps,
the ring armature and the cylinder arma-
ture are the commonest. The armature
shown in Fig. 13 is of the cylinder type.
Here the wire is wound only on the out-
side of the core. A single cotton-covered
wire, starting at say A, passes to J3, through
the grooves, provided on the surface of
the core for its reception. It then de-
scends to O, in the curved path shown,
turns inwards and passes on to D, when it
76
ELECTRIC STREET RAILWAYS.
again crosses through the groove to JSJ and
so on. All the wires which are left pro-
jecting on the left-hand side are intended
FIG. 13. ARMATURE IN PROCESS OF WINDING.
to be connected to the part called the com-
mutator, the object of which will be ex-
plained subsequently.
A particular form of commutator is
shown in Fig. 14. It consists, as shown,
THE MOTOR.
77
of a number of segments of copper placed
longitudinally on the surface of a cylinder,
each strip bein^ insulated from the adia-
-L O J
FIG. 14. FORM OF COMMUTATOR.
cent strips by means of a thin plate of
mica. The commutator strips, segments, or
bars, as they are called, are connected to
the free ends of the wires which are
78
ELECTRIC STREET RAILWAYS.
soldered into the clips left for them. Fig.
15, shows a completed armature, or the
appearance of the armature in Figs. 12 and
FIG. 15. WOUND ARMATURE.
13, when the process of connecting and
soldering is complete.
It now remains to explain the manner in
which the electric current passing through
the armature causes it to rotate. When
THE MOTOR. 79
the current enters the armature conductors
at one brush and circulates around the
coils of wire wrapped on its surface, it
also passes through the coils of wire
around the field magnets. By these means
both the armature and the field poles are
rendered magnetic, and it is to the mag-
netic attractions and repulsions that take
place between the movable armature and
the fixed field poles, that the rotation of
the armature and the mechanical force it
develops are due. Since, however, the
form of electric motor employed in the
street car is very compact and difficult to
understand, it will be preferable first to
consider a few simpler types of electric
motors.
It is a well known fact that when two
magnets are brought near together, their
unlike poles ; i. e., the north pole of one
80 ELECTRIC STREET RAILWAYS.
and the south pole of the other, will
attract, while their like poles will repel,
so that if one of the magnets be free to
move, it will come to rest in such a posi-
FIG. 16. ACTION BETWEEN MAGNET AND ACTIVE COIL.
tion that opposite poles are adjacent. A
conductor carrying an electric current,
acts like a magnet, so that if a magnet be
approached to an active coil of conductor ;
i. e., a coil carrying a current, as shown in
Fig. 16, an attraction will take place be-
tween the unlike pole of the magnet and
the active coil. In the case of the coil of
THE MOTOR. 81
insulated wire, shown in Fig. 16, the faces
of the coil become magnetic, as marked at
S and N. If the direction of the current
through the coil be reversed, the polarity
of the coil will be reversed, so that, if the
coil were free to move, it would turn
around and present its opposite end to the
magnet ; or, if prevented from doing this,
would be repelled bodily by the magnet.
If now the coil, instead of being sus-
pended by the two wires which carry
the current into and out of it, is placed
as shown in Fig. 17, that is, suspended
flat and horizontally in the position
a b c d, by the two wires before the
north pole JV, of the bar magnet, then, as
soon as a sufficiently powerful current is
passed through the coil, it will set itself at
right angles to the magnet into the posi-
tion a b' c' d', as shown by the dotted
82 ELECTRIC STREET RAILWAYS.
lines. If the current through the coil be
reversed, the coil will turn around and
present its opposite face to the magnet.
This action can be intensified by employ-
FIG. 17. DEFLECTION OF ACTIVE COIL BY MAGNET.
ing two bar magnets with opposite poles
at j^and xSJ as shown in Fig. 18 ; for, each
magnet attracts the opposite face of the
coil. By corn bining the two bar magnets
into a single horseshoe magnet in the
manner shown in Fig. 19, the action on
THE MOTOR.
83
the coil can be rendered still more power-
ful.
In the simple form of apparatus shown
in Figs. 17 to 19, the coil has been sup-
FIG. 18. DEFLECTION OF ACTIVE COIL BY OPPOSITE
POLES OF Two MAGNETS.
ported in air. If, however, the coil be
wound upon a cylinder of iron, as shown
in Fig. 20, the magnetic power with which
it tends to rotate is very much increased.
Moreover, instead of employing a perman-
ent horseshoe magnet, we may wind a. coil
84
ELECTRIC STREET RAILWAYS.
of insulated wire C C, around the soft iron
horseshoe magnet core, shown in Fig. 20 ?
and by passing an electric current through
this wire we may obtain a more powerful
FIG. 19. DEFLECTION OF ACTIVE COIL BY HORSESHOE
MAGNET.
magnet than would be possible with any
permanent magnet of steel. By this
means we obtain a still more powerful
electromagnetic twist or pull, technically
THE MOTOR.
85
called the torque, when the current is
allowed to pass through the armature coil.
It is evident that in the preceding cases
FIG. 20. DEFLECTION OF ACTIVE COIL WOUND ON IRON
CORE BY ELECTROMAGNET.
the motion of the coil will cease as soon as
it sets itself at right angles to ibhe line
joining the magnetic poles. If, however,
the current in the coil could be automati-
86 ELECTRIC STREET RAILWAYS.
cally reversed; i. e., changed in direction,
as soon as this position was reached, the
armature would turn round, or rotate,
through half a revolution, when it would
again come to rest at right angles to the
line joining the poles ^VJ S. The device,
whereby the direction of the current
through the coils is automatically reversed
every time that the coil sets itself in the
neutral or dead position, so as to ensure
another half rotation, is called a com-
mutator, because it commutes or changes
the direction of current in the coils at the
desired moment.
Early forms of electric motors employed
only a single coil on the armature, as
represented in Fig. 20, but later forms
invariably employ a number of coils dis-
posed at uniform angular distances around
the surface of the armature so as to main-
THE MOTOR.
87
tain the twisting power or torque uni-
form in all positions.
The continuous-current electric motor,
FIG. 21. STATION AKY ELECTRIC MOTOR.
as in actual use on street cars, consists sub-
stantially of a suitable combination of the
parts just described; namely, of the anna-
88 ELECTRIC STREET RAILWAYS.
ture, of the field magnets and their poles,
and of the commutator. A practical form
of stationary electric motor is shown in
Fig. 21, where N and /SJ are the poles
of a powerful electromagnet wound with
many turns of insulated wire, and ^4,
the armature, which rotates between these
poles. C\ is the commutator upon which
the brushes B, B, rest in such a manner
that, by the rotation of the armature, the
direction of current in the loops of wire is
changed at the moment required to ensure
a continuous rotation.
Motors are made in a great variety of
forms. For example, instead of having only
two poles, four or more poles may be em-
ployed. Thus Fig. 22, shows a form of
four-pole or quadripolar motor, with its
four magnetizing coils N, /SJ N, 8, pro-
vided to produce the four poles. In this
THE MOTOR.
89
particular case four sets of brushes B, B,
are employed, of which only three are
visible in the cut. The armature A,
FIG. 22. STATIONARY QUADRIPOLAR MOTOR.
revolves in the space between the four
poles, and the current is supplied to this
armature from the brushes B, B, through
90 ELECTRIC STREET RAILWAYS.
the commutator M. Here the field frame
F F F, is of cast iron.
Street-car motors are almost always of
the quadripolar type. Owing to the fact
that these motors have a very small space
allotted them under the car, and are re-
quired to be very light, the four magnet
poles are as short as possible, and the field
frame, instead of being made of cast iron,
is of soft cast steel, which is much more
advantageous from a magnetic point of
view. In the motor of Fig. 11, there are
four poles, two only of which, the upper
and lower, are wound with coils of wire.
The poles on the side being unwound or
being, as they are sometimes called, conse-
quent magnetic poles. Fig. 23, shows the
castings for another form of quadripolar
street-car motor. In this case, each of the
four poles -ZVJ S, N, S, is surrounded by a
THE MOTOE.
91
magnetizing coil, and the whole field frame
F F F, is of cast steel. In order to permit
access to the interior of the field frame, it
Q
FIG. 23. FIELD-FRAME CASTINGS OF QUADRIPOLAR
STREET-CAR MOTOR.
is made in halves and the upper is movable
on a hinge P. The armature for this
motor is shown in Fig. 24 in three succes-
sive conditions. At -4, is seen the un-
92 ELECTRIC STREET RAILWAYS.
wound core composed of sheets of iron
punched with radial teeth, so as to form,
when assembled, a compact cylinder with
grooves or slots as shown. At J5, the
FIG. 24. ARMATURE FOR MOTOR OF FIELD' FRAME IN
FIG. 23.
insulated conductors have been placed in
these grooves ready for connection to the
commutator at the distant end of the core,
while at C 9 the finished armature is shown.
The appearance of a similar motor, after
being assembled, is shown in Fig. 25.
Here A, is the armature geared to the main
THE MOTOR.
93
axle through reducing gear, covered by the
gear cover G G. B, B, are two brushes,
FIG. 25. ASSEMBLED MOTOR OPEN FOR INSPECTION.
the armature winding being such that only
two brushes need to be employed. This
is the plan generally adopted with street-
car motors, while stationary quadripolar
OF THE
NTIVERSITT
94
ELECTRIC STREET RAILWAYS.
machines usually employ four brushes or
sets of brushes, as shown in Fig. 22. N, S,
are the two poles in the upper half of the
field frame, each being surrounded by a
FIG. 26. COMPLETED STREET-CAR MOTOR.
magnetizing coil. The completed motor,
closed and ready for suspension, is shown
in Fig. 26. Here J5 7 shows one set of
brushes protected from dust and mud by
the shell F F, is the field frame, G 6f,
THE MOTOE.
95
the gear cover. A, the armature shaft
and Ji y the truck-wheel shaft. C\ C, C,
the terminals of the motor from which
wires lead to the controller or car switch.
FIG. 27. BRUSH HOLDER.
A form of brush holder employed in the
motor of Fig. 11, is shown in Fig. 27.
This brush holder is of metal and is clamped
in the slot C, to its supporting frame
96 ELECTRIC STREET RAILWAYS.
through which it receives the electric cur-
rent. The brush slides freely in the guides
(r, G. The brush being composed of a
rectangular block of carbon, the arm A,
pivoted at JP, maintains a uniform pressure
FIG. 28. CARBON BRUSH.
at the back of the brush under the tension
of the spiral spring S t thus pressing the
brush against the surface of the "commuta-
tor beneath. The arm A, can be with-
drawn, and the brush lifted, by pulling
with the finger upon the tongue D. A
form of such brush is shown in Fig. 28.
OP THE
MDTKI.VERSITT
CHAPTER V.
CAES AND CAR TRUCKS.
A STREET car, as it appears on the street,
is composed of two distinct parts ; namely,
the car body, or the enclosed space for the
passengers, and the car truck, or the part
upon which the car body rests. Limiting
our present consideration to the car truck,
we find that this consists generally of a
frame resting upon the axles of the wheels,
through journal boxes.
There are three methods of supporting
car bodies on trucks ; viz.,
(1) By the use of a single rigid truck
Avith four wheels and two axles, the axles
97
98 ELECTRIC STREET RAILWAYS.
remaining sensibly parallel in all positions
of the car, whether on curves or on straight
tracks.
(2) By the use of two trucks, one at
each end of the car. In this case the car is
usually supported upon the swivel centre
of each truck.
(3) By t-lis use of three trucks, the car
being supported on the end trucks, and
the centre truck being movable, so that the
car axles are only parallel en straight
tracks, and are radial on curves.
A single truck is commonly used for
short cars and the double or triple truck
for long cars.
Fig. 29, shows a particular form of
single truck. F, F, F, are solid forged
side frames. B, B, are the journal boxes,
in which the axles run, and on which the
CARS AND CAR TRUCKS. 99
weight of the car rests, through the double
spiral springs 8, S. The car body is sup-
ported on the steel beams B ', B ', which, in
their turn, rest upon the side frames
through the four spiral springs, and the
.
FIG. 29. SINGLE TRUCK.
two elliptical springs on each side. The
wheels are provided with brake shoes L, L.
A form of truck for a double-truck car
is shown in Fig. 30. Here the motor is
mounted so as to drive the left-hand axle,
and the weight of the car is so disposed
upon the truck as to throw the principal
share of the weight upon this pair of
100
ELECTRIC STREET RAILWAYS.
wheels in order to provide sufficient trac-
tion and prevent the rotation of the motor
from causing the wheels to slip.
Fig. 31, shows another form of truck for
a double-truck car called a maximum trac-
FIG. 30. TRUCK OF DOUBLE-TRUCK CAR.
tion truck. This truck has two axles, and
two pairs of wheels of different diameters.
The motor is suspended in such a manner
as to drive the larger pair, nearly 9/10ths
of the weight of the car being distributed
CARS AND CAR TRUCKS.
101
upon these wheels so as to obtain the
maximum tractive effort.
Fig. 32, shows a triple-truck support,
called a Robinson radial truck. Here the
FIG. 31. MAXIMUM TRACTION TRUCK.
car is supported upon the centres of the
end trucks in such a manner that these
may swivel freely, carrying the middle
truck between them. Fig. 33 illustrates
the action of these trucks when going
around a curve. It will be seen that the
middle truck is pulled over to that side of
102
ELECTRIC STREET RAILWAYS.
the car body which is on the outside of
the curve. The advantage of double and
FIG. 32. ROBINSON RADIAL TRUCK.
triple trucks is considerable with long cars,
but for short cars they are usually con-
sidered unnecessary, although they save
some power and wear going around curves.
FIG. 33. ACTION OP RADIAL TRUCK.
The appearance presented by a single-
truck car is illustrated in Fig. 34, which
I
104 ELECTRIC STREET RAILWAYS.
represents a car body 21 feet long and 28
feet in length over all, with a width over
wheels of 6 feet, a total width over all of
7 1/2 feet, and capable of seating 30
persons. The truck weighs without mo-
tors 3,500 pounds, and the body 5,250
pounds, making a total weight, without
motors or passengers, of 8,750 pounds.
Fig. 35 shows a double-truck car. The
car body is 25 feet long, and 33 feet over
all. The width over wheels 6 feet, and
over all 7 1/2 feet. This car will seat 36
persons. The weight of the truck with-
out motor is 5,200 pounds, and the body
5,850, making a total weight, without
motors or passengers, 11,050 pounds.
A form of journal boos is shown in Fig.
36. Here the lid Z, can be moved aside
for examination, or for filling the box. The
entire box is dust tight. The side frames
106 ELECTRIC STREET RAILWAYS.
are clamped to and riveted in the grooves
, B, so that the weight of these frames,
and, therefore, the entire weight of the car
FIG. 36. FORM OP JOURNAL Box AND SUPPORT.
pulls down upon the yoke A, and presses
the double spiral spring S, upon the box
L. The double spiral springs on all the
CARS AND CAR TRUCKS.
107
boxes, therefore, bear the entire weight of
the car. Fig. 37, shows a cross-section of
FIG. 37. SECTION OF Box SHOWN IN FIG. 36.
these journal boxes taken through the axis
of the shaft. A, is the axis, B, B, the
brasses from which the weight is trans-
108 ELECTRIC STREET RAILWAYS.
mitted to the axle, W, is the mass of lubri-
cating material, S, the double spiral spring
supporting under compression the yoke Y.
P, is the spring packing faced with
leather to keep out dust. J?, is a repair
piece which is marked C\ in Fig. 36. This
repair piece, when removed by withdraw-
ing two bolts, permits the frame to be
lifted clear of the axles.
Wheels for electric street cars are usu-
ally 30 inches, 33 inches or 36 inches in
diameter, and weigh from 300 to 400
pounds each. The tread of the wheel ;
i. e., its running face, is usually chilled to
a depth of 1/2 or 3/4 inch to improve its
wearing qualities. A good wheel should
run 30,000 miles. Wheels are usually
forced upon their axles by hydraulic pres-
sure, but in some cases they are bolted to
collars on the axle, which collars are them-
CARS AND CAR TRUCKS. 109
selves forced hydraulically on the axle.
There are two types of wheel, the open
and the dosed. Fig. 38, shows a form of
FIG. 38. OPEN CAR WHEELS.
open wheel and Fig. 39, a form of closed
wheel.
Motors may be mounted on the trucks
in several ways. The most usual method
is to support each motor partly on the
110 ELECTRIC STREET RAILWAYS.
axle it drives, and partly on a cross beam
extending between the side frames. This
is shown in Fig. 40, where the motor J/ of
FIG. 39. CLOSED CAR WHEEL.
the type shown in Fig. 11, is supported on
the cross beam B J3, which is itself sup-
ported from the side frames by the spiral
springs s, s. These spiral springs are, of
course, employed to reduce the vibration,
or jolting of the motor, when running over
an uneven track. The cross beams, instead
CARS AND CAR TRUCKS.
Ill
of passing beneath the motor may pass
above it, or on a level with its surface, as
shown in Fig. 41, where the beam B B.
FIG. 40. METHOD OF MOTOR SUSPENSION.
rests above the spiral springs instead of
beneath them. In Fig. 42, another method
is shown where the beams B B, from which
the motor is suspended, are longitudinal
and rest on spiral springs, which them-
selves rest upon cross beams secured to
112 ELECTRIC STREET RAILWAYS.
the side frame of the truck. In this case
very little of the motor's weight comes
immediately upon the driving axle, almost
FIG. 41. METHOD OF MOTOR SUSPENSION.
all being transmitted to the axle from the
side frames.
A plan and side view of the ordinary
motor suspension in a single-truck car are
shown in Fig. 43, where the two motors
M, J/, are seen, each connected to one of
the main axles through the gear G, 6r.
The motors are suspended partly upon the
main axles and partly upon the cross
CARS AND CAR TRUCKS.
113
beams B B, and B B, the four wheels
TFJ W, W, W, are thus directly driven
from the motor through the gears.
FIG. 42. METHOD OF SUSPENDING MOTOR.
The gearing employed in connection
with the electric street railway cars, is
effected by means of a steel pinion upon
the armature shaft, such as shown in
Fig. 44. This pinion has 14 teeth, which
are mechanically cut so as to mesh freely
114
ELECTRIC STREET RAILWAYS.
into the teeth of the gear wheel fixed
rigidly upon the car axle. This gear wheel
is usually made of cast iron in two parts,
. rib
^ rfti ^
FIG. 43. PLAN AND SIDE ELEVATION OF MOTOR
SUSPENSION.
as shown in Fig. 45. The gear wheel
shown has 67 teeth. The ratio of speed
reduction between the motor and the car
nH
axle is, therefore, in this case, jj = 4.786.
In other words, the car- wheel axle runs
CARS AND CAR TRUCKS. ' 115
4.786 times more slowly than the motor
shaft. If we consider a car with 33 inch
wheels, the circumference of the wheels
will be 103.67 inches or 8.639 feet. This
will be the distance through which the
car will move for one complete revolution
FIG. 44. ARMATURE PINIONS.
of the wheels. A speed of 1 mile per hour
over the track, is a speed of 88 feet per
minute, and, therefore, a rotatory speed of
88 -* 8.639 = 10.186 turns per minute of
the car wheels. The speed of the motor
armature will be 4.786 times this amount
or 48.76 turns per minute. Consequently,
for every mile per hour that the car runs,
116 ELECTRIC STREET RAILWAYS.
the motors will make 48.76 revolutions
per minute. Thus at 10 miles per hour
FIG. 45. AXLE GEARS.
they will each make 487.6 revolutions per
minute.
Pinions are sometimes constructed of
hot pressed steel. Thus Fig. 46, shows a
CARS AND CAR TRUCKS. 117
steel cylinder before pressing and the com-
pleted pinion wheel pressed from such a
cylinder.
AFTER.
FIG. 46. HOT-PRESSED PINION, BEFORE AND AFTER
PRESSING.
The motors which we have hitherto
considered are all single-reduction motors^
that is to say, there is only one reduction
118 ELECTRIC STREET RAILWAYS.
in speed effected by gearing between the
motor axle and the car axle. During the
early application of the street car motor it
was very difficult to obtain good slow-speed
motors of light weight, and, consequently,
FIG. 47. DOUBLE-REDUCTION MOTOR.
the expedient was adopted of reducing the
speed down to that required for the car
axle by a double reduction. Figs. 47 and
48 show a type of double-reduction motor.
