Electric railways

By James R. Cravath

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Title: Electric railways

Author: James R. Cravath

Contributor: Harris C. Trow

Release date: February 4, 2025 [eBook #75289]

Language: English

Original publication: Chicago: American School of Correspondence, 1907

Credits: deaurider, Robert Tonsing, and the Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive)


*** START OF THE PROJECT GUTENBERG EBOOK ELECTRIC RAILWAYS ***



[Illustration: INTERIOR OF 160-TON B. AND O. ELECTRIC LOCOMOTIVE.

  General Electric Company.]




                            Electric Railways

                           _A Treatise on the_
      MODERN DEVELOPMENT OF ELECTRIC TRACTION, INCLUDING PRACTICAL
               INSTRUCTION IN THE LATEST APPROVED METHODS
                     OF ELECTRIC RAILROAD EQUIPMENT
                              AND OPERATION

                            ELECTRIC RAILWAYS
                         _By_ +James R. Cravath+
               Western Editor “The Street Railway Journal”

                    THE SINGLE-PHASE ELECTRIC RAILWAY
                       _By_ +Harris C. Trow+, S.B.
 American Institute of Electrical Engineers. Editor Textbook Department,
                    American School of Correspondence

                               ILLUSTRATED

                                 CHICAGO
                    AMERICAN SCHOOL OF CORRESPONDENCE
                                  1908


                           +Copyright 1907 by
                   American School of Correspondence+

                   Entered at Stationers’ Hall, London
                           All Rights Reserved




                                Foreword


In recent years, such marvelous advances have been made in the
engineering and scientific fields, and so rapid has been the evolution
of mechanical and constructive processes and methods, that a distinct
need has been created for a series of _practical working guides_, of
convenient size and low cost, embodying the accumulated results of
experience and the most approved modern practice along a great variety
of lines. To fill this acknowledged need, is the special purpose of the
series of handbooks to which this volume belongs.

¶ In the preparation of this series, it has been the aim of the
publishers to lay special stress on the _practical_ side of each
subject, as distinguished from mere theoretical or academic discussion.
Each volume is written by a well-known expert of acknowledged authority
in his special line, and is based on a most careful study of practical
needs and up-to-date methods as developed under the conditions of
actual practice in the field, the shop, the mill, the power house, the
drafting room, the engine room, etc.

¶ These volumes are especially adapted for purposes of self-instruction
and home study. The utmost care has been used to bring the treatment
of each subject within the range of the common understanding, so that
the work will appeal not only to the technically trained expert, but
also to the beginner and the self-taught practical man who wishes to
keep abreast of modern progress. The language is simple and clear;
heavy technical terms and the formulæ of the higher mathematics have
been avoided, yet without sacrificing any of the requirements of
practical instruction; the arrangement of matter is such as to carry
the reader along by easy steps to complete mastery of each subject;
frequent examples for practice are given, to enable the reader to test
his knowledge and make it a permanent possession; and the illustrations
are selected with the greatest care to supplement and make clear the
references in the text.

¶ The method adopted in the preparation of these volumes is that which
the American School of Correspondence has developed and employed so
successfully for many years. It is not an experiment, but has stood the
severest of all tests—that of practical use—which has demonstrated it
to be the best method yet devised for the education of the busy working
man.

¶ For purposes of ready reference and timely information when needed,
it is believed that this series of handbooks will be found to meet
every requirement.

[Illustration]




                            Table of Contents


+Car Equipment+                                                 Page 3

  Classification of Electric Railways — Motors — Armature Winding
  — Armature and Field Coils — Armature and Motor Leads —
  Brushes and Brush-Holders — Gearing — Lubrication — Bearings —
  Motor Suspension — Electric Locomotive Motors — Controllers —
  Rheostat and Series-Parallel Control — Controller Construction —
  Multiple-Unit Control (Sprague, General Electric, Westinghouse
  Electro-Pneumatic) — Car-Heaters — Car Wiring — Electric-Car
  Accessories (Canopy Switches; Circuit-Breakers; Fuses; Lightning
  Arresters; Lamp Circuits; Trolley-Base; Trolley-Poles, Wheels,
  and Harp; Contact Shoes; Sleet Wheels) — Single Trucks —
  Swivel Trucks — Maximum-Traction Trucks — Car Wheels — Brake
  Rigging — Air-Brakes (Compressor, Automatic Governor, Storage
  Tanks) — Momentum Brakes — G. E. Electric Brake — Westinghouse
  Electromagnetic Brake — Track Brakes — Motors as Emergency Brakes
  — Brake Shoes — Track Sanders — Drawbars and Couplers.


+Car Construction+                                              Page 67

  Car Bodies — Steel Car Framing — Car Weights — Car Painting.


+Line Construction+                                             Page 73

  Overhead Construction — Trolley-Wire — Clamps and Ears — Span
  Wires — Brackets — Feeders — Section Insulators — High-Tension
  Lines — Third-Rail System — Conduit Systems — Contact Plow —
  Current Leakage — Track Construction — Girder Rail — Trilby
  Groove Rail — Shanghai T-Rail — Common T-Rail — Track Support
  — Ballast — Joints (Welded, Cast-Welded, Electrically Welded,
  Thermit-Welded) — Bonding and Return Circuits — Feeder Systems —
  Block Signals — Electrolysis and Its Prevention.


+Power Supply and Distribution+                                 Page 98

  Direct-Current Feeding — Booster Feeding — Alternating-Current
  Transmission — Interurban Distribution — Power-House Location
  — Alternating-Current Generators — Double-Current Generators
  — General Plan of Power Stations — Switchboards — Generator
  D. C. Panels — Starting Up a Generator — Feeder Panel —
  Alternating-Current Switchboards — High-Tension Oil-Switches —
  Storage Batteries in Stations — Three-Phase Motors — Single-Phase
  Motors.


+Operation of Electric Railways+                                Page 115

  Power Taken by Cars — Road Tests of Cars — Economy in Power —
  Sliding and Spinning Wheels — Testing for Faults — Bond Testing
  — Motor-Coil Testing — Grounds — Burn-Outs — Defects of Armature
  Windings — Sparking at Commutator — Failure of Car to Start —
  Open-Circuit Tests — Short-Circuit Tests — Fuse-Blows — Armature
  and Field Tests for Grounds — Reversed Fields — Car Repair Shops.


+The Single-Phase Electric Railway+                             Page 137

  Commutator Type Single-Phase Motor — Advantages and Disadvantages
  of Single-Phase System — Lines in Operation.


+Index+                                                         Page 149


[Illustration: HEAVY-DUTY CROSS-COMPOUND CONDENSING ENGINE, DIRECT
  CONNECTED TO 1,500 K.W. RAILWAY GENERATOR.

  St. Louis Transit Company’s Power House.
  Fulton Iron Works.]




                           ELECTRIC RAILWAYS.

                                 PART I.


The general name “electric railway” is applied to all railways
employing _electric motors_ to supply power for the propulsion of
cars. On all electric railways in commercial use to-day, the electric
motor is used to furnish power to the driving wheels of the car or
locomotive, the electric motor being the most efficient known means of
transforming electrical into mechanical energy.

Electric railways are usually classified according to the methods by
which current is supplied to the moving car. Thus, where an overhead
trolley wire is used, as on the great majority of electric railways,
the term _trolley road_ is applied. Where an insulated steel rail
is laid alongside the track rail for supplying current, as on the
“elevated” roads in America and on a few interurban roads, the term
_third-rail road_ is used. Where, as on the street railways of a few
large cities, the conductors are placed in a conduit underneath the
surface of the street, and current is taken by means of a plow or
shoe running in the conduit, the name _electric-conduit railway_ is
most commonly applied. There are also a few systems using conductors
buried beneath the pavement, and having contact buttons or sections of
conductor rail on the street surface, which sections are supplied with
current by automatic electromagnetic switching apparatus as the car
passes, but which are normally dead and harmless. The overhead trolley
and the third-rail systems are by far the most common.

A further general classification of electric railways has recently
been made because of the introduction of alternating-current railway
motors. The great majority of electric railways employ direct-current
motors. Where alternating-current motors are used, the road is spoken
of as one using single-phase alternating-current motors or three-phase
alternating-current motors, as the case may be.

All electric railway systems in commercial use are operated on an
approximately constant potential or voltage, and the various electric
motor cars operating on the system are connected across the lines in
parallel. The most common practice is to utilize the rails and ground
as one side of the circuit, and the overhead trolley wire or “third
rail” as the other side, as in Fig. 1. The trolley wire or third rail
is, of course, thoroughly insulated from the ground. The positive
poles of the generators at the power house are usually connected to
the trolley wire, and the negative poles to the rails and ground. The
various electric motor cars, being connected in parallel or multiple
between the trolley wire and the ground, draw whatever current is
necessary for their operation. Where the conduit system is used, both
sides of the circuit are insulated from the ground, and the contact
shoe or plow collects current from two conducting rails in the conduit,
one of these conducting rails being positive and the other negative.
A double-trolley system is also in use to a limited extent. In this
system, both the positive and the negative sides of the circuit are
insulated from the ground, one trolley wire being positive and the
other negative.

[Illustration: Fig. 1.]

[Illustration: Fig. 2. Railway Motor.]

Further discussion of the matters just outlined will be taken up in the
succeeding pages.




                             CAR EQUIPMENT.

                                 MOTORS.


The voltage most commonly employed by electric railways is 500 to
600; and the motors are 500-volt direct-current series-wound motors,
designed especially for railway service. The electric railway motor
must be dustproof and waterproof because of the position it occupies
under the car. For this reason electric railway motors are made in
the form of a steel case (Fig. 2), which entirely surrounds the
field-magnet poles and takes the place of the yokes or frames that
support the fields on stationary motors. Cast steel is the material now
usually employed for railway motor cases and fields, on account of its
mechanical strength and its high magnetic permeability. The four poles
project inwardly from the case, as seen in the open motor case, Fig. 3,
which is that of a Westinghouse No. 69 motor.

[Illustration: Fig. 3. Railway Motor. Upper Field Raised.]

Railway motors have usually four poles because this permits of a
symmetrical and economical arrangement of material around the armature,
and hence permits the motor to be placed in the small space available
on the car truck. Two-pole motors have been used in the past, but they
were not as compact as the four-pole type.

=Characteristics of Railway Motors.= The curve sheet, Fig. 4, for the
Westinghouse No. 69 motor represents in general the characteristics of
all direct-current railway motors.

The figures for each curve are found with names corresponding to
the curve to which they apply, at each side represented by vertical
distance on the sheet. The amperes, represented by the horizontal
distance, are marked at the bottom, and apply in common to all the
curves.

The tractive effort at different current consumption is represented by
a line curving upwards somewhat. This shows that the tractive effort
increases, in a proportion greater than directly, as the current
increases.

The torque required in starting may be many times greater than that
necessary to maintain the car at full speed. The series-wound motor,
therefore, furnishes this great starting torque more economically than
a shunt-wound motor the torque of which is proportioned to the current.
This feature of the series-wound motor makes it especially adapted to
street railway work.

[Illustration:

  WESTINGHOUSE
  No. 69 RAILWAY MOTOR
  500 VOLTS

  GEAR RATIO, 14 TO 68.      WHEELS, 33″

  CONTINUOUS CAPACITY, 25 AMPERES AT 300 VOLTS,
  OR 23 AMPERES AT 400 VOLTS.

  Fig. 4. Characteristic Curves of Railway Motor.]

The efficiency curve shows the motor to have an efficiency of about 83
per cent with gears. Much other information may be obtained by a proper
study of the curves. The fields are worked near the point of magnetic
saturation. This economizes metal and space and is also an advantage
because of the fact that when so worked the armature reactions have
very little effect on the fields. The neutral points between fields are
consequently shifted very little and it is therefore not necessary to
shift the brushes when the motor is reversed.

[Illustration: Fig. 5. Armature Winding.] General Data on Street
  Railway Motors.

=Armature Winding.= The armature winding is what is commonly known
as the series or wave winding, shown developed in the paper on
Direct-Current Dynamos. This winding is shown in Fig. 5, which is an
end view of an armature and commutator. In the figure, however, the
armature is shown with a much smaller number of slots than a railway
armature should have in practice. One reason for the employment of the
wave or series winding on railway motor armatures, is that with this
winding no cross-connections are necessary when only two brushes are
used, and these two brushes may be placed 90° apart in a convenient and
accessible position. Another reason is that the current, in flowing
from one brush on the commutator to another, must always pass through
the magnetic field of all four of the motor poles. This makes it
impossible for any unbalancing of the magnetic circuit to cause more
current to flow through one portion of the armature than is flowing
through another portion. In a railway motor it has been found quite
possible to have one pole or pair of poles exerting a greater magnetic
attraction on the armature than another pair, owing to differences in
the iron and differences in the clearance between the armature and pole
pieces, which differences cause more magnetic lines of force to flow
from some pole pieces than from others. With the lap-armature or the
ring-armature winding, since the various portions of the armature under
different poles are in parallel with one another, any difference in the
magnetic flux between different poles will cause a different amount of
current to flow in the various paths through the armature.

========+======+=====+=====+======+======+======+======+========+=========+=======+==========+=========+=====+=======
Type of |Horse |Amp- |Speed|Total |Slots.|Cond- |Commu-| Weight |Armature | Gears |Commutator| Pinion  |Dia- |Length.
 Motor. |Power.|eres.|Full |Field |      |uctors|tator |complete|Complete.|  and  | Bearing. |Bearing. |meter|
        |      |     |Load.|Turns.|      | per  |Bars. |  with  |         |Casing.|          |         |Arma-|
        |      |     |     |      |      | slot |      | Gears. |         |       |  Inches. | Inches. |ture.|
--------+------+-----+-----+------+------+------+------+--------+---------+-------+-----+----+----+----+-----+-------
General |      |     |     |      |      |      |      |        |         |       |     |    |    |    |     |
Electric|      |     |     |      |      |      |      |        |         |       |     |    |    |    |     |
     51 |  82  |     | 640 |  56  |  37  |  12  | 111  |  3875  |   953   |  338  |  3  | 5¾ | 3¼ | 8¼ | 16  | 10½
     52 |  27  |     | 640 | 155.5|  29  |  24  |  87  |  1725  |   357   |  265  |  2½ | 6⅜ | 2¾ | 7¾ | 11  |  9
     57 |  52  |     | 470 | 110  |  33  |  18  |  99  |  2972  |   704   |  340  |  2⅝ | 6⅜ | 3¼ | 8¾ | 14  | 12
     55 | 160  |     |     |      |  47  |   6  | 141  |  5415  |  1550   |  490  |  3¼ | 7½ | 3¾ |11  |     |
     67 |  40  |     |     | 110  |  37  |  18  | 111  |  2385  |   595   |  385  |  2⅝ | 6⅛ | 3  | 8  |     |
     54 |  25  |     |     |      |      |      | 115  |  1831  |   395   |  285  |  2½ | 6  | 2¾ | 7¾ |     |
     74 |  65  | 113 |     |  70.5|      |      |      |  3534  |   845   |  415  |  3⅛ | 6¾ | 3⅝ | 8¾ |     |
--------+------+-----+-----+------+------+------+------+--------+---------+-------+-----+----+----+----+-----+-------

--------+------+-----+-----+------+------+------+------+--------+---------+-------+-----+----+----+----+-----+-------
Westing-|      |     |     |      |      |      |      |        |         |       |     |    |    |    |     |
 house  |      |     |     |      |      |      |      |        |         |       |     |    |    |    |     |
     68 |  40  |     |     |      |  55  |  12  | 109  |  2280  |   505   |  330  |  2¾ | 6¾ | 3  | 7¾ | 14  |  8
     69 |  30  |     |     |      |  35  |      | 105  |  1950  |   385   |  330  |  2¾ | 6  | 2¾ | 7  | 13  |  6¾
     76 |  75  |     |     |      |  39  |      | 117  |  3840  |   505   |  860  |  3¼ | 8  | 3½ | 9  | 16½ |
     56 |  55  |     |     |      |  39  |      | 117  |  3000  |   315   |  720  |  3  | 7½ | 3¼ | 8½ | 14  | 12
     50c| 150  |     |     | 144  |  55  |   6  | 115  |  5550  |  1500   |       |     |    |    |    |     |
     49 |  35  |     |     | 114  |  59  |      | 117  |  1925  |   438   |  327  |  2¾ | 6  | 2¾ | 7½ | 13⅝ |  6½
--------+------+-----+-----+------+------+------+------+--------+---------+-------+-----+----+----+----+-----+-------

By reference to the winding diagram given in Fig. 5, it may be noted
that a complete circuit through two coils ends at the segment adjacent
to the one from which the start was made. It may also be noted in the
table of motor data that all of the armatures have an odd number of
segments and an odd number of slots. It is absolutely necessary in a
wave winding to have an odd number of segments. Otherwise the winding
could not be made symmetrical and the circuit through two coils be made
to return to a segment adjacent to that from which the start was made.
With equal spacing between the top and bottom leads of the two coils,
an even number of segments would make the circuit return either on the
segment from which the start was made or two segments from it.

The first drum-wound street railway motor armatures had as many slots
in the armature as there were coils and segments. The great number of
slots necessarily made the teeth very thin and consequently weak. This
is very objectionable as sometimes the armature bearings wear away,
allowing the face of the armature to drag on the pole pieces and thin
teeth are bent out of shape.

Armatures are now almost entirely constructed with either two or
three coils to a slot. When two coils are used in each slot with an
odd number of slots an even number of coils results. If these were
all connected to the commutator an even number of segments would be
necessary. As this is not possible with a wave winding, one of the
coils is “cut out.” The ends are cut short and taped and it is termed
a “dead” coil. This makes the winding somewhat unsymmetrical, all the
coils not bearing the same angular relation to the commutator segments
to which they are connected. This difference is, however, not great
enough to affect the operation of the machine.

The Westinghouse 49 motor is an example of an armature with a dead
coil. By reference to the table of motor data it will be seen that this
armature has 59 slots. Two coils in each slot would make 118 coils. One
of these, however, is cut out, giving 117 segments.

Cutting out a coil can be avoided by putting three coils in each slot.

An odd number of coils results then no matter what the number of
slots may be. In the majority of examples given in the table there
are three times as many segments as slots. The sides of the slots of
modern street railway armatures are straight. The coils are prevented
from flying out by bands of wire extending over the tops of the coils
around the armature. Steel or silicon bronze wire of about No. 14 gauge
is used. Recesses are made in the armature teeth for the reception
of these bands so that the wire when wound will come flush with the
face of the armature. The bands are usually ¾ to 1½ inches wide. The
wires are well soldered together to secure them in place. One trouble
experienced with armatures is the slipping off of these bands. The
heated armature expands and stretches them. When the armature cools the
bands are loose and then often slip off. When they do so the coils fly
out by centrifugal force, strike the pole pieces and ground the motor.

[Illustration: Fig. 6. Armature Coil.]

=Armature Coils.= Railway motor armatures are to-day universally
constructed with form-wound coils, which are wound on a form of proper
shape and carefully insulated before being placed in the armature.

The coils of the smaller motors (those up to 40 or 50 horsepower) are
usually wound with round wire. The cotton covering of the wire is
depended upon for insulation. To strengthen this, however, the coils
after being wound are immersed in an insulating compound and then baked
in an oven. The whole coil is usually wrapped with insulating tape (See
Fig. 6). The armatures of larger motors have coils made of copper bars.
Mica is often placed between and around the bars for insulation, though
oiled linen cloth tape cut bias is also employed, especially in repair
work.

=Field Coils.= Field coils are so constructed that they may be readily
removed should they become grounded or short-circuited. Some makers
wind them on a brass shell or form which is slipped over the pole
piece. In some motors the field coils are composed of copper ribbon,
wound bare, with ribbons of insulating material between the turns.
Field coils of wire for the smaller motors, if not wound on shells,
are wound on forms and before completion are taped in such a manner
that they will hold their shape without being enclosed in a spool. The
terminals are brought out where they will be of easy access when the
field is in place (See Fig. 7).

[Illustration: Fig. 7. Field Coil.]

=Armature Leads.= In Fig. 3 is seen a completed armature in the motor
casing of a Westinghouse No. 69 motor. Since the motors are four-pole,
the two sides of any one coil occupy slots 90° apart in the armature
coil, as indicated in Fig. 5. The ends of the coils are connected to
commutator bars 180° apart. The relative position of the commutator
connections of any armature coil can, of course, be varied so as to
bring the brushes in the most convenient position in the motor casing.
Brushes are always of carbon, and are placed where they can be easily
reached from the opening in the motor casing over the commutator.

=Motor Leads.= The reversing of the current through the armature,
independent of the field current, to secure reversal of direction of
rotation of the armature, makes it necessary that four wires enter
the motor. The portions of these wires connected permanently to the
motor are termed the motor leads because they “lead out” the current.
Sometimes an ordinary two-way connector is used in connecting these
leads to the wires of the cable, but often a jack-knife connector is
employed to facilitate connecting and disconnecting. Considerable
difficulty has been experienced by the wearing away of the insulation
of the leads where they rest on the motor shell. To avoid this there
has recently come into use a lead protected by a spiral metal covering.
=Brushes.= That the motor may operate in either direction equally
well, the carbon brushes are placed radially or nearly so. No provision
is made for shifting their position relative to the fields. They
usually occupy a position equidistant between pole tips. The common
types are either ½ or ⅝-inch thick and from 2¼ to 4 inches wide.

[Illustration: Fig. 8. Brush Holder.]

=Brush Holders.= Two methods of securing the brush holders are
employed. In Fig. 3, the brush holders may be seen to be secured in
position by being bolted through the end of the motor shell. Fig. 8
shows the brushes mounted on a yoke which is secured to the motor
shell. The yoke is of wood and provides the necessary insulation. Where
the holders are fastened directly to the shell a block and washers
of vulcabeston or other insulating material intervene to furnish
the insulation between the shell and the holder. In practice the
greatest difficulty experienced with brush holders is preventing them
from becoming grounded by dirt and carbon dust which collects on the
insulation.

=Opening Cases for Inspection.= Accessibility for inspection and
repairs is essential in all railway motors. A lid is always provided
directly over the commutator to facilitate inspection of the commutator
and brushes. To open up the motor casing for more extensive inspection
or repairs, three general schemes are employed. One is to have the
lower half of the casing swing downward on a hinge as in Fig. 9, which
illustrates the Westinghouse No. 38 B motor. The armature may be placed
either in the lower half, as shown in Fig. 9, or in the upper half.
When a motor of this type is to be opened the car is run over a pit,
and the repair men work entirely from below.

Often the hinge pins are removed and the lower shell containing the
armature is dropped down by means of a jack placed underneath.

Two handholes are usually provided in the bottom shell for observing
the clearance between the armature and the pole pieces and also for
removing dirt that may collect in the bottom of the shell. Another
scheme is to have motors open from the top, either by hinging the upper
part of the motor casing, as in Fig. 3, or by having the top part of
the casing lift off. Where this form of motor is used, the car body is
hoisted clear of the truck, and the trucks are run out from under the
car body before work is done on the motors. In this case, all the work
can be done from above without the use of pits.

[Illustration: Fig. 9. Railway Motor. Lower Half of Casing Swung Down.]

A third design is the box-frame motor casing, from which the armature
can be removed endwise only. Such an arrangement is shown in Fig. 10,
which is a view of a No. 66 motor of the General Electric Company. In
this motor a sufficiently large opening is provided in the ends of
the motor casing to permit of the armature being removed endwise. A
plate or head, which accurately fits into this opening, carries the
armature bearing. In removing armatures from motors of this kind, the
usual method is to take the motor out of the trucks and stand it on end
with the pinion up. The bolts being removed from the end plate, the
armature can then be hoisted out of the case by means of a special hook
attached to the pinion. Another plan that has been used in removing
armatures from such motors, is to place the motor in an apparatus where
the armature shaft can be held between centers, as in a large lathe.
The motor casing is then moved along in a direction parallel to the
armature shaft, until the armature is exposed.

This latter box-frame type of motor is very compact; a stronger casing
can be made for a given weight and space than if it were divided
horizontally. Moreover, the magnetic circuit cannot be disturbed by
imperfect contact between two parts of the casing. Where this type
of motor is used, the bearings project inward under the commutator
and armature, thus getting long bearings with a short motor, which is
important where the room is limited, as, for example, in the case of a
large motor mounted on a standard-gauge truck.

[Illustration: Fig. 10. Box-Frame Motor.]

=Gearing.= In most cases, spur gearing is used to transmit power
from the armature shaft to the car axle, although a few motors with
armatures mounted directly on the car axle are in use. Various gearings
other than the simple spur gear have been tried, such as worm gears,
chain and bevel gears. Practically all have been abandoned in favor of
the single-reduction spur gearing, which is the most satisfactory from
the standpoint of wear and efficiency. This gearing is shown in Figs.
3 and 9. The gearing is covered with a gear case (Fig. 9), which is
usually of steel, though gear cases of thin sheet metal and wood are
sometimes used. A solid gear is shown in Fig. 11, and a split gear in
Fig. 12. The gear ratios in common use vary from 5 to 1 to 2 to 1, the
larger ratio being common on the smaller motors. A ratio often used on
motors of 30 to 50 horsepower is 4.78 to 1, the gear having 67 teeth,
the pinion 14 teeth.

Street car wheels are usually 33 inches in diameter. This makes
necessary 612 revolutions per mile. With a gear ratio of 4.78 the
armature revolves 2,925 times per mile. At 15 miles per hour, this
gives 731 r.p.m.

[Illustration: Fig. 11. Solid Gear.]

[Illustration: Fig. 12. Split Gear.]

=Lubrication.= The lubrication of railway motors was for a number of
years carried on almost exclusively with grease, which it was customary
to place in the gear casing and in grease boxes over the armature and
car-axle bearings. Grease becomes most efficient as a lubricant only
when the bearing is heated sufficiently to make the grease run like
oil. Oil is now being used to a considerable extent, especially for
larger motors. It is fed to the bearings by various devices that allow
a very slow feed, such as wicks and lubricators adjusted to pass a
small amount of oil per hour.

=Bearings.= Railway motor bearings are usually of Babbitt metal, which
metal is cast into a steel shell. This shell fits into receptacles in
the motor casing, which can be seen in Figs. 3 and 9. A steel shell is
used so that the worn-out bearings can be easily renewed and the shells
taken to a Babbitt melting furnace to have new Babbitt poured into them.

The motor has two sets of bearings, those for the armature and those
for the axle upon which the motor is mounted. The axle bearings are
always split diametrically to avoid removing a wheel when a bearing is
replaced. On the later designs of motors these are of brass, no Babbitt
metal being used. The armature bearings are distinguished by the terms
“gear end” and “commutator end” bearings. The gear end bearing is
usually of larger diameter and of greater length because of the thrust
of the gears it must take in addition to the weight of the armature.
This bearing is split so that it may be removed and replaced without
the removal of the gear. The commutator end bearing is in one piece.
Armature bearings are shown in Fig. 13.

[Illustration: Fig. 13. Armature Bearings.]

=Motor Suspension.= Two methods of suspending motors flexibly on trucks
are in common use. That end of the motor which has bearings on the car
axle cannot, of course, be flexibly suspended with regard to the axle;
but the other end of the motor can be placed on springs, or rest on
a bar supported on springs, as shown in Fig. 14. This suspension is
commonly called _nose suspension_. Instead of having a special bar and
special springs for the nose of the motor, the nose may rest upon some
part of the truck that is carried upon springs. Thus, on the M. C. B.
type of swivel truck, the nose usually rests on the truck bolster, and
thus gets the benefit both of the bolster springs and of the equalizer
springs of the truck. Another general plan of suspension is that known
in one form as _cradle suspension_, and in another form as _side-bar
suspension_. A side-bar suspension is shown in Fig. 15. Here a larger
percentage of the weight of the motor is evidently taken by the springs
than in the case of nose suspension. It is desirable to relieve the
car axle of as much dead weight as possible. By dead weight is meant
weight resting upon it without the intervention of springs.

[Illustration: Fig. 14. Nose Suspension.]

[Illustration: Fig. 15. Side-bar Suspension.]

=Motors of the New York Central Electric Locomotive.= These motors
are a radical departure from the usual type of railway motors. The
locomotive on which they are mounted has four driving axles, upon each
of which is mounted an armature, direct, no gears being used, Figs.
16 and 17. The motors are remarkable for three special features: The
method of mounting the armature, the shape of the pole pieces, and
the path of the magnetic flux. [Illustration: Fig. 16. Longitudinal
Section of New York Central Locomotive.]

[Illustration: 95 TON ELECTRIC LOCOMOTIVE FOR NEW YORK CENTRAL RAILROAD.
  General Electric Company.]

The mounting of the armature upon the driving axle and the motor fields
on the truck frame makes it necessary to have flat pole pieces in order
that the armature may play up and down as the journal box and axle
slide in the guides of the truck frame. The shape of the pole pieces
may be observed in the drawing Fig. 16. When in the central position
there is a ¾-inch air gap between the armature and pole pieces. The
magnetic flux is continuous through the fields of all four of the
motors. It returns through the cast steel side frames of the truck and
two bars placed in the path.

The brush holders are so mounted that the brushes occupy a fixed
position relative to the armature. The armature is removed by lowering
it with the wheels and axle upon which it is mounted. This can be done
without disturbing the fields of the motor.


                             CONTROLLERS.

In an ordinary electric car, current is taken from the wire through the
trolley wheel and pole, and is first led from the trolley base through
overhead switches or a circuit breaker, and then to the controller,
from which it passes through the motors and thence through the motor
frames, car truck, and wheels to the rails and ground. If the car is
designed to be operated from either end, an overhead switch or circuit
breaker is placed over each platform of the car so that current can
instantly be cut off entirely from the controllers by throwing the
switch or circuit breaker at either end of the car.

[Illustration: Fig. 17. Armature Axle and Wheels.]

The lighting circuit is run from the trolley base independently of the
motor circuit, and has its own switch and fuse box. Current for the
lights is taken from the trolley circuit before it reaches the main
switches or circuit breakers. Current for electric heaters, if such are
used, is likewise taken from a separate circuit. On a 500-volt system
five 100-volt lamps are usually connected in series for car lighting.
As many multiples of five can be employed as are necessary to light the
car.

=Rheostat Control.= The simplest form of controller is that employed
where only one motor is used on a car. A rheostat is placed in series
with the motor when started, just as on a stationary motor; and
the function of the controller is to short-circuit this resistance
gradually until it is entirely cut out and the motor operates with the
full voltage. The controller also has a reversing switch by means of
which the relative connections of the armature and fields are reversed,
which, of course, changes the direction of rotation of the motor
armature. Such a simple equipment as this, however, is rarely to be
found in practice.

=Series-Parallel Control.= Single-truck cars usually have two motors,
one on each axle; and on such cars a series-parallel controller is the
kind usually employed. Diagrams of connections on the various points of
a series-parallel controller (Type K6) of the General Electric Company,
are given in Fig. 18.

[Illustration: Fig. 18. Diagram of K6 Controller Combinations.]

From these diagrams it is seen that the motors are first operated in
series until all the resistance is short-circuited by the controller.
When this has occurred, the cars are running at about half speed. The
next point on the controller puts the two motors in multiple, with
some resistance in the circuit, which resistance is cut out upon the
following points, until at full speed the two motors are in multiple,
without any resistance in the circuit.

=Four Motors.= Where four motors are used on a car, as is frequently
the case with double-truck cars, the motors on each truck are usually
controlled just as in case of the two-motor equipment that has been
described; but each pair of motors is operated in multiple. That is,
on the first points of the controller, the two motors of a pair are in
series, as in Fig. 19, and the two pairs are in parallel; and on the
last points of the controller, all the motors are in parallel, as in
Fig. 20.

[Illustration: Fig. 19. Motor in Series.]

[Illustration: Fig. 20. Motor in Parallel.]

=Controller Construction.= The controller (Type K) shown open in Fig.
21, which in its various forms is the type most commonly used on street
cars in the United States, has a contact cylinder or drum mounted upon
the main shaft of the controller. This contact drum carries contact
rings insulated from the drum, and is suitably interconnected, as
indicated in Fig. 22, which shows the contact rings of the controller
as they would appear if rolled out flat. Contact fingers are placed
along the left side of the controller, as seen in Fig. 21, one for each
ring on the drum; and as the controller handle is turned to revolve
this drum, the contact fingers make contact with the rings on the drum
and give the various connections. Alongside the main controller drum
is a reverse drum which simply reverses the armature connections of
the two motors. =Controller Wiring.= The connection between motors,
controllers, and resistances, with two motors and a K6 controller is
shown in Fig. 22. A careful study of this will show the combinations to
be the same as indicated in the diagram, Fig. 18. The wiring is rather
complicated; and in practice, to avoid confusion, the ends of each wire
are labeled with tags showing the terminals to which they belong.

[Illustration: Fig. 21. Controller.]

[Illustration: Car Wiring for K-6 Controllers with two Motors Fig. 22]

[Illustration: Fig. 23. Motors in Series.]

[Illustration: Fig. 24. Motors in Parallel.]

With the aid of Figs. 22, 23 and 24, the wiring of a type K6 controller
with two motors may be followed. Figs. 23 and 24 are for a different
controller but can be used to assist in an understanding of the
complicated diagram 22. The current leaves the choke or kicking coil
of the lightning arrester and passes through the blow out coil of the
controller. It then goes to the top finger T of the controller. On
the first point the circuit is as shown in Fig. 23. The top segment
A makes contact with the top or trolley finger. All but the lower
five segments of the cylinder are electrically connected together by
means of the iron cylinder upon which they are mounted. On the first
point then the current passes from the cylinder over R₁, and with
straight series connections of the resistances, it goes through all
of the rheostats under the car, and returns to the controller over
the last resistance lead, R₇. Behind the motor cut-out switches at
the base of the controller this lead is tapped into a wire one end of
which leads to finger 19 of the controller, and the other end through
the cut-out switch and reverse cylinder to No. 1 armature. The current
takes the latter path, passes through the armature of the motor and
returns by way of the reverse cylinder, thence through the fields of
No. 1 motor and then through the cut-out switch of No. 1 motor and to
finger E₁, of the controller. Segments O, M, N and L, shown in Fig.
23, and corresponding segments of Figs. 22 and 24, are insulated from
the remainder of the controller cylinder. From finger E₁ and segment
O (Fig. 23) the current passes over finger 15 through No. 2 cut-out
switch and the reverse cylinder to the armature of No. 2 motor.
Returning it passes through the reverse cylinder, then back through the
fields of No. 2 motor and to the ground, which is usually through a
connection on the motor casing.

On points 2, 3, 4 and 5, the successive series points of the controller
R₁, R₂, etc., make contact with segments B, C, etc., Figs. 23 and 24,
until finally finger 19 rests on segments J, the resistance is all cut
out and the motors are connected in series directly across the line.
A further movement of the controller handle changes the motors from
series to multiple connection and inserts in the circuit a portion of
the external resistance. There are four separate stages in making this
change. First, the resistance fingers slide off their segments and
the resistance is inserted in the line. Second, fingers E₁ and G make
contact with segments P and Q. Motor No. 1 is then across the line
in series with the resistance; the circuit being from E₁ to ground
over G. When the lower finger E₁ makes contact with P, the upper one
has not yet left segment O. This short-circuits No. 2 motor, the path
being from the ground, up wire G, thence by way of segments P and Q
and through connecting clip V, between the two E₁ fingers back through
finger 15 to the motor.

A further movement of the controller handle causes the fingers to leave
segments M and O and No. 2 motor is open-circuited until finger 15
makes contact with segment N. When this takes place the motors are in
multiple. On the successive points after this the external resistance
is cut out in the same manner as previously described.

By reference to Fig. 22, it will be noticed that the leads to
the motors and the resistances are tapped on wires of the cables
connecting the two controllers on the ends of the car. The two ends
of these wires, with the exception of the armature wires, lead to
similar binding posts on the two controllers. The armature wires are
interchanged connecting at one controller into binding post A A, while
the other end connects into binding post A. This change of connection
is necessary in order that the reverse handles be forward for forward
direction of movement of the car.

[Illustration: Fig. 25. Forward Position of Reverse.]

To reverse a series motor it is simply necessary to reverse the
direction of flow of the current in either the armature or field. For
several reasons, it is advantageous in the case of the street railway
motor to reverse the current in the armature rather than in the field.
Figs. 25 and 26 show how this is accomplished. The squares shown in the
figures represent the lugs on the reverse cylinder as shown in Fig.
21. With the reverse handle in one position (Fig. 25), the large lugs
are under the reverse fingers, and current passes from finger 19 to
finger A₁, and from finger 15 to finger A₂. Fig. 26 shows the relative
position of reverse fingers and lugs for the reverse position of the
controller handle. In this case the current passes from finger 19 to
AA₁, and from finger 15 to finger AA₂. The effect is to change the
direction of flow in the armatures while that in the fields remains the
same as may be observed by the arrows.

[Illustration: Fig. 26. Reverse Position of Reverse.]

=Wiring of Type L Controllers.= The type L controller, shown in Fig.
27, while accomplishing the same results as the type K, is wired
in a radically different manner. The circuit is opened in changing
from series to multiple connections. The controller handle makes
two complete revolutions in moving from the series to the multiple
position. It is geared to the rheostatic cylinder in such a manner that
the first half of both the first and second revolutions gives this
cylinder one complete turn. During the second half of the revolution
the cylinder is returned to its original position. The controller
handle is so connected to the commutating arm that this stands in a
central position for the off position of the handle. At the beginning
of the first revolution it is swung to the left, throwing the motors in
series. At the beginning of the second revolution it is moved to the
right, putting the motors in multiple.

The rheostats instead of being wired in series are connected in
multiple. Current passes from the blow-out coil to the bottom fingers
of the controller S, and thence to the rheostats. On the first point
the current returns over R₁ to the controller cylinder. It passes off
through a collar at the base of the cylinder through No. 1 cut-out,
and the reverse, which is shown in the central position, to No. 1
motor. On returning to the controller over E₁ it passes to the upper
section of the commutating arm. In the diagram this is shown in the
central position. In series it is thrown to the left. The current then
passes from the commutating arm to No. 2 cut-out, and to No. 2 motor.
Movement of the controller handle further multiplies the paths through
the rheostats and finally, when fingers S rest on the cylinder, the
rheostats are short-circuited. If the controller handle is moved still
farther, the rheostat cylinder is returned to the off position and the
commutating arm is thrown to the left. With the arm in this position
the current divides, one portion passing to No. 1 motor as before and
to ground by way of the upper section of the commutating arm; while the
other branch goes by way of the lower section of the commutating arm to
the cut-out switch for No. 2 motor and thence to the motor.

[Illustration: +Diagram of Connections+ _for_ L2 +Controller+ Fig. 27.]

Reversing is accomplished by one-quarter revolutions to the right and
left of the segments shown. It is evident that this will connect either
A₁ or A A₁, to the trolley. And likewise connect the other armature
leads.

=Reversal.= The reversing handle and the main controller handle are
made interlocking so that the motors cannot be reversed without first
throwing the controller to off position. This is to prevent damage to
the motors through careless or inadvertent throwing of the reverse
handle when the controller is on some of its higher points. Such a
reversal would cause an enormous current to flow through the motors,
and would be likely to damage them and to open all the circuit breakers
and fuses in that circuit. The reason for the enormous flow of current
is, of course, that the counter-electromotive force of the motors,
when reversed with the car going at some speed, would materially add
to the electromotive force of the trolley line, instead of opposing
it as when the cars are in operation. The current flowing through the
motor circuit would then be equal to (_electromotive force of line_
+ _electromotive force of motors_) ÷ (_resistance of motors_), which
would result in a very large current.

=Magnetic Blow-Out.= On the Type K controller as well as on most other
successful controllers, the flashing or arcing between contact rings
and fingers, which occurs when the circuit is broken, is materially
reduced by a magnet that produces what is called the magnetic blow-out
to extinguish the arc. This magnet derives its current from the main
circuit, and is so arranged as to create a strong magnetic field in
the neighborhood of the place where the arc is formed. Fig. 21 shows a
Type K controller open with the magnetic blow-out magnet thrown back
on a hinge. The coil which produces this magnet is seen in the right
side of the controller. The main contact drum is in the middle, and the
reversing drum at the right hand. There are in use a number of other
controllers built upon these same general principles but differing in
mechanical arrangement.

=Controller Notches.= All controllers are provided with some device
which prevents the motorman from stopping the controller handle between
the various points or notches, as the stopping between points might
result in drawing an arc or an imperfect contact. The most common
arrangement to prevent this is a notched wheel on the controller shaft,
against which bears a small wheel of just the right size to enter the
notches. The small wheel is held against the notched wheel by a strong
spring. As the tendency of the small wheel is to seek the bottom of the
notches, it is difficult to stop the controller handle anywhere between
notches, and the motorman is thus given a guide which tells him without
any effort on his part just where the notches are.

To prevent advancing the controller handle too rapidly and avoid the
jerking of passengers, excessive currents and slipping of wheels during
acceleration, several devices have been planned. On the multiple unit
control systems, a limit switch is usually provided which prevents the
controller advancing when the current exceeds a predetermined amount.
A device to accomplish the same results on the K type of controllers
is termed the Automotoneer. A cam connected with a dash pot prevents
movement of the controller handle to the successive notches faster than
a previously prescribed rate.

A switch is usually provided in a controller, for cutting out of
service one motor or a pair of motors if defective, and allowing the
car to proceed with the good motor or motors.

[Illustration: Fig. 28a. Car Wiring for G. E. Train Control System.]

[Illustration: WESTINGHOUSE 300 K.W. DIRECT CURRENT ENGINE TYPE
  THREE-WIRE GENERATORS.

  Pittsburgh, Cincinnati, Chicago and St. Louis Railroad, Columbus,
  Ohio.]


                        MULTIPLE-UNIT CONTROL.

A system called “multiple-unit control” or “train control” has come
into use where it is desired to operate motors under a number of
different cars in a train; all the motors being controlled from the
head of the train or from any other point on the train where the
motorman may be stationed.

There are several types of multiple-unit control. In all of them there
is on each car a controller of some kind which controls the current
flowing to the motors on that car. This controller is operated from
a distance by means of electro-magnetic or electro-pneumatic devices
controlled by circuits called _pilot circuits_, which circuits are
connected to the motorman’s controller. All the pilot circuits of a
train are connected together by means of train plugs which make the
connections between the cars. The pilot circuits of each car are
connected to a motorman’s controller on that car and this makes it
possible to operate the train from any controller.

=Sprague Multiple-Unit System.= In the earliest form of multiple-unit
control—which was that devised by F. J. Sprague—the motors on each car
were controlled by an ordinary Type K controller, which had geared to
its shaft a small pilot motor. The pilot motor was controlled by the
pilot circuits connected with the motorman’s controller.

In the more recent forms of multiple-unit control, the use of main
controllers having contact cylinders has been practically abandoned.
The contacts are made instead by a number of electro-magnetic or
electro-pneumatic contact devices sometimes called _contactors_.

=General Electric Train Control.= In the General Electric train-control
system each contact for the motor circuits is made by a solenoid magnet
which draws together two heavy copper contact fingers to establish the
circuit. A magnetic blow-out coil in series with the contact is also
provided. The contactors make contact only when energized by a small
amount of current from the master or motorman’s controller. In Fig.
28_a_ is a diagram of the car wiring for a motor car equipped with
this system. The motorman’s controller is a drum controller, but is
comparatively small since it has to handle only the small amount of
current necessary to operate the solenoid magnets of the contactors.
It is evident that by connecting together the pilot circuits, which
are connected to the motorman’s controller, so that the pilot circuits
will be continuous for the entire length of the train, any number
of cars equipped with the train-control system can be operated; and
similar contacts will be made by the contactors under all the cars
simultaneously, by virtue of the circuits established by the master
controller at any platform.

Besides controlling the contactors, the master or motorman’s controller
must control an electro-magnetic reversing switch, or _reverser_, to
change the direction of car travel.

The handle of the motorman’s controller is provided with a push button,
which must be depressed while the current is turned on. Should the
motorman release this push, the circuit through the controller will be
opened and all the contactors will fall open. This handle is called the
_dead man’s handle_ because it is put there to provide for cutting off
the current should the motorman fall dead or in a faint at his post.

The flow of the current in the control circuits, which operates the
reverser and picks up the contactors on the several points may be
followed in the diagram Fig. 28_a_. With the reverse handle in the
forward position and the controller on the first point, current passes
from the main circuit through a single-pole fused switch called the
control switch and through the auxiliary blow-out coil to a finger
bearing on the upper section of the master controller cylinder by which
connection is established to the adjacent finger and thence to the
reverse cylinder. It leaves this over wire No. 8, passing by way of the
connection board and control cut-out switch to the forward operating
coil of the reverser, thence through the forward blow-out coil and over
wire 81, through the switch underneath contactor No. 2 and to ground G,
by way of wire B 2 after passing through the fuse shown. The current
through the operating coil of the reverser, having thrown this, the
path is changed somewhat. The current then instead of passing from
the reverser over wire 81, is conducted through wire 15, through the
operating coils of contactors No. 1, 2, 3, and 11 in series, through
the switch under contactor No. 12, and to ground through finger 1 of
the controller. Contactors 1 and 2 are in multiple and when raised
connect the trolley with the contactors controlling the resistance
leads. Contactor 3 connects R to the line while contactor 11 places
the two motors in series. The motors then operate with all of the
resistance in circuit. When contactor 2 raises, it opens the switch
immediately below it, making it impossible for the reverse to operate
while current is flowing through the motors. On the second notch of
the controller an additional path is opened by way of finger 3 of the
controller. This path leads from finger 3 through four of the control
circuit rheostat coils, through contactor No. 5 and to ground over 32.
On the 3rd, 4th and 5th points contactors 6, 7 and 9 respectively are
raised. The motors are then in full series. Between the 5th and 6th
points all the control circuits are broken preparatory to starting the
multiple connections of motors. On the 6th or the first multiple point
the ground through finger 1 of the master controller is opened while a
ground through finger 3 is established. The current from the reverser
then, after raising contactors 1 and 2 as before, instead of passing
through contactors 3 and 11, passes through the coils of 4, 12 and 13,
through the switch under contactor 11 and to ground over finger 2.
Contactor 12 connects motor No. 2 to R₇, while contactor 13 grounds No.
1 motor. The motors now operate in parallel and on successive notches
of the controller, contactors 6, 7, 8, and 9 are raised, cutting out
all of the resistance. The switches underneath contactors 11 and 12
make it impossible for 11 to raise with 12 and 13 or vice versa. The
reason for this arrangement is very evident, as a direct ground for R₇
would result.

=The Westinghouse Electro-Pneumatic System of Control.= In this system
of multiple unit or train control, the current to the motors is
supplied through a set of unit switches or circuit breakers which are
sometimes placed in a circular case or turret underneath the car and in
other cases are ranged in a row under the car. The opening and closing
of these unit switches is done with compressed air acting on a piston
in an air cylinder. When the circuit is to be closed, compressed air
is admitted behind the piston and forces it down against the tension
of a seventy-pound spring, and the contacts are brought together.
When the switch is to be opened, the air is let out of the cylinder
and the spring forces the piston back. The air supply is obtained
from the storage tanks of the air brake system. The valve controlling
the air supply to the cylinder of each unit switch is operated by
electromagnets which derive current from a seven cell, fourteen-volt,
storage battery. The small master controller operated by the motorman,
makes and breaks the battery connections to the magnets controlling the
air valves.

[Illustration: Fig. 28b. Car Wiring for Westinghouse Control System.]

An advantage of this over other multiple-unit systems is that by
the use of battery current the control system is not disturbed by
interruptions of the main supply of current. The chief advantage of
this is that it makes it possible to reverse the motors and operate
them as brakes in emergencies at all times.