In each figure, A, is the armature bearing
CARS AND CAB TRUCKS.
119
through which the axle passes. B, is an
intermediate shaft carrying a double-gear
wheel at on end as shown in Fig. 48,
meshing with a double pinion on the arma-
ture shaft ; while, at the other end, it
FIG. 48. DOUBLE-REDUCTION MOTOR.
carries a pinion meshing into a gear wheel
on the car-wheel shaft passing through
the bearing C. In this type of machine
the double redaction in speed varies from
9 to 19, according to the size of the motor
and requirements of speed and power.
In recent times the double-reduction motor
OF THE v
0HIVERSI1
CALIF?
120 ELECTRIC STREET RAILWAYS.
has almost disappeared. One difficulty
with the double-reduction motor was the
noise made by the rapidly rwnning arma-
ture pinion. To reduce this, rawhide
pinions ; i. e., pinion wheels made up of
FIG. 49. RAWHIDE PINION.
discs of rawhide, cut into the proper
shape, assembled and clamped together,
were employed, of the type shown in Fig.
49. The lifetime of such rawhide wheels
was never very extended.
CARS AND CAR TRUCKS.
121
The life of steel and iron gearing
depends largely upon the care with which
the dust is excluded from them. In prac-
FIG. 50. GEAR CORES.
tice an increased life is ensured by enclosing
the gear in a dust-proof gear cover, as
shown in Fig. 50.
122 ELECTRIC STREET RAILWAYS.
It is evident that for safety of running
cars through crowded thoroughfares, it is
absolutely necessary to be able to stop a
car with certainty in a short distance. In
order to effect this, various forms of brake
mechanism are employed. These are either
operated by hand, or by the electric current.
Pneumatic car brakes have not come into
any extended use up to the present time
for this purpose, since they require the
addition of a pneumatic compressor to the
car equipment.
A common form of lever brake, operated
by hand, from either end of the car, is
shown in Fig. 51 and also in Fig. 43. R,
H', are the projecting rods to one or other
of which the power is applied by a chain
and handle. Fig. 52 shows the ordinary
brake handle at the car platform. By
rotating this handle the chain C, is wound
CARS AND CAR TRUCKS. 123
upon the handle shaft, thus hauling upon
the brake rod H'. .P, is a pawl engaging
with the pinion wheel on the brake handle
shaft so as to hold or release the brake as
desired. Fig. 51, shows that when one of
FIG. 51. HAND BRAKE MECHANISM.
the brake rods, say H, is pulled by the
chain, the lever X, is drawn forward and
by the action of the short bar C, or brake
beam clevis, the brake beam S is forced
backwards, so as to cause the brake shoes
H, H, to press against the treads of the
wheel W, W. At the same the brake
124 ELECTRIC STREET RAILWAYS.
frame L R R R R L', is forced forward,
thus drawing the other brake beam B 1 ^
forward, and causing the shoes H ', H ', to
bear against the tread of the wheels
FIG. 52. BRAKE HANDLE AND CHAIN.
W W'. As soon as the tension is
released from the brake rod, the brake
frame L R R R R L', releases and
throws the shoes off the wheels.
CARS AND CAR TRUCKS. 125
When the arm is applied to the brake
handle H, Fig. 52, the pull so delivered is
multiplied by the leverage of the handle
over the chain. This pull being delivered
at R', is again multiplied by the leverage
of the brake lever L. The combined
leverage of the brake staff and brake lever
is usually about 50, so that a pull of 100
pounds weight, delivered horizontally at
the brake staff handle, represents a pull of
about 5,000 pounds delivered at all four
brake shoes, or about 1,250 pounds total
pressure between each shoe and the wheel
it grips. The effect of this pressure is to
produce about l/8th of the pressure as a
frictional retarding force, so that if 1,250
pounds pressure be supplied to each
wheel, the retarding drag applied at the
wheel tread is about 160 pounds.
The turnbuckle T T, enables the play
126 ELECTRIC STREET RAILWAYS.
of the brake rods and brake arm to be ad-
justed so that any unnecessary delay in
applying the brakes may be avoided.
A form of electric car brake, which
FIG. 53. ELECTRIC BRAKES MOUNTED ON STREET CAR
TRUCKS.
promises to come into extended use, is
represented in Fig. 53. A truck is here
represented with two motors M, M, in
place, of the same character as shown in
Fig. 11. In addition to the ordinary hand
brake mechanism operating through the
CARS AND CAR TRUCKS 127
brake rods r, r, the brake levers I, I'
the brake beam m, and the shoes 5, 5,
there is supplied an electric brake B, on
each car axle. This brake is in two
parts ; namely, a cast iron disc (7, rigidly
keyed to the car wheel axle, and, therefore,
revolving with the car wheel, and a cir-
cular shoe or compact electromagnet D,
facing C, clamped to the motor and frame
of the car, and, consequently, not rotating
whether the car be running or at rest.
When the car is running there is no fric-
tion between the shoe D, and the disc C.
As soon as it is desired to stop the car,
the trolley circuit is first broken at the
trolley switch by the motorman, thus cut-
ting off the power from the line. As
soon as this is done the motors which are
still running by the momentum of the car,
act as ordinary dynamos, and are capable
of furnishing a temporary electric current
128 ELECTRIC STREET RAILWAYS.
as soon as a circuit is closed to their
E. M. F. The coil of insulated wire in the
interior of the magnet shoes D, D, of the
brakes are placed in circuit with the motor
armatures so as to receive this current.
Under these circumstances a powerful
electromagnetic attraction occurs between
the shoes D, D, and their iron discs C, C,
tending to clutch them together and stop
the wheels. The faster the car is running
at the moment these brakes are applied,
the more powerful is the current that is
generated by the motors acting as dynamos,
and, consequently, the higher the brake
action.
There are two methods of controlling
this brake, the first automatic, and the sec-
ond under the control of the motorman.
The braking power, if uncontrolled, would
CARS AND CAR TRUCKS. 129
be so great that the wheels would be in-
stantly locked and would skid or slide on
the track. An automatic switch is placed in
the circuit in such a manner that the cur-
rent strength from the motors through the
brakes is limited to that which will apply
the maximum braking power without per-
mitting skidding with a light car. More-
over, the braking current passes through
the controller to be subsequently described,
and is thus regulated in strength by the
raotormaD, so that he can apply the elec-
tric brake either suddenly , or gradually, as
he may desire. The advantage of the elec-
tric car brake is the power it possesses, the
swiftness with which it can be applied, and
the fact that it is independent of all current
taken from the trolley wire, since the
moving motors supply the energy needed.
The mechanism can, moreover, be attached
to any car without great expense, while
130 ELECTRIC STREET RAILWAYS.
the ordinary brake is left untouched for
use in cases of emergency. A special ar-
rangement is made to lubricate the rotating
surfaces by means of a graphite brush car-
ried in the shoes J9, D. This prevents ex-
cessive wear and heating; for, in this brake,
the retardation is very largely a magnetic
pull rather than a mechanical friction, and,
in this way, effective brake action is
secured without excessive rubbing.
When the rails are slippery, by reason of
a thin film of mud or frost, an application
of the brake is apt to cause adhesion of the
shoe to the brake wheel, and a skidding or
slipping of the wheel on the track, instead
of an adhesion between the wheel and the
track and a slipping of the brake shoe on
the wheel. The result of this skidding is
to wear the tread of the wheel at the point
of its periphery at which it slips along the
CARS AND CAR TRUCKS. 131
track, whereas in the normal application of
the brake, this wear is uniformly distrib-
uted over the entire wheel surface against
the brake shoe. Under these conditions
the wheel tends to flatten at the point of
skidding, and once a depression is formed,
there is a continual tendency to increase
the amount of flattening. Flat wheels are
not only difficult to brake properly, but
produce an uneven jarring motion very dis-
agreeable to the passengers. In order to
increase the adhesion between the wheel
and track, so as to be greater than that
between the brake shoe and the wheel, sand
is sometimes poured upon the track with
the effect of producing a greater friction.
Various forms of sand boxes have been de-
vised for sprinkling a small quantity of
sand directly beneath the wheel on the
track where it is required. One of these
forms is shown in Fig. 54. The sand box
132
ELECTRIC STREET RAILWAYS.
S, is mounted within the car close to the
platform. The motorman, by pressing with
his foot upon the foot-button F, depresses
the lever L, which is pivoted at P, and
FIG. 54. SAND Box.
thus causes the rod H, to move forward in
the direction of its length against the ten-
sion of the spiral spring G. This opens
the valve outlet and allows sand to pour
through the tube T, upon the track
beneath.
CARS AND CAR TRUCKS. 133
On the truck of a car there is mounted a
car body familiar to all our readers. These
bodies are of four types ; namely, the open
or summer car, the closed car, the converti-
ble car, and the double decker. The latter
is not in use on overhead trolley lines.
CHAPTER VI.
ELECTRIC LIGHTING AND HEATING OF CARS.
THE advantages possessed by electric
lighting, as obtained from incandescent
lamps, are so evident, that this method of
artificial illumination is almost invariably
employed in trolley cars. The current
required for the lighting of these lamps is,
of course, taken from the same source
which drives the car, that is to say, a
special circuit is taken from the trolley to
the track, through the lamps to be lighted.
The type of incandescent lamp employed
varies with the number placed in the car.
If, as is commonly the case, there are five
lamps, three in the centre and one at each
134
LIGHTING AND HEATING OF CARS. 135
end, they are connected in series, so that
the current passes successively through
each, and they are placed in a special cir-
cuit directly between the trolley and the
track as represented in Fig. 55. Here
Tr
k?
L.
ITk
FIG. 55. DIAGRAM OF LAMP CIRCUIT OP CAR.
the wire leading to the trolley wheel is
marked Tr, and enters the switch S, from
which it passes through the nVe lamps
L<b .Z/2, X 3 , L, 1;^ in succession, finally pass-
ing to the track T~k, through the frame-
work of the truck.
In this case since the total pressure be-
tween the trolley and track is approxi-
136 ELECTRIC STREET RAILWAYS.
naately 500 volts, and there are five
lamps in series, the drop in each lamp will
be 100 volts, the current strength being
about 2/3rds ampere. The total activity
developed in the lamps will be roughly
500 volts X 2/3rds ampere = 333 watts,
or less than one- half of a horse-power.
When nine lamps are employed to light
the car, in three clusters of three each, all
nine are placed in one series, the drop in
50
each lamp being approximately - - = 55.5
y
volts. The current strength in this case
will be a little more than 1 ampere and
the activity in the lighting circuit will
be nearly 500 volts x 1.1 amperes = 550
watts, or 3/4ths horse-power. This activity
has to be sustained during the operation
of the cars at night time whether the car
be running or not. If five lamps are
employed, each lamp must be made for a
LIGHTING AND HEATING OF CARS. 137
pressure of roughly 100 volts, while if
nine lamps are employed, each lamp must
be made for a pressure of roughly 55 volts.
FIG. 56. CAR LAMP.
Fig. 56 shows a common form of lamp
employed in street cars. Fig. 57 shows
another form in which the incandescing
filament is anchored or supported at its
138
ELECTEIC STREET RAILWAYS.
centre for the purpose of preventing the
filament from being injured by excessive
vibration. Incandescent lamps for street
FIG. 57. RAILWAY LAMP WITH ANCHORED OR NON-
VIBRATING FILAMENT.
car use have usually an efficiency of l/4th
candle per watt ; i. e., when operated at
the pressure for which it is designed, it
LIGHTING AND HEATING OF OAKS. 139
gives normally l/4th of a candle per watt
of activity absorbed, so that a 16 candle-
power lamp would require normally 64
watts.
FIG. 58. FORM OP FIXTURE FOR CAR LAMP.
A common form of lamp fixture is
shown in Fig. 58 and a cluster suitable for
three lamps is shown in Fig. 59.
A form of switch for turning the car
lamps on and off, is shown in Fig. 60.
This switch box is screwed up inside the
140 ELECTKIC STREET RAILWAYS.
car near the ceiling and has a projecting
key K, for turning the lamps on or off.
The action of the key is illustrated by the
switch shown in Fig. 61, where A and B,
FIG. 59. FORM OF THREE-LAMP CLUSTER FOR CAR.
are the binding posts connected to one
side with the trolley wheel and the other
with the lamps. On turning the key D,
the brass piece (7, may be made to bridge
metallically across between the posts A
and B, thus closing the circuit through all
the lamps. The switch box, in Fig. 60,
LIGHTING AND HEATING OF CARS. 141
also contains a safety fuse or cut-out.
This simple device consists of a wire of
lead or other alloy that will melt, and
thus automatically break the circuit, if the
current becomes excessive.
FIG. 60. SWITCH AND CUT-OUT FOR CAB LAMPS.
It will be evident that for every 16
candle-power incandescent lamp operated
in the car, about 64 watts activity will be
required; or, roughly, 1/1 2th of a horse-
power per lamp at the car, which may
represent say l/8th of an indicated horse-
power at the engine.
142 ELECTRIC STREET RAILWAYS.
When street cars are running in cold
climates the artificial heat required at cer-
tain seasons of the year may be obtaiped
either by the use of an ordinary coal stove,
D
FIG. 61. SWITCH FOR CAR LAMPS.
or by electric heaters. Although the coal
stove is the cheaper of the two, yet it pos-
sesses several inconvenient features. In
the first place it occupies useful space ; in
the second place it requires attention and
introduces more or less dust, smoke or dirt
into the car, while the heat which it gives
LIGHTING AND HEATING OF CARS. 143
is principally developed in the upper por-
tion of the car, the air near the floor
remaining comparatively cold. Moreover,
some time is required to start a fire in
a stove.
In contrast with these inconveniences,
the electric heater possesses such marked
advantages, that, despite its extra cost, it
has come into use for the heating of electri-
cally propelled cars. When an electric
current passes through a wire, heat is de-
veloped therein. Thus, we have already
seen that when a current passes through a
trolley wire, a certain amount of power
will be expended in heating the trolley
wire. Under practical conditions the
trolley wire will never get sensibly warm
by the current it. carries for the reason
that the surface it freely exposes to the
air is so great, that, taken in connection
144
ELECTRIC STREET RAILWAYS.
with its mass, the comparatively small
amount of heat developed within it is
rapidly liberated. If, however, the same
amount of electric resistance which ex-
ists in a mile of trolley wire, were obtained
FIG. 62. HEATING COILS OP CAB HEATER.
in a short length of copper or iron wire,
then the same amount of heat would be
produced in a much smaller mass of iron,
having a greatly reduced surface, with the
result of producing a much higher tem-
perature in the wire.
The coils of wire used in a particular
form of car heater are shown in Fig. 62.
LIGHTING AND HEATING OF CARS. 145
Here the heating coil consists of galvanized
iron wire which is wrapped in the form of
a close spiral and then placed in a spiral
groove on the outside of a porcelain tube.
This construction affords a great length of
heating coil in a small space, so supported
as to prevent the coil changing its form
when heated and yet practically permit-
ting nearly all of its surface to give off
heat to the surrounding air. In the heat-
ing coil shown in the figure, which is about
3' 6" long, there are 392' of wire ; the size
of wire being No. 20 A. W. G. iron wire,
having a diameter of 0.032", or 32 mils.
The total surface exposed by the coil
in a single heater is 1.642 square feet.
The coil is placed in a metal case, so pro-
vided with openings as to permit the free
flow of air entering at the bottom of the
case to flow around the heater, come in
contact with the heated wire and to
146 ELECTRIC STREET RAILWAYS.
escape through a grating at the top.
When so desired, the air may be taken in
directly from the outside of the car. The
coil in its metal case, ready for fastening
in position below a seat, is represented in
FIG. 63. ELECTRIC CAR HEATER.
Fig. 63. The heater is sometimes placed
with its grating flush with the riser be-
neath the seat. In this case the form of
heater is that shown in Fig. 64. For cars
of the ordinary size, four or six heaters are
employed ; i. <?., two or three on each side
of the car. The heaters are placed in the
HEATING AND LIGHTING OF CARS. 147
risers of the seats near the floor. In Fig.
65 the interior of a car is shown equipped
with six heaters, four of which are seen
beneath the seats at the points A, J3, C\ D.
CFrcrf r-rrrTrrrrrj^ri-rc-:"
FIG. 64. FORM OF ELECTRIC CAR HEATER.
In order to regulate the amount of heat
required to meet the changes in tempera-
ture, a temperature-regulating switch is
employed, by means of which the separate
heaters may be connected in series or in
parallel groups between the trolley and
the track, or by means of which one or
more of the heaters may be removed at
will. By this means the amount of cur-
.
-Xf^C-t
f V^ OF THE
/UNIVERSITY
^
148 ELECTRIC STREET RAILWAYS.
rent which passes through the heaters, and,
therefore, the amount of heat they develop
can be adjusted. When the switch is
turned, so as to place all the heaters in
series, the resistance in the heating circuit
is greatest and the heat produced is least.
When all the heaters are employed in three
parallel groups of two each, the maximum
current is supplied and the maximum heat
is obtained.
Fig. 66, represents the interior of the
temperature-regulating switch, by which
these varied connections are made. Fig.
67, shows the exterior appearance of the
switch. There are five positions of this
switch when the current is passing through
it, numbered respectively, 1, 2, 3, 4 and 5,
and the particular position is indicated by
the numeral appearing through the open-
ing at W, in the switch casing. The
I
150
ELECTRIC STREET RAILWAYS.
switch is so constructed that before chang-
ing from one number to another, the cir-
cuit of the heaters is opened. In position
5, as shown in the figure, the full current
FIG. 66. INTERIOR TEMPERATURE-REGULATING SWITCH
(FIVE INTENSITIES).
strength of about 12 amperes passes
through the heater, representing a total
activity of about 500 volts x 12 amperes =
6,000 watts = 6 KW = 8 HP approxi-
mately. This activity is entirely expended
in heating the wire, and, therefore, in
LIGHTING AND HEATING OF OAKS. 151
warming the air which comes in contact
with the wire. Position No. 1, corre-
sponds to the minimum activity and allows
about 2 amperes to pass through the
FIG. 67. EXTERIOR TEMPERATURE-REGULATING SWITCH.
heater, representing a total activity of
about 500 volts X 2 amperes = 1,000
watts = 1 KW = 11/3 HP, approximately.
In practice, it is found that in cold
weather about 6 amperes have to be main-
tained in the heaters, representing an
152
ELECTRIC STREET RAILWAYS.
activity of roughly 3 KW. The cost of
producing a KW-lwur, or 1,000 joules-per-
second for 3,600 seconds = 3,600,000 joules,
FIG. 68. CAR HEATER.
varies considerably with the size of the
electric plant supplying the current, but,
speaking generally, a fair average may be
considered as being 1 1/2 cents per KW-
hour, so that the expense of heating the
cars electrically during severe weather may
be estimated roughly as 4 1/2 cents per
hour.
LIGHTING AND HEATING OF CARS. 153
Another form of car heater and its en-
closing case is shown in Figs. 68 and 69.
FIG. 69. CAR HEATER, DESIGNED TO ATTACH TO SEAT
RISER.
This operates on practically the same
principles.
CHAPTER VII.
CONTROLLERS AND SWITCHES.
IT is necessary in the practical operation
of a street car to place both its speed and
the direction of its running under the con-
trol of the motorman. Moreover, the ap-
paratus employed to do this should require
for its operation no more than ordinary
intelligence, that is, should be capable of
being operated without any electrical skill
on the part of the motorman. On electric
trolley cars, as is well known, the motorman
controls the car by means of two handles,
the right hand one of which controls the
mechanical brake apparatus and the left
hand one the electric apparatus called the
154
CONTROLLERS AND SWITCHES. 155
controller. This latter apparatus is con-
tained within a vertical metal case
provided on its upper plate with notches,
corresponding to different speeds of the
car. By this apparatus the electric cur-
rent is turned on and off and the power
and speed of the motor controlled.
Different systems of electric traction
employ different forms of controllers, but
all operate on essentially the same plan.
It will, therefore, suffice, in pointing out
the method in which the controller
operates, to limit the description to a par-
ticular form in common use.
4
The external appearance presented by
this controller will be seen by an inspec-
tion of Fig. 70. One of these controllers
is mounted on the front platform and a
156 ELECTRIC STREET RAILWAYS.
similar one on the back platform of the car.
It is operated by the movement of the
handle H. The small handle A, controls
an emergency switch used for reversing the
motion of the car when necessary. Coin-
ing now to the controller, >, is a stop to
limit the range of motion of the handle.