The battery is charged from the main line through lamps as resistance,
or may be charged by being connected in series with the air compressor
motor.

In the accompanying diagram, Fig. 28_b_, there are two batteries
shown which are charged in series with the compressor motor. By means
of two double-pole, double-throw switches, first one and then the
other battery is connected for charging and for service. The battery
is charged in shunt with a resistance and a relay is connected in
the circuit as shown, so as to open the battery circuit whenever
the current through the motor stops, and thus prevent the battery
discharging through the resistance.

The master controller has a double set of segments in order to decrease
the length of the shaft. The handle, therefore, is moved only one-sixth
of a revolution from off to full speed. The various circuits can be
traced by the letters and numbers each wire bears, so that the circuits
will not be gone over in detail. The first position of the master
controller throws the reverser switch in the proper direction and
also closes the main circuit breaker. On the second point the motors
are connected in series with all resistance in circuit, and these
resistances are automatically cut out one by one. On the next point
of the controller the motors are in multiple and the resistances are
automatically cut out in a similar manner. The automatic cutting out
of resistances is accomplished by a limit switch in conjunction with
operating and holding coils on the electro-pneumatic valves. This
limit switch is a kind of a relay which has the current from one of
the motors flowing through its coil and which acts to open a certain
battery circuit which operates the electro-pneumatic valves whenever
the current in the motor circuit in question exceeds the amount for
which the limit switch is set. The automatic acceleration or cutting
out of resistance is accomplished as follows:

Each electro-pneumatic valve has two magnet coils, one of which is
an operating coil and the other a holding coil for holding the valve
open after it is operated. When first the current flows through a
circuit to one of the electro-pneumatic valves, it flows through the
operating coil and operates the valve to close the corresponding
switch or switches of the main circuit by turning the air into the
cylinders. As soon as the main switch is closed, it cuts into circuit
the holding coil of its corresponding electro-pneumatic valve and
this coil will, with the battery current, hold the switch closed even
though the circuit to the operating coil may be opened momentarily by
the limit switch as each step of resistance is cut out. This prevents
the switches from opening when they are once closed and allows the
operating coils to open an air valve each time the current through
the limit switch coil falls below the amount for which it is set. The
contacts which close the holding coil circuit on each valve whenever a
main switch is closed, are called interlocks and are indicated on the
diagram.

[Illustration: Fig. 29. Diagram of Electric Heaters.]

The main line circuit breaker, which is electro-pneumatically operated,
will open automatically on overload and can be reset by the motorman
on all the cars of a train by closing a switch located beside each
controller.


                             CAR HEATERS.

=Electric Heaters= for warming cars in winter, consist of iron wire
coils which are warmed by the passage of electric current through
them. The heat so evolved varies as the resistance multiplied by the
square of the current. The iron wire coils of the heater are mounted on
non-combustible insulating supports, and are arranged so that there is
a free circulation of air through them. The coils are surrounded with
a perforated metal case, the object of which is to prevent injury to
the coils and to prevent persons or clothing coming in contact with the
hot, live wires of the coils. Heaters are sometimes arranged so that
they can be connected in series or parallel to give different degrees
of heat.

The diagram, Fig. 29, shows the most common arrangement of electric
heaters recently. The tap from the trolley should be taken off on the
trolley side of the circuit breaker. After passing through a fuse the
circuit goes to the switch. Each of the heaters contains two coils,
one of higher resistance than the other. Two independent circuits
are run from the switch, through the heaters and to the ground. One
circuit passes through the high resistance coils of the several heaters
while the other goes through the low resistance coils. The switch
has three points. On the first point a circuit is made through the
high resistance coils. The second point connects the low resistance
coils while the third point puts both circuits in service. With this
arrangement three gradations of heat may be obtained.

To avoid complicated wiring sometimes but one circuit is employed. In
such a case the heat must either be all on or off, no gradations being
possible.

The chief difficulty encountered with electric heaters is the breaking
of the wires because of the scale of oxide that forms gradually when
they are run at a high temperature or because of water striking them
from passengers’ clothing on wet days, which causes the wires to snap.

The Consolidated Car Heating Company gives the following data on the
current required to heat cars:

====================+=================+=================
                    |  Length of Car  |    Amperes.
                    |      Body.      +-----------------
                    |                 |Switch Positions.
                    |                 +-----------------
                    |                 |   1     2     3
--------------------+-----------------+-----------------
                    | { 14 to 20 feet |   3     4     7
Average conditions  | { 20 to 28  ”   |   3     6     9
                    | { 28 to 34  ”   |   4     7    11
                    |                 |
Severest conditions | { 18 to 24 feet |   4     7    11
                    | { 28 to 34  ”   |   6     8    14
--------------------+-----------------+-----------------

In his Electrical Engineers’ Hand Book, Mr. Foster gives results of
tests made on Brooklyn cars as follows:

=========================+================+====================
          Cars.          | Temperature F. |    Consumption.
-------+--------+--------+----------------+--------------------
Doors. |Windows.|Contents|Outside.|Average|Watts.|   Amperes
       |        | cu. ft.|        |in car.|      |at 500 volts.
-------+--------+--------+--------+-------+------+-------------
   2   |   12   |  850½  |   28   |  55   | 2295 |   4.6
   2   |   12   |  850½  |    7   |  39   | 2325 |   4.6
   2   |   12   |  808½  |   28   |  49   | 2180 |   4.3
   2   |   12   |  913½  |   35   |  52   | 2745 |   4.5
   4   |   16   | 1012   |    7   |  46   | 3038 |   6.
   4   |   16   | 1012   |   28   |  54   | 3160 |   6.3
-------+--------+--------+--------+-------+------+-------------

When not watched carefully considerable current may be wasted by
allowing the heaters to remain turned on when not needed. Many
companies hang out signs where motormen may observe them, indicating
when the heaters shall be turned on and to what point.

[Illustration: Fig. 30. Electric Heater.]

The best practice in electric heating is to have plenty of heaters and
run the wire at a low temperature, rather than attempt to heat with a
few at high temperature. The greater the number of heaters the larger
the radiating surface around which the air can circulate and a given
amount of car heating can be accomplished with less current than with a
few high temperature heaters. The depreciation of the heater wires is
less the lower the temperature at which they are operated. An electric
heater is shown in Fig. 30.

=Hot-Water Heaters= are frequently used on large electric cars.
Hot-water pipes are placed along the sides of the car, and connected
with a stove containing hot-water coils at one end of the car.
The water, as it is heated in the stove or heater, expands, and
consequently becomes lighter per cubic inch or other unit of volume;
it therefore tends to rise when balanced against the colder water in
the car pipes. Hot water leaves the top of the heater, flows up to
an expansion tank and then down through the car piping, and back to
the bottom of the heater. The car piping slopes continuously down from
the top connection to the bottom connection of the heater. At the top,
an opening to the atmosphere is provided through a small water tank,
called an _expansion tank_. This prevents water pressure bursting the
pipes as they become heated, and allows any steam that may have formed
to escape. The most modern hot-water heaters for cars are completely
closed except as to the ash pit at the bottom and a small feed door in
the top. The latter is locked so that the fire cannot come out even
if the car is tipped over in a wreck. Fig. 31 shows the pipes of a
hot-water heating installation.

[Illustration: Fig. 31. Pipes for Hot-Water Heating.]


                              CAR WIRING.

The wires from motors to controllers, when placed in exposed position
under the car, are bunched in cables or covered with hose. In some
cases special runways are provided in the bottom of the car to
accommodate the car wiring. All the wiring in a car should be heavily
insulated with moisture-proof rubber-covered wire, and further
protected from mechanical abrasion by a tough outer covering.

Stranded rubber insulated wire is used almost exclusively for wiring
all parts of the car. A general idea of the path of the motor circuit
wiring may be obtained by reference to Fig. 22. The main lead after
leaving the trolley stand is cleated to the trolley board on top of
the car. At the end of the car it passes through the roof and to the
circuit breaker. On leaving the breaker it is led down a post, through
the floor and to the choke coil and lightning arrester underneath the
car. It then passes to the trolley terminal of the controller.

The tap for the light wiring (although shown otherwise in the drawing)
is usually taken off the main circuit before the circuit breaker is
reached. This arrangement allows the lamps to be burned when the
circuit breaker is open. After passing through fuses and switches in
the motorman’s cab the circuit for the lights is led through the car in
moulding concealing it.

The wires running between the motors, controllers and resistance
frames underneath the car, as has been stated, are often carried in
canvas hose. Usually two cables are made up, for should all the wires
necessary be placed in one cable this would become too bulky to be
properly cleated up. To make the canvas hose waterproof and to prolong
its life it is usually given several coats of asphaltum paint.

The wiring of the new cars of the New York subway is an example of
the most advanced practice. All the wires under the cars are carried
in “loricated” conduit, which consists of a wrought-iron tube heavily
enameled both inside and out. The motor leads and the other larger
wires are carried in separate conduits. The conduits are usually hung
to the steel beams of the floor framing by strap bolts. This method of
wiring gives a reasonable assurance that it will not become defective.
Moreover, it lessens fire risk. The conduits are all grounded and
should one of the wires come in contact with the conduit carrying it,
the dead ground resulting would cause the fuse to blow instantly, and
all danger would cease.


                             RESISTANCES.

The type of resistance now most common for heavy motor equipment is in
the form of cast-iron grids, which are assembled together and connected
in series. These grids are sufficiently stiff to render unnecessary any
solid insulation between them, and hence they can radiate heat to the
best advantage. The only difficulty experienced with them is from the
warping or cracking. Resistances for lighter equipment are composed of
sheet-steel ribbons wound in coils. Each turn of a coil is insulated
from the next by asbestos. Other forms of sheet-steel resistance with
asbestos insulation between the turns, have also been used. In Fig. 32
is shown a Westinghouse grid type diverter for street railway equipment.


                       ELECTRIC CAR ACCESSORIES.

=Canopy Switch.= An overhead switch, sometimes called a “canopy
switch,” is commonly placed over each street-car platform where
a controller is located, usually in the deck or canopy above the
motorman’s head. This is simply a single-point switch that may be used
by the motorman to cut the trolley current off from the controller
wiring so that the controllers will be absolutely dead. When two such
switches are used, one on each end of the car, they are connected in
series.

[Illustration: Fig. 32. Grid Type of Resistance.]

=Car Circuit Breaker.= Frequently on large equipments an automatic
circuit breaker is provided instead of this overhead switch. This
circuit breaker can be tripped by hand to open the circuit whenever
desired; and is also equipped with a solenoid magnet, which can
be adjusted so that it will trip or open the circuit breaker at
approximately whatever current it is set for. This circuit breaker
protects the motor and car wiring from excessive current, such as would
occur in case of a short circuit in motors or car wiring, or in case
the motorman turned on current so rapidly as to endanger the windings
of the motors. Circuit breakers, however, are most commonly used on
cars having controllers located at only one end in a motorman’s cab.

=Wiring of Circuit Breakers and Canopy Switches.= Figs. 33, 34, and 35
show the methods of wiring circuit breakers and canopy switches for
double-end cars.

[Illustration: Fig. 33.]

In the parallel connection as shown in Fig. 33, the trolley leads after
passing through the choke coils go directly to the blow-out coil of the
controllers. Aside from the fact that two lightning arresters and choke
coils are required, this method is preferable for automatic circuit
breakers.

[Illustration: Fig. 34.]

Fig. 34 shows the hand-operated circuit breakers connected in series.
This method is used where non-automatic breakers are employed, but for
automatic breakers it has the objection that an overload would throw
the breaker set at the lowest point. This might be the breaker on the
opposite end to that occupied by the motorman and in such an event
would necessitate a trip to the other end to set the breaker. Fig.
35 shows a method of parallel connection requiring but one lightning
arrester. This method has the objection that the motorman on the front
end would have no assurance that by throwing the breaker over him the
power would be cut off. The rear breaker might have been carelessly
left set.

[Illustration: Fig. 35.]

[Illustration: Fig. 36.]

=Fuses.= A fuse is placed in series with the motor circuit before it
enters the controller wiring, but where circuit breakers are used
instead of canopy switches, the fuse box may sometimes be dispensed
with. The fuse box on street cars is usually located underneath one
side of the car body where it is accessible for replacing fuses, but
where a motorman’s cab is used, the fuse may be placed in the cab. The
fuse may be of any of the types in common use, either open or enclosed.
In the Westinghouse fuse box it is necessary only to open the box
and drop in a piece of straight copper wire of the right length and
size. The closing of the box clamps this wire to the terminals and
establishes a circuit through the copper wire as a fuse. Of course this
copper wire is of small enough size to be fused by a dangerously heavy
current.

=Lightning Arresters.= A lightning arrester is used on all cars taking
current from overhead lines. The lightning arrester is connected to
the main circuit as it comes from the trolley base, before it reaches
any of the other electrical devices on the car, so that it may afford
them protection. A common type of lightning arrester is shown in Fig.
36. One terminal of the lightning arrester is connected to the motor
frame so as to ground it, and the other is connected with the trolley.
In most forms of lightning arrester, a small air gap is provided, not
such as to permit the 500-volt current to jump across, but across which
the lightning will jump on account of its high potential. To prevent
an arc being established across the air gap by the power house current
after the lightning discharge has taken place and started the arc, some
means of extinguishing the arc is provided. In the General Electric
Company’s lightning arrester, the arc is extinguished by a magnetic
blow-out, which is energized by the current that flows through the
lightning arrester. The instant the discharge takes place the current
flows across the air gap. The magnetic blow-out extinguishes the arc,
and this opens the circuit, leaving the arrester ready for another
discharge. In the Garton-Daniels lightning arrester a plunger contact
operated by a solenoid opens the circuit as soon as current begins to
flow through the arrester. This plunger operates in a magnetic field,
which extinguishes the arc. A choke coil, consisting of a few turns
of wire around a wooden drum, is placed in the circuit leading to the
motors at a point just after it has passed the lightning arrester tap.
This choke coil is for the purpose of placing self-induction in the
circuit, so that the lightning will tend to branch off through the
lightning arrester and to ground, rather than to seek a path through
the motor insulation to ground.

[Illustration: Fig 37. Diagram of Light Circuit.]

Often, however, the choke coil is omitted, the coils in the circuit
breaker and the blow-out coil in the controller being depended upon to
prevent the lightning charge from passing.

=Lamp Circuits.= The lamp circuit of a car is protected by its separate
fuse box, and usually each lamp circuit has a switch. As explained
before, five 100-volt or 110-volt lamps are placed in series between
the trolley wire side of the circuit and ground. If one lamp in the
series burns out, of course, all five are extinguished until the
defective lamp is replaced with a new one. Enclosed arc lamps are
sometimes used for car lighting.

Cars to be operated from either end are often wired so that by turning
a switch the platform light on the front end, a light for the sign
and another for the headlight on the rear end will be extinguished
and corresponding lights on the rear and front ends lighted. This is
accomplished by the method of wiring shown in Fig. 37. The interior
of the car is lighted by six lights. Headlights of 32 candle power
are used. This method requires the use of two switches. In all light
wiring schemes a switch should be placed on the trolley side of the
lights. This permits the current to be cut off in the event of a ground
occurring in the system.

On interurban cars arc headlights are almost invariably used. The
circuit for the headlight after passing through a switch in the
motorman’s cab goes through a resistance frame usually underneath the
car and terminates in a socket near the car bumper. The brackets on
which the lamp is hung are grounded so that whenever the plug from the
lamp is inserted in the socket and the switch in the cab is turned on,
the circuit is made.

Usually there is a pressure of about 60 to 70 volts at the terminals
of the lamp. The remainder of the voltage drop, from 500 or 600 volts
(or whatever the line may be), is in the resistance under the car.
The current through the lamp is usually about four amperes. With 60
volts at the arc and 500 volts on the line, this gives a consumption
in the lamp of 240 watts and a loss in the resistance under the car of
2,000 watts, or about 90 per cent. The use of the headlight resistance
to cut the voltage down is therefore a very inefficient method. Some
schemes of wiring use the incandescent lamps used in lighting the car
as resistance for the headlight. Another way is to light the interior
of the car with arc lamps placed in series with the arc headlight.

=Trolley Base.= The trolley base upon which the trolley pole
swivels, and which furnishes the tension that holds the trolley wheel
against the wire, is designed to maintain, by means of springs, an
approximately even tension against the trolley wire, whether the
trolley wire is high above the track or near the car roof. This is done
by changing the relative leverage which the springs of the trolley base
have on the trolley pole according to the height of the trolley pole.

[Illustration: Fig. 38. Trolley Base.]

[Illustration: Fig. 39. Trolley Wheel.]

Fig. 38 shows one form of trolley base. The trolley base is bolted to
a platform constructed for it on the roof of the car; and the supply
wire to the motors and other electrical devices on the car, except in
cases where a wooden trolley pole is used for certain special reasons,
is connected directly to the trolley base. An insulated trolley wire is
run down the wooden trolley pole, and connected through a flexible lead
to the car wiring.

=Trolley Poles.= The trolley poles in general use are of tubular steel,
which gives the greatest strength for a given weight, and which can
usually be straightened if the pole has been bent by striking overhead
work when the trolley wheel leaves the wire.

=Trolley Wheels.= Trolley wheels are from four to six inches in
diameter over all, the small wheels being used in the city service, and
the large wheels in high speed interurban service. A typical trolley
wheel is shown in Fig. 39. Various companies use various forms of
groove in the trolley wheels, some adopting a groove approximately
V-shaped. The U-shaped groove, however, is the most common. The trolley
wheel is made of a brass composition selected for its toughness and
wearing qualities.

[Illustration: Fig. 40. Trolley Harp.]

=Trolley Harp.= The trolley harp, which is placed on the end of the
trolley pole and in which the trolley wheel revolves, usually has some
means for making electrical contact with the wheel in addition to the
journal bearing. In the harp illustrated in Fig. 40, which is a typical
form, this additional contact is secured by a spring bearing against
the side of the hub of the wheel.

[Illustration: Fig. 41. Third Rail Shoe.]

Since trolley wheels revolve at a very high speed, some unusual means
of lubrication must be provided, since there is no opportunity for
ordinary oil or grease lubrication. Graphite, in the shape of what is
called a “graphite bushing,” is most commonly used. This is a brass
bushing, which is pressed into the hub of the trolley wheel. In this
bushing is a spiral groove filled with graphite which is supposed to
furnish sufficient lubrication as the bushing wears. Roller-bearing
trolley wheels have been used to a limited extent, with considerable
success in some cases. Some companies have done away with the graphite
bushing, and have provided a very long journal for the trolley wheel
instead of the usual short bushing.

=Contact Shoes.= The contact shoe most commonly used on roads employing
the third rail is shown in Fig. 41. This is simply a shoe of cast iron
hung loosely by links. The weight of the shoe is sufficient to give
contact. The motion of the links permits the shoe to accommodate itself
to unusual obstructions and variations in the height of the third rail.
The shoe is fastened to the truck frame by means of a wooden plank
which furnishes the necessary insulation.

[Illustration: Fig. 42. Sleet Wheel.]

The Potter third-rail shoe which has been used to a limited extent,
employs a spring for giving the necessary tension to make electrical
contact between the shoe and the third rail. In some ways this is
superior, because a spring tension is quicker in its action than
gravity, and the shoe accommodates itself better to variations in the
height of the third rail at very high speed. The wear on the shoe,
however, is likely to be greater.

=Sleet on Trolleys and Third Rails.= The deposit of sleet on trolleys
and third rails hinders greatly the operation of cars. Often sleet
wheels of the type shown in Fig. 42 are used as a trolley wheel. These
cut the sleet off instead of rolling over it.

On the third rail, scrapers and brushes in advance of the contact shoe
are usually effective where trains are frequent. Several roads are now
melting the sleet on the rails by the use of a solution of calcium
chloride. The solution is stored in a tank on the car and is led
through small pipes to the rail immediately in front of the collecting
shoe. About one gallon of solution is used per mile, making the cost
about 7½ cents per mile. The effects of one treatment last for two or
three hours during the continuance of a storm.

Solutions of common salt have been used in the same manner, but it is
claimed that the corroding action on the iron of the calcium chloride
is not as great as that of a salt solution.


                                TRUCKS.

Electric railway cars are classified generally as _double-truck_ and
_single-truck_ cars. Double-truck cars are those that have a truck
that swivels at each end of the car. A single-truck car is one having
four wheels.

[Illustration: Fig. 43. Brill 21-E Car Truck.]

=Single Trucks.= A great many types of single trucks have been
designed. It would be out of the question to discuss them all here. In
general, however, it may be said that truck builders have aimed to make
a truck frame in itself a complete unit independently of the car body,
so that the car body will simply rest upon the trucks and there will be
no strain on the car body in maintaining the alignment of the truck.
Most single trucks, therefore, consist of a rectangular steel frame,
either cast or forged, riveted or bolted together. This frame holds the
journal boxes in rigid alignment. Usually a spring is placed between
each journal box and the truck frame. This spring may be either spiral
or elliptic. The principal springs, however, are between the truck
frame and the car body. Most truck builders have used a combination
of spiral and elliptic springs between the car body and truck frame,
as this combination is considered to give better riding qualities
and greater freedom from teetering or galloping than either spiral
or elliptic springs alone. Fig. 43 shows a Brill single truck, which
illustrates all of the features enumerated.

=Swivel Trucks.= Swivel trucks, commonly called _double trucks_, are
made in many forms, but the most common is that known as the M. C.
B. type of truck. This truck is similar to the standard truck which
is in universal use on steam railroad passenger cars in the United
States. Different truck builders have introduced many variations in
this general type of truck, in adapting it to electric service. Some
modifications from the steam railroad standard truck were necessary to
accommodate the electric motors and to permit in some cases a low-hung
car body. Such trucks are made in a great variety of sizes.

[Illustration: Fig. 44. St. Louis Car Company Truck.]

Fig. 44 shows one of these trucks built by the St. Louis Car Company.
In this type of truck the car body is fastened to the truck only by
the kingbolt on which the truck swivels. This kingbolt is placed in
the center of the truck bolster. There are also side bearings between
the car body and the ends of the bolster, to prevent tipping of the
car body when it is unbalanced. The arrangement of this part of the
truck is shown in Fig. 45. Under this bolster are elliptic springs
which rest on what is called the _spring plank_. This spring plank
is hung from the rectangular frame of the truck by links which allow
a side motion. This side motion gives easier riding, especially upon
entering and leaving curves. All trucks having this feature are known
as _swing bolster trucks_. The weight, being transmitted to the transom
and truck frame through the swinging links just referred to, is then
taken by the equalizer springs that support the rectangular truck frame
on equalizing bars, which equalizing bars rest on the journal box at
either end and are bent down to accommodate the springs located between
them and the truck frame. The truck frame holds the journal boxes in
alignment by means of guides which permit an up-and-down movement
without movement in any other direction, just as on all other types
of truck. It is thus seen that there are two sets of springs between
the car body and car journals; one set of spiral springs between the
equalizing bar and truck frame; and one set of elliptic springs between
the spring plank and the bolster. All shocks must be transmitted first
through the spiral springs and then through the elliptic springs. The
motors used on this type of truck usually have nose suspension, the
nose of the motor resting either on the bolster of the truck or on the
truck frame.

[Illustration: Fig. 45. Bolster, Links and Spring Plank.]

[Illustration: Fig. 46. Steel Tire Wheel.]

There are a number of swivel trucks made which have departed
considerably from M. C. B. lines, but nearly all retain the features
of a bolster mounted by springs on a spring plank, a spring plank hung
from a transom, a transom rigidly fastened to the rectangular truck
frame of which it forms a part; and a truck frame with one or more sets
of spiral springs between it and the journal boxes. =Maximum Traction
Trucks.= A type of swivel truck that once was very popular but has
largely been superseded by the type just described is the “maximum
traction truck.” This truck has two large wheels on an axle which
carries 60 to 70 per cent of the weight on the truck, and two small
wheels carrying the balance of the weight. The motors are on the large
wheels.

=Car Wheels.= The car wheels most commonly used are of cast iron.
In order to make a tread and flange upon which the wear comes, hard
enough to give a good mileage, the tread and flange are chilled in the
process of casting. Around the periphery of the mould in which the
wheels are cast, is a ring of iron instead of the usual sand. When
the molten cast iron comes in contact with this ring of iron, which
is called a “_chill_,” the iron is cooled so suddenly that it becomes
extremely hard. The balance of the wheel, cooling more slowly since it
is surrounded by sand, has the hardness of ordinary cast iron. A steel
tire wheel is shown in Fig. 46.

[Illustration: Fig. 47. Elevated Car Axle.]

Wheels with steel tires are coming into use for elevated and interurban
cars because their flanges are not so brittle as those of cast-iron
wheels. In wheels of cast metal there is always a liability that
the flanges and tread will chip and crack. On high-speed cars the
falling-out of pieces of flange may be a serious matter and result in
a wreck. Steel-tired wheels have a hub and spokes either of cast or
forged steel or iron. On to this wheel a steel tire is shrunk. The
tire is heated in a furnace built for the purpose, and is then slipped
over the wheel. It is made just such a size that it will slip over the
wheel when hot, and when it is cool it will shrink enough to make a
very tight fit. When the tire is to be removed after it is worn out, it
is heated until it has expanded sufficiently to drop off. An axle for
elevated car is shown in Fig. 47.

When cast-iron wheels are worn to an improper shape or have flat spots
upon them, due to the sliding of the wheels with the brakes set, an
emery wheel grinder must be used to grind them down, as nothing else is
hard enough to have any effect on the iron.

[Illustration: Fig. 48. Standard M. C. B. Flange.]

When steel-tired wheels are worn, they can be put in a lathe and the
surface of the tire turned off, as this surface is of metal soft enough
to be workable with ordinary tools.

[Illustration: Fig. 49. Brake Shoes and Levers.]

The types of wheel tread and wheel flange in use vary greatly among
different electric railways. There is a standard Master Car Builders’
wheel tread used on steam railroads, which is shown in Fig. 48.
Electric railways, however, are usually obliged to use a smaller flange
and narrower tread. Street railway special work, such as switches and
crossings, usually has too shallow a flange way to permit a standard
M. C. B. flange to pass through. Some street railways use flanges as
shallow as ⅜-inch, although ¾-inch is most common on city work. The
width of the tread on street railway cars, that is, the width of the
wheel where it bears on the rail, is usually from 1¾ inches to 2¼
inches. There is a tendency, however, on electric railways, on account
of the increasing number of interurban cars which must use city tracks,
to build tracks that will accommodate wheels approaching the M. C. B.
standard of steam roads. A few roads have adopted wheel treads and
flanges very near to the M. C. B. standard.

[Illustration: AUTOMATIC AIR BRAKE CAB EQUIPMENT.
  Westinghouse Air Brake Co.]

=Brake Rigging.= The brake rigging on a single-truck car may be
arranged in a variety of ways, but should be such that a nearly equal
pressure will be brought to bear on the brake shoes on all four wheels.
A typical arrangement of brake shoes and levers for single-truck cars
is shown in Fig. 49. The rods R terminate in chains winding around the
brake staff upon which the motorman’s handle or hand wheel is mounted.

[Illustration: Fig. 50. Brake Levers and Air Brake.]

For double-truck cars the brake rigging is necessarily more
complicated, as it must be arranged to give an equal pressure on all
eight wheels of the car. Brake shoes are sometimes placed between the
wheels of a truck and sometimes outside. The arrangement of brake shoes
between wheels is apparently finding most favor, as when the shoes are
applied in this position there is less tendency to tilt the truck frame
when the brakes are applied, and this adds to the comfort of passengers
in riding. Fig. 50 shows one form of arrangement of brake levers common
on a double-truck car equipped with air brakes, with inside-hung brake
shoes.

=Brake Leverages and Shoe Pressure.= The levers between the air
cylinder and the brake shoes are usually so proportioned that with an
air pressure of 70 lbs. per sq. in. in the brake cylinders the total of
the brake shoe pressures on the wheels will be equal to about 90 per
cent of the weight of the car. The diagram Fig. 51 has shoe pressures
and strains in the several rods marked on shoes and rods.

The following example, based on the diagram, will explain the lever
proportioning. Only round numbers are given on the diagram.

Assume a four-motor car weighing 40,000 pounds. A brake cylinder 7
inches in diameter is used. This gives 38.5 square inches and at 70
pounds air pressure a total force on the piston rod of 2,695 pounds.
The weight of the car is 40,000 pounds. Taking 90 per cent of this
gives a total of 36,000 pounds to be exerted by the brake shoe when an
emergency stop is made. Each of the eight shoes will press against the
wheels with a force of 4,500 pounds.

The dimensions of the truck are such that the “dead levers,” those
fixed at one end and which carry shoes, cannot be over 13 inches long.
The shoe will be hung three inches from one end, making the proportions
10 to 3, and the pressure on the strut rod between shoes will be 4,500
× ¹⁰⁄₁₃ or 3,461 pounds. To clear the truck frame the live lever
extends 14 inches above the point of application of the brake shoe.
To obtain 4,500 pounds pressure on the shoe, the distance between the
brake shoe and the strut rod, which we will call “_x_,” will be found
by regarding the upper end of the lever as fixed and the power applied
at the lower end.

                                     14 + _x_
                       4500 = 3461 × ———————— or
                                        14

                            _x_ = 4.2 inches.

Now to obtain the force required in the rod to the truck quadrant,
the bottom end of the live lever must be regarded as the fulcrum. The
equation is

                                 4.2
                   _x_ = 4500 × ———— = 1038 pounds.
                                18.2

As the pull rods from each side of the truck are attached to the truck
quadrant, the stresses in the brake rods are double this, or 2,076
pounds.

[Illustration: Fig. 51. Diagram of Brake Shoe Pressures and Strains.]

The position of the brake cylinder under the car restricts the length
of the “live” and “dead” cylinder levers to 16 inches. To obtain 2,076
pounds pull on one end of the levers with the previously computed 2,695
                                             2076   _x_
pounds on the other, the proportions must be ———— = ———, since 2076 +
                                             477    16
2695 = 4771. Then _x_ = 7 inches, the distance from the brake piston to
the pivotal point.

Since 2,695 pounds pressure is exerted and 36,000 pounds results the
proportion of the whole system of levers is 36,000 to 2,695 or 13.3
to 1. In other words the travel of the piston in the cylinder will
be 13.3 times that of the shoes if there were no lost motion to be
taken up. The piston travel should be from 4 to 5½ inches. This gives
about ⅜-inch travel of the brake shoes. Increased travel of the brake
shoes necessary to set them as they wear away causes increased travel
of the piston of the air cylinder. Not only is more air used at each
application of the brakes but the brakes are slower in acting. It is
therefore necessary to adjust the brakes frequently. This is done
in the system shown in the diagram by the use of a turnbuckle in the
connecting rod between the live and dead levers of the truck.

When two motors are on one truck and none on the other, allowance must
be made in the levers for the increased weight of the motor truck and
the inertia of the armature. The leverage on the motor truck must be
greater than on the other.

=Air Brakes.= Air brakes used on electric railway cars are usually of
what is called the _straight air brake_ type in distinction to the
_Westinghouse automatic air brake_. A straight air brake is one in
which the air is stored in a reservoir; and, when the brakes are to
be applied, air from this reservoir is turned directly into the brake
cylinder, in which works a piston operating the brake levers. Air
admitted behind the piston forces it out with a pressure which applies
the brakes. When the air is let out of the brake cylinder, a spiral
spring forces the piston back to its original position and the brakes
are released. The motorman’s valve by which he applies the brakes,
therefore, provides, first, for turning air from the storage reservoir
to the brake cylinder to apply the brakes, and, second, for closing the
opening to the storage reservoir and opening an exhaust passage from
the brake cylinder so that the air can escape from the brake cylinder
to release the brakes.

Straight air brakes of this kind would not be suited to the operation
of long trains, because, if the air-brake hose connection between
cars should be broken, the brakes would be useless; but for trains of
one or two cars, such as are common in electric railway practice, the
simplicity of the straight air brake outweighs its disadvantages and
this is the type of brake usually employed. (See Fig. 52.)

The Westinghouse and other forms of automatic air brake are used on
electric railways where cars are operated in long trains; but it is out
of the province of this paper to describe these brake systems fully, as
they are rather complicated. It may be said in general, however, that
the Westinghouse automatic air brake is so arranged that, should the
hose connection between cars be broken, should the train pull in two,
or should anything happen to reduce the pressure which is maintained
in the train pipe that runs the length of the train, the brakes would
immediately be applied on the entire train. [Illustration: Fig. 52.
Diagram of Straight Air Equipment.]

=Compressors.= A small air compressor driven by an electric motor is
frequently employed on electric cars to keep the storage reservoir of
the car supplied with air. These air compressors are carried under
the car or in the motorman’s cab. They are generally arranged with an
automatic device which closes the motor circuit and starts the motor as
soon as the air pressure falls below a certain amount; and the motor
will continue in operation pumping air until the pressure rises to the
amount for which the automatic device is set. The pressure carried in
the storage reservoir is usually from 60 to 90 pounds per square inch,
which, as a general thing, is considerably more than is required to
apply the brakes hard enough to slide the wheels.

=Automatic Governor for Air Compressors.= Automatic governors are often
installed in connection with air compressors in order that a fairly
even air pressure may be maintained in the storage reservoir. In these
the fall and rise of the air pressure within certain limits closes and
opens the circuits to the motor. In some styles the air acting on a
piston operates the circuit breaker.

The diagram shown in Fig. 53 shows the principle of the Christensen
governor, in which the air pressure is employed to make and break a
secondary circuit.

When the pressure in the storage reservoir falls below a predetermined
value, the hand of the air gauge makes contact with lug A. This closes
the circuit through solenoid No. 1. Lug D, mechanically connected to
the armature of the solenoids is pulled in contact with lug C, and this
closes the circuit to the motor, and shunts the winding of solenoid No.
1. When the air pressure rises to a predetermined value the hand of the
air gauge is thrown in contact with lug B. This energizes solenoid 2
by connecting it across the motor terminals. The armature is pulled to
the right and the circuit to the motor is broken. When this is done it
is evident that the current through the energized solenoid is broken.
It is evident from the description that current passes through the
solenoids only during the short periods that the armature is moving
from one position to the other and the air gauge never has to break a
circuit in which there is an appreciable voltage so that there is no
arcing at lugs A and B.

[Illustration: Fig. 53.]

A blow-out coil in series with the motor is provided immediately under
lug C which extinguishes the arc at that point when the motor circuit
is broken.

A Westinghouse air compressor is shown in Fig. 54.

=Storage Air Brakes.= The storage air-brake system does not have a
small independent compressor on each car, but is equipped with a large
storage tank, in which air is carried under high pressure—250 to
300 pounds per square inch. This storage tank is filled at regular
intervals when the car passes some point on its route at which a
compressor is located. In this case the car is obliged to stop long
enough to make connection to the tank of the compressor plant, and
to allow the car storage tank to be filled. This operation, however,
does not take long. The advantages of the system are a saving of the
weight and a saving in the maintenance of a small compressor on each
car. From the main storage tank under the car, air is led through a
reducing valve to an auxiliary storage tank. This reducing valve allows
enough air to pass through to maintain a pressure of about 50 pounds
per square inch in the auxiliary storage tank. The auxiliary storage
tank corresponds to the regular storage tank on a system employing
compressors on each car. The method of operation after the air has
entered the auxiliary storage tank is the same as with any air-brake
system.

[Illustration: Fig. 54. Westinghouse Air Compressor.]

Fig. 55 shows the arrangement of the apparatus under the cars of the
St. Louis Transit Company. The two storage tanks are each 6 feet long
by 18 inches in diameter and are mounted one on each side of the car.
Their combined capacity is equivalent to about 100 cubic feet at 45
lbs. pressure. The tanks are charged through an outlet near one side of
the car. This outlet contains a check valve and cock to prevent leakage.

The service or low pressure reservoir has a capacity of about 2½ cubic
feet. The position of the reducing valve between the high and low
pressure valves may be noted in the illustration.

=Momentum Brakes.= Momentum or friction brakes have been used to some
extent both on single-truck and on double-truck cars, but particularly
on single-truck cars. They derive the power to operate the brakes from
the momentum of the car by means of a friction clutch on the car axle.
The difference in various kinds of momentum brakes lies chiefly in the
design of the clutch mechanism. The clutch must evidently be arranged
to act very smoothly, and must be under very accurate control, as the
force with which the brakes are applied depends directly upon the pull
exerted by the clutch.

[Illustration: Fig. 55. Arrangement of Storage Air Brake Apparatus.]

In the Price momentum brake a flat disc is cast on the car wheel, which
is turned off to a smooth surface. Against this disc a friction clutch
acts, which has a leather face. The clutch is operated by a motorman’s
lever through a set of levers. A small movement in the motorman’s lever
forces the clutch against the disc on the car axle. The clutch winds up
the brake chain, and thus supplies power to apply the brakes.

Other momentum or friction clutch brakes have been devised, most of
which also use an application of leather on iron for the clutch, as
this has been found to be most reliable, and to be least affected
by the grease and dirt that is liable to work in between the clutch
surfaces.

=G. E. Electric Brake.= The General Electric Company’s electric brake
makes use of current generated by the motors acting as dynamos, to stop
the car. In order to accomplish this, a brake controller is provided
which reverses the armature connections of the motors, and so connects
them to operate as dynamos sending current through a resistance in the
circuit; the amount of current flowing and the braking effect depending
on the car speed and the resistance. In some forms of brake controller,
the two controllers are combined in one cylinder, so that the motorman,
to apply the electric brake, simply continues the movement of the
handle past the “off” position. In others, the brake-controller drum is
separate, but is interlocked with the main controller so that it can be
used only when the main controller is off.

However the controller may be arranged, the principle involved is
that when the motors are revolving by the motion of the car, and the
armature connections are reversed as they would be to reverse the
direction of motion of the car, the motors begin to generate current as
series-wound dynamos. The amount of current generated and the retarding
effect will depend on two things—namely, the speed of the car, with
the consequent electromotive force in the motors, and the amount of
resistance in the circuit. The amount of resistance is regulated by the
motorman by means of his electric brake controller. The function of
the electric brake controller is to reverse the motors and to insert
enough resistance in the circuit to make a comfortable stop. This
current in the motors acting as dynamos, in itself acts as a powerful
brake to retard the motion of the car. In the General Electric type of
electric brake, the current generated in the motors, in addition to
having this retarding effect in the motors themselves, is conducted to
brake discs that act as magnetic clutches against one of the car wheels
on each axle. The car wheel has a disc cast upon it, and against this
the magnetic disc acts. The magnetic disc contains a coil which is in
series in the brake circuit.

In applying an electric brake of this kind the motorman first puts
the controller on a point that inserts considerable resistance in the
circuit. When the motors have slowed down, the electromotive force, of
course, drops, so that to maintain the same braking current there must
be a reduction of the amount of resistance, until, when the car is
almost at a standstill, the resistance is nearly all cut out. It might
seem at first that the current would die down before the car came to
a stop, but it is found that there is enough induction in the motor
fields to cause current to flow for a short time after the car has
stopped. The residual magnetism in the steel in the fields of the motor
is sufficient to cause the motors to begin to generate current when the
electric-brake controller is first turned on.

The greatest advantage of an electric brake using motors as generators
is in the fact that the braking current instantly falls in value as
soon as the wheels begin to slide, and releases the brake until the
wheels again revolve. In fact, it is almost impossible to skid the
wheels as they are sometimes skidded by being locked by brake shoes.
This not only prevents flat wheels but insures a quick stop, because
when the wheels are locked and sliding, the braking or retarding power
is only about one-third what it was before the wheels began to slide.
The electric brake requires extra large motors because of the heating
caused by the current generated while braking.

[Illustration: Fig. 56. Magnetic Brake Shoe.]

=Westinghouse Electromagnetic Brake.= The Westinghouse magnetic brake
is in principle similar to the General Electric brake as far as the use
of motors as generators is concerned; but, instead of assisting the
motors by means of a magnetic brake disc acting against the car wheel,
a magnetic brake shoe is used (see Fig. 56), which acts against both
car wheel and track. This not only retards through the medium of the
wheels but acts directly on the track. It is not dependent upon the
coefficient of friction between the wheels and track; and it should,
therefore, be possible to stop much more quickly than with any form of
brake depending upon the coefficient of friction between the wheels and
track.

[Illustration: MAGNETIC BRAKE SHOWING METHOD OF ATTACHING TO CAR FRAME
  AND TRUCKS.

  Westinghouse Air Brake Co.]

=Track Brakes.= Track brakes have been used to some extent on very
hilly electric roads. These have a shoe fastened to the truck frame,
which acts directly on the track.

=Motors as Emergency Brakes.= The motors can of course be used to brake
the car by simply reversing them if current is applied to them from the
line. But in case the trolley flies off or if the circuit breaker or
the fuse opens the circuit, or the supply of current is interrupted for
any other reason, they may be used as brakes by throwing the reverse
lever and moving the controller handle to the multiple position of
a two-motor equipment or by simply throwing the reverse lever of a
four-motor equipment. These movements throw the motors in multiple and
connect the fields and armatures of the motor in such relation that
they can generate current. One of the motors then acts similarly to a
generator in a power house, deriving its power from the momentum of the
moving car instead of from an engine, and sends current through the
other motor of the pair which acts like any auxiliary motor trying to
revolve its wheels in the opposite direction from that in which they
are revolving. The motors of a four-motor equipment are permanently
connected in two multiple groups as long as the reverse is not in the
central position. In the two motor equipment such connections are not
made until the controller handle is turned to the multiple position.
As the external resistance is beyond the junction of the two motor
circuits, the braking effect is not increased by cutting out the
resistance.

The difference in the residual magnetism of the fields or in the
magnetic qualities of the fields of the two motors is primarily the
cause of the generation of the current. The motors at first act in
opposition, but one of them generates the higher voltage and forces
a current through the other. This current overcomes the residual
magnetism of the second motor, thereby changing its polarity and
both motors then act in series to send the current through the low
resistance path afforded by the windings. Any current passing increases
the strength of the fields and consequently the voltages, so that
abnormal currents are generated and the braking action is consequently
severe.

This generating action does not take place before the reverse lever is
thrown because the connections of the armatures and fields are such
that any current generated by reason of the residual magnetism of the
fields, flows in such a direction through these that this magnetism is
destroyed. The current then ceases to flow. This explains why current
is not generated in No. 2 motor with a K type of controller during the
change-over period when it is short-circuited, or in equipments when
the trolley flies off and the controller is turned on.

[Illustration: Fig. 57. Pneumatic Sander.]

=Brake Shoes.= The subject of brake shoes is of very little importance
on the smaller cars traveling at slow speeds and controlled alone by
hand brakes. On the larger high speed interurban cars, the brake shoe
question becomes an important item because of the rapidity with which
they are worn away. On such cars shoes sometimes last but about one
week. This means eight shoes per week per car or an expense of about
$4.00 per car per week.

Brake shoes are usually of soft gray cast iron with inserts of steel,
although some companies use very hard iron. They are usually fastened
by means of a key to a brake shoe head permanently attached to the
brake rigging. The brake levers are so adjusted that the shoes clear
the wheels about ³⁄₁₆-inch when the brakes are released. This distance
increases as the shoes wear, so that the brakes must be adjusted
frequently to take up the slack and prevent waste of air.

=Track Sanders.= A sprinkling of sand on the rail increases wonderfully
the adhesion of the rail and wheel. There is usually on cars some
provision made for scattering sand on the rails immediately in front
of the leading wheels. From sand boxes placed under the seats in the
smaller cars, or on the truck of the larger ones, flexible hose or
pipes drop within an inch or two of the rail in front of the leading
wheels. A valve under the control of the motorman regulates the flow of
sand to the rail. Sometimes air pressure is used to blow the sand out
of the sand box into the hose. In this case air pressure is obtained
from the air brake system, and an air valve leading to the sand box is
placed in the motorman’s cab. A section through a pneumatic sander of
this kind is shown in Fig. 57.

[Illustration: Fig. 58. Curves of Braking Tests.]

=Coefficient of Friction.= It has been found by experiment that the
coefficient of friction between the car wheel and rail is about 25
per cent of the weight on the wheel when the rails are dry; that is,
a car wheel having a weight of 2,000 pounds upon it would not be able
to exert either an accelerating or a retarding force exceeding 25 per
cent of this, or 500 pounds. This is when the wheel is rolling. There
is apparently a kind of locking or inter-meshing of the rough surfaces
of wheel and rail when the wheel is rolling, because it is found that
when a wheel begins to skid or slide, the coefficient of friction falls
off about two-thirds. The maximum braking or retarding force that can
be obtained, therefore, in a dry rail, amounts to 25 per cent of the
weight of the car. If the rail is slippery this is much reduced; or
if the wheels are allowed to slide it is also much reduced. If more
retarding force than can be obtained through the medium of a wheel
rolling on the rail is desired, it must be obtained either by the track
brakes or by magnetism.

[Illustration: Fig. 59. Automatic Coupler.]

=Rate of Retardation in Braking.= The rate of retardation of cars in
braking is usually 1 to 2 miles per hour per second. In other words a
car going at a speed of 40 miles an hour will usually be stopped in 40
to 20 seconds.

The plotted results of some braking tests (Fig. 58) show a higher rate
of acceleration. These tests were made on an interurban car weighing
about 63,000 pounds, equipped with straight air brakes. Of the six
curves shown, that giving the highest rate of retardation is No. 4.
This shows a stop from a speed of 38 miles per hour in 9½ seconds or a
rate of retardation of about 4 miles per hour per second. All of the
curves shown are for emergency stops. They show about the highest rate
of retardation that could be made with the equipment.

=Drawbars and Couplers.= For small surface cars a crude drawbar is
usually provided consisting simply of a straight iron bar pivoted under
the car and provided with a cast-iron pocket near the end. A coupling
pin passing through the pocket of one coupler and through a hole in the
end of the bar of the other, holds the two cars together.

The requirements of a coupler for heavier cars such as those used on
interurban and elevated roads are more exacting. The ends of the bars
are usually pivoted under the car about five feet back from the bumper.
A spring cushion intervenes between the pivot point and the drawbar
head. The illustrations, Figs. 59 and 60, show the action of the Van
Dorn Automatic coupler, which is the one used by all the elevated lines
in the United States. The link is placed in one of the drawbar heads
and the pin in the other. As the cars come together the wedge-shaped
end of the link forces its way between the pin and a spring. When the
faces of the drawbar heads meet, the spring forces the link to engage
the pin. The mechanism is designed especially to prevent lost motion
between coupler heads because, unlike steam railroad drawbars, electric
car drawbars must swivel to round curves and a great amount of play at
the point of coupling with swiveling drawbars would allow the couplers
to bend under a pushing strain.

[Illustration: Fig. 60.]




                            CAR CONSTRUCTION.


=Car Bodies.= In cities there are three general types in common use;
namely, box cars, suited for winter use only; open cars, suited for
summer use only; and semi-convertible cars, which can be adapted to
either summer or winter use. The open and box cars are the older types.
The semi-convertible car is usually provided with a center aisle, and
cross seats on each side of this aisle. [Illustration: Fig. 61. Side
Elevation and Plan of Car.] The windows are large, so that they can be
lowered or raised in summer to make something approaching the character
of an open car. The car bottom, which forms the basis for the entire
car structure, is constructed with longitudinal sills either of steel
or of wood combined with steel. One form of construction employs as
the main supports two steel channel bars extending the full length
of the car. Steel I-beams are sometimes used. Where wood is used in
combination with steel for longitudinal sills, the steel is usually in
the form of flat steel plates between the timbers. Most cars seat about
one passenger per foot of length over all.