In the position shown the current is turned
off, and, as the handle is turned around
in a clockwise direction, the motors are
gradually brought into action with increas-
ing speed, until, when the projection of the
handle strikes the stop $, on the other
side, after nearly one revolution, the maxi-
mum speed of the car is attained.
In order to open the controller, a sheet
iron door is provided, closed with screw
bolts, which can be manipulated by hand,
the hinges of these bolts being shown
CONTROLLERS AND SWITCHES. 157
FlG. 70. CONTROLLEK, CLOSED.
158 ELECTRIC STREET RAILWAYS.
The interior construction of the con-
troller is shown in Fig. 71. The lid L L,
has been thrown back by withdrawing the
bolts at the hinges j, j. By further with-
drawing the small bolt, e/J shown separately
beneath the lid, an iron cover (7, hinged
on the core <?, of the electromagnet M, is
also thrown back from the cylinder Y,
leaving it exposed to view.
The switch cylinder is turned by the
movement of the handle If. It carries
eleven rings of insulating material r ly r,, /
etc., upon which are mounted metallic con-
ducting segments s t , s a , s s , of different
lengths and in different positions, so that,
when the cylinder is turned, they come
into contact at different times with the row
of eleven fixed contact springs p t , p*, p a , p*,
etc. It is these contacts which effect the
changes in the connections for producing a
CONTROLLERS AND SWITCHES. 159
FIG. 71. CONTROLLER, OPEN.
160 ELECTRIC STREET RAILWAYS.
change in speed of the car. In the posi-
tion shown, while the handle is at the first
notch and against its stop, none of the
segments are in contact with their springs,
and the trolley is disconnected from the
motors. The small handle h, rotates a
small cylinder y, carrying eight sets of me-
tallic segments and having a row of eight
fixed metallic contact springs q ly q^ q*. By
throwing the handle A, over about 60, the
segments in contact with the springs q,
can be changed and also the direction of
the current through the armatures of the
motors. The direction of rotation of the
motor can thus be reversed, backing the
car. At TFJ is a star wheel, which renders
it necessary that all the successive contacts
be made and none omitted when the
handle is turned.
After contact has been made between
CONTROLLERS AND SWITCHES. 161
the motors and the trolley, so as to pass the
usual current strength through the circuit ;
then, on breaking contact either at the
trolley, or at the ends of two wires in the
circuit on the car, a spark or metallic arc
will form, which may be from two inches
to five inches in length. This is the char-
acteristic arc which is seen when the trolley
wheel jumps from the wire. It will be
readily understood that the formation of
arcs of this character within the con-
troller, would soon cause its destruction.
This is avoided in the form of controller
shown in the figure by means of a device
called the magnetic blow-out. The current
through the motors passes through a coil
wound on the magnet M, around the iron
core c. This makes the core <?, a powerful
electromagnet, and its projection, or pole-
piece CJ becomes a large magnetic pole.
AVhen this pole -piece is close down in its
162 ELECTRIC STREET RAILWAYS.
normal position the polar ridges P, P, P,
rest close to the contact strips p^p^p*.
While the motors are running, the magnet
M, being excited, produces a powerful
magnetic flux surrounding the contact sur-
faces p h p^ PS. As soon as any break in
the circuit occurs either in changing con-
nections during running of the motors, or
particularly when the current is entirely
shut off, the severe sparking, which would
occur, is prevented because the arcs are
blown out under the influence of the
magnetic flux from this magnet. In other
words, an arc cannot be maintained in the
presence of a sufficiently powerful magnetic
field.
It remains now to explain the manner
in which the different positions of the
handle H, alter the speed of the car.
There are altogether eleven notches or sue-
CONTROLLERS AND SWITCHES. 163
cessive positions which the handle IT, and,
consequently, the switch cylinder, can
assume. The first corresponds as already
mentioned, to no current, as in Fig. 71.
There are thus left ten positions, at which
the speed of the motor can be varied.
When the handle is pushed to the first
working position, the segments s^ s 2j s 3 ,
engage with their corresponding springs.
The effect of this is to establish the con-
nections shown in Fig. 72. H ly H%, is a
resistance made up of a coiled insulated
strip of iron. M l and M 2 , are the motors.
It is evident, therefore, that the current
has in this case to pass successively from
the trolley T, through the resistance
j?!, R%, and the two motors to the ground
6f. The resistance H 19 R%, may be 1 ohm,
that of each motor armature 0.4 ohm, and
that of each field 0.8 ohm. The total
164 ELECTRIC STREET RAILWAYS.
resistance of the circuit between the
trolley and the track is, therefore, 3.4 ohms.
If we assume that the usual pressure is
steadily maintained between trolley and
T ,Ri
FIG. 72. CONNECTIONS CORRESPONDING TO FIRST WORK-
ING NOTCH OF CONTROLLER.
track at 500 volts, then the maximum
current strength which may pass through
the car circuit under these conditions is,
by Ohm's law, 500 volts divided by 3.4
CONTROLLERS AND SWITCHES. 165
ohms = 147 amperes. Iii practice the
current never rises to this amount for two
reasons; namely,
(1) As soon as the circuit is closed, the
excitation of the field magnets causes a
powerful development of magnetic flux in
the motors, which momentarily sets up a
C. E. M. F. tending to check or oppose
the establishment of the current. This
C. E. M. F. is of very brief duration, say
about one second, so that if the motor was
prevented from running, the full current
strength according to Ohm's law would
soon be reached. This is called the
C. E. M. F. of self -induction } because it is
produced by the magnetic inductive effect
of the current on its own circuit.
(2) As soon as current passes through
the motor it begins to turn and in so
doing acts as a dynamo to produce a
C. E. M. F. which permanently checks the
166 ELECTKIC STREET RAILWAYS.
current, and the faster the motor runs the
greater this C. E. M. F. This C. R M. F.
of rotation is far more important than the
C. E. M. F. developed by self-induction,
since it always operates while the motors
are running, whereas the C. E. M. F. of self-
induction only exists during changes in
current strength.
It now remains to be explained how the
C. E. M. F. of rotation automatically
regulates the strength of current and,
therefore, the amount of electric activity
supplied to the car. Let us first suppose
that the motors are disconnected from the
car axles, and allowed to revolve freely
without any friction whatever. If such a
state of things were possible, the torque,
or rotary effort of the armature produced
by the current which first enters them,
would soon bring the armatures to a high
CONTROLLERS AND SWITCHES. , 167
rate of speed, under which circumstances
the C. E. M. F. generated by them would
be so great that very little current would
pass through them. Thus, if the total
resistance of the motor circuit, as shown
in Fig. 72, was 3.4 ohms, and the amount
of power required to drive the motors
light and frictionless, was only 1 HP, or
say 750 watts, this would mean a cur-
rent strength of but 1.5 amperes, since
500 volts x 1.5 amperes = 750 watts.
In order to limit the current strength to
1.5 amperes in a circuit of 3.4 ohms, the
effective pressure must be 5.1 volts, since
5.1 VOltS rpn re ,.
= 1.5 amperes. Ihe effective
3.4 ohms
pressure between trolley and track must,
therefore, under these circumstances, be
only about 5 volts, and this will be pro-
duced by such a speed of the motor as to
develop a C. E. M. F. of 495 volts; for,
168 ELECTRIC STREET RAILWAYS.
since 500 volts is the E. M. F. supplied,
and 495 is the C. E. M. F., the difference
serving to drive the necessary 1.5 amperes
through the resistance of the circuit will
be 5 volts.
If now some small frictional resistance
or load be applied to the motors; or, in
other words, if the motors be required to
do some little work, the activity which
they will require to be supplied with to
perform this work may amount to 2 HP
or, approximately, 1,500 watts (1.5 KW).
Under these circumstances the current
strength must increase to 3 amperes, since
3 amperes at a pressure of 500 volts
represents the needed activity of 1,500
watts. In order to permit 3 amperes
to pass through the resistance of the cir-
cuit (3.4 ohms) the effective pressure
must be 10.2 volts, since 10.2 volts *- 3.4
CONTROLLERS AND SWITCHES. 169
ohms = 3 amperes. The E. M. F. applied
being 500 volts, the C. E. M. F. must be
490 volts and the speed of the motors will
drop sufficiently to produce only 490 volts
C. E. M. F., instead of 495. In the same
way if we suppose the motors to be
coupled to their respective car axles, and
work to be required from them to drive
the car, to an amount of say 10 HP,
then the power which must be sup-
plied to the motors to make up for losses,
both frictional losses in the gears and
bearings, and electrical losses in the arma-
ture and field coils, may be 15 HP, or
15 x 746 = 11,190 watts = 11.19 KW.
This is the electric activity which must be
supplied from the circuit to the motors,
and will represent a current strength of
22.38 amperes at a pressure of 500 volts.
The effective pressure required to drive
22.38 amperes through a resistance of 3.4
OF THE
UNIVERSITY
170 ELECTRIC STREET RAILWAYS.
ohms, will be 76.09 volts. The C. E. M. F.
required to limit the effective pressure to
approximately 76 volts, will be 500 76
= 424 volts, and the motors will drop in
speed until this is the C. E. M. F. which
they supply.
Proceeding in this way, the more load
we put on the motors ; i. e., the more we
load the car, or the steeper the grade it is
necessary to ascend, the greater the electric
activity which must be supplied to drive
the car, and the greater the current
strength which must be passed through
the motors to produce this activity.
Under these circumstances the motors will
continue to slacken in speed so as to per-
mit the current to pass, and will always
attain such a speed as will permit the
required activity to enter them in order to
perform the work they have to do. When,
CONTROLLERS AND SWITCHES. 171
finally, the load is so great that the motors
are unable to run, the activity received
will be that defined by Ohm's law, shortly
after the circuit is closed. In this limiting
case, all the activity is expended as heat in
the resistance H ly R^ and in the motors M,
M. In all other cases, when the motors
are running, some of the activity is devel-
oped as heat, but by far the greater part is
developed as mechanical activity in pro-
pelling the car.
On the other hand a reduction in the
load of the motors must be followed by an
increase in their speed. This increase, how-
ever, will be arrested as soon as the C. E. M.
F. is increased to the value which limits the
current strength to that required for the rate
at which work is being mechanically done.
In all cases it will be evident that the E.
172 ELECTRIC STREET RAILWAYS.
M. F. existing between the trolley and the
track, which we have assumed to be
maintained at 500 volts, is to be met by
an equal total C. E. M. F. in the car circuit
T, G. If the motors are at rest, this C. E.
M. F. must be entirely due to drop in the
resistance, represented by the product of
the current strength in amperes and the
resistance in ohms. For example, with the
car held at rest, we know that the current
will be 147 amperes in the case of Fig. 72,
and this multiplied by the total resistance
of 3.4 ohms, represents a drop of pressure
amounting to 500 volts.
When, however, the motors are running,
their C. E. M. F. of rotation will necessi-
tate a smaller drop in the resistance of
their circuit. Thus, if the motors are pro-
ducing together a C. E. M. F. of 400 volts,
then the drop in the resistance H ly 7? 2 , will
CONTROLLERS AND SWITCHES. 173
be only 100 volts, and if the motors pro-
duced together a C. E. M. F. of rotation of
490 volts, the drop will be reduced to 10
volts. The activity available for mechani-
cal work is the product of the C. E. M. F.
of rotation and the current strength. For
example, if the motors in Fig. 72 develop to-
gether a C. E. M. F. of rotation amounting
to 490 volts, and the drop in the resistance
of motors and rheostat is, therefore, 10
volts, the current strength, which will pro-
duce this drop, will be by Ohm's law
10 volts , -,
2.94 amperes, approximately.
The total activity taken from the circuit
between T and 6r, will, therefore, be 500
volts X 2.94 amperes = 1,470 watts. Of
this, the amount capable of producing me-
chanical activity is 490 volts X 2.94 amperes
= 1,440 watts, while that only capable of
producing heat is 10 volts x 2.94 amperes
174 ELECTRIC STREET RAILWAYS.
= 29.4 watts. It is evident that the
greater the proportion of C. E. M. F. of
rotation to the drop in the circuit T, G,
for any given current the greater will be
the activity used for propelling the car.
We will now explain the use of the resist-
ance R^, H 2 . In the first place if the resist-
ance jffj, J? 2 , be removed from the circuit in
Fig. 72, the total resistance between T, and
6r, will be reduced to 2.4 ohms, and the
possible current strength by Ohm's law,
such as would exist when the car was
absolutely prevented from moving, would
500 volts
be 208 amperes, approxi-
2.4 ohms
mately. In other words, a current of 208
amperes would maintain a drop of 500
volts in a total resistance of 2.4 ohms.
The first rush of current would, therefore,
be greater, and the current strength dur-
CONTROLLERS AND SWITCHES. 175
ing the time when the motors were acceler-
ating and reaching their limiting speed of
rotation would be greater, so that the car,
would start from rest with a greater jerk,
and, moreover, waste a greater amount of
power in the process. The greater the
amount of resistance which is introduced
into the circuit of the motors at the start,
the smaller the current which will pass
through them, the more quietly the car will
start and reach the speed which limits the
C. E. M. F. of rotation, and the less the
activity which will be wasted during that
period in which the motors are accelerating
up to this speed.
On the other hand, the continued use of
a resistance H ly H z is more or less wasteful
after the car has been brought up to speed,
because it produces a drop in the circuit
and prevents the C. E. M. F. of rotation
176 ELECTRIC STREET RAILWAYS.
from coming into full play. For example,
if the current which the circuit must re-
ceive under given conditions of load is 50
amperes, the drop in the resistance of 1
ohm at Hi, Hz, will be 50 amperes X 1
ohm = 50 volts, and the effect is tempor-
arily the same as though the motors J/j,
M& were connected to the trolley circuit
between T and G, without a resistance,
but with 450 volts pressure. The activity
expended in the motors, both as drop in
their resistance, and as available energy
against their C. E. M. F. of rotation, will
be 450 volts x 50 amperes = 22,500 watts.
The circuit between T&nd ff, supplies a
total activity of 500 volts X 50 amperes =
25,000 watts.
The effect, therefore, of constantly main-
taining the resistance H l9 JR 2j in the circuit
of Fig. 72, is to expend activity in it as
CONTROLLERS AND SWITCHES. 177
heat, and thus prevent the motors from
reaching as high a speed as they otherwise
would, while, of course, it is an advantage
to be able to run slowly, it is nevertheless
FIG. 73. STREET CAR RESISTANCE COIL.
a disadvantage to waste power in the re-
sistance for this purpose. The use of a
certain amount of resistance is, therefore,
beneficial during periods of starting, and
where the advantage of running at low
speeds offsets the disadvantage of wasting
power.
178 ELECTRIC STREET RAILWAYS.
The resistance R^ H 2 , is commonly made
in the form shown in Fig. 73. Here the
coils are placed in an iron box of such
dimensions as to permit it to be attached
by screws or bolts at the lower part of the
car body. It is purposely left open to per-
mit the circulation of air and thus carry off
the heat generated in the coils.
Let us now inquire what happens when
the controller is turned to the next or sec-
ond working notch. The effect of this is
shown diagrammatically in Fig. 74. An
inspection of the figure will show that half
the extra resistance is cut out of circuit ;
namely, R v . This has the effect of reducing
the drop of pressure in the resistance for a
given current strength passing through the
circuit. Consequently, the motors have to
ran faster to make up the total C. E. M. F.
of 500 volts, so that the speed of the car is
CONTROLLERS AND SWITCHES.
179
increased. For example, if in the case of
Fig. 72, a drop of 100 volts occurs in the
resistance j? b J2 2 , requiring 400 volts to be
FIG. 74. CONNECTIONS CORRESPONDING TO SECOND
WORKING NOTCH OF CONTROLLER.
made up by the motors in C. E. M. F. of
rotation and drop in their resistances, then,
when the resistance H iy is cut out, as in Fig.
180 ELECTRIC STREET RAILWAYS.
74, with the same current strength there
will be only 50 volts drop in that half of
resistance R%, remaining in the circuit, and
450 volts must be made up by the two
motors in C/ E. M. F. of rotation and
drop ; they will, therefore, increase in speed
to this extent. Consequently, the effect of
cutting out resistance from the circuit is to
cause the car to increase in speed to an ex-
tent which will depend entirely upon the
amount of drop reduced, which in its turn
will depend upon the load of the car. If
the car is very light, and is steadily running
on a level portion of the track, the drop in
the resistance will be very small and the
effect of halving this drop will be very
small, so that the car will receive very lit-
tle increase in its steady speed by moving
to the second notch. If, on the contrary,
the motor is heavily loaded, or is running
up a steep grade, there will be a heavy
CONTROLLERS AND SWITCHES. 181
drop in the resistance JR ly J? 2 , especially on
starting, due to the stronger current and
greater activity required, so that cutting
out half the resistance and drop will pro-
duce a greater increase in speed.
Fig. 75, shows the effect of turning the
controller handle to the third notch. Here,
as will be seen, all the resistance H ly R^ is
cut out, so that the motors have to make
up in drop and C. E. M. F. of rotation, the
full line E. M. F. existing between trolley
and ground. They will, therefore, require,
other things remaining the same, to main-
tain a higher speed than in either of the
preceding positions of Figs. 72 and 74.
The total resistance of their circuit between
jTand 6?, is 2.4 ohms.
Turning the controller handle to the
next, or fourth working notch, the effect
182
ELECTRIC STREET RAILWAYS.
produced is represented diagrainmatically
in Fig. 76. Here, as in Fig. 75, the extra
resistance is entirely cut out and in addition
FIG. 75. CONNECTIONS CORRESPONDING TO THIRD
WORKING NOTCH OP CONTROLLER.
the field magnet coils of each motor are
provided with a by-path or shunt $i, S%, so
that the current through the circuit divides
CONTROLLERS AND SWITCHES.
183
at each field magnet, a part only going
through the magnets, and the remainder
going around through the shunt, all of the
T
FIG. 76. CONNECTIONS CORRESPONDING TO FOURTH
WORKING NOTCH OP CONTROLLER.
current, however, passing through each
armature.
The effect of shunting the field magne-
tizing coils is to weaken them ; i. #., haa
tTHlVEBSlTT
184 ELECTKIC STREET RAILWAYS.
f
the same effect as taking wire off the coil,
or of reducing the equivalent current
strength. The magnetism produced by
the field magnets of the motors, will,
therefore, be reduced, and in order to
make up a given C. E. M. F., with this
reduced magnetism, a greater speed must
be attained by the armatures. The car
has, therefore, to run faster owing to the
introduction of the shunts. At the same
time, if the grade and load remain the
same the greater speed of the car will call
for a greater expenditure of mechanical
power, and, consequently, a greater ex-
penditure of electric current and activity,
so that, since each motor is called upon to
produce a total C. E. M. F. of 250 volts
in drop and in rotation, this C. E. M. F.
will be developed by a greater speed in
the weakened magnetic fields, but with a
greater current supply and to that extent
CONTROLLERS AND SWITCHES. 185
a greater drop ; for, if the current strength
supplied was insufficient to maintain the
increased activity of the car, then a de-
crease in speed would occur until the cur-
rent supply was made up.
The connections corresponding to the
fifth working notch are the same as those
shown in Fig. 74, that is to say, the re-
sistance 7? 2 , is first restored to the circuit
before changing the connections at the
next step.
The condition of affairs when the con-
troller is turned to the sixth working
notch is represented in Fig. 77. Here, it
will be observed that the shunts around
the field magnets are withdrawn, and the
resistance R^ is restored to the circuit,
while the second motor M& is completely
cut out. The first motor J/ has now to
186
ELECTRIC STREET RAILWAYS.
make up the full' pressure of the line with
the aid of the drop in half the resistance.
Excluding the drop in the resistance
FIG. 77. CONNECTIONS CORRESPONDING TO SIXTH
WORKING NOTCH OP CONTROLLER.
the speed will be roughly double that
corresponding to the connections in Fig.
75 ; for, the single motor armature must
produce, roughly, double the C. E. M. F.
CONTROLLERS AND SWITCHES. 187
of rotation that it produces when it was
aided by the motor M 2 .
The connections of the seventh working
notch are the same as for the sixth, or re-
main as shown in Fig. 77. This is merely
for the purpose of not making the next
change too suddenly, requiring the motor-
man to take a certain time in turning his
handle for two notches, so as to avoid
abrupt changes in speed.