[Illustration: Fig. 62. Cross-Section of Car Body.]

Many more difficulties are met in the construction of passenger
cars for electric railways than in steam coach construction. The
electric car must have low steps and platforms and turn short curves.
The difficulties are largely in the floor framing of the car. The
platforms at each end are usually eight to ten inches lower than the
floor of the interior. As the car must frequently be designed to pass
around curves of small radius, often of only thirty or forty feet,
sufficient clearance must be provided for the swing of the trucks.
This necessitates that the trucks of a double truck car be set far
enough back towards the center of the car to clear the dropped platform
timbers, shown in Fig. 63. In the illustration shown, Fig. 61, the
truck centers are but 21 feet 8 inches apart, while the ends overhang
the truck centers 11 feet 4½ inches. It is difficult to support this
overhanging weight properly. The difficulty is increased by the fact
that the rear platform is often crowded with passengers having an
aggregate weight of one ton or more. Trusses manifestly cannot be
employed to give rigidity to the long platform. This is usually given
in cars of wood construction by reinforcing the platform timbers
with steel plates as shown in the figure. In order that the dropping
tendency of the platform shall not bow up the body of the car between
the trucks this portion must be braced rigidly. The space below the
windows and above the side sill is utilized for this purpose. The side
sill is moreover strengthened by having steel plates bolted to it.

[Illustration: Fig. 63. Reinforcing Plates.]

The longitudinal members of the body framing are termed sills. These
are usually of long leaf yellow pine. Various combinations of wood and
steel are employed for sills, an example of which is seen in Figs. 61
and 62. The sills are kept the proper distance apart by “bridgings”
or cross sills mortised into them at intervals and by “end sills.”
The whole framing is tied together by the rods running parallel to
the bridging. These tie rods are often provided with turn buckles for
tightening when occasion may require. The outer sills are termed side
sills; those nearest the center of the car, the center sills or draft
timbers; while those between are called intermediate timbers.

The remaining portion of the car is constructed much after the manner
of a steam coach. The posts between the windows are mortised into
the side sill at the bottom and into a top sill at their upper end.
They are laterally braced by a belt rail immediately under the window
opening, both the belt rail and the posts being gained out so that the
rail fits flush with the posts. A wide letter board gained into the
post just below the side plate adds to the bracing of the side of the
car, as does also an iron truss usually one-fourth to one-half inch
thick and two to three inches wide which is gained into the posts on
the inside running just under the windows between the truck centers,
and then descends to pass through the side sills and fasten by a bolt
underneath.

The roof consists of the upper and lower decks. That portion over the
platform or vestibule is termed the hood. Rigidity is given to the
whole upper portion of the car by the end plates resting on the corner
posts and extending between the side plates at either end of the car
body proper, and by steel carlins which conform to the peculiar shape
of the roof and extend between the side plates. The steel carlins
are usually placed over alternate side posts. Bolted on either side
of them and placed at intervals of about twelve inches between are
wood carlins. The wood carlins of the lower deck extend from the side
plate, to which they are fastened by screws, to the top sill, which is
immediately below the windows of the upper deck. Above these windows is
the top plate, supporting the carlins of the upper deck, which extend
between and a few inches beyond the two top plates. Poplar sheathing
three-eighths or one-half inch is nailed over carlins and on this heavy
canvas usually of six or eight ounce duck is stretched tightly. Several
coats of heavy paint on the canvas and a trolley board for supporting
the trolley stand complete the roof. On the underside of the carlins
the headlining, usually of birch or birdseye maple, is secured. This
forms the interior finish of the ceiling of the car.

=Steel Car Framing.= As a result of the demands of the officials of
the New York Subway for cars of greater strength and less subject to
danger from fire, much progress has been made in the last few years
in the construction of cars with steel framing. Steel construction is
much more expensive than that in which the framing is of wood and is
considerably heavier. The advantages lie partly in the fact that it is
more durable, but the great reason for the interest with which the new
style of construction has been received is that the danger of collapse
and consequent injury to passengers, in case of accident, is greatly
diminished.

=Car Weights.= The total weight of a street car with a body 16 feet
long over corner posts mounted on a single truck with two motors is
approximately 14,000 pounds. Of this the body weighs about 4,500
pounds, the truck 4,400 pounds, and the motors and the electrical
equipment the remaining 5,100 pounds. The weights of the separate
parts of a certain interurban car measuring 52 feet 6 inches over the
bumpers mounted on double trucks, one of which carried two motors, is
body 34,065, motor truck 9,565, trail truck 6,670, electrical equipment
12,800; total 63,100.

An interurban car of about the same size as the one just mentioned
but equipped with four motors gave the following weights: Body with
controller and resistance grids 39,000 pounds, trucks 19,130 pounds,
motors 15,420 pounds; total 73,550 pounds.

=Car Painting.= A great deal of attention is given to the proper
painting of cars. A car painted with care and proper materials always
presents an attractive appearance, while one carelessly painted is
readily noticeable. New cars go through an elaborate painting process.
The time required is from two to three weeks. The following scheme may
be regarded as an example of a good process:

  A coat of primer is given the car the first day. On the third
  day all irregularities are puttied up smooth. On the fourth and
  fifth days a heavy primer is applied, one coat on each day. A
  coat of filler is given on the sixth day and allowed to harden
  the following day. The next paint applied is termed a guide coat.
  This is of a color different from the preceding ones and serves
  as a guide for the rubbers, who on the following day go over the
  car with mineral wool, fine sandpaper, or pumice stone, and rub it
  until the guide coat is worn away. This assures an even and smooth
  surface. On the tenth day the car is allowed to stand. A coat of
  the color desired is applied, one on each of the following three
  days. On the fourteenth and fifteenth days the car is striped
  with the desired ornaments and lettered. This is usually done in
  aluminum or gold leaf. The car is then given three coats of varnish
  on alternate days, and the work is completed. The best practice
  brings the cars in once each year to be revarnished.

[Illustration: TYPICAL HIGH GRADE TRACK CONSTRUCTION
  J. G. White & Co.]




                           ELECTRIC RAILWAYS.

                                PART II.

                         OVERHEAD CONSTRUCTION.


[Illustration: Fig. 64.]

=Trolley Wire.= The trolley wire is suspended from the span wires or
brackets in such a way as to permit of an uninterrupted passage of an
upward pressing trolley wheel underneath it. The trolley wire itself
may be either round, grooved, or figure 8 in section. Where a round
wire is used, No. 00 B. & S. gauge is the most common size. Figure
8 wire, so called from its section, which is shown in Fig. 64, is
designed to present a smooth under surface to the trolley wheel, which
will not be interrupted by the clamps or ears used to support it.
Clamps are fastened to the upper part of the figure 8. The grooved wire
is rolled with grooves into which the supporting clamps fasten. This
wire also presents a smooth under surface to the trolley wheel.

[Illustration: Fig. 65. Trolley Wire Clamp and Ear.]

=Trolley-Wire Clamps and Ears.= The trolley is supported either by
clamps or by soldered ears. One type of clamp grasps the wire by virtue
of screw pressure. A soldered ear is shown at E, Fig. 65. This ear has
small projections at each end, which are bent around the wire to assist
the solder in holding the wire to the ear. Another form of ear, used to
some extent, holds the wire by virtue of having the edges of the groove
offset or riveted around the wire.

The ear or clamp screws to a bolt which is insulated from the metal
ear through which passes the span wire. A cross-section through a
common type of trolley-wire hanger is shown in Fig. 66. Here there is
an outer shell of metal, which is adapted to hook to the span wire. In
this shell is an insulating bolt, that is, a bolt surrounded with some
form of insulating material which is very strong mechanically and not
likely to be cracked by the hammering action of the passing trolley
wheel. Most of the insulating compounds used in making trolley-wire
insulators are trade secrets. Another kind of insulator called the “cap
and cone” type is shown at C, Fig. 65. In these insulators, the metal
part B which fastens to the span wire does not completely surround
the insulation C. Wood has sometimes been used for the insulation of
trolley-wire hangers.

[Illustration: Fig. 66. Cross-Section Trolley Wire Hanger.]

=Span Wires.= In city streets, the trolley wire is commonly suspended
from span wires stretched between poles located on both sides of the
street. These span wires are of ¼-inch or ⅜-inch galvanized stranded
steel cable. In order to add to the insulation between the trolley
wire and the poles at the side of the street, what is called a _strain
insulator_ is placed in the span wire. This is an insulator adapted to
withstand the great tension put upon it by the span wire. One of these
is shown in Fig. 67. Means are usually provided for tightening the
span wires as they stretch and as the poles give under the strain. The
insulator in Fig. 67 has a screw eye for that purpose.

[Illustration: Fig. 67. Strain Insulator.]

[Illustration: Fig. 68. Overhead Construction.]

=Brackets.= In the bracket type of overhead construction, a trolley
wire is fastened to brackets placed on poles near the track. This
construction is used on suburban and interurban lines where the
presence of poles near the track is not objectionable. It has been
found that a rigid connection of the trolley wire to a bracket is
likely to result in the breaking of the trolley-wire insulators. For
this reason the brackets now commonly used provide for a flexible
suspension of the trolley-wire hanger from the bracket. A bracket
employing such flexible construction, made by the Ohio Brass Company,
is illustrated in Fig. 68.

An example of standard straight-line bracket construction is shown in
Fig. 69.

=Feeders.= Where additional conductivity is needed beyond that
furnished by the trolley wire itself, feeders are run on insulators
along the poles at the side of the track. Such feeders are connected to
the trolley wire at regular intervals. Where span-wire construction
is used, the feed wire may be substituted for the span wire at the
pole where the connection between feed wire and trolley wire is made.
In such a case, of course, a trolley-wire hanger is used which has
no insulator, so that the current feeds directly through the hanger.
Another method is to run the feed connection parallel with a span wire
and a short distance from it.

[Illustration: Fig. 69. Standard Straight Line Construction.]

=Section Insulators.= Section insulators are usually placed in the
trolley wire at regular intervals. Such a section insulator is shown
in Fig. 70. Its purpose is to insulate one section of trolley wire
from the next, so that in case the trolley wire of one section breaks,
or is grounded in any other manner, that section can be disconnected
and the other sections on either side kept in operation. In large
city street-railway systems, each section of trolley wire usually has
its own feeder or feeders, independent of the other sections. This
feeder is supplied through an automatic circuit breaker at the power
house. In case a certain section of trolley wire is grounded the large
current that immediately flows will open the circuit breaker supplying
that section; but, unless the ground contact is of an extremely low
resistance, it will not affect the operation of the other feeders.
Should it be of sufficiently low resistance to cause all the generator
circuit breakers to open, it would, of course, interrupt the entire
service temporarily; but usually the circuit breaker on any individual
feeder will cut that feeder out before all the circuit breakers will
open.

[Illustration: Fig. 70. Section Insulator.]

=High-Tension Lines.= Where high-tension alternating-current wires are
run, as in the case where the road is of such length as to require the
establishment of several substations, these high-tension circuits are
usually carried some distance above the 500-volt direct-current trolley
and feeders. An example of interurban overhead construction is shown
in Fig. 69. Here the high-tension wires are carried on large porcelain
insulators of a size necessary for 26,000 volts. These insulators
are placed 35 inches apart. High-tension wires are kept so far apart
because of the danger that arcs will in some way be started between the
lines, as the high-tension current will maintain an extremely long arc.
The blowing of green twigs across the lines, or birds of sufficient
size flying into the lines, is likely to establish arcs which will
temporarily short-circuit the line. The greater the distance apart of
the wires, the less danger that such things will occur.

Both glass and porcelain insulators are successfully used on lines of
very high tension. Glass is the cheaper and porcelain has the greater
mechanical strength.

High-tension wires are usually of hard-drawn copper or of aluminum made
up in the form of a cable of several strands. Aluminum is lighter for
a given conductivity than copper; and, at the market price controlling
at the present time, is cheaper. It is, however, more subject to
unevenness of composition, which leaves weak spots at certain points
in the wire; and that is the reason why aluminum is now always used
in the form of a stranded cable rather than as a single conductor.
Aluminum, being considerably softer than copper and melting at a lower
temperature, is more likely to be worn through as a result of abrasions
or to be melted off by a temporary arc. These slight objections are
balanced against its smaller first cost as compared with the cost of
copper.

The calculation of the proper amount of feed wire for a given section
of road is somewhat similar to the calculation of electric light and
power wiring as already outlined. It is first necessary to estimate
approximately the amount of current required at different portions of
the line. The amount of drop to be allowed between the power house and
cars must be decided arbitrarily by the engineer. A drop of 10 per cent
is probably the one most commonly figured upon in designing feeding
systems. The resistance in ohms of the copper feeders required to
conduct a given current with a given loss in volts, can be calculated
by dividing the volts lost by the current, according to Ohm’s law. By
the aid of a table which gives the conductivity of various sizes of
wire according to the methods outlined in connection with “Electric
Wiring,” the proper number and size of the feeders can be determined.
The most difficult thing to determine is the load that will be placed
upon any section of the line. Of course, there will be times when cars
are bunched together owing to blockades. It is out of the question
to provide enough feeder copper to keep the loss in voltage within
reasonable limits at such times. The ordinary load upon any feeder is
used as the basis of calculation in most cases. The amount of current
required per car depends on the weight of the car and the character of
the service. This will be taken up later under the head of “Operation.”


                              THIRD RAIL.

[Illustration: Fig. 71. Third-Rail Insulator.]

=Location.= The third-rail system of conducting current to electric
cars, as most commonly employed in the United States, follows the
example set by the Metropolitan West Side Elevated Railway of Chicago.
All the elevated roads in the United States are now operated by means
of third rails located at one side of the track. The third rail is
an ordinary T-rail and is located with the center of its head 20
inches outside of the gauge line of the nearest track rail, and 6³⁄₁₆
inches above the top of the track rail. On a few interurban roads this
distance has been increased in order to accommodate certain steam
railroad rolling stock which must at times be operated over the line.

=Insulators.= The third rail is supported every fifth tie on an
insulator. These insulators on first construction were made of wooden
blocks boiled in paraffine, but at the present time more substantial
forms of insulation are being used.

One form of third-rail insulator, known as the “Gonzenbach,” has a
base of cast iron resting on the tie. Over this is placed a cap of
insulating material similar to that used in strain and trolley-wire
insulators. Over this insulating material is another cast-iron cap upon
which the third rail rests. The weight of the third rail holds it in
position, and there is no clamping together of the various parts of the
insulator.

Another form of third-rail insulator is made of what is called
“reconstructed granite,” and another of vitrified clay. Fig. 71 shows
one of the latter.

=Switches.= Where the third rail is used, a contact shoe is placed on
each side of both trucks of the motor car. At switches it is necessary
to omit the third rail for a short distance on one side of the track,
and place a short section of third rail on the other side of the track
so that the current supply to the car will be uninterrupted.

=At Highway Crossings.= Where the third-rail system is employed on
interurban surface lines, it is necessary to omit a section of it at
every highway crossing. If the crossing is too wide to be bridged
across by a car, the car must have sufficient momentum to drift over
such crossings when it comes to them. To connect across the break in
the third rail at such points, an underground cable is generally used.
This cable must be thoroughly protected against leakage of moisture
into the insulation where it comes to the surface for connection to the
third rail.

Another form of third rail, laid several years ago on some of the lines
of the New York, New Haven & Hartford Railroad, was of an inverted
V-shape, and was laid midway between the track rails with its top 1
inch above them and its bottom only 1⅝ inches above the ties. It was
supported on wooden blocks. This location of the third rail has never
been popular, because of the poor insulation with the rail located so
close to the ties between the rails.

=Conductivity.= The conductivity of a steel rail varies considerably. A
rail of the ordinary composition used on steam railroads is too high in
carbon to give the best conductivity. Such a rail has about one-tenth
the conductivity of the same cross-section of copper. Steel can easily
be obtained, however, which will have one-seventh the conductivity of
copper, and the additional cost of obtaining such special steel is
quite low, so that the majority of roads installing the third-rail
system have seen fit to pay the extra cost and thereby secure a softer
rail than that usually employed in track rails.

=Cost.= The cost of the third-rail system is less than an overhead
trolley system, provided enough copper is placed in the trolley feeders
to make the conductivity of the trolley system equal to that of the
third-rail system. It is very seldom, however, that a trolley system is
so constructed on an interurban road; and hence the trolley system, as
usually constructed, is cheaper than the third-rail system, because it
is not of equal conductivity to a third-rail system.

=Advantages in Operation.= Where very heavy cars or trains are to
be operated, the third-rail system is decidedly an advantage, for
two reasons. In the first place, it affords the cheaper method of
conducting a given heavy volume of current; and in the second place,
the contact shoes that conduct the current from the third rail to the
moving car or train are built to carry a much larger volume of current
than the trolley wheel, which has only a small area of contact on
the trolley wire. Ordinarily there are two of these contact shoes in
multiple for every motor car.

Another advantage of the third rail over the trolley is that the
trolley may leave the wire at high speeds or in passing switches.
On well-constructed roads, where the trolley wire is kept in good
alignment and the track is smooth, there is little trouble from this
source; but it is undoubtedly a convenience to be able to operate cars
or trains without giving any attention to a trolley pole.

[Illustration: Fig. 72. Cross-Section of Conduit.]


                           CONDUIT SYSTEMS.

The underground conduit system, in which the conductors conveying the
current to the cars are located in a conduit under the tracks, is in
use in two cities of the United States—New York City and Washington,
D. C. The cost of this system, and the danger of interruption of the
service where the drainage is not excellent, have prevented its more
extensive adoption.

The New York type of conduit is a good example of this construction.
The conductors consist of T-bars (CC) of steel supported from porcelain
cup insulators located 15 feet apart in the conduit. A cross-section
of the conduit is shown in Fig. 72. At each insulator a handhole is
provided (Fig. 73), so that access may be had to the insulator from the
street surface. Manholes are provided at intervals of about 150 feet,
so that the dirt which collects in the conduit can be scraped into
these manholes and removed at intervals. The manholes also serve as
points of drainage to the sewer system.

[Illustration: Fig. 73. Handhole.]

=Contact Plow.= Current is conducted to the car through a pair of
contact shoes commonly called a _plow_ (Fig. 74). This plow has the
two shoes insulated from each other, and from the frame of the plow.
They are provided with flat springs that hold the shoes against the
conducting bars in the conduit. The shank of the plow is thin enough
(⁹⁄₁₆ inch) to enter the slot of the conduit. The conductors pass up
through the middle. These plows can, of course, be removed only when
the car is over an open pit.

=Cost.= A conduit system of this kind is very expensive to build
because of the fact that a very deep excavation must be made in the
street to accommodate the conduit. The track rails, slot rails, and
sheet-steel conduit lining are held in alignment by cast-iron yokes
placed 5 feet apart. The entire space around and underneath these yokes
is filled with concrete in order to give rigidity and a permanent
track. Three expensive items, therefore, enter into the construction
of a conduit road—namely, the deep excavation, which may call for the
changing of other underground pipes or conduits in the street; the
large amount of iron and steel needed for the yokes and slot rails; and
the large amount of concrete needed.

On American conduit roads the slot and conduit are placed under the
middle of the track. Some of these roads are simply reconstructed
cable-conduit roads in which the old cable conduit has been used for
electrical conductors. In the conduit road at Buda-Pest, Hungary, the
slot is placed alongside one of the track rails.

=Current Leakage.= The leakage on an underground conduit road is
considerable, because the insulators are necessarily located in a damp,
dirty place, which causes leakage over the surface of the insulators.
This leakage, however, is not prohibitive so long as the conductor
rails are not under water. If on account of poor drainage the conductor
rails become submerged, the leakage becomes so great that it is
impossible to operate the road.

[Illustration: Fig. 74. Contact Plow.]

It will be noticed that the conduit system as illustrated here employs
two conductor rails—one for the positive side of the circuit and the
other for the negative. The track rails, therefore, are not used
as conductors, and one side of the circuit is not grounded as in
the ordinary trolley system, although the leakage to ground may be
considerable from one or both conductor rails.


                          TRACK CONSTRUCTION.

=Girder Rail.= A great variety of track rails are used in electric
railways. The most common at one time was the girder, a typical section
of which, with joint, is illustrated in Fig. 75. This is an outgrowth
of the old tram rail used on horse railways. It has a tram alongside
of the head, on which vehicles may be driven. Its chief advantage from
the standpoint of the railway company is that there is plenty of room
for dirt and snow to be pushed away by the flanges of the cars. If the
company maintains the paving, it may be to its advantage to have teams
use the steel track rather than the paving, although this advantage in
maintenance is probably more than compensated for by the delay of cars
through the regular use of the track by teams.

[Illustration: Fig. 75. Girder Rail.]

=Trilby Groove Rail.= A modification of the girder rail, known as the
_Trilby_, and sometimes as the _grooved girder_, is shown in Fig. 76.
A rail similar to this is used in several large cities of the United
States. It has a groove of such a shape that the flanges of the car
wheels will force snow and dirt out of it instead of packing it into
the bottom of the groove, as in the case of the regular European
narrow-grooved rail. A narrow-grooved rail in which the grooves
correspond closely to the shape of the car-wheel flanges is sure to
make trouble in localities where there is snow and ice, as the grooves
become packed and derail the cars.

[Illustration: Fig. 76. Grooved Rail.]

=Shanghai T-Rail.= In some systems a T-rail is used. Where the T-rail
is to be used with paving, the popular form is the Shanghai T, shown
in Fig. 77. This rail is high enough to permit the use of high paving
blocks around it.

[Illustration: Fig. 77. Shanghai T-Rail and Joint.]

=Common T-Rail.= The T-rail used by steam railroads is known as the A.
S. C. E. standard T-rail, because it follows the standard dimensions
recommended for T-rails by the American Society of Civil Engineers.
A standard 65-pound T-rail of this kind is shown in Fig. 78. Other
weights of this rail have the same relative proportions. Such a rail
is used for interurban roads, and for suburban lines in streets where
there is no block paving. The high rails are used to facilitate paving
with high paving blocks.

[Illustration: Fig. 78. Standard A. S. C. E. Rail and One Joint Plate.]

=Track Support.= The greater portion of track is laid on wooden ties.
These ties, in the most substantial wooden tie construction, are 6
inches by 8 inches in section, and 8 feet long. They are spaced two
feet between centers. Sometimes smaller ties, spaced farther apart,
are used in cheaper forms of construction; but the foregoing figures
are those of the best construction known in American railway practice.
In paved streets, ties are usually employed, although sometimes what
is known as “concrete stringer” construction is used instead of ties
to support the rails. A strip of concrete about 12 inches deep is
laid under each rail, and the rails are held to gauge by ties or tie
rods placed at frequent intervals. Sometimes the concrete is made
a continuous bed under the entire track. In most large cities the
concrete foundation is used under all paving; and consequently, when
concrete is used instead of ties to support the rails, this concrete is
simply a continuation of the paving foundation. Where ties are used,
they are laid sometimes in gravel, crushed stone, or sand, although
frequently, in the largest cities, they are embedded in concrete.
Sometimes this concrete is extended under the ties, and sometimes it is
simply put around the ties.

=Ballast.= A ballast of gravel, broken stone, cinders, or other
material which is self draining and which will pack to form a solid bed
under the ties, should be used to get the best results under all forms
of tie construction, whether in paved streets or on a private right
of way, as on an interurban road. Of course, if concrete is placed
under the ties, the gravel or rock ballast is not necessary. If ties
are placed directly in soft earth, which forms mud when wet, they will
work up and down under the weight of passing trains, and an insecure
foundation for the track will be the result. =Joints.= The matter of
securing a proper joint for fastening together the ends of rails so
as to make a smooth riding track without appreciable jar or jolt when
the wheels pass a joint, has been given much study by electric railway
engineers. A section through an ordinary bolted angle-bar joint is
shown in Fig. 75. This joint is formed by bolting a couple of bars, one
on each side of the rails. The edges of these bars are made accurately
to such an angle that they will wedge in between the head and base of
the rail as the bolts are tightened; hence the name _angle bars_. This
is the form of joint generally used on steam railroads and on electric
roads in exposed track, or in track where the joints are easily
accessible, as in dirt streets. In paved streets, the undesirability
of tearing up the pavement frequently to tighten the bolts on such
joints, has led to the invention of several other types, which will be
described later. Nevertheless very good results have been obtained in
recent years with bolted joints laid in paved streets where care has
been given to details in laying the track, and where the joints have
been tightened several times before the paving is finally laid around
them.

=Welded Joints.= Several forms of welded joints are in use. All these
welded joints fasten the ends of the rails together so that the rail
is practically continuous—just as if there were no joints—so far as
the running surface of the rail is concerned. It was thought at one
time that a continuous rail would be an impossibility because of the
contraction and expansion of the rail under heat and cold, which, it
was thought, would tend to pull the rails apart in cold weather and to
cause them to bend and buckle out of line in hot weather. Experience
has conclusively shown, however, that contraction and expansion are not
to be feared when the track is laid in a street where it is covered
with paving material or dirt. The paving tends to hold the track in
line, and to protect it from extremes of heat and cold. The reason
that contraction and expansion do not work havoc on track with welded
joints, is probably that the rails have enough elasticity to provide
for the contraction and expansion without breaking.

It is found that the best results are secured by welding rail joints
during cool weather, so that the effect of contraction in the coldest
weather will be minimum. In this case, of course, there will be
considerable expansion of the track in the hottest weather, but this
does not cause serious bending of the rails; whereas occasionally, if
the track is welded in very hot weather, the contraction in winter will
cause the joint to break.

[Illustration: PORTABLE CUPOLA FOR CAST-WELDING JOINTS OF STREET CAR
RAILS.]

=Cast-Welded Joints.= The process of cast-welding joints consists in
pouring very hot cast iron into a mould placed around the ends of the
rails. These moulds are of iron; and to prevent their sticking to
the joint when it is cast, they are painted inside with a mixture of
linseed oil and graphite. Iron is usually poured so hot that, before it
cools, the base of the rail in the center of the molten joint becomes
partially melted, thus causing a true union of the steel rail and
cast-iron joint. This makes the joint solid mechanically and a good
electrical conductor. To supply melted cast iron during the process of
cast-welding joints on the street, a small portable cupola on wheels is
employed. Fig. 79 gives an idea of the process of making cast-welded
joints.

[Illustration: Fig. 79. Process of Cast-Welding Joint.]

=Electrically Welded Joints.= An electrically welded joint is made
by welding steel blocks to the rail ends. A steel block is placed on
each side of the joint, and current of very large volume is passed
through from one block to the other. This current is so large that
the electrical resistance between the rail and steel block causes
that point to become molten. Current is then shut off, and the joint
allowed to cool. There is in this case a true weld between the steel
blocks and the rails and joint. An electric welding outfit being
expensive to maintain and operate, this process is used only where a
large amount of welding can be done at once. Current is taken from the
trolley wire. A rotary converter set takes 500-volt direct current
from the trolley wire, and converts it into alternating current. This
alternating current is taken to a static transformer which reduces
the voltage and gives a current of great quantity at low voltage, the
latter current being passed through the blocks and rails in the welding
process. A massive pair of clamps is used to hold the blocks against
the rails, and to conduct the current to and from the joint while it is
being welded. These clamps are water-cooled by having water circulated
through them so that they will not become overheated at the point of
contact with the steel blocks.

=Thermit Welding.= A process of welding rail joints which was developed
after the cast-welding and electric-welding processes, is known as the
_Goldschmidt process_, which makes use of a material called “thermit”
for supplying heat to make the weld. A mould is placed around the joint
and the thermit is put in this mould and ignited. The heat produced by
the thermit is so intense as to reduce the iron in the thermit mixture
and make a welded joint. The thermit consists of a mixture of finely
powdered aluminum and iron oxide. When this is ignited, the aluminum
oxidizes, that is, absorbs oxygen so rapidly that an intense heat is
the result. In the process of oxidation, the aluminum takes the oxygen
from the oxide of iron, leaving molten metallic iron, which metallic
iron makes the weld by union with the molten rail ends. This process
has the advantage over other welding processes, of not requiring
an elaborate apparatus and a large crew of men to operate it; and
consequently it can be used where but a few joints are to be welded.

[Illustration: Fig. 80. Channel Pin Bond.]

=Bonding and Return Circuits.= When the track rails are used as the
conductors, as is usually the case, it is necessary to see that the
electrical conductivity of the rail joints does not offer too high a
resistance to the passage of the current. For this reason, when bolted
or angle-bar joints are used, the rails are bonded together by means
of copper bonds. It was soon found after electric roads were in use a
short time, that unless the rail ends were so bonded, the resistance
of the joints was so great as to cause great loss of power in the
track. First, small iron bonds were used; but these bonds were so
insufficient that large copper-wire bonds soon began to be used; and
at the present time, on large roads, bonds of heavy copper cable are
common. The resistance of a steel rail, such as used in city streets,
is about eleven times that of copper. In order to secure as great
carrying capacity at the rail joint as is afforded by the unbroken
rail, it is therefore necessary to install bonds having a total
cross-section ¹⁄₁₁ that of the rail. Where welded joints are used,
bonding is unnecessary, except at crossings and switches where bolted
joints are employed. Where track is welded, however, cross bonds should
be put in at frequent intervals from one rail to another, and, if the
track is double, from one track to the other, so that if one of the
track rails breaks at a joint there will be a path around the break for
the current.

[Illustration: Fig. 81. Chicago Rail Bond.]

[Illustration: Fig. 82. Rail Bond.]

A great many schemes have been devised to insure good contact between
the copper bond and the rail, as the terminal is the weak point in any
bond. One of the earliest and most efficient of small bonds was made
by the use of channel pins, Fig. 80. This bond consisted of a piece
of copper wire having its ends placed in the holes in the rail ends.
Alongside this wire, a channel pin was driven in. The objection to the
channel pin was the small area of contact between the copper bond and
rail.

Next after the channel pin came the Chicago type of bond, Fig. 81,
which is a piece of heavy copper wire with thimbles forged on the
ends. These thimbles were placed in accurately fitted holes in the
rail ends, and a wedge-shaped steel pin was driven into the thimbles
to expand them tightly into the hole in the rail. Several other bonds
using modifications of this principle are in use.

A type of bond in very common use consists of solid copper rivet-shaped
terminals, Fig. 82. Between these terminals is a piece of flexible
stranded copper cable, made flat to go under the angle bars. In one
type the terminal lugs are cast around the ends of the cables, and in
another type the cables are forged at their ends into solid rivet-like
terminals. These terminal rivets were first applied as any other
rivets, with the use of a riveting hammer. Because of the difficulty of
thoroughly expanding such large rivets into the holes made for them in
the rails, it has become customary to compress these rivets either with
a screw press or a portable hydraulic press, which brings such great
pressure to bear on the opposite ends of the rivet that it is forced
to expand itself so as to fill the hole in the rail completely. This
expansion is made possible by the ductile character of the copper. This
great ductility characteristic of copper, however, has been the source
of one of the difficulties in connection with rail bonding, because the
soft copper terminal has a tendency to work loose in the hole made for
it in the rail. It is practically impossible to maintain good bonding
where the rail joints are so loose as to allow considerable motion
between the rail ends.

Several types of bonds have been introduced, in which the contact
between the rail and bond is made by an extra piece or thimble.

Another method of expanding bond terminals into the holes made to
receive them, is that employed in the General Electric Company’s
bond. In it a soft pin in the center of the terminal is expanded by
compression of the terminal so that it forces the copper surrounding
it outward. The copper terminal, in expanding to fill the hole, is
therefore backed by the steel center pin.

All types of bonds must be installed with great care if they are to be
efficient. Unless the bond terminal thoroughly fills the hole and is
tightly expanded into it, moisture will creep into the space between
the copper and the iron, and the copper will become coated with a
non-conducting scale which destroys the conductivity of the contact.
The _plastic_ rail bond, so called because it depends for the contact
between the rail and the bond upon a plastic, putty-like alloy of
mercury and some other metal, is applied in a number of different ways.
One form consists of a strip of copper held by a spring against the
rail ends under the fish-plate. The rail ends at the point of contact
with this strip of copper are amalgamated and made bright by the use
of a mercury compound similar to the plastic alloy. These points of
contact are then daubed with plastic alloy, and the copper bond plate
applied. It is not necessary, with any form of plastic bond, that the
mechanical contact be unyielding, as the amalgamated surfaces with the
aid of the plastic alloy between them, maintain a good conductivity
in spite of any slight motion. The plastic alloy can be applied in a
number of other ways, one of which is to drill a hole forming a small
cup in the rail base in adjacent rail ends, fill these cups with
plastic alloy, and bridge the space between them with a short copper
bond having its ends projecting down into the cups.

=Resistance of the Track.= The resistance of the return circuit is
usually much higher than it should be owing to the bad contact of the
bonds. The resistance of rails varies greatly with the proportions of
carbon, manganese and phosphorus. The following figures, however, may
be regarded as the average.

Weight per Yard.   Resistance Single Rail per Mile.
       50                     .0253 ohms
       60                     .0211  ”
       70                     .0180  ”
       80                     .0159  ”
       90                     .014   ”

A track laid with continuous rails as in the case of welded joints,
would have one-half the resistance given since there are two rails to
be considered.

Tests of new unbonded track constructed with rails 60 feet long show
that the joints cause an increase of .25 ohms or more per mile.

Several roads in testing bonds consider a bond good when the bond and
one foot of the rail over it have a resistance equal to five feet of
the solid rail. =Supplementary Return Feeders.= On some large roads
it is necessary to run additional return feeders from the power house
to various points on the system, to supplement the conductivity of
the rails. Otherwise the track rails near the power house would have
to carry all the current, and in some cases there are not enough such
lines of track passing the power house to do this properly. Sometimes
these feeders are laid underground in troughs; sometimes they are laid
bare in the ground, and sometimes on overhead pole lines. When laid in
the ground, frequently old rails are used instead of copper or aluminum
cables. The old rails are, of course, thoroughly bonded together with
bonds giving a conductivity nearly equal to that of the unbroken rail.


                            FEEDER SYSTEMS.

[Illustration: Fig. 83.]

There are two general schemes of direct current feeding in common use.
One of these is shown in Fig. 83. Here the trolley wire is continuous
and is fed into at different points. The long feeders supplying the
more distant portion of the road are larger than those supplying the
trolley near by, so as to maintain as nearly as is feasible the same
potential the entire length of the line. With such a system of feeding,
in order to maintain absolutely the same voltage at all points, it
would be necessary to have just one trolley feeder and that feeding
into the extreme end of the line farthest from the power station and
further to make the resistance per 1,000 ft. of trolley and feeder the
same as the resistance per 1,000 ft. of the track return circuit. The
plan shown in Fig. 83 evidently does not fully carry out these rather
impracticable requirements but is in the nature of a compromise, giving
a higher potential near the power station than at distant points but
nevertheless much more even potential than if the heaviest feeders
were feeding into the trolley near the power house.

The other plan, shown in Fig. 84, divides the trolley wire into
sections and feeds each section through a separate feeder which is
calculated of such size as to maintain the same voltage on all the
sections with the ordinary load.

In calculating a feeder system a certain probable load is assumed at
certain points along the line. This load will manifestly depend on the
size and number of cars in operation, grades and many local conditions.

[Illustration: Fig. 84.

  Drop in rail
    section          3.1 Volts      2.1 Volts       1.05 Volts
  Total drop in
    rail             3.1   ”         5.2  ”         6.25   ”
  Drop in trolley   20.5   ”        20.5  ”        20.5    ”
  Drop in feeder    36.4   ”        34.3  ”        33.25   ”
  Resistance
    feeder            .728 Ohms       .686 Ohms      .665 Ohms
  Feet per ohm      7253           23000          39700
  Size of wire     No. 1         250,000 C. M.  420,000 C. M.]

The following example will show the method pursued. The figures
resulting from the calculations are placed immediately below the
sections to which they refer in Fig. 84. The rails are assumed to be 70
pound to the yard. These have a resistance of about .018 ohms per mile.
Adding one-sixth for additional resistance of bonds gives .021 and
since the track is composed of two rails the resistance of the track
will be one-half of this or .0105 ohms per mile.

The maximum drop in any section occurs when the car is farthest from
the power house. Each car is assumed to take 50 amperes and the feeders
are to be so designed as to allow a 10 per cent or 60 volts drop.

The current in the two miles of track nearest the power house is 150
amperes, in the next section 100 amperes, and in the last section 50
amperes. The drop in each section is as shown. The drop in the trolley
which is 00 wire is, in each section, 20.5 volts. Subtracting from 60
volts the drop in the return circuit and trolley, gives the allowable
drop in the feeder.

The resistance of each feeder can be calculated, since the current in
each one is 50 amperes. The first feeder is one mile long, the second
3 miles and the third 5 miles, and with these figures the feet per ohm
can be computed. The size of wire may be obtained by reference to a
table of copper wire resistances.


                 BLOCK SIGNALS FOR ELECTRIC RAILWAYS.

The simplest block signal used by electric roads is a hand-operated one
constructed on the principle shown in the diagram Fig. 85. A double
throw switch is placed at each terminal of the section of track that is
to be protected.

[Illustration: Fig. 85.]

The switches have no central position, the knife blade always making
contact with one or the other of the terminals shown. If the lamps are
lighted, throwing either one of the switches will put them out. If they
are not burning, they will be lighted by throwing either one of the
switches.

A motorman on reaching a section of track finding the lamps not burning
throws the switch. Lamps now burn in each switch box and show that the
section is in use. On arriving at the other terminal of the block the
switch is thrown, extinguishing the lights and showing that the block
is clear.

Automatic signal systems have been devised on the same principle, in
which magnets, operated by contacts made by the passage of the trolley
wheel, cause the lamps to be lighted and extinguished automatically.


                             ELECTROLYSIS.

Much has been said about the possibilities of electrolysis of
underground metal by the action of the return current of electric
railways, when such railways are operated with grounded circuits, as
they usually are. If electric current is passed through a liquid from
one metal electrode to another, electrolysis will take place; that is,
metal will be deposited on the negative pole, and the positive pole or
electrode will be dissolved by becoming oxidized from the action of the
oxygen collecting at that pole.

[Illustration: Fig. 86. Showing Electrolytic Action.]

In an electric-railway return circuit, there is necessarily a
difference of potential between the rails at outlying parts of the
system and the rails and other buried pieces of metal located near
the power house. Just what this total difference of potential is,
depends on the loss of voltage in the return circuit. Thus, suppose
there is 25 volts drop in the return circuit between a certain point
on the system and the power station. There is, therefore, a pressure
of 25 volts tending to force the current through the moist earth
from the rails at distant portions of the line, to the rails, water
pipes, and other connected metallic structures located in the earth
near the power station. The amount of current that will thus flow to
earth in preference to remaining in the rails, depends on the relative
resistance of the rails, the earth, and the other paths offered to the
current to return to the power house.

To take a very simple case, let us suppose a single-track road, Fig.
86, with a power house at one end, and a parallel line of water pipe
on the same street passing the power house. If the positive terminals
of the generators are connected to the trolley wire, the current
passes, as indicated by the arrows, out over the trolley wire through
the cars and to the rails. When it has reached the rails it has the
choice of two paths back to the power house. One is through the rails
and bonding; the other is through the moist earth to the line of water
pipe and back to the power house, leaving the pipe for the rails, at
the power house. Should the bonding of the rails be very defective,
considerable current might pass through the earth to the water pipe.

Remembering now the principles of electrolysis, we see that the
oxidizing action of this flow of current from the rails to the water
pipes at the distant portion of the road will tend to destroy the
rails, but will not harm the water pipe at that point, as it will tend
to deposit metal upon it. When, however, the current arrives at the
power house, it must in some way leave this water pipe to get back to
the rails, and so to the negative terminals of the generators.

Here we see that there is a chance for electrolysis of the water pipe,
because at this point the water pipe forms the positive electrode,
which is the one likely to be oxidized and destroyed. This very
simple case is taken merely for illustration. In actual practice the
conditions are never so simple as this, for there are various pipes
located in the ground running in various directions, which complicate
the case very much; but we can see from this simple example that the
principal place electrolysis of water pipe is to be feared is at points
where a large volume of current is leaving the water pipe to take to
some other conductor.

As an indication of how much current is likely to be leaving the
water pipes at various points, it is customary to measure the voltage
between the water pipes and the electric railway track and rails.
When this voltage is high, it does not necessarily mean that a large
volume of current is leaving the water pipes at the point where these
pipes are several volts positive with reference to the rails; but such
voltage readings indicate that, if there is a path of sufficiently
low resistance through the earth, and if the moisture in the earth is
sufficiently impregnated with salts or acids, there will be trouble
from an electrolytic action due to a large flow of current. There is
obviously no method of measuring exactly the amount of current leaving
a water pipe at any given point, since the pipe is buried in the earth.
Voltmeter readings between pipes and rails simply serve to give an
indication as to where there is likely to be trouble from electrolysis.
The danger to underground pipes and other metallic structures from
electrolysis has been much overestimated by some people, as the trouble
can be overcome by proper care and attention to the return circuit.
Trouble from electrolysis, however, is sure to occur unless such care
is given.

=Prevention of Electrolysis.= Remedies for electrolysis may be
classified under two heads—general and specific. The general remedy
is obviously to make the resistance of the circuit through the rails
and supplementary return feeders so low that there will be but little
tendency for the current to seek other conductors, such as water and
gas pipes and the lead covering of underground cables. This remedy
consists in heavy bonding, in ample connections, around switches and
special work where the bonding is especially liable to injury, and
in additional return conductors at points near the power house to
supplement the conductivity of the rails.

It is important that all rail bonds be tested at intervals of six
months to one year in order that defective bonds may be located and
renewed, as a few defective bonds can greatly lower the efficiency of
an otherwise low-resistance circuit.

The specific remedy for electrolysis which may be applied to reduce
electrolytic action at certain specific points, consists in connecting
the water pipe at the point where electrolysis is taking place, with
the rail or other conductor to which the current is flowing. Thus, for
example, if it is found that a large amount of current is leaving a
water pipe and flowing to the rails or to the negative return feeders
at the power house, the electrolytic action at this point can obviously
be stopped by connecting the water pipe with the rails by means of
a low-resistance copper wire or cable, thereby short-circuiting the
points between which electrolytic action is taking place. There are
certain cases in which it is advisable to adopt such a specific remedy.
It should be remembered, however, that a low-resistance connection
of this kind, while it reduces electrolysis at points near the power
house, is an added inducement to the current to take to the water pipes
at points distant from the power house, because of the decrease in
resistance of the water-pipe path to the power house resulting from the
introduction of the connection between the water pipe and the negative
return feeder at the power house. With the water pipes connected to the
return feeders in the vicinity of the power house, the current which
flows from the rails to the water pipes at points distant from the
power house will obviously cause electrolysis of the rails but not of
the water pipes, since the current is passing from the earth to the
pipe, and the pipe is negative to the earth. In this case the principal
danger is that the high resistance of the joints between the lengths
of water pipe will cause current to flow through the earth around each
joint, as indicated on some of the joints, Fig. 86, and will cause
electrolytic action at each joint. It is evident, however, that the
conditions of the track circuit and bonding must be very bad if current
would flow over a line of water pipe, with its high-resistance joints,
in sufficient volume to cause electrolysis, in preference to the
rail-return circuit, especially since ordinarily the resistance offered
to the flow of current over the water pipes back to the power house
must include the resistance of the earth between the tracks and water
pipes.

It is usually considered inadvisable to connect tracks and water pipes
at points distant from the power house, because of the danger of
electrolysis at water-pipe joints, as just explained.

Methods of testing rail bonds in the track will be explained under the
head of “Tests.”




                     POWER SUPPLY AND DISTRIBUTION.


=Direct-Current Feeding.= As already explained, the majority of
electric railways are operated on a 500-volt constant-potential
direct-current system with a ground return. A constant potential of 450
to 550 volts is maintained between the trolley wire and track. Where
the trolley wire is not sufficient, additional feeders are run from the
power house and connected to the trolley wire, the number of feeders
depending on the distance from the power house and the traffic.

=Booster Feeding.= Boosters are sometimes used on long feeder lines
where there is a heavy load only a small portion of the time. These
boosters are direct-current dynamos that are connected in series with
the feeder upon which the voltage is to be raised above the regular
power-house voltage. The booster may be driven either by a small
steam engine or by an electric motor. The simplest form of booster
is a series-wound dynamo. A booster armature must, of course, be of
sufficient current capacity to pass all the current that will be
required on its feeder. The voltage yielded by this dynamo, plus the
power-station voltage, is the voltage of the boosted feeder as it
leaves the power house. Supposing that a series-wound booster will give
125 volts at full load; it is obvious that being series-wound it will
give no voltage at no load. The voltage will increase approximately
as the load on the feeder increases; and since the drop in voltage on
the feeder for which the booster is to compensate also varies with the
load, the action of the booster is simply to add sufficient voltage to
its feeder at any instant to compensate for the line loss upon that
feeder and to maintain approximately constant potential at the far end
of the feeder. Boosters raising the power-station voltage of a feeder
more than 250 volts above the normal power-station voltage, are not
common, though cases are on record where a feeder has been boosted as
high as 1,100 volts above the power-station voltage. Since all the
power used in driving a booster is wasted in line loss, this method of
feeding is not economical; but where used only a few days out of the
year it is sometimes to be preferred to a heavy investment in feeders.
The investment in feeders might involve more interest charges than the
cost of power wasted in booster feeding would amount to.

=Alternating-Current Transmission.= High-tension alternating-current
transmission _to_ substations, with direct-current distribution _from_
substations, is extensively used on long interurban roads, and on
large city street-railway systems where power is to be distributed
over a wide area. In such cases the power house is equipped with
alternating-current dynamos supplying high-tension three-phase
alternating current to high-tension transmission lines or feeders.
These high-tension feeders are taken to substations located at
various points on the road, where the voltage is reduced by step-down
transformers; and these transformers supply current to operate rotary
converters, which convert from alternating to direct current for use on
the trolley.

The advantage of this system of high-tension distribution is that,
owing to the high transmission voltage, there is but a small loss
in the high-tension lines, which lines can be made very small, and
will thus involve but little copper investment. The substations can
be located at frequent intervals, so that the distance the 500-volt
direct-current must be conducted to supply the cars is not great.
Current from one power house can thus be distributed over a very
large system in cases where, if the 500-volt direct-current system of
distribution were used, the cost of feeders for distributing such a
low-voltage current would be prohibitive. Were the alternating-current
high-tension scheme of distribution not used, it would be necessary
to have a number of small power houses at various points on the
system instead of one large power house. The cost of operation of
several small power plants per kilowatt output, is likely to be
much greater than that of one large power plant. The first cost of
the alternating-current distributing system, including power house
and substations, is likely to be considerably higher than would
be the cost of a number of small power houses; but in cases where
alternating-current distribution has been installed, it has been
figured that the cost of operation of the central power house with
alternating-current distribution would be sufficiently low as compared
with several small ones to pay more than the interest on this extra
investment.

[Illustration: Fig. 87. Diagram of Distributing System.]

=A System of Distribution for an Interurban Railway.= The typical
features of a high tension system of distribution for an extensive
interurban railway system are shown in Fig. 87, which represents the
electrical transmission and distribution system of the Indiana Union
Traction Company. The central power station at Anderson feeds into
thirteen rotary converter substations from 7 to 65 miles distant from
the power house. The substations east of Indianapolis are fed at 16,000
volts and are placed about 11 miles apart. The substations due north of
Indianapolis are located at intervals of about 17 miles and are fed at
30,000 volts.

The power station at Anderson has a total capacity of 5,000 K. W. The
substations vary in capacity from 250 to 1,500 K. W.