The conditions produced when the
eighth working notch is reached are
indicated diagrammatically in Fig. 78.
Here the second motor M 2 , which was
withdrawn from the circuit in Fig. 77, is
replaced in parallel with J/i, instead of in
series ; that is to say, the current through
the circuit divides, half passing through
MI, and half through M 2 . Each motor,
188
ELECTRIC STREET RAILWAYS.
however, must make up, disregarding drop
'in J? 2 , the full pressure of 500 volts be-
tween trolley and track, and the speed of
rotation would remain practically un-
FIG. 78. CONNECTIONS CORRESPONDING TO EIGHTH
WORKING NOTCH OF CONTROLLER.
changed, except that the current, being
approximately halved through each mag-
net, the strength of the magnetic field is
weakened, and the armatures have to run
CONTROLLERS AND SWITCHES.
189
faster to make up the required C. E. M. F.,
in this weakened magnetism. The speed
of the car will, therefore, be greater than
in the case represented in Fig. 77.
FIG. 79. CONNECTIONS CORRESPONDING TO NINTH
WORKING NOTCH OF CONTROLLER.
The effect of turning the controller
handle to the ninth working notch is repre-
sented in Fig. 79. Here the resistance J? 2 ,
is completely cut out of circuit and the
two motors are in parallel as in the last
190
ELECTRIC STREET RAILWAYS.
case ; or, as it is sometimes called, are con-
nected in multiple. The speed will be
increased, owing to the fact that the drop
previously existing in J? 2 , now requires to
be made up by the motors alone.
AAAAAAPAAAAAA
FIG. 80. CONNECTIONS CORRESPONDING TO TENTH
WORKING NOTCH OF CONTROLLER.
Fig. 80, represents the connections cor-
responding to the tenth and last working
CONTROLLERS AND SWITCHES. 191
notch ; i. e., the connections for full speed.
Here the only change from the connec-
tions of Fig. 79 lies in the restoration of
the shunts around the field magnets, thereby
reducing their excitation and requiring
an increased armature speed in order to
maintain the C. E. M. F. Each motor, as
before, has to produce, in C. E. M. F. and
drop, the full pressure of 500 volts, and
when the field is weakened, the speed for
a given C. E. M. F. of rotation has to
increase.
It will be observed, therefore, that the
movement of the controller handle through
the successive notches, results in an in-
creasing speed of the car. Of course
movement in the opposite direction results
in changing the connections in opposite
order of succession ; and, consequently,
slows the car.
192 ELECTRIC STREET RAILWAYS.
There is no definite or precise speed
which corresponds to each notch, since that
will depend upon the load of the car and
the gradient at which it runs. In other
words, it will depend upon the activity
which the motors exert. The lighter the
load -for any given notch or set of connec-
tions, the faster the motors will run. On
the contrary, an increase of load at any
time, even without touching the controller
handle, will result in a diminution of
speed.
The function of the small handle A, is to
reverse the direction of current through the
two motor armatures, and, consequently,
to reverse their direction of rotation.
As this cannot be safely accomplished
during the running of the motors, the
handle A, is so arranged mechanically that it
cannot be turned until the controller handle
CONTROLLERS AND SWITCHES. 193
H, is at the " off position " on the first
notch ; so that before the car can be reversed
the current must first be shut off. This
prevents any arcing on the contacts of the
reversing cylinder y. All the arcs wnich
tend to form on the contact segments of
the large cylinder are extinguished by the
action of the magnet M, which is always
in the circuit.
At the bottom of the controller are two
switches m and n, respectively. These
are commonly employed to cut out one of
the motors on the car, if by any accident
it should become disabled. For example,
if the brushes of motor M, should fail to
make good contact, or give other electrical
trouble, that motor can be entirely cut out
of circuit. Similarly, by lifting the switch
handle n, the motor M^ can be entirely cut
out of circuit. In such a case the car is
194 ELECTRIC STREET RAILWAYS.
operated by the remaining motor, and
only such notches can be used with the
controller handle as will be available for
the operation of that motor.
H
FIG. 81. STREET CAR CONTROLLER.
Another form of controller is shown
in Figs. 81 and 82, Here, as before, we
CONTROLLERS AND SWITCHES.
195
have the main controller handle If, and a
small reversing handle k. The method of
operation is substantially the same in
FIG. 82. CONTROLLER OF FIG. 81 OPENED FOB
INSPECTION.
all controllers. In this case, however,
no attempt is made to blow out the arcs
magnetically when breaking the circuit.
Instead of this the arc is caused to occur
196 ELECTRIC STREET RAILWAYS.
simultaneously at a number of segments in
series, so as to produce a number of small
arcs instead of a single large one. This
greatly reduces the heat and deflagrating
FiG."83. FORM OF CONTROLLER RESISTANCE.
power of the arcs. The contact points
at which they occur are renewed from
time to time.
Fig. 83, shows a form of resistance
employed with the controller represented
CONTROLLERS AND SWITCHES. 197
in Figs. 81 and 82. Here the resistances
are formed of strips of sheet iron, wound
upon insulating frames, in coils or
cylinders, three of which are stowed in the
iron box shown, in such a manner as to
allow free circulation of air to carry off
the heat that may be generated in them.
There are four screw terminals t iy t 2 , t& 4 ,
placed on an insulating slab at the top
of the case for the wires to connect with.
The controller of a car may be regarded
as a complex switch capable of effecting
the different connections such as we have
indicated. Usually there is one controller
at each end of the car. The handle H,
is carried from one controller to the other
according to the direction in which the car
is to be run.
In order to protect the controller or
198 ELECTRIC STREET RAILWAYS.
motors from any excess of current, an
automatic cut-out or safety fuse is employed
in the circuit. This consists of a copper
wire, of such size that it will melt when
the current attains an excessive strength.
FIG. 84. FUSE BLOCK.
The wire is enclosed in a box or block
called a fuse block, placed in a suitable
position on the car, usually on the plat-
form overhead, where it can be readily
inspected. A form of fuse block is repre-
sented in Fig. 84. The block, as it
CONTROLLERS AND SWITCHES. 199
appears when closed, is shown at C, and, as
it appears open, at 0. A block of hard
wood j5, carries, secured to its edge, two
screw binding posts S l and S& and tongues
T ly T 2 . The clips are permanently in con-
nection w T ith the trolley on one side, and
the controller on the other, so that the
current has to pass from the trolley
through the fuse block by means of these
clips. Connection is made between the
clips through a wire, usually either No.
12, or No. 14, A. W. Gr., running around
the edge of the block B, and having its
extremities clamped under the screws ^
and Sg. The lid Z, of the box, as well as
its interior, are lined with asbestos cloth to
prevent damage through the melting of
the copper fuse,
In addition to the controller and fuse
block there is usually added a canopy
200 ELECTRIC STREET RAILWAYS.
switch at each end of the car. This switch
is provided for the purpose of permitting
the motorman to turn the current on or off
the car as desired, when, for example, he
wishes to inspect a fuse block or con-
troller, without pulling down the trolley
FIG. 85. CANOPY SWITCH.
pole. It receives its name of canopy
switch from its position beneath the
canopy or roof of the platform.
Fig. 85, shows a form of canopy switch.
A cast iron box B, encloses the working
COMTROLLERS AND SWITCHES. 201
parts and screws up against the canopy.
The handle H, projects from this box and
can be moved sideways in the slot or groove
provided for the purpose. This insulat-
ing handle is fastened to a metallic blade
which closes a contact with a clip C, thus
establishing the main circuit from the
trolley to the controller. S, S, are two
slotted slabs between which the handle
plays.
To protect the motors and apparatus on
a street car from electrical discharges pro-
duced by atmospheric disturbances ; i. e.,
from lightning discharges, a lightning
arrestor is' usually included in their equip-
ment. A form of lightning arrestor is
represented in the accompanying figure 86.
Here a cast iron box B, B, with its lid
L, L, removed for inspection of its inte-
rior, has a pair of marble slabs, the upper
202
ELECTRIC STREET RAILWAYS.
one of which is shown at Jt/J clamped
together by screws. A groove runs down
their interior surface, between two inetal-
FIG. 86. LIGHTNING AKRESTOR.
lie pieces c l and a , in electrical connection
with the leads or insulated conducting
wires C lt C v This groove is black-leaded
CONTROLLERS AND SWITCHES. 203
in such a manner as to provide a ready
path for discharges of very high E. M. R,
such as those which accompany lightning
discharges, but forms an effectual barrier,
or high resistance path, to currents from a
pressure of 500 volts. Should a lightning
discharge occur between the trolley wire
<7 n and the ground or track wire <7 2 , the
dynamo current will be unable to follow
this discharge owing to the rapidity with
which the heated column parts with its
heat to the marble blocks. In other
words, the conducting path is chilled so
suddenly, after the passage of the momen-
tary high-pressure discharge, that the
dynamo current is unable to follow. If
this were not effected the high-pressure
discharge would establish a very powerful
and dangerous arc between trolley and
track.
CHAPTEE VIII.
TEOLLEYS.
THE existing system of trolleys and
trolley wires for street railway cars, simple
as it seems, has, nevertheless, been the out-
come of no little practical development
and experience. At the present time the
system in almost universal use is the
single-trolley system. In this system, a
current is taken from an overhead wire
suspended over the street. After passing
through the motors the current returns to
the power station, through the track and
ground return.
The well known mechanism provided
204
TROLLEYS. 205
for transferring the current from the trol-
ley wire to the cars, called the trolley mech-
anism, is shown in Fig. 87. As will be
seen, it consists of a light steel pole p,
called the trolley pole, mounted on a base
b, called the trolley base, and provided at
its extremity with a light wheel t, called
the trolley wheel. The rope r, called the
trolley rope, is provided for pulling the
trolley away from the trolley wire w w,
and for aiding in replacing it.
Simple as the trolley mechanism appears,
nevertheless, certain conditions must be
satisfied, in order to ensure efficient opera-
tion. One of the most important of these
is that sufficiently firm pressure or con-
tact be steadily maintained between the
trolley and the wire under which it runs.
Moreover, this contact must be flexible.
The requisite flexibility is obtained both
206 ELECTRIC STREET RAILWAYS.
FIG. 87. PASSENGER CAR WITH TROLLEY.
TROLLEYS. 207
by the flexibility of the trolley wire itself,
and the mounting or support of the trolley
on its base. Means too, are provided for
reversing the direction of the trolley pole,
so that the car may be driven in either
direction. For obvious mechanical reasons
the trolley pole always slants away from
the direction in which the car moves.
The trolley wheel, or trolley, is the name
given to the revolving part which is sup-
ported at the top of the trolley pole, and
maintained in rolling friction upon the
under side of the trolley wire. Its func-
tion is to maintain electric contact with
the wire, so as to take from it the current
required for the operation of the car.
One form of trolley wheel is seen in Fig.
88. As here shown, it consists of a light
wheel TFJ usually of gun metal, sup-
ported in a frame or harp II, and running
208
ELECTRIC STREET RAILWAYS.
freely upon a spindle, not shown in the fig-
ure, passing through both harp and wheel.
The grooved form given to the wheel not
only serves the purpose of ensuring a
FIG. 88. TROLLEY WHEEL AND HARP.
more extended rolling contact surface
with the wire, but also serves to prevent
the trolley from slipping off the wire. The
spring w, pressing against the face of the
trolley, maintains good electric contact
between the wheel and an insulated wire
TROLLEYS.
209
which passes down through the trolley
pole to the car.
FIG. 89. FORM OF TROLLEY WHEEL.
Various forms of trolley wheels have
been devised. It is essential that they
FIG. 90. FORM OP TROLLEY WHEEL.
210 ELECTRIC STREET RAILWAYS.
shall be as light, rigid and freely running
as possible. For this purpose, special
attention is paid to their lubrication,
which is usually effected by employing a
bushing of graphite, or other lubricating
material.
FIG. 91. SECTION OP TIIOLLEY WHEEL, SHOWING
LUBRICATING BUSHING.
As an illustration of some of the various
forms of trolley wheels those shown in Figs.
89 and 90 may be taken. It will be ob-
served that these wheels are ribbed, so as
to ensure strength combined with light-
TROLLEYS. 211
ness. Moreover, should the rim of the
wheel wear out and drop off dining a
trip, the trolley wire will still be
gripped by the ribs It, H. The bushing
of lubricating material is seen at b, Fig. 91,
which shows a section through the wheel of
FIG. 92. LUBRICATING BUSHING.
Fig. 89. Here the lubricating bushing B,
is seen in place at the centre of the hollow
wheel. Fig. 92 shows a form of bushing
ready for insertion.
At times during winter, when the
trolley wire is covered with sleet, some
difficulty is experienced in taking off the
212 ELECTRIC STREET RAILWAYS.
current, ice being practically an insulator.
Various devices have been suggested to
avoid this difficulty. A form of trolley
wheel, which assists in clearing sleet from
o
the wire, and allows the fragments of ice
FIG. 93. SLEET-CUTTING TROLLEY WHEEL.
to escape through the sides of the wheel
is shown in Fig. 93.
The trolley pole is in almost all cases a
steel tube, tapering toward the top. Its
lower end is mounted on the trolley
frame or base. Springs are connected
TROLLEYS.
213
between the base aiid the pole in such a
manner as to maintain the pole in contact
with the wire, with a nearly uniform pres-
sure, under all conditions of dip or devi-
ation of the trolley wire. Various trolley
FIG. 94. TROLLEY BASE.
poles and bases have been employed. A
well known form of trolley base is
shown in Fig. 94. Here the pole P,
terminates in a fork attached to a pair
of sectors 8, 8, forming a frame, capable
of revolving about a vertical axis V,
214 ELECTRIC STREET RAILWAYS.
so as to accommodate the pole and trol-
ley wheel to turns or curves in the
track and trolley wire. The six spiral
springs 6f, maintain a tension upon these
sectors tending to force the pole f,
upwards. This tension can be altered by
the screw adjustment behind the springs.
In order to be able to use the trolley
when the direction of the car is reversed,
the pole is first pulled down from the
trolley wire and then swung around the
vertical pivot V, when it is allowed to
re-engage with the wire in the opposite
direction.
Another frame and pole called the
Boston trolley apparatus is represented in
Fig. 95. The wooden frame F F F F,
is screwed to the roof of the car. It
carries a spindle., working on a horizontal
axis and bearing the pole jP, at its centre.
TROLLEYS.
215
Eight spiral springs G, G, maintain the
requisite tension upon the pole under
the screw adjustment s s. Two smaller
spiral springs g, g, are provided for sup-
porting the pole in the vertical plane, and
FIG. 95. BOSTON TROLLEY BASE AND POLE.
help to keep it from leaving the wire. T,
is the trolley ; H, the harp ; r, the attach-
ment ; and P, the pole.
A simple form of trolley base is shown
in Fig. 96. Here the pole P, is supported
216 ELECTRIC STREET RAILWAYS.
in a fork , carrying two lugs /, /, con-
nected on each side of the pole by rods to
the extremities of stout spiral springs.
The effect of these springs is to maintain
the trolley pole vertical under ordinary
circumstances, and, when the pole is
FIG. 96. FORM OF TROLLEY BASE.
pulled down, it tends to return to the
vertical position by the compression of
one spring and the distension of the other.
The pole and springs together can swing
around the vertical axis upon which they
are mounted so as to accommodate the
trolley to curves.
TKOLLEYS.
217
FIG. 97. TROLLEY POLE AND BASE.
Other forms of trolley poles and bases
are shown in Figs. 97 and 98. The rnech-
FIG. 98. TROLLEY BASE.
anism is sufficiently clear in each case
to be understood by a mere inspection.
218 ELECTRIC STREET RAILWAYS.
The angle which the trolley pole makes
with the roof of the car, under ordinary
circumstances, is about 40. The trolley
wheel is ordinarily pressed upward with
a force of about 30 pounds weight against
the wire.
OF THg
(UNIT* BHSITT)
CHAPTEE IX.
TEOLLEY LIKE CONSTEUCTION".
THE poles which support the trolley
wire over the track are either of wood or
of iron. In the country, wooden poles are
frequently employed, while in cities iron
poles are preferred. The methods most
frequently used for supporting the trolley
wire are either by the use of span wires or
by brackets. Span-wire construction re-
quires poles in pairs, on opposite sides of
the street, while bracket suspension only
necessitates a single line of poles even for
double tracks. Where, however, bracket
poles are used for double tracks they are
open to the objection of requiring to be
219
220
ELECTRIC STREET RAILWAYS.
placed in the middle of the street, thus
tending to obstruct traffic.
Fig. 99, shows the span-wire system,
with two iron poles, P, JP, made of three
FIG. 99. SPAN- WIRE SUPPORT.
tapering lengths of iron tube, s, s, is the
span wire, commonly of No. 1 A. W. G.
iron wire ; n, n, are the insulators sup-
TROLLEY LINE CONSTRUCTION.
221
ported on the span wire, and in their turn
supporting the two trolley wires over
their respective tracks. The poles are
\
FIG. 100. BRACKET POLE FOR DOUBLE TRACK.
commonly 27 to 30 feet long, and are
buried to a depth of 6 feet, being usually
set in concrete. For span- wire construe-
222 ELECTRIC STREET RAILWAYS.
tion, the poles are commonly set slanting
from the tracks so as to enable them
better to stand the strain of supporting
the trolley wires.
FIG. 101. SINGLE-TRACK BRACKET SUPPORT.
The poles for the bracket-support system
are always set vertically and midway be-
tween the tracks. Such a pole is shown
in Fig, 100. Here b, b, is the bracket arm
and n, n, the insulators suspended there-
TROLLEY LINE CONSTRUCTION. 223
from, supporting in their turn the trolley
wires w, w> and w, w.
Forms of single-frack bracket suspension
are shown in Figs. 101 and 102. The
FIG. 102. SINGLE-TRACK BRACKET SUPPORT.
poles are set about 120 feet apart ; i. e.,
about 45 per mile with bracket suspen-
sions, or 90 per mile for span- wire sus-
pension.
In order to attach the span wires to the
224 ELECTRIC STREET RAILWAYS.
iron pole, iron clamps are employed,
generally of the form shown in Fig. 103.
When the clamps are in position facing
each other on opposite sides of the street,
the span wires are stretched between them
FIG. 103. POLE CLAMP.
under considerable tension, depending
upon the weight of trolley wire, but 500
pounds weight is a fair tension. Where
only a single span wire crosses the street,
it is often stretched between insulators at
the top of the poles > as shown in Fig. 99.
Since, of course, the trolley conductor is
TROLLEY LINE CONSTRUCTION. 225
an uninsulated wire, guard wires are often
employed to prevent damage from con-
tact with bare telegraph or telephone
wires, which would thereby become con-
nected with a pressure of 500 volts.
Guard wires are of two kinds ; viz., span
guard wires, which cross the street im-
mediately above the span supports over
the trolley wire, and running guard wires,
which run parallel with and immediately
over the trolley wires to receive and inter-
cept any wire falling from above. The
relative position of guard and suspension
wires is illustrated in Fig. 104. P, P, are
opposite poles, c, c, the pole clamps,
s, s, the suspension span wire, and g, g,
the guard span wires. The trolley wires
are always suspended from the lower
wire s, s, and guard wires are usually sus-
pended over the trolley from the upper
span ff, g.
226
ELECTRIC STREET RAILWAYS.
We will now turn our attention to the
devices adopted both for supporting the
trolley wire from the suspension span wire,
and for enabling the trolley to be stretched
FIG. 104. POLES WITH GUARD AND SUSPENSION SPAN
WIRES.
tightly. It is necessary not only to sup-
port the wire rigidly and to insulate it from
the. span wire, but also to employ devices
for this purpose that shall be as small and
sightly as possible. The simplest way tc
TROLLEY LINE CONSTRUCTION.
227
support a trolley wire from a span wire is
by means of a trolley ear or insulator.
Such a form of ear or insulator is shown in
Fig. 105. e, e, is a metal casting, called
FIG. 105. STRAIGHT-LINE SUSPENSION, AND TKOLLEY
EAR AND INSULATOR.
the ear. It is furnished with a narrow
edge s, Sj having tips which are bent and
soldered over the trolley wire, which lies in
a groove extending under the entire length
of the ear. /,/, is the body of the suspen-
228
ELECTRIC STREET RAILWAYS.
siou, having two flanges at its extremities
as shown. The suspension span wire lies
in these flanges and around the head of the
insulator. The insulator is made in two
FIG. 106. TROLLEY EAR AND SUSPENSION.
parts, A and B, shown separately above,
A, being an insulating cap and >, an insu-
lating cone. These two parts are screwed
together and grip the body between them.