=Efficiency of Transmission Systems.= The average efficiency of a high
tension transmission system for a certain interurban electric railway
system are given below. Current was generated at 380 volts. The step-up
transformers raised it to a potential of 16,000 volts at which pressure
it was transmitted to eight substations at distances from 10 to 40
miles from the power station. It was then stepped down to 380 volts and
converted to direct current by a rotary converter. The tests extended
over a period of three days. The efficiency of the step-up transformers
was 95 per cent; of the high tension line 92.9 per cent; of the
step-down transformers 95 per cent; and of the rotary converters 88 per
cent; giving a total efficiency of the transmission system of 73.5 per
cent.

=Power House Location.= A power house is usually located where coal
and water supply can be cheaply obtained. For this reason it is placed
either on some line of railroad or where coal can be taken to it over
the electric railway.

As it is always desirable to operate the engines in connection with
condensers, on account of the saving in fuel, which is approximately
20 per cent with condensers, power stations are located, when
possible, near rivers and ponds from which a large supply of cold
water for condensation of exhaust steam can be obtained. Where no
such natural water supply is available, it has become customary to
provide means for artificially cooling a sufficiently large supply of
water for condensation. One method is to erect a number of towers, so
constructed that the water when pumped to the top will fall through a
structure that breaks the water up into fine spray as it falls, thus
allowing it to cool by evaporation so that it can be used again for the
condensers when it arrives at the bottom of the tower. Where more room
is available, ponds are sometimes excavated near the power house, and
the water is made to flow back and forth through a series of troughs
located above the pond, and it is thus cooled.

Where a power station is of the direct-current type, operating at
500 to 600 volts, it is desirable to have it as near the center of
electrical distribution as possible, in order to keep down the amount
of investment in the feed wire; but it is more important to have it
located near a cheap coal and water supply than exactly at the center
of distribution.

It is also desirable to have the station located where there is room
for coal storage, on account of the chances for interruption of the
coal supply by strikes, railroad blockades, and other causes beyond the
company’s control. The continuity of the coal supply is also another
argument against placing the station where dependence must be placed
upon wagons or inadequate railroad facilities.

Coal handling, after the coal has reached the station, is done by hand
in the smaller power stations; but in larger power stations it has come
to be the general practice to do as much of the handling as possible by
means of automatic coal conveyors. The most elaborate power stations
have means for dumping coal from cars into hoppers, from which it is
conveyed by an endless chain provided with buckets, called a _coal
conveyor_, to storage bins. Coal conveyors also take the coal from the
storage bins, and deposit it in the hoppers of mechanical stokers in
front of the boilers. Ashes are conveyed from under the boilers by the
same kind of conveyors, and are dumped into hoppers, whence they are
drawn into cars or wagons to be hauled away. The coal, having been
deposited in hoppers at the boiler front, is automatically fed into the
furnaces by automatic stokers. One type of automatic stoker in common
use is of the chain-grate or link-belt type, which is constructed like
an endless sprocket chain, with links composed of heavy cast-iron
blocks that serve as grate bars. This link belt or chain is kept in
constant, slow motion by a small stoker engine or motor which operates
all the stokers of a line of boilers. The coal is fed from the hopper
on to the chain grate, and the chain is slowly moved under the boilers.
As the coal on that part of the grate under the boilers is on fire, the
fresh coal as it enters the furnaces is soon ignited. The grate is run
at such a rate, and the thickness of the coal is so adjusted, that the
coal is burned to an ash by the time it has traveled to the back of
the furnace. There the grate turns down over a sprocket wheel, and the
ashes are dumped into the ash pit as the grate revolves.

The boilers in most common use in large American electric-railway power
houses are of the water-tube type, in which water is contained inside
of a bank of tubes, the ends of these tubes being connected to drums or
headers. The horizontal return-tubular type of boiler is used in many
of the smaller power stations, and vertical boilers are also in use.

The engines in the larger and more economical stations are generally
of the Corliss compound-condensing type, running at speeds of from
60 to 120 revolutions per minute, according to the size of the unit.
The smaller the unit, the higher the speed. In the smaller and older
stations, simple Corliss engines belted to generators are frequently
found, and high-speed engines also are used. It is the almost universal
custom now, to place the generator directly on the engine shaft, making
a direct-connected unit.

Steam turbines, in which the steam acts in jets against the blades of
a turbine wheel, are beginning to come into use at the present time.
These turbines rotate at very high speed, the largest and slowest
speed-units running 600 r.p.m., and others at higher rates. As the
output of any generator varies directly according to its speed, a
very much smaller generator can be used when coupled to a high-speed
steam turbine, to obtain a given output, than if the generator must be
coupled to a Corliss steam engine which revolves at very low speed.
The economy of the steam turbine at full load is about that of a
compound-condensing Corliss engine, but is better on light loads than
the engine. The turbine requires less building space and a much less
expensive foundation.

[Illustration: Fig. 88. Plan of Power House.]

Railway generators or dynamos for direct current are usually built
with compound-wound fields, so that, as the load increases, they will
automatically raise the voltage at their terminals to compensate for
the drop in the feeders and to maintain a constant potential at the
cars. Thus, if the line loss on a system is 10 per cent, or 50 volts
at full load, the generators will be provided with shunt fields of
sufficient strength to give 500 volts at no load, and with series
field coils which will add to the field strength enough to give 550
volts at full load. The amount of “compounding”—which is the term
applied to this method of increasing voltage—may be any amount within
reasonable limits. The pressure maintained at different companies’
electric-railway power houses varies, but is usually between 500 and
600 volts.

=Alternating-Current Generators.= Alternating-current generators used
for generating alternating current to be distributed at high tension,
are generally constructed to give a three-phase current at 25 cycles
per second. The voltage of these alternating-current generators
is sometimes the voltage at which the power is to be transmitted,
if the distances are not too great. A number of stations have
alternating-current generators giving 6,600 volts at their terminals,
which is a voltage well adapted to high-tension distribution within
the limits of a large city. However, generators giving 11,000 volts
at their terminals are now becoming common. For higher voltages than
this, it is considered necessary to use step-up transformers, in order
to raise the voltage to the proper pressure for transmission over long
distances. In such cases there is no object in having a high generator
voltage. At such stations the voltage of the generators adopted may
be anything desired, and it varies according to the ideas of the
constructing engineer. Voltages of 400, 1,000, and 2,300 are among
those in most common use.

=Double-Current Generators.= Double-current generators are sometimes
used, which generators will give direct current at a commutator at one
end of the armature for use on a 500-volt direct-current distribution
system supplying the trolley direct. The other end of the armature
has collector rings from which the three-phase alternating current is
obtained, which can be taken to step-up transformers and raised to a
sufficient pressure, for high-tension transmission to substations at
distant parts of the road. The same generator can therefore be used
on both the direct-current and the high-tension alternating-current
distribution.

=General Plan of Power Stations.= The general plan of an
electric-railway power station is usually such that the building can
be extended and more boilers, engines and generators added without
disturbing the symmetrical design of the station. Thus, the boilers
and engines are placed as in Fig. 88, in parallel rows, although
almost invariably in different rooms separated by a fire wall. By
adding to the row of engines and to the row of boilers, the station
capacity can be increased. Other arrangements are sometimes required
by circumstances; but this is the most common arrangement and gives
the greatest capacity with the minimum amount of steam piping. Large
stations are sometimes constructed with a boiler room of several floors
and with boilers on each floor, in order to save ground space and bring
the boilers near to the large engine units so that there will not be an
excessive amount of steam piping.

[Illustration: Fig. 89_a_. G. E. Circuit Breaker.]

=Switchboards.= Direct-current stations have switchboards, which may
be considered under two general classes—_generator boards_ and _feeder
boards_. Each board consists of panels.

=Generator D. C. Panels.= The generator panel usually contains an
automatic circuit breaker which will open the main circuit to the
generator in case of an overload due to a short circuit. These circuit
breakers consist of a coil in the main circuit, which acts upon a
solenoid. When the current in the coil exceeds a certain amount, the
solenoid is drawn in, and a trigger is tripped which allows the circuit
breaker to fly open under the pressure of a spring. In the General
Electric circuit breaker, the main contact is made by heavy copper
jaws, but the last breaking of the contact is made between points
which are under the influence of a magnetic field. This magnetic field
blows out the heavy arc that would otherwise be established. On the
I-T-E, the Westinghouse and most other types of circuit breaker, the
breaking of the contact takes place between carbon points, which are
not so readily destroyed by an arc as are copper contacts, and which
are more cheaply renewed. The main contact through the circuit breaker,
in either type, is made between copper jaws of sufficient cross-section
for carrying the current without heating. These jaws open before the
current is finally broken by the smaller contacts which take the final
arc.

In Fig. 89_a_ is seen a General Electric circuit breaker with the
magnetic blow-out coils at the top, the solenoid at the left, and the
handle for resetting the circuit breaker at the bottom. The small
handle for tripping the circuit breaker, when it is desired to open the
circuit by hand, is shown just under the solenoid.

An I-T-E circuit breaker is shown in Fig. 89_b_. This is of the type
previously mentioned, in which the break occurs between carbon contacts
and there is no magnetic blow-out.

[Illustration: Fig. 89_b_. I-T-E Circuit Breaker.]

In addition to the circuit breaker there is usually an ammeter, to
indicate the current passing from the generator; and a rheostat handle,
geared to a rheostat back of the board, for cutting in and out more
or less resistance in the shunt field coils of the generator so as to
reduce or raise the voltage. There is a small switch for opening and
closing the circuit through the shunt field coils.

The main leads from the generator pass through two single-pole
quick-break knife switches. The most recent practice is to have the
switches on the switchboard in only the positive and negative leads
from the generator, leaving connection to the equalizer to be made by a
switch located on or near the generator. However, all three leads may
be taken to the switchboard, and a three-pole knife switch may be used
instead of the positive and negative switches spoken of.

In Fig. 90 is given a simple diagram of the general relative connection
of generators and feeders in a direct-current railway power station.
It is seen that the generators are connected in parallel across the
positive and negative bus bar. There is a third bus bar—called an
“equalizing bus”—which connects in parallel the series coils of all
the generator fields. The object of this equalizer is to prevent the
weakening of the series field of any one generator, so as to allow it
to take current and to act as a motor instead of as a generator.

=Starting Up a Generator.= Suppose that a new generator is to be
started up and connected to the bus bars in addition to others
already in operation. The engine of that generator is first brought
up to speed. The switch controlling the shunt field circuit is then
closed, causing current to flow through the shunt fields; and the
generator begins to “build up,” its voltage gradually rising until it
approximates that upon the bus bars. Before the generator is thrown
in parallel with the others by connecting it with the bus bars, it is
important that its voltage be nearly the same as that of the bus bars.
Otherwise, when connected to the bus bars, it might take more than its
share of the load; while, on the other hand, if its voltage were too
low, it might act as a motor, taking current from the bus bars. The
voltage of the bus bars in a railway station is constantly fluctuating,
owing to the varying load and to the fact that generators are often
compounded, as before mentioned, in order to compensate for the line
loss.

[Illustration: Fig. 90. Connection of Generators and Feeders.]

In order that the voltage of the generator to be thrown in shall vary
in accordance with the bus bar voltage, the next step in the operation
is to close the positive switch, assuming that the equalizer switch on
the generator has already been closed. This throws the series field
of the new generator in parallel with the series fields of the other
generators. The voltage of the new generator will therefore vary just
as the voltage on the bus bars; and, by adjusting the resistance of the
shunt field, this voltage can be adjusted so as to be the same as that
on the bus bars. The voltages on the bus bars and on the new generator
are measured usually by a large voltmeter on a bracket at the end of
the generator switchboard. By means of a voltmeter plug or of a push
button on the generator panel, the voltmeter can be connected either
to the bus bars or to the new generator. When the two voltages are the
same, the negative switch of the new generator can be closed, and it
will operate in parallel with the other generators, taking its share of
the load. If the attendant sees that any generator is not taking its
share, he can raise its voltage by cutting out some of the resistance
in series with its shunt field, and this makes that generator take more
load.

[Illustration: Fig. 91. Railway Switchboard.]

=Feeder Panel.= The feeder panel is simpler than the generator panel,
since it usually handles only the positive side of the circuit.
Frequently two feeders are run on a single panel side by side.
The feeder panel has an automatic circuit breaker, an ammeter for
indicating the current on that feeder, and a single-pole switch for
connecting the feeder to the bus bar. All generators feed into a common
set of bus bars; and the positive bus bar continues back of the feeder
panels so that all feeders can draw current from the bus bars. Fig.
91 shows a railway switchboard with 7 feeder panels at the right; 4
generator panels at the left; and, in the middle, a panel with an
ammeter and recording wattmeter for measuring total output.

In some stations two and even three sets of bus bars are used, as it
may be desired to operate different parts of the system at different
voltages or to feed a higher voltage to the longer lines than to those
near the station. In such a case double-throw switches are provided for
connecting feeders and generators to either set of bus bars.

=Alternating-Current Switchboards.= In an alternating-current station,
generator switchboards are radically different from those in a
direct-current station. Practice in alternating-current generator
switchboards has not yet been so fully standardized and is not so
uniform as in direct-current railway switchboards. There is always,
however, a three-pole main switch for opening and closing the main
three wires from the three-phase generator. Automatic circuit breakers
are usually provided, as well as indicating ammeters and wattmeters to
show the output.

Indicating wattmeters, recording the number of watt hours passing
through them, are frequently used both on alternating and
direct-current generator panels.

A station usually has what is called a “total load” panel, which has
a recording wattmeter measuring the total output of the station in
kilowatt hours. This panel also has an ammeter indicating the total
station load.

=High-Tension Oil Switches.= Alternating-current generators for high
voltages usually have oil switches to interrupt the main circuit, that
is, switches in which the contact is made and broken under oil. These
switches have been found very efficient in preventing the formation
of a destructive arc upon the opening of a high-voltage circuit, on
circuits up to 60,000 volts. Some of the larger oil switches are
operated by electric motors or solenoids. The machine-type oil switch
of the General Electric Company has the motive power for operating the
switches, stored up in a spring. The spring is wound up by a small
electric motor. This motor operates every time the switch is opened or
closed, and winds up the spring enough to compensate for the amount it
was unwound in operating the switch. Each circuit is broken under oil
in a long tube, and these tubes are mounted in individual cells, each
cell being separated from the next by a masonry wall so that there can
be no flashing across from one leg of the circuit to another in case
of any defect in the switch. All the high-tension wiring to and from
such switches, is taken either in lead-covered cables, or on bus bars
separated from each other by masonry walls to prevent the spread of
short circuits. These precautions are necessary because of the great
length of arc that may be established between adjacent high-tension
conductors.

Where alternating-current generators of low voltage are used in
connection with step-up transformers, one practice is to have the
switches for each generator directly in the generator leads, between
the generators and the step-up transformers, in the low-voltage circuit.

Another practice which has recently been introduced, is to consider
each generator with its step-up transformers as a unit and to connect
the generator permanently with its bank of transformers, and to
control this unit by a single three-pole machine-operated oil switch.
In this case there are no switchboard switches between generators and
transformers, and this simplifies the switchboard considerably. There
must be switches on the high-tension side of the transformers in any
event. The switchboard for rotary converters in the substations is, of
course, a combination of alternating and direct-current apparatus. The
direct-current ends of the rotary converters are treated almost exactly
like direct-current railway generators; and their switchboard panels
are similarly equipped, except that usually there is a rheostat that
can be connected in series with the armature whereby a rotary converter
can be brought up to speed from a state of rest by connecting it with
the direct-current bus bars of the substation.

The alternating-current end of the rotary converter is supplied
through switches in the alternating-current leads from the step-down
transformers. A rotary converter can be started from a state of rest
by connecting it to the alternating-current leads through the medium
of compensating coils which reduce the voltage. A very heavy current
is required to do this, as the motor thus starts as a very inefficient
induction motor with a very low power factor.

[Illustration: Fig. 92. Connection of Substations.]

There are usually but two direct-current feeder panels in a substation
of an interurban electric road. One of these feeders is to supply the
trolley or third rail extending in one direction from the substation,
and the other feeds that extending in the other direction from the
substation. The trolley or third rail has a section insulator directly
at the substation. When both feeders are connected to the bus bars,
it is evident that this section insulator is short-circuited through
the medium of the substation bus bars, every substation on the line
being connected in this way, as indicated in Fig. 92. It is seen that,
should a short circuit occur on any section, it would open the circuit
breakers at the substations at both ends, and that section would not
interfere with the balance of the road. At the same time, when the
road is in normal operation and there is an unusually heavy load
between any two substations, the other substations along the line can
help out those nearest to the load by feeding through the bus bars of
the nearest substation. The high-tension apparatus at a substation
consists usually of a bank of high-tension lightning arresters;
high-tension switches, for shutting off the high-tension current; and
step-down transformers, for reducing from the high transmission voltage
to the 370 volts commonly fed to the alternating-current end of railway
rotary converters.

=Storage Batteries in Stations.= Storage batteries are frequently
used both in substations and in direct-current power stations. They
may be connected directly across the line and allowed to “float,” as
it is termed; or they may be used in connection with storage-battery
boosters, which will cause the storage battery to take the fluctuations
in the load and to give a constant load on the rotary converters or
power station. The action of storage-battery boosters which cause the
storage battery to be charged automatically at light loads and to
discharge and assist the station at heavy loads, is explained in the
paper on “Storage Batteries.”


                     ALTERNATING-CURRENT SYSTEMS.

So far this paper has been devoted almost entirely to electric railway
systems employing 500-volt direct-current motors on the cars, since
this is the system almost universally employed on electric railways
at the present time. There are, however, several systems employing
alternating-current motors on cars, which have already been used
experimentally and to some extent commercially. Some of these give
promise of coming into extensive use.

=Three-Phase Motors.= On several roads in Europe three-phase induction
motors are employed. These induction motors are operated by three-phase
alternating current taken direct from the trolley wires. As three
conductors are necessary, two trolley wires are used, with the rails
as the third conductor. The two principal objections to the system are
the necessity of two trolley wires, and the fact that the induction
motor operates very much like a direct-current shunt motor in that it
is a constant-speed motor and not adapted to variable-speed work. The
power factor is low in starting; that is, a great volume of current
is taken, although, owing to the voltage and the current not being in
phase, the actual energy consumed is small. =Single-Phase Motors.= The
Westinghouse Electric & Manufacturing Company has brought out a railway
motor adapted to operate on single-phase alternating-current circuits.
This motor is very similar in construction to the ordinary series-wound
500-volt direct-current railway motor. It has, however, more field
poles than the ordinary direct-current motor; and the pole pieces are
laminated to avoid heating of the iron by eddy currents caused by the
influence of the alternating current. There are also other special
features in the design that reduce the sparking at the commutator,
which sparking was for several years the greatest obstacle to the use
of alternating-current motors of this kind. In the Westinghouse system
the current is taken from the trolley wire at high potential, and is
reduced by an auto-transformer on the car. This auto-transformer is
connected with an induction regulator so arranged that a low voltage
can be supplied to the motor in starting or for slow running, and
this voltage increased to increase the speed. There is thus no need
to reduce the trolley voltage by wasting part of it in a rheostat,
as is the case with direct-current motors; and the efficiency during
acceleration is, therefore, higher with this alternating system than
with the direct current. Several other single-phase railway motors
are also being worked out at the present time, including that of the
General Electric Company.

=Alternating-Current Motor Advantages.= There are two great advantages
secured by the use of an alternating-current railway motor. The first
is a reduction in investment and operating expenses by doing away
with substations containing rotary converters. Such substations are
necessary on long lines of railway operating with direct-current
motors. The second advantage is that, owing to the fact that a high
tension current can be used on the trolley wire and reduced by a
transformer on the car, the difficulties of collecting a large amount
of energy from a trolley wire are much reduced.

First, in regard to the substations, it will be seen that with the
alternating-current motor system, high-tension current can be conducted
from the power house to substations along the line which contain
nothing but static transformers. Since these transformers have no
revolving parts they do not require the constant attendance that a
rotary converter does. Furthermore, the investment in rotary converters
is entirely dispensed with, and this makes a considerable reduction in
the total cost of the distribution plant. With the alternating-current
system, current is fed direct to the trolley wire from the secondary
terminals of the transformers at the substations.

As regards the advantages of carrying a high voltage on the trolley
wire, it will readily be seen that, since the amount of power, or the
watts required by a car, is equal to the product of the voltage and
current, an increase in the voltage reduces the volume of current
necessary. By having high voltage on the trolley wire, even a large car
can be operated with a small volume of current, and this current can be
taken through an ordinary trolley wheel without difficulty. Where 500
volts is the pressure used on the trolley wire, there is considerable
flashing and burning of trolley wheel and wire when large cars and
locomotives are run, owing to the heavy current conducted; and this has
been one of the principal reasons for the adoption of the third rail
instead of the trolley on certain roads. Even with the third rail, the
volume of current that must be conducted to large electric locomotives
involves some difficulties in the way of heated contact shoes and
considerable loss of energy. The use of high voltage on the trolley
wire, with transformers on the car to reduce the voltage to a safe
pressure for use on the motors, overcomes many of the difficulties that
would otherwise be found in the use of electricity for heavy railroad
work.




                               OPERATION.


=Power Taken by Cars.= The amount of power required in the practical
operation of a car depends upon so many variable elements that many of
the calculations sometimes given for determining the power required
by a car are of little value. The theoretical horsepower required to
maintain a car at a certain speed on a level, is evidently the tractive
effort in pounds multiplied by the speed in feet per minute and divided
by 33,000. What the tractive effort per ton of car will be, depends
on the condition of the rail and on several other uncertain factors.
For street-railway motor cars, 20 pounds per ton is the usual tractive
effort assumed as necessary. A calculation of this kind, however, takes
no account of the losses in the motors and gears, nor of the fact
that the greater part of the power required to propel a street car in
practical service is used in accelerating the car from a state of rest
to full speed. In interurban service, of course, the power required
in acceleration is not so great a proportion of the whole.

[Illustration: Fig. 93. Plotted Data of Road Test.]

The safest figures to use in engineering calculations as to the amount
of power required, are those taken from actual results obtained in
everyday commercial service. The power required by an eight-ton car in
service in a large city like Chicago, is in the neighborhood of one
kilowatt hour per car-mile run. On outlying lines this figure may be
reduced to .7 kilowatt hour, and in the down-town districts may run up
to 1.5 kilowatt hours per car mile. Double-truck cars in city service,
weighing from 20 to 25 tons, take from 2½ to 4 kilowatt hours per car
mile at the power station. Interurban cars around Detroit, weighing
about 32 tons, in interurban service, making 25 miles per hour,
including stops, in level country, and geared to 43 miles per hour,
take about 3 kilowatt hours per car mile at the power station. However,
interurban railway conditions are extremely variable.

The reports of several Indiana electric railways show an average power
consumption of 1.48 kilowatt hours per car mile for city cars and 5.18
kilowatt hours for interurban cars, including line and distribution
losses.

An interurban car weighing 31½ tons and equipped with two 150
horsepower motors, on a test run of 50 miles at an average speed of
39 miles per hour consumed 2.20 kilowatt hours per car mile. This car
made 18 stops. A similar car under the same conditions made the same
run at an average speed of 26 miles per hour with 44 stops, consumed
2.44 kilowatt hours and a third car, making 12 stops and at a speed of
33 miles per hour, consumed 2.10 kilowatt hours per car mile. These
individual car test figures are from measurements taken at the car and
do not include line losses.

=Road Tests of Electric Cars.= Of late considerable attention has been
given to making road tests of electric cars. The results of the tests
are usually plotted in the form shown in Fig. 93. Time is plotted
horizontally in seconds, while volts, amperes, speed and per cent grade
are plotted vertically. The diagram referred to is the result of a
continuous run of 6 minutes of a 32.5 ton car equipped with two motors.
The line voltage, motor consumption and other readings may be obtained
for any instant of time. The acceleration in miles per hour per
second may be obtained by noting the increase in height of the speed
curve in one second. In making such a test the necessary instruments,
voltmeters, ammeters, wattmeters and speed indicators are mounted
direct on the car and are read at intervals of a few seconds.