Fig. 106 shows another form of street line
TROLLEY LINE CONSTRUCTION. 229
suspension and ear, differing from the
former merely in details of construction.
The outer iron cap G, has the cover v,
screwed down upon it in such a manner as
to enclose the insulating tube t. This insu-
lating tube encloses in its turn the bolt
which is screwed into the ear. The sus-
FIG. 107. DOUBLE-CURVE SUSPENSION.
pension span wire is gripped tightly be-
tween the flanged projections f,f, of the
body and the outside of the iron cap c.
A great variety of line suspensions are
employed. Fig. 107 shows a common form
called a double-curve suspension, named
230 ELECTEIC STREET RAILWAYS.
from the two lugs of the hood or cover.
On the insertion of this form of suspension,
the span wire has to be cut and the two
ends fastened into the rings r, r. In other
respects the suspension is practically the
same as that shown in Fig. 106. The
FIG. 108. SINGLE-CURVE SUSPENSION.
double-curve suspension possesses the ad-
vantage that all the tensions exerted upon
it, with the exception of that produced by
gravitation, are exerted in the horizontal
plane ; that is to say, the span wire pulls
sideways upon it in almost the same plane as
the tension of the trolley wire lengthways.
TROLLEY LINE CONSTRUCTION. 231
Another form of suspension, called the
single-curve suspension is shown in Fig.
108. This suspension is introduced at
curves in the track or line where only a
e
^^BB^HBRsss
H
FIG. 109. BRACKET SUSPENSION EAR.
single pull is exerted on the trolley wire,
instead of requiring a span.
A form of bracket suspension ear, is
shown in Fig. 109. Here the cylinder (7,
232 ELECTRIC STREET RAILWAYS.
is damped firmly by the screw clamp P,
upon a bracket arm, while from the
cylinder is supported the insulator 7J and
ear e e, upon the bolt b b.
'When two lengths of trolley wire have
to be connected together, the connection is
always made at an ear, or point of support.
FIG. 110. SPLICING EAR.
Such an ear is for this reason called a
splicing ear. A form of splicing ear is
shown in Fig. 110. The two ends to be
connected are brought respectively to the
ear at w and w', under the grooves to x and
x', and then through the holes in the ear at
the openings o and o. The wires are
then soldered in at w, x and o. The
TROLLEY LINE CONSTRUCTION. 233
ear is bolted to its supporting insulator
at B.
Instead of soldering the ends of the
wire in a splicing ear they may be clamped
in a device called an automatic ear, shown
in Fig 111. Here the two wires are laid
FIG. 111. AUTOMATIC OR CLAMP-SPLICING EAR.
in the jaws of the clainp at O, C. The
jaws are then pressed together and secured
by a bolt.
The necessity for maintaining a taut
trolley line, so as to ensure a good and
continuous contact with the trolley wheel,
requires that the line be anchored about
234
ELECTRIC STREET RAILWAYS.
every 1,000 feet. An anchor-strain ear
is shown in Fig. 112. Strain wires are
a b
FIG. 112. ANCHOR-STRAIN EAR.
attached to the lugs a and , and are made
fast, through insulators, to equidistant
poles as shown in Fig. 113. The insula-
FIG. 113. ANCHORING FOR SINGLE AND DOUBLE TRACK.
TKOLLEY LINE CONSTKUCTION. 235
tors which are employed for this purpose
are called strain insulators, and are of
various forms. A common form, is shown
in Fig. 114. The two lugs are cast into a
spherical insulating mass.
FIG. 114. STRAIN INSULATOR.
Trolley wire insulators have two func-
tions to fill ; namely, a mechanical function ;
i. e., in providing an adequate support,
and an electrical function ; i. e., as an elec-
trical insulator. In order to be sufficiently
strong, suitable material must be employed
and so arranged as safely to support the
stresses exerted upon it. From an electri-
cal point of view, the insulation afforded
by an insulator is never that of the mater-
236 ELECTRIC STREET RAILWAYS.
ial of which the insulator is formed, and
is always, in practice, the insulation of the
surface. That is to say, the electric leak-
age, which takes place through an insulator,
is practically all over the surface of the
insulator, scarcely any passing through the
substance of which it is formed. The con-
dition of the surface, therefore, greatly
affects the efficient action of the insulators ;
for, if dirty or dusty, a thin film of moist-
ure will entail a considerable electric
leakage. Assuming the same surface con-
ditions, a spherical insulator, such as that
shown in Fig 114, would permit consider-
ably greater leakage than a cup insulator
of the type shown in Fig. 106, especially
in wet weather. The electric leakage,
however, which can be permitted on a
trolley system is far in excess of that
which can be allowed on a telegraph or
telephone circuit; since, if the total line
TROLLEY LINE CONSTRUCTION. 237
leakage gave rise to a loss of activity
amounting to 1 KW, which would represent
a total leakage current of 2 amperes under
a pressure of 500 volts, or a total insulation
resistance of only 250 ohms; the cost of
this would be one or two cents per hour.
The insulation of trolley systems usually
averages from 2,000 to 100,000 ohms to
the mile according to the weather.
When a trolley road branches, it is
necessary to branch the trolley wire.
This is accomplished with the aid of a
device, called a trolley frog. Fig. 115,
shows three forms of trolley frogs. At A,
is a V-frog, or simple two-way frog, in an
inverted position, so as to show the guides.
#, is a metallic guide on the side of the
single track, and b and c, are the two
guides on the side where the road bifur-
cates. When the car has to be driven,
238
ELECTRIC STREET RAILWAYS.
say from a to b, the rails on the track are
so switched as to carry the car in that
direction, and the trolley follows from the
FIG. 115. TROLLEY FROGS.
guide a, to the guide b. During the pass-
age from the guide a, to guide b, the trolley
wheel will either maintain contact with
the line through its metal frame, or may
TROLLEY LINE CONSTRUCTION. 239
make a momentary flash at the point of
crossing. B, shows an inverted right-
hand frog and C an inverted left-hand
frog. Where a line divides into three
branches special frogs, called three-way
?, have to be employed.
B
4*
FIG. 116. TROLLEY CROSSING.
At the intersection of two streets where
trolley wires- necessarily cross each other,
the crossing is effected through the
medium of a device similar to a frog,
and called a trolley crossing. Forms of
240 ELECTRIC STREET RAILWAYS.
trolley crossings are shown in Fig. 116.
A, is a right-angle crossing, and B, an
acute-angle crossing. The trolley wires
are soldered in the groove over the four
guides, and as a result, the trolley wheel
has to drop slightly at a crossing to pass
beneath the guides. Special forms of
crossings are employed when it is desired
to insulate the two crossing trolley wires
from each other.
Trolley wires are made in all sizes from
No. 4 A. W. G., with a diameter of 0.204",
to No. 000 A. W. G., with a diameter of
0.410". The commonest size is No. 0,
of 0.3249" diameter. The material is
usually hard-drawn copper, although
alloys are occasionally used. A No. 0,
hard-drawn copper wire will safely
bear a tension of 2,500 Ibs. weight, and
usually breaks at a tension of 5,000 Ibs.
TROLLEY LINE CONSTRUCTION. 241
weight. A hard-drawn copper wire of
this size has a resistance of, approximately,
0.52 ohm at 60 F., its resistance being
about 2 1/2 per cent, in excess of the re-
sistance of the same size wire in soft
copper, whereas silicon-bronze wire has
sometimes about 21/2 times the resist-
ance of the same size of soft copper wire.
CHAPTER X.
TRACK CONSTRUCTION.
IT is frequently a matter of surprise
that the installation of a trolley road is
almost invariably attended by the recon-
struction of the track. The necessity for
this reconstruction is to be found in the
fact that electric cars are much heavier
than ordinary horse cars, and contain run-
ning machinery which is liable to injury
from excessive jolting. This liability to
injury from a weak and inferior track is
increased by the greater speed at which
electric cars run. Moreover, in a badly
constructed track difficulty is experienced
in maintaining an efficient running contact
242
TRACK CONSTRUCTION. 243
between the trolley and the trolley wire.
For these reasons the construction of the
roadbed and track requires careful at-
tention.
In cities more care and expense are
naturally taken with both line and track
FIG. 117. TRACK CONSTRUCTION.
construction than in the open country, but
the tendency is towards the employment
of a steel girder rail weighing 90 Ibs. per
yard. These rails are laid directly on
wooden sleepers to which they are spiked.
This construction is shown in Fig. 117,
where the girder rails R, R, are spiked to
244
ELECTRIC STREET RAILWAYS.
the sleeper S, S, and are also bound to-
gether by the tie rod T y 2} the roadbed
being paved in this case with Belgian
blocks. The rails are laid with their ends
close together, no difficulty having been
experienced from expansion in summer
FIG. 118. TRACK AND SLEEPERS, SHOWING METHOD OF
BREAKING JOINTS.
time. It is common to break these joints
so that the joints of the rails on one side
of the track shall come opposite to the
middle of the rail on the opposite side.
This is represented in Fig. 118, where
<7, e/, </, and J"', </', show the relative
positions of the joints of each rail. The
TRACK CONSTRUCTION. 245
sleepers in this case are also so distributed
as to be closer together near the joints, as
shown, fy f, is the fish-plate with twelve
bolts which pass through the rail and are
screwed up against a similar fish-plate on
the other side of the rail.
With the use of a ground return it is
necessary to ensure as intimate a contact be-
tween the rails as possible, so as to secure
a continuous metallic path and to lessen
the resistance that would otherwise be
introduced into the circuit. Mere contact
of the ends of the rails with their connect-
ing fish-plates is not sufficient, since rust at
this surface produces a very considerable
resistance. In order to avoid this, various
methods of bonding the rails have been
proposed. This is attempted in a variety
of ways, but the object is always to secure
a permanent metallic connection between
246
ELECTRIC STREET RAILWAYS.
successive rails. One of these rail bonds
is represented in Fig. 119. To use this
bond the rails are drilled close to the fish-
plate and a bent copper rod of the shape
shown at A, has its two ends pressed into
the holes, one end in each rail. A section
FIG. 119. CHICAGO RAIL BOND.
of the rail with the end of the copper rod
projecting through it is shown at a. The
plug B, is then driven with the hammer
into the opening of the rod so as to wedge
it tightly into the iron rail. A cross-section
of the rail, rod and plug is shown at G.
TRACK CONSTRUCTION. 247
A somewhat similar method of effecting
a rail bond consists in the use of stout
copper wire in place of the copper rod.
Here the wire is passed twice through
holes in the rail each side of the fish plates
and copper wedges are driven in so as
FIG. 120. WIRE RAIL BOND.
completely to wedge the wire against the
metal rail. At intervals this wire is
led directly across the track and enters
into a bond with the other rail, thus effec-
tively connecting the two rails together.
A wire bond of this character is shown in
Fig. 120.
248 ELECTRIC STREET RAILWAYS.
The most efficient bond from a purely
electric point of view is the welded rail
bond obtained by welding the rails together.
For this purpose a very powerful electric
current is passed through the ends of the
rails, and pieces of iron, called chucks,
which are used in place of the fish-plates.
When completed, this joint is as solid and
strong as the rest of the rails, thus afford-
ing a practically continuous iron rail, and
therefore a continuous return circuit.
Another method of accomplishing the
same result consists in pouring melted cast
iron around the ends of the rails after
cleaning them, and so effecting a solid
joint. Although success has not yet been
perfectly obtained with continuous rails,
yet it would appear that the stresses pro-
duced by expansion and contraction in a
uniform continuous rail are well within the
limits of the elasticity of the steel.
OF THE
CHAPTER XL
ELECTROLYSIS.
WHEN an electric current is sent through
a vessel containing ordinary tap water, the
passage of the current is attended with the
decomposition of the water into its con-
stituent elements, oxygen and hydrogen.
These elements are liberated, in the gaseous
state, only at the points of entrance and
exit of the current from the water, the
hydrogen beiug liberated where the cur-
rent leaves the water, and the oxygen
where the current enters the water. If
the conducting surface at which the cur*
rent enters is oxidizable like iron, copper,
lead, zinc, and nearly all ordinary metals
249
250 ELECTRIC STREET RAILWAYS.
it becomes corroded or oxidized, while a
similar metal surface or electrode provided
for the exit of the current from the water
is unaffected, the hydrogen being usually
disengaged in bubbles. Decomposition
effected in this manner, by an electric cur-
rent, is called electrolytic decomposition, and
the corrosion of metals in liquids in this
manner is called electrolytic corrosion.
The earth or ground is only capable of
acting as a return circuit by virtue of the
moisture which is practically always pres-
ent. Consequently, in all cases where the
ground-return circuit is used, the metallic
surfaces by which the current enters and
leaves the ground are liable to electrolytic
action. Where the current leaves the
metallic conductors to enter the ground, or
the moisture within the ground, there will
be electrolytic corrosion, but where the
ELECTROLYSIS.
251
current enters a metallic conductor on
leaving the ground there will be no
electrolytic corrosion, although there may
be a liberation of hydrogen. On the con-
trary, there will be an electric protec-
tion afforded the metal, at such points the
FIG. 121. SIMPLE TROLLEY CIRCUIT.
oxidation being less than that of similar
metal, exposed to ordinary conditions in
the absence of electric currents.
The simplest condition of a trolley sys-
tem is represented in Fig. 121. Here the
252 ELECTRIC STREET RAILWAYS.
generator 6r, has its positive pole con-
nected to the trolley, that is, the current
enters the trolley from the generator, passes
through the car motors, and returns to the
generator, partly by the track and partly
by the ground ; i. e., the water in the
ground, as a supplementary or auxiliary
conductor. If the track had no electric
resistance, or conducted perfectly, all the
current would return through the track
and none would pass through the ground.
If, on the other hand, the track were dis-
connected at some point, for instance at
each rail joint, then its resistance would be
indefinitely great and practically all the
current would pass through the ground.
The better the electric conditions of the
rail bonds, and the low r er the resistance of
the track, the greater will be the pro-
portion of the current which will pass
ELECTROLYSIS. 253
through the track and the less the propor-
tion which will pass through the diffused
circuits in the ground. Where the current
leaves the rails on the track, to enter the
ground, there will be corrosion or oxidation
of those rails, but where the current re-
turns from the ground to the track, or other
buried metal at the power house connected
with the generator, there will be no corro-
sion, and even a tendency to prevent corro-
sion.
When electrolytic corrosion takes place
the amount is perfectly definite. One
coulomb of electricity passing through
water will dissolve 0.000,002361 Ib. of
lead electrode, and 0.000,000,6393 Ib. of
iron electrode. Since an ampere* is a rate
of flow of one coulomb-per-second, a cur-
rent strength of one ampere will dissolve
0.000,002361 Ib. of lead per second, or
254 ELECTRIC STREET RAILWAYS.
0.000,000,6393 Ib. of iron per second, and
therefore, if an ampere be steadily main-
tained for one year it will dissolve by cor-
rosion 74.46 Ibs. of lead and 20.16 Ibs. of
iron. If the current be increased to ten
amperes, the amount of lead or iron cor-
roded will be ten times as great, the chemi-
cal action being directly proportional to
the quantity of electricity which is passed.
In the case of Fig. 121, corrosion will
occur over the surface of the track where
it lies in contact with moist earth. The
corrosion will not be uniform, but will
proceed faster at some points than others,
the rate of corrosion depending upon the
distribution of current over its surface ; i. e.,
on the local facility with which the current
escapes into the earth. The total amount
of electrolytic corrosion will depend only
on the total quantity of electricity, in
ELECTROLYSIS. 255
ampere-hours or coulombs passing from
the metal.
If, however, the generator has its nega-
tive pole connected to the trolley wire,
and its positive pole connected to the
track, the electrolytic conditions will be
reversed; for, the current will now leave
the metallic surfaces for the moist ground
in the vicinity of the power house, and
there the corrosion will take place to an
aggregate amount depending entirely
upon the total quantity of electricity pass-
ing into the ground. There will now be
no corrosion where the current re-enters the
track.
Were the corrosion which occurs with
street .car systems limited to the track, the
consequences would not be so serious, but
in cities the corrosion affects the metallic
256
ELECTRIC STREET RAILWAYS.
masses of the gas and water pipes, and
their corrosion may lead to serious damage.
Fig. 122 diagrammatical!} 7 represents a
street car system in which the positive pole
of the generator is connected to the trolley,
and the negative pole to the track. This
FIG. 122. DIAGRAM OF TROLLEY SYSTEM IN NEIGHBOR-
HOOD OP BURIED PIPE. NEGATIVE POLE GROUNDED.
case differs from that of Fig. 121, only in
the fact that a system of water pipes, W,
W, is supposed to lie in the vicinity of the
track. If we suppose that a current of
1 ,000 amperes is steadily flowing from the
generator through the car motors, 500
ELECTROLYSIS. 257
amperes or half the current may return
directly to the generator through the
bonded track, 100 amperes may return
through the ground, escaping from the
track at more distant points and returning
to it in the neighborhood of the station,
while the balance, or 400 amperes, may find
its way into the good conducting path pre-
sented by the system of water pipes, enter-
ing it in the distant areas and leaving it in
the vicinity of the power house.
Under the circumstances above men-
tioned, there will be electrolytic action at
A, where the current leaves the track, and
at B, where it leaves the water pipe. The
area of B, will be a comparatively narrow
one, and, consequently, the rapidity of cor-
rosion will be comparatively great, since
400 amperes maintained day and night,
represents a total corrosion of roughly
258 ELECTRIC STREET RAILWAYS.
8,000 pounds per annum spread over a
comparatively small area. If we connect
the water pipe system with the generator's
grounded terminal, as shown by the dotted
lines, we reduce the quantity of electricity
which leaves the surface of B, through the
ground, since it will largely pass directly
through the new connection. By this
means the electrolytic corrosion of the
water pipes will be diminished.
If the negative pole of the generator be
connected to the trolley and the positive
pole be connected with the track, as shown
in Fig. 123, then, all other things remaining
the same, there will be corrosion at A
and B ; namely, at the portions of the water
pipe remote from the power house and
at the portions of the track near it. In
this case, however, the area of water pipe
over which the corrosion takes place is
ELECTROLYSIS. 259
more extended, and, consequently, the
amount of corrosion on any one length of
pipe in the district will be correspondingly
less.
*-rA *** r*
in*'-* /-* - - - ~\~\ i
1111
w W
FIG. 123. DIAGRAM OP TROLLEY SYSTEM IN NEIGHBOR-
HOOD OF BURIED PIPE. POSITIVE POLE GROUNDED.
There are, therefore, two methods of
dealing with the dangerous influences of
electrolytic corrosion upon neighboring
metallic pipes. The first is to ground the
positive pole of the generator or generators
at the power house, and so spread the cor-
rosion over a large area of pipe distant
260 ELECTRIC STREET RAILWAYS.
from the power house, trusting to the en-
larged area and the slowness of corrosion
to avoid serious effects. In this case there
is no advantage to be gained, so far as
avoiding corrosion is concerned, by directly
connecting the water pipe system with the
grounded generator terminal. In fact
there will be an advantage in avoiding
such connections. The second method is
to ground the negative pole of the gener-
ator at the power house, as in Fig. 122, so
as to bring the area of corrosive action
within the neighborhood of the power
house. If this course be adopted it be-
comes important to protect this area by
not only connecting the pipes with the
grounded generator terminal, but also by
securing good electric connections between
the track and the grounded terminal of the
generator through bonding and ground
feeders.
ELECTROLYSIS.
261
Whichever method be adopted the use
of ground feeders, rail welding, and effi-
cient bonding necessarily reduces the
danger of corrosion by offering a better
FIG. 124. IRON PIPE CORRODED BY ELECTROLYSIS.
metallic conducting path to the return
current. Fig. 124 represents a piece of
pipe destroyed by the influences of electro-
lytic corrosion.
CHAPTEE XII.
SWITCHBOARDS.
IF we trace the trolley wires of any
street car railway system we will find
them to form an interconnected network
maintained at, approximately, 500 volts
pressure relatively to the track. From
this network the feeders pass to the power
house, either suspended overhead on poles
and insulators, or underground through
lead covered cables placed in suitable con-
duits. Tracing these feeders to their
origin we will find them terminating at
what is called the switchboard. The use of
the switchboard is to enable the attendant
at the power house to learn at a glance the
SWITCHBOARDS. 263
electric condition of the system, and also to
enable him to control or modify the electric
condition with swiftness and convenience.
To this end the switchboard is provided
with a number of electric measuring in-
struments, called respectively voltmeters,
for measuring the electric pressure in volts,
and ammeters, for measuring the electric
current in the various circuits in amperes.
Fig. 125, shows a form of railroad
switchboard intended for use with three
separate dynamo generators and three
separate feeders: This switchboard con-
sists of seven vertical panels formed of
marble, a good insulator. The three
pauels on the right hand are feeder panels,
and a generator is connected to and con-
trolled by each. The central panel is a
total-current and pressure panel, for measur-
ing the entire current supplied to the three
264 ELECTRIC STREET RAILWAYS.
FIG. 125. SWITCHBOARD FOR RAILWAY POWER HOUSE.
SWITCHBOARDS. 265
feeder panels, and the main pressure of
the power house. /SJ &, $, are the three
generator switches, consisting each of three
metallic knife blades maintaining connec-
tion between metallic clips. In the posi-
tion shown, all three switches are closed
and all three generators are at work to-
gether. Beneath the generator switches
are rheostat boxes, R, ~R, H, for control-
ling the current supplied by each respective
generator. A, A, A, are automatic circuit-
breakers, which are so arranged that the
current, supplied by their respective gener-
ators, passes through stout coils or spirals
of copper rod, so that when this current
strength becomes dangerously great, indi-
cating an overload upon the generator, the
magnetic action of the spirals releases a
lever, which under the action of the spring
flies back and breaks the circuit. M,M,M,
are three ammeters, each in circuit with its
266 ELECTRIC STREET RAILWAYS.
respective generator, so that the pointer
or index shows at a glance the current
strength and, therefore, the load upon that
generator. L, L, L, are lightning arres-
tors, intended to carry to ground any
discharges due to lightning, thus avoiding
damage to the system. Turning to the
feeder panels, s, s, s, are the three feeder
switches. On closing one of these switches
the particular feeder which supplies it is
connected with the generator or generators,
which may be in use, so that if all three
of the switches shown be opened, the
the entire load will be taken off the gene-
rators, even though these be maintained
running. #, a y a, are automatic feeder cir-
cuit-bredkerSy similar in their action to
those already alluded to at A, A, A.
/, I, I, are lightning arrestors, connected
to each feeder, similar to those at Z, Z, L.
JVj is the main ammeter, supplied by all
SWITCHBOAKDS. 267
three generator ammeters, M, M, M, to-
gether, and supplying in its turn, the
various feeders. FJ is the voltmeter
showing the pressure between generator
terminals at the station in volts.
The automatic cut-outs A, A,. A, and
a, a, a, are constructed as shown on a
larger scale in Fig. 126. The current sup-
plied by the generator passes from the
clip P 9 with its attached carbon plate JV,
across the metal frame of the switch H,
to the opposite metal clip P , and its
attached carbon plate N', thence by the
terminal A, through the three turns of
the metallic coil or spiral (7, to the terminal
J?, from whence it passes to the line. On
lifting the handle H y into the position
shown on the left hand, a metallic connec-
tion is established between the clips, and
the switch is kept in position by a detent.
268
ELECTRIC STREET RAILWAYS.
The current passing through the three
turns of the coil C, magnetizes them and
tends to lift the iron core in its interior.
FIG. 126. CARBON-PLATE AUTOMATIC CIRCUIT-BREAKER.
As soon as the current strength exceeds a
certain limiting safe value, the raising of
the iron core by the increased magnetic
SWITCHBOARDS. 269
attraction lifts the detent, and permits the
switch H, to be thrown out of the clips
into the position shown on the right hand
side. As soon as connection at the clips
P, P, is broken, a powerful arc would
probably form which might melt the
switch. Contact is, however, maintained
through the medium of the carbon plates
JVJ N, and the carbon rods J?, R, which
brush against them. The arc which takes
place when this latter contact is broken is
a carbon arc, instead of a copper arc, and
such burning as does occur can only result
in burning some of the carbon parts, which
can be readily replaced from time to time.
Another form of automatic circuit
breaker is shown in Fig. 127. Here the
circuit is normally closed from the terminal
H, through the three turns of the spiral <?,
the metallic projections B, B, and the
270
ELECTRIC STREET RAILWAYS.
bridge of flexible copper strips t, t, between
them. As soon as the current strength
passing through the apparatus exceeds the
FIG. 127. MAGNETIC CIRCUIT-BREAKER.
limiting amount for which it is set, the
coil O, attracts its armature against the
tension of the spiral spring t, and permits
SWITCHBOAKDS. 271
the larger spring S, to withdraw the bridge
t, t, from the blocks B, B. A shunt cir-
cuit, is, however, retained between J3, B,
for a little while after this contact is
broken through the two magnet coils
M, M, and a smaller set of contacts in the
upper part of the apparatus. The magnets
become powerfully excited by the passage
of the current through them and produce
magnetic poles over the iron surfaces
jP, Pj P, and P, one pole being, say north,
and the other south. Between these pole
pieces, the second or auxiliary contact is
broken by the descent of the lever , after
the main contact is broken at B B, and t.
The arc, which tends to follow the inter-
ruption of the auxiliary contact, is instantty
extinguished by the influence of the mag-
netic flux between the polar projections,
as already explained in the chapter on
controllers.
272 ELECTRIC STREET RAILWAYS.
Should one of the generators, or one of
the feeders, become overloaded, the auto-
matic circuit-breaker will open its circuit
and protect the generator placed therein.
In many cases the overload may have been
due to an accidental temporary short-cir-
cuit, which almost immediately disappears.
In such cases it is usual to reset the circuit-
breaker by the use of the handle H, until
it is found that after three trials the appa-
ratus refuses to remain set. It is then
usual to allow the circuit to remain broken
and to search for the short-circuit.
Fig. 128, shows a form of ammeter, such
as is seen at M, M, M, in Fig. 125. Here
the metallic pieces A, B, form the termi-
nals of the massive coil C. having two
o
turns placed directly in the circuit. The
iron core 0, is attracted towards this helix,
by the electromagnetic action of the cur-
SWITCHBOARDS.
273
rent, this attraction increasing with the
current strength. The core O, is suspended
from a short balance arm pivoted at v, and
V
FIG. 128. FORM OF AMMETER.
having a long pointer or index p, moving
over a scale. When the current is cut off,
the counterpoise overweights the iron core,
and the pointer moves into a position
274 ELECTRIC STREET RAILWAYS.
opposite to the zero point on the left hand
of the scale. As the current strength
through the coil (7, increases, the magnetic
pull tends to overcome the gravitational
pull on the counterpoise, and the pointer
moves further and further towards the
right.
A form of voltmeter, shown at V, in Fig.
125, is represented on an enlarged scale in
Fig. 129. The principle and action of the
apparatus are similar to that of the amme-
ter in the preceding figure. The principal
difference, however, is in the winding of
the coil O y which, instead of consisting of
but two turns carrying a powerful current,
has very many turns carrying a feeble cur-
rent. Resistances of insulated wire wound
on frames JR It, are placed in circuit with
the vertical coil (7, and the terminals of the
generator. The current strength passing
SWITCHBOARDS.
275
in this circuit will be determined by Ohm's
law. For example, if the total resistance
of the coil C, and the two resistances H, R,
FIG. 129. VOLTMETER.
is 5,500 ohms, and the pressure at the gen-
erator terminals is 550 volts, then the cur-
rent strength passing through the circuit
276 ELECTRIC STREET RAILWAYS.
will be 55Q volts = th ampere = 100
5,500 10
milliamperes. The counterpoise t, is so ar-
ranged that at this particular current the
pointer^, stands vertical and indicates 550
volts. Should the pressure rise 10 per
cent., or to 605 volts, the current in the
circuit of the coil (7, would increase 10 per
cent., and its increased magnetic attrac-
tion on the iron core within it would
deflect the pointer to a position which
is marked 605 volts on the scale. It is
evident, therefore, that this voltmeter is
essentially an ammeter with a high resist-
ance in its circuit.
The general connection which is effected
by the switches on the switchboard, omit-
ting all details of ammeters, voltmeters,
cut-outs and lightning arresters, is diagram-
matically represented in Fig. 130. Here
SWITCHBOARDS.
277
two main bars, or bus-bars, B _Z?, B'B' a
contraction for omnibus bars, so called be-
B
G,
tf
FIG. 130. GENERAL CONNECTION BETWEEN GENERATORS
AND FEEDERS AT POWER HOUSE.
cause they receive the entire current from
the generators, are connected, one to the
feeders and the other to the track, ground
278 ELECTRIC STREET RAILWAYS.
feeders, or ground connection. Between
these bus-bars the station pressure of say
550 volts is maintained. One or more of
the generators G^ G& G& are connected
across the bus-bars according to the amount
of load on the lines ; i. e., according to the
number of cars that are running, and the
work they are doing. If only a few cars
are on the line the current required will be
small, the electric activity small, and a
single generator may be sufficient. Thus
the switch /Si, may be closed, leaving G^ to
take the entire load. If more cars are run
the total current strength supplied to the
feeders may require the addition of a sec-
ond generator G 2 , by bringing it up to
speed and excitation and closing the switch
$2, and so on for the other generators.
CHAPTER XIII.
GENERATORS AND POWEK HOUSES.
now from the switchboards to
the generators which supply them, we
notice two distinct types ; namely, the belt-
driven generator, and the direct-driven
generator; i. e., a generator directly con-
pled to the driving engine. The modern
tendency in large power houses is to em-
ploy very large generators, of say 1,000
HP each, and to connect these directly
to a driving-engine. In some power
houses, however, belt-driven generators
are employed. The belt-driven generators
have usually four poles, and very rarely
have less than this number. The large
279
280 ELECTRIC STREET RAILWAYS.
direct-driven generators have usually more
than four poles, since it is found more con-
venient and economical to construct gener-
ators of large output with a greater
number of poles. Fig. 131 shows an
example of a belt-driven generator of 500
KW output. Fig. 132 shows a direct-
driven generator.
Turning to Fig. 131, N 9 S, N, 8, are the
four magnet poles wound with coils of
insulated wire. In nearly all cases rail-
way generators are compound-wound / i. e.,
there are two windings on each coil, one
of very stout conductor and of very few
turns, connected directly in the armature
circuit, the other of many turns of fine
wire, connected in a shunt, or by-path
around the armature. The object of com-
pound winding is to maintain the pressure
automatically constant at the brushes, or
282 ELECTRIC STREET RAILWAYS.
at the switchboard bus-bars, notwithstand-
ing changes in the number of cars, or load.
The armature A, revolves within the
annular space provided between the four
pole- pieces, and with it the commutator
C. On the surface of this commutator
four sets of collecting brushes H, H, are
fixed on a frame, capable of slight adjust-
ment in angular position by means of the
wheel shown at the base of the pedestal.
T, is one of the main terminals, with
which the brushes are connected. B, is
the driving belt.
In Fig. 132, similar letters refer to
similar parts. Here there are also four
poles and four sets of brushes, capable of
being rotated together within certain
limits by the projecting handle. The
engine E, is coupled directly to the arma-
!"-
J)
a
>
u
284 ELECTRIC STREET RAILWAYS.
ture shaft through powerful springs con-
tained within the coupling K. F, is a
fly-wheel and P, a cluster of six incandes-
cent lamps in series, called pilot lamps.
FIG. 133. ARMATURE OF DIRECT-DRIVEN GENERATOB.
A particular armature intended for a
direct-driven railroad generator is shown
in Fig. 133. Here the armature consists
GENERATORS AND POWER HOUSES. 285
of two distinct parts ; namely, a body or
core of iron, and conducting wires. The
core is laminated, that is, formed of a
number of thin, soft, sheet-iron discs, pro-
vided with slots in their external edges, so
that when assembled in the shape of a
short cylinder, a number of longitudinal
slots or grooves are provided for the recep-
tion of the wires. Without considering
the winding in detail, it will suffice to say
that the conductors are laid in the slots
S 9 S, and are then connected to the
separate bars or segments of the commu-
tator C, C 7 G. Fig. 134, shows the opera-
tion of winding another form of railway
generator armature, with the wires W, W,
passing through the slots of the iron arma-
ture core A. In this case the commutator
is not yet placed on the shaft. A com-
pleted armature is, however, shown below
at JB, with its commutator at O.
286 ELECTRIC STREET RAILWAYS.
During the revolution of the armature
through the magnetic flux produced by
the field magnets of the generator,
E. M. Fs. are induced in the winding, and
when their circuit is closed through the
feeders produce currents in them. The
value of the E, M. F. developed by the
armature during its rotation, depends
upon the total amount of magnetic flux
passing through the armature and its
wires, the total number of wires wound
over the surface of the armature in the
various grooves, and the number of revo-
lutions which the armature makes per
minute ; i. e., its rotary speed. The cur-
rent strength which a given armature can
maintain steadily, depends upon the size
of the wires ; i. e., upon the resistance of
the armature and its capability of readily
disengaging the heat developed by the
current in that resistance. The limiting
288 ELECTRIC STREET RAILWAYS.
current strength is usually determined in
practice by the heating of the armature,
which in good practice does not exceed
40 C. above the surrounding air, during
continuous running.
Illustrations of generator rooms in
power-houses, employing respectively the
belt-driven and direct-driven types, are
shown in Figs. 135 and 136. Fig. 135
shows the interior of the Fifty-second
Street power house of the Brooklyn street
railway system, containing twelve belt-
driven generators, each of 500 KW ca-
pacity, capable of a total output of
6,000 KW, and representing 12,000 am-
peres at 500 volts ; or, approximately,
11,000 amperes at 550 volts. These gen-
erators are, however, capable of standing
a considerable overload for a limited time.
The switchboard $ is seen on a gallery
at the end of the room.
1
5
i a
290 ELECTRIC STREET RAILWAYS.
A view of the interior of another Brook-
lyn railway power house ; namely, that at
Kent Avenue, is shown in Fig. 136. Here,
instead of being placed on the floor beneath
the generators and connected to the latter
by belts, as in Fig. 135, the engines are
mounted side by side with the generators
and directly coupled to the armatures.
There are four large generating units in
the room of the type shown at 1, 2, 3 and
4 respectively. Each generator has twelve
magnet poles, between which revolves the
armature -4, with its commutator C, at a
speed of 75 revolutions per minute. The
armature is driven by a double engine
E, JS. The engine is a double, horizontal,
compound-condensing engine, the generator
being placed between the two halves.
f, F, is the engine fly-wheel placed on
the main shaft, close to the armature.
Each of these large generators has a
w
ii
f Jd
g
w
292 ELECTRIC STREET RAILWAYS.
capacity of 3,000 amperes at a pressure of
550 volts, representing an activity at full
load of 1,650 KW, and a total output,
when all are at full load, of 6,600 KW, or
8,800 HP, approximately. The switch-
board 8, is seen at the end of the room
through the fly-wheels of the two engines,
on the left hand side of the figure. One
of the generators in the figure; namely,
No. 3, is shown incomplete, the field mag-
nets being not yet assembled. The most
recent development in street railway
practice is in the direction of powerful
slow-speed engines and direct-connected
generators of this type.
Fig. 137, shows a plan view of the
engine and generator room in the Delaware
Avenue railway power house at Phila-
delphia. Here the general plan of engines
and generators is similar to that shown in
a 1 !
294 ELECTKIC STREET RAILWAYS.
Fig. 136. There are four generating units
marked 1, 2, 3, 4, each consisting of a
1,650 KW, 12 -pole generator, with its
armature keyed to the shaft of a large
compound-condensing engine of 2,000 HP
(about 1,500 KW), arranged in two parts,
one part on each side of the generator.
S, /8J is the switchboard, behind which the
feeders are seen. jP, is the air-pump con-
nected with all the engines, and 5, is a
small 300-KW direct-driven unit for light
loads. One of the larger generator units
is said to have operated as many as 212
cars at one time. If working at full load
this represents a mean activity of 8 KW
per car. At this rate all four units could
operate 850 cars. Each generator will
stand the application of full load without
any change in the position of its brushes,
and will stand an overload of 50 per cent,
with a slight movement of the same.
II
296 ELECTRIC STREET RAILWAYS.
Fig. 138 shows a section of the power
house represented in plan in Fig. 137.
Here E, E, shows one of the engines, and
g, g, one of the large generators on the
lower floor. On the floor above are
placed the boilers in two rows, one on
each side, with an auxiliary 6r, G, between
their fronts. The boiler accommodation
is for ten batteries, each of 500 HP, repre-
senting an aggregate capacity of 5,000 HP
nominally. B, B, are the boilers, shown
in cross-section on the right hand and inside
view on the left. The steam pipes de-
scend to the ceiling of the generator room,
and the engine exhausts are led to the
cellar where they are dripped, and the main
exhaust pipe X, X, is led to the roof.
CHAPTER XIV.
OPERATION AND MAINTENANCE.
THE amount of power which a street
car requires, depends, as we have seen,
upon its size, weight, the number of pas-
sengers it is carrying, its speed, and the
gradient on which it runs. It may vary
from no power, when running down hill,
to 100 KW when climbing a steep hill.
It is often a matter of surprise to those
who have been accustomed to see a pair of
horses pull a street car through the city
streets, that power, representing say more
than 100 horses acting together, may be
needed on occasions to propel electric
cars. The reasons, however, are very
297
298 ELECTRIC STREET RAILWAYS.
clear. An electric car weighs from 15,000
to 20,000 pounds without passengers,
while a horse car weighs only about 5,000
pounds without passengers. The electric
car will carry many more passengers than
a street car, runs at a greater speed, and
will climb grades impossible to be sur-
mounted by two horses.
A good rule to remember is that on the
average, over a city street railroad system,
an electric street car takes 1 KW for every
mile per hour it averages, that is to
say, if a car runs at 8 miles per hour
it absorbs roughly 8 KW of electric
power ; or, in 1 hour, would absorb a
total amount of work equal to 8 kilowatt-
hours. This rough estimate is, of course,
independent of the power required to
heat the car when electric heating is em-
ployed.
OPERATION AND MAINTENANCE. 299
The output of a station, that is, the load
on the generators, varies markedly at
different hours of the day. As a rule the
heaviest load occurs in the morning and
evening hours. The reason for the in-
creased load is not only because a greater
number of cars are running and the cars
are more heavily laden, but the startings,
which require considerable power, occur
more frequently during the time of greatest
load. Fig. 139 shows load diagrams taken
in Boston, Mass., on June 16-19, 1895.
It will be observed that the load varies
from practically at 4 A. M., to 12,000
amperes and 800 cars, and that the total
activity correspondingly varies from nearly
to about 6,000 kilowatts.
It has been found from a report in 1894,
of 232 American electric street railways,
operating 5,120 miles of track with a total
300
ELECTRIC STREET RAILWAYS.
capital of $316,700,000, and a funded debt
of $279,000,000, that the operating ex-
15000
14000
"13000
^12000
K 11000
gjlOOOO
| 9000
j 8000
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FIG. 139. LOAD DIAGRAMS AT BOSTON, JUNE 16-19, 1895.
penses were 62.8 per cent, of the gross
receipts, and the fixed charges 22.9 per
OPERATION AND MAINTENANCE. 301
cent., leaving a net income of 14.3 per
cent, of the gross receipts.
The power required to be installed at
the power house varies with a number of
local conditions, but averages 20 KW per
car in use. The cost of installing this
power is about $70 per KW for steam
plants, including engines and boilers, and
about $30 per KW of combined steam and
electric plant, or $100 per KW of total
machinery. The cost of the electric
equipment of a car, including two 25 HP
motors and controllers, is about $1,000, and
the cost of a car so equipped complete,
roughly $2,300. The line construction
costs roughly $5,000 per mile of double
track, excluding track construction, but
varies considerably, under different condi-
tions. The total expense of a car mile,
i. e.j a run of one mile per car, varies of
302 ELECTEIC STREET HALLWAYS.
course considerably with the size, the kind
of system and the nature of the traffic, but
a fair average may be considered as being
from 15 to 25 cents per car mile. Of this
the cost of supplying electric power is usu-
ally only from 1 cent to 2 cents per car
mile. In small systems all these costs are
likely to exceed those given.
The size and style of the car which is
adopted, varies with the nature of the
traffic, and the speed at which the car is
expected to run. Under some conditions
heavy cars running slowly are desirable,
while in others light, high-speed cars are
preferable.
The population per mile of street rail-
way track in the United States is, approxi-
mately, 4,600, varying between 3,000 in
the New England States, and 10,000 in the
OPERATION AND MAINTENANCE. 303
Southern States. In Canada, it is about
11,600. The total street car mileage in
the United States is about 6 per cent, of
the total steam railroad mileage, and the
gross earnings about 50 per cent, of the
total passenger steam railroad earnings.
For the purpose of facilitating repairs
on the line, special wagons drawn by
horses are employed, called tower wagons,
arranged so as to bring the workmen
within easy access of the trolley wire.
These wagons carry a light platform,
which is either rigid or is capable of being
raised and lowered. Both the frame of this
wagon and its tower being of wood, the
men working upon it are practically insu-
lated, except in wet weather.
In latitudes where snow falls the track
is kept clear by an electric snow sweeper.
304
ELECTRIC STREET RAILWAYS.
One of these snow sweepers is shown in
Fig. 140, where the track has been swept by
the rotation of the brushes of the car.
Fig. 141 shows one of these cars in action.
FIG. 140. ELECTRIC SNOW SWEEPER.
There are four motors on one of these
cars, usually of 25 HP each. Two of the
motors are connected with the driving
axles in the usual way, and the other two
OPERATION AND MAINTENANCE. 305
are wound for a higher speed and are con-
nected so as to drive the revolving
FIG. 141. SNOW SWEEPER IN ACTION.
brushes. These sweeping brushes are
fixed at an angle of 45 with the front of
the car.
The overhead trolley system has been
objected to in cities on account of its
unsightliness. The use of trolley poles
306 ELECTRIC STREET RAILWAYS.
with their span, guard, and trolley wires
are certainly far from being a pleasing
ornament to the streets of a well built city.
For this reason attempts have been made
to replace the overhead trolley system by
an underground or conduit system of trol-
leys, and also by storage-battery propulsion.
The overhead trolley system is, however,
considerably more economical to erect and
maintain than either a storage battery or
conduit system. In large cities, where an
increased cost is preferred to the unsightli-
ness of the overhead trolley system, the
underground trolley may find a successful
use. It is already being tried in Washing-
ton, D. C., and elsewhere in the United
States, while in the city of Buda Pesth,
Austria, an extended system of under-
ground trolley roads has been running
successfully for several years.
B
Of THE
IVERSITT,
MUFORHj*
CHAPTEE XV.
STOKAGE BATTERY SYSTEMS.
THE admitted unsightliness of the over-
head trolley system and the difficulty of
maintaining efficient operation of the
underground trolley, under all conditions
of climate, have led to many efforts to
obtain a self-contained system of electric
railways ; that is, a system in which each
of the cars will carry its own electric
driving power. In the early history of
the art this was attempted by means of
the primary battery. Primary batteries
are now recognized as being altogether too
expensive for this purpose, owing to the
fact that they derive their motive power
307
308 ELECTRIC STREET RAILWAYS.
from the consumption of zinc in a solution,
a fact which will effectually prevent such
batteries from competing with other types
of motive power so long as the price of
the zinc, and the solution in which it is
dissolved, maintain anything like their
present values.
%
The nearest approach to the successful
solution of the problem of an electrically
propelled car, which carries its own stored
electric energy, is found in the use of the
secondary or storage cell. In this system
the storage cells derive their charge, or
stored electric energy, from electric cur-
rent supplied to the cells at some central
station. As some time is required to
charge the cells, they are usually removed
from the car to receive their charge.
Before proceeding to the general descrip-
tion of the storage battery equipment of a
STORAGE BATTERY SYSTEMS. 309
car, a brief account of the construction and
operation of storage batteries will be
necessary.
A great variety of forms have been
given to the secondary or storage cell. In
practically all cases, the material of which
their plates or elements are formed is lead.
If two sheets of lead be immersed in a
solution of dilute sulphuric acid, and an
electric current be sent through the solu-
tion from one plate to the other, an
electrolytic decomposition will occur,
whereby the positive plate, or the plate at
which the current enters, becomes oxi-
dized, while the negative plate, or that at
which the current leaves the cell, liberates
bubbles of hydrogen gas. During this
process a C. E. M. F. is set up in the cell
amounting, probably, to about 2.5 volts,
and every coulomb, or ampere-second of
310 ELECTRIC STREET RAILWAYS.
electricity, which passes through the cell,
does work in it amounting to 2.5 volt-
coulombs or 2.5 joules. At a rate of 1
ampere, or 1 coulomb per second, the work
so expended in the cell would amount in
one hour, to 3,600 X 2.5 == 9,000 joules or
2.5 watt-hours.
If there were no resistance in the
cell; and if, moreover, no free hydrogen
gas escaped from it, all the above
work would be expended in chemical
action, which would be stored up in the
cell in the form of chemical products. So
far as the C. E. M. F. is due to the drop
of pressure through the resistance, the
work is expended as heat, but so far as it
is produced by the C. E. M. F. of chemi-
cal action, it is theoretically possible to
store the work in chemical combinations.
If after having been charged in this way
STORAGE BATTERY SYSTEMS. 311
the cell is removed from the charging
circuit and its plates are connected
through a wire, it will act as a primary
battery ; that is to say the oxidized plate
will behave like the copper plate of an
ordinary bluestone cell, and the unoxidized
plate like the zinc of such a cell.
During discharge, the E. M. F. of the cell
may, perhaps, average 2 volts, and each
coulomb of electricity supplied through
the circuit by this E. M. F. represents a
delivery of 2 joules of work. During
discharge, and the performance of work,
the surface of the oxide on the posi-
tive plate becomes partially deoxidized,
while the plain lead or negative plate
becomes partially oxidized. Finally,
when the cell is completely discharged,
the two plates are superficially the same,
each being partially oxidized. A cell is,
312 ELECTRIC STREET RAILWAYS.
however, never permitted to completely
discharge. In order to restore the cell to
its active condition, it is necessary to once
more charge it by passing through it the
requisite quantity of electricity.
In the case of a primary cell, in which
the two plates or elements have essentially
different chemical composition, the com-
plete discharge is accompanied by the con-
sumption of one of the plates ; namely,
the zinc plate. It is impossible, in prac-
tice, to restore the active condition of the
primary cell by sending a charging cur-
rent through it, and the plates have to be
renewed. In the secondary cell, instead
of renewing the discharged plates, the
electric current is permitted to reverse
the chemical changes which have accom-
panied discharge and thus restore the active
condition.
STORAGE BATTERY SYSTEMS.
313
Instead of using plain lead plates,
special forms of lead plates are employed
to expose a very large surface to the
active liquid. A form of storage cell is
FIG. 142. FOKM OF STORAGE CELL.
shown in Fig. 142. Here the glass cell or
jar C, C, contains seven flat plates, three
of which are connected with the positive
terminal jP, and four to the negative termi-
nal N. The solution of sulphuric acid
314
ELECTRIC STREET RAILWAYS.
and water is poured in until the plates are
covered.
A positive plate is shown in Fig. 143.
Here thirty-nine circular buttons, or discs
I T'T
FIG. 143. POSITIVE PLATE.
of peroxide of lead, are held tightly in a
frame or grid of antimonous lead. The
addition of antimony in sufficient quantity
prevents the lead grid from being chemi-
STORAGE BATTERY SYSTEMS. 315
cally attacked by the solution during
charge or discharge. Fig. 144 shows a
negative plate, with sixty-four square
buttons of soft porous or spongy lead
FIG. 144. NEGATIVE PLATE.
similarly held in an antimonous lead
frame. The small holes in the centres
of the buttons play no part in the action
of the cell, and are made during the
mechanical construction of the buttons.
316 ELECTRIC STREET RAILWAYS.
The principal difficulty which has been
encountered with the use of storage cells
in electric traction, has been in the electric
overloads which have sometimes been
necessary, and which greatly decrease the
life of the plates. If the cars invariably
ran upon a level grade and their load
remained uniform, it would not be a diffi-
cult matter to ensure an absence of electric
overloads, or undue calls for power upon
the batteries. In practice, however, owing
to the existence of curves and grades
and over-discharging, the cells are gener-
ally soon injured, so that their mainten-
ance becomes very expensive. Moreover,
the great weight of the batteries adds
largely to the non-paying weight of the
car. Considerable improvements have,
however, recently been effected in the
storage battery whereby better results
may be expected.
STORAGE BATTERY SYSTEMS.
317
A form of storage battery car truck at
present in use on Madison Avenue, New
York City, is shown in Fig. 145. Here
by turning the motors outwards towards
the ends, that is supporting them on the
opposite side of the axle to that usually
adopted, the space A B G D, is reserved
FIG. 145. STORAGE BATTERY TRUCK.
in the centre of the truck for the recep-
tion of the storage battery. A truck with
a storage battery in place is shown in Fig.
146. In this truck sixty storage cells are
arranged in two batteries of thirty cells
each. Since the mean E. M. F. of dis-
charge in a storage cell is, approximately,
318 ELECTRIC STKEET RAILWAYS.
2 volts, this represents a pair of batteries
each having an E. M. F. of 60 volts. Each
cell has 400 ampere-hours capacity ; that
is, is capable of supplying 40 amperes for
10 hours, or 20 amperes for 20 hours, or 10
amperes for 40 hours, etc., the total quan-
tity of electricity being 400 X 3,600 =
FIG. 146. CAR TRUCK WITH BATTERIES IN PLACE.
1,440,000 coulombs. The above men-
tioned 1,440,000 coulombs, representing as
they do the capacity of its battery, should,
theoretically, be discharged whether the
duration of discharge is long or short, that
is to say, whether the cells are allowed
to discharge in a few minutes or in many
hours.
STORAGE BATTERY SYSTEMS. 319
In practice, however, there is always
a marked diminution in the avail-
able quantity of electric discharge when
the duration is too brief, say below three
hours. If the E. M. F. of discharge aver-
ages 2 volts, the total amount of energy
available from each cell is 2 X 1,440,000
= 2,880,000 coulomb-volts, or joules, and
60 such cells should hold a total quantity
of energy of 172,800,000 joules. Since 1
watt-hour is 3,600 joules, and 1 KW hour
3,600,000 joules, the total energy in the
battery is 48 KW-hours. Consequently,
the activity of the battery, assuming no
loss, by very rapid discharging, would be
8 KW maintained for six hours, or 12
KW maintained for four hours. Of this
power some will necessarily be lost in the
motors and gears, so that, perhaps, only
about 75 per cent, may be available at the
car axles.
320
ELECTRIC STREET RAILWAYS.
Fig. 147 shows diagrammatically the
connections obtained in the different posi-
tions of the controller of this car. In posi-
tion 1, the two batteries are placed in
parallel, making an effective E. M. F. of 60
FIG. 147. CONTROLLER POSITIONS.
volts at main terminals, while the two
motors are in series, each motor receiving
30 volts. If under these conditions, the
activity of the battery is 12 KW, the cur-
rent strength received by the two motors
in series will be
12,000
60
= 200 amperes.
STORAGE BATTERY SYSTEMS. 321
In the second position, a shunt is thrown
around the field magnets of the motors,
thereby diminishing their magnetic power,
and requiring a greater speed from the
armatures in order to develop the neces-
sary C. E. M. F. of 60 volts in all.
In the third position, the two batteries
are thrown in series, representing a total
E. M. F. available at terminals of 120
volts, and a corresponding increase in the
speed of the unshunted motors to produce
this C. E. M. F.
In the fourth position, a shunt is again
thrown around the field magnets of the
two motors, and their speed is correspond-
ingly increased.
In the fifth position, the two unshunted
motors are thrown in parallel, instead of in
322 ELECTRIC STREET RAILWAYS.
.series, thus calling upon each motor to de-
velop a total C. E. M. F. of 120 volts.
In the sixth and last position, the mag-
nets of the motors are shunted, requiring
the armatures to run faster in order to pro-
duce 120 volts total C. E. M. F. in the
motor under these conditions.
When the car returns to the car house
and the battery has been sufficiently dis-
charged, it is lifted bodily from the truck
and replaced by a charged battery.
OP THE ^X
TJNIVERSITT)
- -^
CHAPTER XVI.
ELECTEIC LOCOMOTIVES.
WITHIN large cities, municipal ordinances
generally limit the speed of street cars to
about eight miles per hour. In suburban
districts, however, a speed is usually per-
mitted as high as fifteen miles per hour,
while in inter-urban traffic, speeds of thirty
miles per hour or more are sometimes
reached. As the velocity of the cars in-
crease, the electric activity which must be
supplied to them increases in nearly the
same proportion ; for, the torque exerted by
the motors on a given gradient remains
nearly the same at all the above men-
tioned speeds, the rate only varying at
which that torque is exerted.
824 ELECTRIC STREET RAILWAYS.
At still higher speeds than the preced-
ing, the friction between axles arid journals,
and the wheels and the track, does not sen-
sibly increase, but the friction between the
surface of the car and the air does sensibly
increase, so that, at speeds above 100 miles
per hour, the track and journal friction
would probably commence to be small
compared with the resistance to air dis-
placement and friction. Consequently, for
very high speeds, the form of the moving
car becomes nearly as important as the form
of the hull of a steamer ; only in the case
of the latter, the hull only is exposed to the
friction against the water, while in the case
of the car, the entire surface is moved
through the air.
The question has often arisen as to the
early probability of replacing steam pro-
pulsion on ordinary railroads by electric
ELECTRIC LOCOMOTIVES. 325
propulsion. The schedule speeds of ex-
press trains on steam roads have altered but
little during the last twenty years, judg-
ing from an inspection of railroad time
tables included in that period. There is
no doubt, however, that the introduction
of the electric locomotive would permit
much higher speeds to be safely attained,
and, when this fact is taken in connection
with the manifest advantages possessed by
electric propulsion, it would seem that in
electricity, steam has a formidable rival in
this field. The question, however, is one of
public demand, and economy of transpor-
tation. There can be no doubt, that so far
as regards economy in long-distance trans-
portation, steam propulsion is cheaper than
electric propulsion, owing to the cost of the
plant, since the cost of transmitting power
electrically increases rapidly with the dis-
tance. Consequently, for freight and slow
326 ELECTRIC STREET RAILWAYS.
traffic, it does not seem that the immediate
future will witness the displacement of the
steam locomotive, but for high-speed pas-
senger transportation, the extra cost of the
electric equipment may be repaid by the
increased economy in time of transit, so
that it does not seem improbable that in
the near future the high-speed passenger
locomotive may come into use on railroads.
As an example of experiments which
have been tried in the direction of high-
speed electric railroads, we may mention
the bicycle railroad shown in Fig. 148.
Here the car runs on a single rail and rests
on two wheels, which, instead of being
placed side by side, as in the ordinary
truck, are in the same plane, like a bicycle,
one being placed in the front and the other
in the rear. The ends of the car are tap-
ered, as shown. To prevent the car from
328 ELECTRIC STREET BAILWAYS.
falling sideways when at rest, it is sup-
ported by guide wheels pressing upon the
upper or guide rail, which serves the double
FIG. 149. SECTION OF BICYCLE CAB.
purpose of a support and an electric
conductor. A cross-section of a double
deck car is shown in Fig. 149. It will be
seen that these cars are only of half width,
ELECTEIC LOCOMOTIVES. 329
two being able to pass each, other with nine
inches clearance within the space occupied
by an ordinary 4' 8 1/2" track. The ad-
vantage claimed for this construction is
that it not only enables the traffic to be
doubled upon any existing railroad by
erecting the upper or trolley guides, one
for each existing rail, but it also enables
the weight of the cars to be materially
reduced, since the narrow car enables
the necessary structural strength to be
obtained with less material, and the
weight of the loaded car, per passenger
carried, would be about four times less than
with the existing construction, thus econo-
mizing in activity expended against journal
friction and grades. The electric propul-
sion is obtained from a single motor M, in
the front wheel of the car. On the track
shown in the figure, speeds of 45 miles per
hour are readily obtained, and speeds of
330 BLEOTUIO 8TKEIST RAILWAYS.
over 60 miles an hour are claimed to have
been reached on a track 1 1/2 miles in
length. By giving a lean to the upper or
guide rail no difficulty has been found in
going around sharp curves, since no appre-
ciable strain is produced. A disadvantage
of the system is that it can only provide
seats for two in the width of the car.
Another purpose to which the electric
locomotive has already been applied is to
the drawing of trains of cars through long
tunnels on steam roads. As is well
known considerable difficulty is experi-
enced in ventilating long tunnels when
steam locomotives pass tli rough them fre-
quently. This difficulty is entirely over-
come by the use of the electric locomotive.
Here the requirements are not for high
speed, but for a powerful draw-bar pull.
An example of this type of electric loco-
LOCOMOTIVES. 331
motive is seen in the licit Line Tunnel at
I>a.llimore. This tunnel is about u mile
Mild a luilf loni; 1 , Mild has a ^radicnt of
about, forty-two feet to the mile. Since
the freight trallic. is heavy, a powerful
hx'oniolix c is ivipiiivd to dnivv th(^ tr.'iins.
I^ig. ir>() shows th(5 eiitr;i.n<T to I lie tunnel
with the electric overhead conductors (\
(', in pl,'K5(i. One of th(^se conductors is
provided for e.'ich of the two tnicks. <u\
tt\ nre the copper supj)ly wires, und /if, K,
.ire tin- supporting catenaries or rod
chains,
Kii;\ lf)l shows OIK' of the conductor sup-
ports from the. cM.tciiM.i-y. r, v, ju-e the rods
of the cM.t.c.nary. /, is t he conie;il iusuhitor.
//, //, (,he, suspension i-ods From this insu-
l.-itor. A', />', is the IJCMIU supported by
these rods, and < ', (\ I he conductoi's \\hich
are formed <>!' iron bars, arnin;j;ed o[posit,e
332 ELECTRIC STREET RAILWAYS.
FIG. 150. THE ENTRANCE TO THE TUNNEL.
ELECTRIC LOCOMOTIVES.
333
each other, so as to leave a slot between
them and enclose an inverted conduit. In
this conduit slides a brass shoe supported
FIG. 151. OVERHEAD CONDUCTOR SUPPORT.
on a flexible rod from the top of the loco-
motive. Wj is a cross-section of the sup-
ply wires or feeders, which are stranded
334 ELECTRIC STREET RAILWAYS.
copper cables about one inch in diameter
clamped directly to the beam as shown.
The method of supporting the conduct-
ors in the tunnel is shown in Fig. 152.
Here M, M, M, is the masonry arch of
the top of the tunnel, B, B, are bolts let
FIG. 152. METHOD OP SUPPORTING CONDUCTORS IN THE
TUNNEL.
into the masonry, and supporting a chan-
nel frame by two conical insulators i, i,
at the ends. Two other insulators i f , i r ,
support the conductors c, c.
Fig. 153 shows the electric locomotive
pulling a steam locomotive and train
through the tunnel. F, F, is the flexible
336 ELECTRIC STREET RAILWAYS.
conductor corresponding to the trolley pole
of an ordinary street car, and carrying at
its extremity the shoe running in the con-
ductor overhead. An end view of the
locomotive is shown in Fig, 154. The
trolley fastened to the top of the locomo-
tive is shown in side and end view at Fig.
155. S, is the shoe, and c/, t/J the joints in
the structure, which automatically lengthen
and shorten the trolley pole to conform
with the varying height of the trolley con-
ductor. This locomotive weighs ninety-
six short tons in all, and is supported on
two trucks and four pairs of driving
wheels. A motor is mounted directly
on each driving axle, thus placing four
motors in the locomotive. One of
these motors is shown in Fig. 156.
Here the iron-clad armature A, A, is
mounted in a sextipolar field frame F, F.
These motors being mounted on the driv-
ELECTRIC LOCOMOTIVES. 337
FIG. 154. END VIEW OF ELECTRIC LOCOMOTIVE.
338 ELECTRIC STREET RAILWAYS.
ing axles through special flexible connec-
tions without the intervention of gears, are
called gearless motors. The method of
mounting them in the truck is shown in
FIG. 155. SIDE AND END VIEWS OF TROLLEY.
Fig. 157. Here S, S, is the side frame
c/J J, are the journal boxes of the two
axles in the truck, and M, M, the motors
mounted flexibly over each axle.
ELECTRIC LOCOMOTIVES.
339
The current is supplied to each motor
armature through six pairs of carbon
FIG. 156. MOTOR OF ELECTRIC LOCOMOTIVE.
brushes arranged around the periphery of
the commutator. The total current sup-
plied to each motor is normally about 500
340
ELECTRIC STREET RAILWAYS.
amperes at full load. The pressure of sup-
ply is about 600 volts. The normal
activity absorbed by each motor at full
load is, therefore, 300 KW, or, roughly,
about 400 HP. Since there are four
motors, this powerful locomotive absorbs
FIG. 157. TRUCK, SHOWING MOTORS IN POSITION.
a total activity of about 1,600 HP, and
the locomotive is rated at 1,500 HP. The
locomotive is designed so as to exert a
steady pull of 40,000 pounds, or 20 short
tons, at the draw bar when drawing a train
twelve miles per hour. This represents
a useful activity of 1,280 HP in addition
ELECTRIC LOCOMOTIVES.
341
to that required to move the locomotive
itself. The maximum available draw-bar
pull is stated to be 60,000 pounds. The
FIG. 158. "TERRAPIN BACK" ELECTRIC MINING
LOCOMOTIVE.
draw-bar pull in an electric locomotive is
uniform, whereas the draw-bar pull in the
steam locomotive is necessarily variable at
different portions of the stroke. The
342 ELECTRIC STREET RAILWAYS.
draw-bar pull of a powerful 60 short-
ton steam engine does not usually exceed
25,000 pounds.
Electric traction has recently been
adopted on two short branches of road in
connection with steam railroads. These
are at Nantasket Beach, Mass., and Mount
Holly, N. J. The road between Mount
Holly and Burlington is about seven miles
long, and is operated by electric cars
equipped with 100 HP motors; the speed
being about thirty miles an hour, and
the schedule time for the trip twenty-one
minutes, including stops. It is not at all
improbable that this is but the beginning
of an extensive use of electric traction for
suburban traffic, in connection with steam
railroads.
The electric locomotive has recently
ELECTRIC LOCOMOTIVES. 343
found a field of application in mining
operations. It is especially fitted for such
work from the ease with which it is con-
trolled. Fig. 158 shows a form of mining
locomotive suitable for hauling trains of
trucks through the galleries of a mine.
It will be noticed that the trolley pole is
of the same general type as that described
in connection with the locomotive of the
Baltimore tunnel.
THE
INDEX.
Active Coil, 80.
Coil, Deflection of, by Electromagnet, 85.
Coil, Deflection of, by Horseshoe Magnet,
84.
Coil, Deflection of, by Opposite Magnet
Poles, 83.
Coil, Deflection of, by Single Magnet Pole,
82.
Active Conductor, 80.
Activity, International Unit of, 23.
, Practical International Unit of, 24.
, Unit of, 21.
Acute-Angle Crossing, 240.
Ammeter for Railway Generator Switchboard, 263.
for Railway Switchboard, 272 to 274.
Ampere, 28.
Analogy between Liquid and Electric Flow, 3 to 7.
345
346 INDEX.
Anchored Filament for Electric Street Car Lamp,
138.
Anchor-Strain Ear, 234.
Armature Coils of Car Motor, 72.
Core, Lamination of, 74.
Core, of Car Motor, 72.
, Cylinder, 75.
Pinion, 115 to 117.
, Ring, 75.
Windings of Car Motor, 72.
Arrester, Lightning, 201 to 203, 266.
Automatic Car Switch, 129.
Circuit-Breaker, 265.
- Cut-Out, 198.
- Ear, 233.
Feeder Circuit-Breaker, 266.
Axle Gears, 116.
B
Back Electric Pressure, 47.
Water Pressure, 45.
Bars of Commutator, 77.
Base, Trolley, 205.
Belt-Driven Generator, 297.
Berlin Industrial Exhibition of J 79, Electric Rail-
way of, 12.
INDEX. 347
Bicycle Railroad, 326 to 330.
Block, Fuse, 198.
Blow-Out, Magnetic, 160.
Bond, Welded Rail, 248.
Bonding of Rails, 245, 246.
Bonds, Rail, 246.
Box, Sand, 131, 132.
Boxes, Journal, 104.
, Rheostat, 265.
Bracket Pole for Double Track, 221.
Support for Single Track, 222.
Suspension Ear, 231.
Suspension for Single Track, 223.
Brackets, 219.
Brake Handle, 122.
Mechanism, 122.
Shoes, 99.
Breaker, Automatic Circuit, 265.
Broken Circuit, 27.
Bus-Bars, Generator, 278.
By-Path or Shunt, 182.
c
Canopy Switch, 199, 200.
Car Body, 97.
Brake, Electric, 126 to 128.
348 INDEX.
Car Brake, Pneumatic, 122.
Controller, Definition of, 155.
- Controller for Storage Battery System,
320 to 322.
Controller, Interior Construction of, 158,
159.
Controller, Method of Operation of, 162 to
191.
Heater, Heating Coils of, 144, 145.
Heating, Temperature-Regulating Switch
for, 147 to 151.
Lamp, 136, 137.
- Lamps, Circuit of, 135.
Lamps, Efficiency of, 138.
- Lamps, Fixtures for, 139, 140.
- Mile, 301.
- Motor, Armature Core of, 72.
Motor, Armature Windings of, 72.
Motor, Commutator of, 72.
- Motors, Gear Wheels of, 69.
- Truck, 67, 68, 97.
- Trucks and Cars, 97 to 133.
Trucks, Methods of Supporting, 97, 98.
- Trucks, Storage Battery, 317.
Wheels, Closed, 110.
Wheels, Gearing for, 113.
Wheels, Open, 108.
INDEX. 349
Car Wheels, Skidding of, 129.
Wheels, Tread of, 109.
Cars and Car Trucks, 97 to 133.
, Electric Lighting and Heating of, 134 to
153.
Carbon-Plate Automatic Circuit-Breaker, 267,268,
269.
Cell, Secondary, 309.
, Storage, 309.
Chicago State Fair, Street Car Line of '84, 14.
- Rail Bond, 246.
Circuit-Breaker, Carbon-Plate Automatic, 267,
268, 269.
Breaker, Magnetic, 269 to 272.
Breakers, Automatic Feeder, 266.
, Broken, 27.
-, Closed, 27.
, Electric, 27.
, Hydraulic, 30, 31.
, Made. 27.
, Open, 27.
or Line, Drop in, 54.
Climbers, Pole, 224.
Clamp, Splicing Ear, 233.
Closed Car Wheels, 110.
Circuit, 27.
Coil, Active, 80.
350 INDEX.
Coils, Armature, of Car Motor, 72.
Collecting Brushes of Generator, 282.
Commutator of Car Motor, 72.
of Generator, 285.
Segments, 77.
Strip, 77.
Compound- Wound Generator, 280.
Conductance, 40.
Conducting Wires, Resistance of, to Electric
Flow, 34.
Conductor, Active, 80.
Conductors, Feeding, 64.
Conduit Trolley System, 306.
Coney Island, Street Car Line of '84, 14.
Consequent Magnet Poles, 90.
Continuous Rail, 248.
Controller, Diagram of Connections for First
Working Notch, 164.
Controllers and Switches, 154 to 203.
Corrosion, Electrolytic, 250.
Coulomb, 48.
Counter-Electromotive Force, 45, 47.
Electromotive Force of Rotation, 166.
Electromotive Force of Self -Induction, 165.
Crossing, Right-Angle, 240.
, Acute-Angle, 240.
, Trolley, 239.
INDEX. 351
Current, Electric, 28.
, Electric, Unit of, 28.
Currents, Eddy, 74.
Cut-Out, 141.
, Automatic, 198.
Cylinder Armature, 75.
D
Davenport, 8.
Davidson, 8.
Decomposition, Electrolytic, 250.
Diagram of Load, 299.
Direct-Driven Generator, 279.
Double-Curve Suspension, 229.
Gear Wheels, 119.
Pinion, 119.
Reduction Motors, 118.
Track Bracket Pole, 221.
Truck, 99.
Dr. Ohm, 35.
Drop in Line or Circuit, 54.
E
E. M. F., 29.
Ear, Anchor-Strain, 234.
, Automatic, 233.
352 INDEX.
Ear, Bracket-Suspension, 231.
Clamp, Splicing, 233.
, Splicing, 232.
Eddy Currents, 74.
Edison, 13.
Efficiency of Car Lamps, 138.
of Line Circuit, 59 to 63.
of Motor or Generator, 57 to 59.
of Motor or Generator, Effect of Load on,
58, 59.
Effective Pressure, 47.
Eighth Working Notch, Diagram of Connections
of, 188.
Electric Car Brake, 126 to 128.
Car Heaters, Advantages of, 143, 144.
Car, Weight of, 298.
Circuit, 27.
Current, 28.
Current, Unit of, 28.
Gradient, 46.
Lighting and Heating of Cars, 134 to 153.
Street Car Lines of the United States,
Statistics of, 14.
Locomotive, Motor of, 339.
Locomotives, 323 to 342.
Locomotives of the Baltimore Tunnel, 330,
331.
INDEX. 853
Electric Mining Locomotive, 341.
Motor, 67.
Railroad System, Self-Contained, 307.
Resistance, 34, 35.
Snow-Sweeper, 303, 304.
Electricity, Quantity of, 42.
Electrolysis, 249 to 261.
Electrolytic Corrosion, 250.
Decomposition, 250.
Electromagnetic Pull, 84.
Twist, 84.
Electromotive Force, 29.
Elementary Electrical Principles, 16 to 66.
Elements of Storage Cell, 309.
Emergency Switch, 156.
F
Farmer, 10.
Feeder Panels, 263.
System, 65.
Feeders, 64.
Feeding Conductors, 64.
Points, 65.
Field, 13,
Magnet Coils, Effect of Shunting, on
Motor Speed, 183, 184
354 INDEX.
Filaments, Anchored, for Car Lamps, 138.
, Non-Vibrating, for Car Lamps, 138.
Fixtures for Car Lamps, 139, 140.
Flattening of Wheels, 131.
Flow, Electric, 28.
, Electric and Liquid, Analogy between, 3
to 7.
Foot-Pound, 18.
Pound-per-Second, 21.
Force, Counter- Watermotive, 45.
, Counter-Electromotive, 47.
, Electromotive, 29, 31.
, Electromotive, Unit of, 32.
Four-Pole Electric Motor, 88.
Fourth Working Notch of Car Controller, Dia-
gram of Connections of, 183.
Frog, Left-Hand, 239.
, Right-Hand, 239.
, Three- Way, 239.
, Two- Way, 237.
Fuse Block, 198.
, Safety, 198.
G
Gear Covers, 120.
Wheel, Double, 119.
INDEX. 355
Gear Wheels of Car Motors, 69.
Gears, Axle, 116.
Gearing for Car Wheels, 113.
Generator, Belt-Driven, 279.
Bus-Bars, 278.
, Collecting Brushes of, 282.
, Commutator of, 285.
, Compound- Wound, 280.
, Direct-Driven, 279.
, Efficiency of, 57 to 59.
, Laminated Core of, 285.
Rooms of Power House, Illustrations of,
288 to 294.
Switches, 265.
Generators and Power House, 279 to 296.
Gradient, Electric, 46.
, Hydraulic, 44.
Green, 11.
Grid or Frame of Storage Cell, 314.
Guard-Wire Span, 225.
Wires, 225.
Wires, Running, 225.
H
Hand Brake Mechanism, 123 to 125.
Heaters, Electric, Car, Advantages of, 143, 144.
356 INDEX.
Heating and Lighting of Cars, 134 to 153.
Coils of Car Heater, 144, 145.
Horse-Power, 22.
Horseshoe Magnet Core, 84.
Hydraulic Circuit, 30, 31.
Gradient, 44.
Insulators, Strain, 235.
, Trolley Wire, 235.
International Unit of Activity, 23.
j
Joule, 18.
per-Second, 23.
Journal Boxes, 104.
Kilowatt, 24.
Hour, 53.
Lamination of Armature Core, 74.
Lamp, Car, 136, 137.
INDEX. 357
Lamp Circuit of Car, 135.
Lamps, Pilot, 284.
Law, Ohm's, 42.
Left- Hand Frog, 239.
Lever Brake, 122.
Lichtenfeld Railway Line, 13.
Lightning Arrester, 201 to 203.
Arresters, 266.
Line Circuit, Efficiency of, 59 to 63.
or Circuit, Drop in, 54.
Liquid and Electric Flow, Analogy between, 3
to 7.
Flow, Resistance of, 33.
Load, 278.
Diagram, 299.
, Effect of, on Efficiency of Motor or Gene-
rator, 58, 59.
Locomotives, Electric, 323 to 342.
Lubricating Bushing of Trolley Wheel, 210, 211.
M
Made Circuit, 27.
Magnet, Permanent Horseshoe, 83.
Poles, Consequent, 90.
Magnetic Blow-Out, 160.
358 INDEX.
Magnetic Circuit-Breaker, 269 to 272.
Maintenance and Operation, 297 to 306.
Maximum Traction Truck, 100.
Mechanism of Brake, 122.
, Trolley, 205.
Meter, Efficiency of, 57.
Milliamperes, 276.
Mining Locomotive, Electric, 341.
Motor, Carbon Brushes for, 96.
, Electric, 67.
, Electric, Four-Pole, 88.
, Electric, Quadripolar, 88.
Load, 170.
of Electric Locomotive, 336.
, Street Car, 67 to 96.
Suspension, Method of, 111 to 114,
Motors, Double-Reduction, 118.
, Single-Reduction, 117, 118.
, Slow-Speed, 118.
N
Negative Plate of Storage Cell, 309.
Ninth Working Notch, of Car Controller, Dia-
gram of Connections of, 189.
Non-Vibrating Filament for Car La^np, 138.
INDEX. 359
o
Ohm, 35.
, Practical Definition of, 41.
Ohm's Law, 42.
Open Car Wheels, 107.
Circuit, 27.
Operation and Maintenance, 297 to 306.
Output of Station, 299.
P
Page, 9.
Panel, Pressure, 263.
Panels, Feeder, 263.
Parallel Connection of Street Cars, 187, 188.
Permanent Horseshoe Magnet, 83.
Pilot Lamps, 284.
Pinion Armature, 115 to 117.
, Double, 119.
, Rawhide, 120.
Pinkus, 9.
Plate of Storage Cell, 309.
Pneumatic Car Brake, 122.
Points, Feeding, 65.
Pole, 32.
Climbers, 224.
, Trolley, 205.
360 INDEX.
Port rush Electric Car Line, 13.
Positive Plate of Storage Cell, 309.
Practical Definition of Ohm, 41.
. International Unit of Activity, 24,
Pressure, Back Electric, 47.
, Back Water, 45.
, Effective, 47.
- Panel, 263.
Pull, Electromagnetic, 84.
Q
Quadripolar Electric Motor, 88.
Street Car Motor, 91.
Quantity of Electricity, 42.
, Unit of Electric, 48.
R
Radial Truck, Action of, 101.
Rail Bond, 246.
Bond, Chicago, 246.
Bond, Welded, 248.
, Bonding of, 245, 246.
-, Continuous, 248.
Railroad, Bicycle, 326 to 330.
INDEX. 361
Railway, Electric, of Berlin Industrial Exhibition
of '79, 12.
Lamp, 136.
Rate-of-Doing-Work, 20.
of Electric Flow, 28.
Rawhide Pinion, 120.
Resistance Coil for Street Car, 177.
, Electric, Unit of, 35.
of Conductor, Influence of Cross Section
on, 38.
of Conductor, Influence of Length on, 38.
to Electric Flow, 33.
Wires, Effect of Dimensions of, on Resist-
ance, 36 to 38.
Rheostat Boxes, 265.
Right- Angle Crossing, 240.
Hand Frog, 239.
Ring Armature, 75.
Robinson Radial Truck, 101.
Rope, Trolley, 205.
Rotation, Counter-Electromotive Force of, 166.
Running Guard Wires, 225.
s
Safety Fuse, 11, 198.
Sand Box, 131, 132.
362 INDEX.
Second Working Notch of Car Controller, Diagram
of Connections of, 179.
Secondary Cell, 309.
Segments, Commutator, 77.
Self-Contained Electric Railroad System, 307.
Self-Induction, Counter-Electromotive Force of,
165.
Shunt or By-Path, 182.
Siemens-Halske, 12.
Single-Curve Suspension, 229.
Reduction Motors, 117, 118.
Track Bracket Support, 222.
Track Bracket Suspension, 223.
Trolley System, 204.
Truck, 98, 99.
Sixth Working Notch of Car Controller, Diagram
of Connections of, 186.
Skidding of Car Wheels, 129.
Sleet-Cutting Trolley Wheel, 210.
Slow-Speed Motors, 118.
Snow Sweeper, Electric, 303, 304.
Span Guard Wires, 225.
Wire, 234.
Wires, 219.
Wire Support, 220.
Wire System, 220, 221.
Splicing Ear, 232.
INDEX. 363
Station, Output of, 299.
Stationary Electric Motor, 87.
Storage Battery Car Truck, 317.
Battery System, Car Controller for, 320 to
322.
Battery Systems, 307 to 322.
Cell, 309.
Cell, Elements of, 309.
Cell, Negative Plate of, 309.
Cell, Positive Plate of, 309.
Cells, Frame or Grid of, 314.
Straight-Line Suspension, 227.
Strain Insulators, 235.
Street Car, Brush Holder for, 95.
Car Motor, 67 to 96.
Car Quadripolar Motor, 91.
Car Resistance Coil, 177.
Street Cars, Parallel Connection of, 187, 188.
Strip, Commutator, 77.
Support, Triple-Truck, 101.
Suspension, Double-Curve, 229.
of Car Motor, Method of, 111 to 114.
, Single-Curve, 230.
, Straight-Line, 227.
Switch and Cut-Out for Car Lamp, 139 to 141.
, Automatic, for Car, 129.
, Canopy, 199, 200.
364 INDEX.
Switch, Emergency, 156.
, Temperature-Regulating, for Car Heater,
147.
Switches and Controllers, 154 to 203.
, Feeder, 266.
Switchboard, Railway Generator Station,262 to 266.
Switchboards, 262 to 278.
System, Feeder, 65.
, Single-Trolley, 204.
Temperature-Regulating Switch for Car Heater,
147.
Tenth Working Notch of Car Controller, Diagram
of Connections of, 190.
Third Working Notch of Car Controller, Diagram
of Connections of, 182.
Three-Way Frog, 239.
Total-Current Panel, 263.
Tower Wagons, 2, 302.
Track Construction, 242 to 248.
, Double, 99, 100.
Truck, Maximum-Traction, 100.
Tread of Car Wheels, 109.
Triple Truck Support, 101.
Trolley Base, 205.
INDEX. 865
Trolley Base, Boston, 214, 215.
- Base, Forms of, 213 to 218.
Crossing, 239.
- Ear, 227.
Frog, 237.
Insulator, 227.
Line Construction, 219 to 248.
Mechanism, 205.
Pole, 205.
- Rope, 205.
System, Conduit, 306.
System, Underground, 306.
Wheel, 205.
Wheel, Forms of, 209.
Wheel and Harp, 208.
Wheel, Lubricating Bushing of, 210, 211.
Wheel, Sleet-Cutting, 210.
Wire Insulators, 235.
Trolleys, 204 to 218.
Truck, 85.
, Robinson Radial, 101.
Twist, Electromagnetic, 84.
Two- Way Frog, 237.
u
Underground Trolley System, 306.
Unit of Activity, 21.
366 INDEX.
Unit of Electric Current, 28.
of Electric Quantity, 48.
of Electromotive Force, 32.
of Resistance, 35.
of Work, 53.
V
V-Frog, 237.
Vanderpoele, 13.
Voltmeter, 54, 263.
for Railway Switchboard, 274 to 275.
w
Wagons, Tower, 302.
Watermotive Force, 31.
Water-pipes, Resistance of Flow through, 33,
Watt, 23.
Watt-hour, 53.
Watt-hours of Storage Cell, 310.
Weight of Electric Car, 298.
Welded Rail Bond, 248.
Wheel, Trolley, 205.
Wheels, Flattening of, 131.
, Tread of, 109.
Wire, Span, 234.
INDEX.
367
Wires, Guard, 225.
, Span, 219.
Work, 17, 18.
, Unit of, 53.
, Units of, 17.
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