The curve of motor consumption gives an idea of the abnormal current
required to get the car under headway.

=Economy in Power.= As already stated, a large part of the energy
taken by a car in city service is used in accelerating the car. Much
of this energy must be destroyed or used up in the brake shoes at the
next stop. The energy stored up in a car by process of acceleration is
represented by the formula:
                     Mass in lbs. × (Velocity in ft. per sec.)²
Energy in ft. lbs. = ——————————————————————————————————————————, which
                                       2
is the formula for kinetic or live energy, the derivation of which is
found in any Instruction Paper on Mechanics. In performing any given
schedule with frequent stops, the more rapid the acceleration the lower
the maximum speed required to make the schedule, and the less the
energy required in acceleration. For city street and elevated service,
therefore, rapid acceleration and low maximum speeds are desirable
because not only more economical but safer.

For economical operation with any given equipment and schedule, it
is important to use as much of the energy stored up in the car as
possible, before wasting it by applying the brakes. Motors are built
of a size to yield the large horsepower required in acceleration, and
consequently are lightly loaded when operating the car at maximum
speed. To economize in power, current should be shut off as soon as
possible after the car has attained full speed; and the car should be
allowed to drift without current as long as possible before the brakes
are applied. In this way the energy stored in the car will propel it
at nearly maximum speed for a considerable distance between stops;
there will be the smallest possible waste of energy in the brake shoes;
and the losses of energy which take place when the current is in the
motors will be prevented as far as possible. Practical tests as well
as theoretical calculations show a possibility of very material saving
in energy in the operation of an electric railway car or train, by the
observance of this simple rule of drifting as much as possible and
using the brakes as little as possible. Whatever energy is used up in
the brake shoes is necessarily wasted. The smaller this waste can be
kept while performing a given service, the greater the economy secured.

=Cost of Power.= The reports of 85 per cent of the railway power
generating stations in Indiana show the average cost at the station per
kilowatt hour to be .755 cent. This was divided as follows: Fuel .526
cents, labor .158 cents, lubricants and miscellaneous supplies .032
cents, repairs .039 cents. The lowest cost reported was .505 cents.

During 1901 the average cost of power generated at the power house of
the Indiana Union Traction Company was .443 cents per kilowatt hour at
the switchboard. Distributed from the substations it was .765 cents per
kilowatt hour. Natural gas was used for fuel. On occasions when this
failed, coal at $1.50 per ton was burned.

=Sliding and Spinning Wheels.= In accelerating a car, however, there
is no economy in turning on current so rapidly as to spin the wheels.
As mentioned in the section on “Brakes,” the tractive effort between
wheels and rails falls off about two-thirds when the wheels begin to
slip; and this slipping of wheels, therefore, reduces the chance of
securing the acceleration which is possible. For the same reason, in
making emergency stops either by the use of brakes or by reversing the
motors, care should be taken not to slide the wheels, as by so doing
the time required to stop the car is much increased.

In the ordinary straight air-brake equipment used on heavy electric
cars, there is much higher pressure carried in the storage reservoir
than it is permissible to turn into the brake cylinder, since, if the
full pressure were turned into the brake cylinder, it would result in
sliding of the wheels—which, it has just been shown, is something to
be avoided, not only on account of making flat spots on the wheels,
but also because of the reduction in the braking force as soon as
the wheels begin to slide. An experienced motorman can tell from the
feeling of the car when the wheels are sliding, and will instantly
release the brake sufficiently to allow the wheels to begin to revolve
as soon as he notices that this has taken place.

The friction between brake shoes and car wheels decreases as the speed
increases. A certain pressure applied to the brake shoes upon a car
running 50 miles per hour, therefore, exerts much less retarding force
than the same pressure at ten miles per hour. In order to give the
same braking or retarding force at higher speeds, the brakes must be
applied harder than at the lower speeds. If they are applied at the
maximum pressure possible without sliding the wheels at higher speeds,
it is evident that this pressure must be reduced as the speed of the
car is reduced, or the wheels will be “skidded.” In the Westinghouse
high-speed automatic air brake used on steam roads, this reduction of
pressure is automatically accomplished.


                          TESTING FOR FAULTS.

[Illustration: Fig. 94. Bond Testing.]

=Bond Testing.= It is important to test the conductivity of rail bonds
from time to time in order to determine if they have deteriorated so
as to reduce their conductivity and introduce an unnecessary amount
of resistance into the return circuits. One way of doing this is to
measure the drop in potential over a bonded joint as compared with
the drop in potential of an equal length of unbroken rail. To do
this, an apparatus is employed whereby simultaneous contact will be
made bridging three or more feet of rail and an equal length of rail
including the bonded joint, as shown in Fig. 94, which illustrates the
connections of a common form of apparatus where two milli-voltmeters
are employed that measure the drop in voltage of the bonded and
unbonded rail simultaneously. If the current flowing through the
rail due to the operation of the cars were constant, of course one
milli-voltmeter might be used, being connected first to one circuit
and then to the other. The current in the rail, however, fluctuates
rapidly, so that two instruments are necessary for rapid work. The
resistance of the bonded joint is usually considerably more than that
of the unbroken rail, and the milli-voltmeter used to bridge the joint
consequently need not be so sensitive as that bridging the unbroken
rail.

In another form of apparatus, a telephone receiver is used instead
of the milli-voltmeter, the resistance of a long unbroken rail being
balanced against that of the bonded joint, as in a Wheatstone bridge,
until, upon closing the circuit, these two resistances when balanced
give no sound in the telephone receiver.

Bond tests of this kind can be made with satisfaction only when a
considerable volume of current is flowing through the rails at the
time of the test, because the drop in voltage is dependent on the
current flowing, and in any event is small. It has sometimes been found
necessary or advisable to fit up a testing car equipped with a rheostat
which will itself use a considerable volume of current, so as to give
a current in the rail which will give an appreciable drop of potential
across a bonded joint. Some of the latest forms of testing cars carry
motor generators which will pass a large current of known value through
a bonded joint, and so cause a drop of potential across the joint large
enough to be easily measured.

=Motor-Coil Testing.= Testing for faults in the motor armature and
field coils is done in a great variety of ways. The resistance of these
coils can be measured by means of a Wheatstone bridge employing a
telephone receiver in place of the galvanometer used in such bridges in
laboratory practice; but other less delicate tests are also in use.

Another method is to pass a known current through the coil to be tested
and to measure the drop in the voltage between the terminals of the
coil, the voltage divided by the current equaling the resistance.

A simple method, and one which involves no delicate instruments, has
lately been introduced into railway shop practice very successfully.
This is known as the _transformer test_ for short-circuited coils. It
requires an alternating current which can easily be supplied either
by a regular motor generator or by putting collecting rings onto an
ordinary direct-current motor and connecting these rings to bars of
opposite polarity on the commutator.

The method of testing for short-circuited armature coils employed in
the shops of the St. Louis Transit Company is indicated in diagram
in Fig. 95. A core built up of soft laminated iron is wound with 28
turns of No. 6 copper wire. This coil is supplied with alternating
current from a 110-volt circuit. The core has pole pieces made to fit
the surface of the armature. When one side of a short-circuited coil
in the armature is brought between the pole pieces of this testing
transformer, as in Fig. 95, the short-circuited armature coil becomes
like the short-circuited secondary of a transformer, and a large
current will flow in it. This current will in time manifest itself by
heating the coil; but it is not necessary to wait for this, as a piece
of iron held over that side of the coil not enclosed between the pole
pieces, as indicated in. Fig. 95, will be attracted to the face of the
armature if held directly over the coil, but will be attracted at no
other point.

[Illustration: Fig. 95. Method of Testing for Short-circuited Armature
  Coils.]

This testing can be done very rapidly, and does not require delicate
instruments or skilled operators.

Tests for short circuits in field coils can be made in a similar
manner, by placing the coils on a core which is magnetized by
alternating current. The presence of a short circuit, even of one
convolution of a field coil, will be apparent from the increase in
the alternating current required to magnetize the core upon which the
field coil is being tested. The insulation resistance of armatures
and fields is frequently tested by means of alternating current, about
2,000 volts being the common testing voltage for 500-volt motor coils.
One terminal of the testing circuit is connected to the frame of the
motor, and the other to its windings. Any weakness in the insulation
insufficient to withstand 2,000 volts will, of course, be broken down
by this test. Alternating current is generally used for such tests
because it is usually more easily obtained at the proper voltage, as it
is a simple matter to put in an alternating transformer which will give
any desired voltage and which can be controlled by a primary circuit of
low voltage.

Open circuits in the armature can be easily detected by placing
the armature in a frame so that it can be rotated, the frame being
provided with brushes resting 90° apart on the commutator. If either an
alternating or direct current be passed through the armature by means
of these brushes, and the armature be rotated by hand, a flash will
occur when the open-circuited coils pass under the brushes. A large
current should be used.

The tests just mentioned are among the best of the methods used by
electric-railway companies for systematic work in the location of
certain classes of faults. A large number of other methods of testing
have also been evolved.

The following are some of the most common faults experienced with
electric railway car equipments:

=Grounds.= As one side of the circuit is grounded, any accidental
leakage of current from the car wiring or the motors to ground will
cause a partial short circuit. Such a ground on a motor will manifest
itself by blowing the fuse or opening the circuit breaker whenever
current is turned into the motor. In case the fuse blows when the
trolley is placed on the wire and the controller is off, it is a
sign that there is a ground somewhere in the car wiring outside of
the motors. Moisture and the abrasion of wires are the most common
causes of grounds in car wiring. In motors, defects are usually due to
overheating and the charring of the insulation.

=Burn-Outs.= Burning out of motors is due to two general causes: First,
a ground on the motor, which, by causing a partial short circuit,
causes an excessive current to flow; second, overloading the motor,
which causes a gradual burning or carbonizing of the insulation until
it finally breaks down.

Short-circuited field coils having a few of their turns
short-circuited, if not promptly discovered, are likely to result
in burned-out armatures, as the weakening of the field reduces the
counter-electromotive force of the motor, so that an abnormally
large current flows through the armatures. Cars with partially
short-circuited fields are likely to run above their proper speed,
though, if only one motor on a four-motor equipment has defective
fields, the motor armature is likely to burn out before the defect is
noticed from the increase in speed.

[Illustration: Fig. 96.]

=Defects of Armature Windings.= Defects in armature windings probably
cause one-third the maintenance expenses of electrical equipment
of cars. Almost all repair shops have men continually employed in
repairing them. The most frequent trouble with armatures is through
failure of the insulation of the coils and consequent “grounding.”
This term is used in connection with armatures and fields and other
electrical apparatus where a direct path exists to ground. As the
armature core is electrically connected to the ground through its
bearings and the motor casing, a break down of the insulation of the
coils in the slots permits the current to pass directly to ground.
This shunts the current around the fields and an abnormal current
flows because of their weakness. The circuit breaker or fuse is
placed in circuit to protect the apparatus in such an emergency, but
usually before such devices break the circuit, several of the coils
of the armature are burned in such a manner as to make their removal
necessary. The coils are so wound on top of one another that in order
to replace one coil alone, one-fourth of the coils of the armature must
be lifted.

[Illustration: Fig. 97.]

With the armature of No. 1 motor grounded the car will not operate and
if the resistance points be passed over, the fuse will usually blow.
When No. 2 motor is grounded the action of No. 1 motor is not impaired
and this latter motor will pull the car until the controller is thrown
to the multiple position. But if the motors are thrown in multiple, the
path through the ground of No. 2 motor shunts motor No. 1. A study of
Fig. 18 will make this evident.

[Illustration: Fig. 98.]

Next to grounding, open circuits are the most serious defects of
armatures. These are usually caused by burning in two of the wires in
the slot, or where they cross one another in passing to the commutator.
Sometimes the connections where the leads are soldered to the
commutator become loose.

The effect of an open circuit is shown in Fig. 96. The circuit is open
at n. The brushes are on segments _a_ and _d_. By tracing out the
winding it will be found that no current flows through the wires marked
in heavy lines. Whenever segments _c_ and _d_ are under a brush the
coil with the open circuit is bridged by the brush and current flows
as in a normal armature. As segment _c_ passes out from under the brush
the open circuit interrupts the current in half the armature and a long
flaming arc is drawn out.

In Fig. 97 is shown the result of a short circuit between two coils.
The short circuit is at _b_, _c_, the two leads coming in contact with
each other when they cross. The effect is to short-circuit all of the
winding indicated by the heavy lines.

[Illustration: Fig. 99.]

=Mistakes in Winding Armatures.= The armature winder is given very
simple rules as to how to wind the armature, but the great number of
leads each to be connected to their proper commutator segment sometimes
so confuse him that misconnections are made. The effect of getting two
leads crossed is shown in Fig. 98. The leads to segments _b_ and _c_
from the right are shown interchanged. This short-circuits the coils
shown in heavy lines. The abnormal current resulting in these would
usually cause them to burn out.

Fig. 99 shows the results of placing all of the top leads, or all of
the bottom leads one segment beyond the proper position. This causes
the circuit starting from _a_ and traveling counter clockwise around
the armature to return on segment _m_ instead of on segment _b_ as is
the case in Fig. 97.

The only result of such connections is to change the direction of
rotation of the armature. It may be noticed by comparing the two
figures that with the positive brush on segments _a_ the arrows show
the currents to be in opposite directions in coils similarly located
with reference to the position of the brushes. Some armatures are
intended to be wound as in the last case mentioned. =Sparking at the
Commutator.= As railway motors are made to operate, and usually do
operate, almost sparklessly, sparking at the brushes may be taken as a
sign that something is radically wrong.

The pressure exerted by the spring in the brush holder may not hold the
brush firmly against the commutator.

If brushes are burned or broken so that they do not make good contact
on the commutator, they should be renewed or should be sandpapered to
fit the commutator.

A dirty commutator will cause sparking.

A commutator having uneven surface will cause sparking, and should be
polished off or turned down.

[Illustration: Fig. 100.]

Sometimes the mica segments between commutator bars do not wear as fast
as the bars and when this is the case, the brushes will be kept from
making good contact when the commutator bars are slightly worn. The
remedy is to take the armature into the shop, and groove out the mica
between the commutator bars for a depth of about ¹⁄₆₄-inch below the
commutator surface.

A greenish flash which appears to run around the commutator,
accompanied by scoring or burning of the commutator at two points,
indicates that there is an open-circuited coil at the points at which
the scoring occurs as in Fig. 100.

The magnetic field may be weakened by a short circuit in the field
coils, as before explained, and this may give rise to sparking.

Short circuits in the armature may give rise to sparking, but will also
be made evident by the jerking motion of the car and the blowing out of
the fuse.

=Failure of Car to Start.= The failure of the car to start when the
controller is turned on may be due to any of the following causes:
Opening of the circuit breaker at the power house.

Poor contact between the wheels and the rails owing to dirt or to a
breaking of the bond wire connections between the rail on which the car
is standing and the adjacent track.

One controller may be defective in that one of the contact fingers
may not make connection with the drum. In this case try the other
controller if there is another one on the car.

The fuse may be blown or the circuit breaker opened. The occurrence
of either of these, however, is usually accompanied by a report which
leaves little doubt as to the cause of the interruption in current.

The lamp circuit is always at hand for testing the presence of current
on the trolley wire or third rail. If the lamps light when the lamp
circuit is turned on, it is a tolerably sure sign that any defect is
somewhere in the controllers, motors, or fuse boxes, although in case
the cars are on a very dirty rail enough current might leak through
the dirt to light the lamps, but not sufficient to operate the cars.
In such a case, the lamps will immediately go out as soon as the
controller is turned on. Ice on the trolley wire or third rail will
have the same effect as dirt on the tracks.


           LOCATING DEFECTS IN MOTOR AND CONTROLLER WIRING.

Defects in the wirings are those due to (1) open circuits, (2) short
circuits. Open circuits make themselves evident by no flow of current,
short circuits usually by a blowing of the fuse or opening of the
breaker. The point of the short circuit or “ground” can be located
roughly by noting on what point the fuse is blown. Accurate location
can be made by cutting out the motors, disconnecting, etc., according
to directions in the following pages. The tests outlined apply
particularly to the K type of controller with two-motor equipment.


                          OPEN-CIRCUIT TESTS.

No current:
  On 1st point,
    Open circuit but not located.
  On 1st point multiple,
    Motors most probably O. K.
  On series-resistance points after trying 1st point multiple,
    Open circuit outside controller and equipment wiring.

With an open anywhere between trolley and ground no current will flow
on the first point. Opens are most likely to occur in the motors and
these may be tested first. However, as will be explained later, one
open in an armature will not stop the current. To test the motors open
the breaker and put the controller on the first point multiple. Then
flash the breaker quickly. Current flowing indicates that one or the
other of the motors has an open circuit. In the series position this
open prevented the flow but in multiple the current flows through
the other motor. Which one is at fault can be quickly determined by
returning the controller to the off position and cutting out one or the
other of the motors by means of the cut-out switch and then trying for
current. The car can in any event be run on the remaining motor. On
returning to the shop the open can be determined definitely by the use
of the lamp bank.

But should no current flow when the breaker is flashed on the 6th point
it is reasonable to presume that the motors are O. K. and that the open
is elsewhere. The ground for such a supposition is that as there is a
path through each motor normally, there would necessarily be an open
in each one to stop the current. It is hardly probable that such a
coincidence would occur.

After failure to find fault with the motors, doubt as to the resistance
may be removed. The controller should be placed on progressive
series-resistance points and the breaker flashed on each one. If
current is obtained on any point, the open is in the resistance or the
resistance lead just behind the one being used. Special care should be
used to flash the breaker quickly for otherwise the fuse may be blown.

The tests indicated are sufficient for the motors, controllers and
resistance wiring. If no current is obtained on either of them, the
trouble is evidently caused by a bad rail contact, ground wire off if
both motors are grounded through the same wire, an open in the blow-out
coil, at the lightning arrester, circuit breaker or on top of the car.

None of the tests applied locate the open definitely, but this can
easily be done in the shop or wherever a lamp bank is at hand. Connect
one terminal of the lamp bank to the trolley just behind the circuit
breaker and the controller on the 1st point series, then with the other
terminal begin at ground and trace backwards up the circuit until the
lamps fail to light. The path in a K type of controller is readily
traced with the help of Fig. 22.


                         SHORT-CIRCUIT TESTS.

The location of short-circuits is much more tedious. The blowing of the
fuse or opening of the breaker will locate them as shown below. The
separate tests can then be followed until location is definite.

These tests it must be kept in mind are more especially adapted to
cases on the road or where no facilities for testing are at hand.

Rather than blow fuses as frequently as indicated it would in most
cases be better to place a lamp bank across the open circuit breaker
and note the flow of the current by the lights.

  =Fuse Blows=:
    I. When overhead is thrown on may be due to:
      1. Grounded controller blow-out coil.
      2. Grounded trolley wire or cable.
      3. Grounded lightning arrester.
   II. On first point:
      1. Grounded resistance near R 1.
      2. Grounded controller cylinder.
      3. Bridging between the insulated sections of cylinder.
  III. Near last point series:
      1. Grounded resistance near R 3, R 4 and R 5.
      2. No. 1 motor grounded.
   IV. Near last point multiple:
      1. No. 2 motor grounded.
      2. Bridging between lower sections of cylinder.
      3. Armature defective.

                                CASE I.

  =Fuse Blows= when overhead is thrown on:
      1. Grounded controller blow-out coil.
      2. Grounded trolley wire or cable.
      3. Grounded lightning arrester.

The blowing of the fuse immediately on closing the overhead switch or
circuit breaker, when the controller is on the off position, indicates
that the fault exists somewhere between the overhead and the upper or
trolley finger of the controller.

Should the defect occur during a thunderstorm, it may be presumed at
once that lightning has grounded the blow-out coil of the controller.

                               CASE II.

  =Fuse Blows= on first point:
      1. Grounded resistance near R 1.
      2. Grounded controller cylinder.
      3. Bridging between sections of cylinder.

When the controller is on the first point all of the wiring of
the system with the exception of the ground wire for No. 1 motor
is connected with trolley. But a defect in the wiring beyond the
resistance will not show itself on the first point by an abnormal rush
of current because the resistance of the rheostats is sufficient to
prevent any excessive flow of current.

[Illustration: Fig. 101.]

[Illustration: Fig. 102.]

The resistance and leads and the controller cylinder are the only parts
to be tested when the fuse blows on the 1st point.

                               CASE III.

=Fuse Blows= on 3rd or 4th point:
      1. Grounded resistance near R 4 or R 5.
      2. No. 1 motor grounded.

With either of the above defects the car will most probably refuse to
move as the current is led to ground before passing through the motors.

[Illustration: Fig. 103. Plan of Car Shop.]

No. 1 motor may be tested by cutting it out of service by means of its
cut-out switch. If this removes the ground, the motor is at fault.

                               CASE IV.

=Fuse Blows= near last point multiple:
      1. No. 2 motor grounded.
      2. Either armature short-circuited.

The fact that the fuse did not blow on the series positions excludes
the resistances and No. 1 motor from investigations for grounds.

Cut out both motors. If the ground still exists the controller is
defective. If not, the fault may be located in either one of the motors
by cutting out first one and then the other.


                      ARMATURE TESTS FOR GROUNDS.

With a lamp bank at hand tests for grounded armature can be made as
follows:

  Throw the reverse on center. Attach one terminal of the lamp bank
  to the trolley. Put the other terminal on the commutator of the
  armature to be tested. No current shows the armature O. K. If
  current flows remove brushes and try again, to be certain that the
  ground is not in the leads.


                       FIELD TESTS FOR GROUNDS.

Disconnect field leads and put test point of the lamp bank on one side
of the terminals. No current indicates that the fields are O. K.


                           REVERSED FIELDS.

In placing new fields in the shell it often happens that one or more
are wrongly connected. Reversed fields make themselves known by
excessive sparking at the brushes in each case.

In Fig. 101 all of the fields are connected correctly. The flow of
magnetism is in one pole and out of the adjacent one. Some of the
magnetism leaks out of the shell and affects a compass held near the
outside. The direction taken by the compass needle in the different
positions is shown. The needle should point in opposite directions over
adjacent coils and should lie parallel to the shell in positions half
way between two coils.

Figure 102 shows the flow of magnetism when one field is reversed. In
such a case the compass will take the position shown. The field marked
“X” is the one reversed.

With one reversed field a machine will usually operate, as the
magnetism in three of the poles is in the normal direction. But an
excessive flow of current that has no effect in turning the armature
will take place on that side of the armature next to the reversed field.


                           CAR REPAIR SHOPS.

Every electric railway system has a repair shop in which the cars are
overhauled. Hardly two shops are built alike. In those shops where only
a few cars are cared for, the work is sometimes all done in one room.
The shop plan shown in Fig. 103 was presented to the American Railway
Mechanical and Electrical Association by W. D. Wright. It contains the
idea upon which the larger shops are now being constructed, having a
transfer table between the separate departments on either side. In the
general design of shops the blacksmith shop, machine shop and truck
shop or equipping shop should be close together as a great deal of
heavy material is carried between these departments. The paint shop
should be separated as much as possible from the other departments in
order that flying dust and dirt be avoided. The wood shop may occupy a
position at a considerable distance from the other departments as no
heavy material is carried from this shop to them.

The tracks of the motor and truck repair shop are usually provided
with pits so that trucks and electrical equipment may be repaired and
inspected from below. The tracks in shops are usually about 15 or 16
feet between centers. This gives a clearance of about 6 or 8 feet
between cars when adjacent tracks are occupied.

A large portion of the work done in the average shop consists of the
repairing of trucks and the motors mounted on them. With the smaller
car, especially those with single trucks, much of this work is done
from the pit below while the trucks are in position under the cars. In
this case the armatures are either removed by letting them down with
the lower half of the motor shell by means of a pit jack, or the lower
half of the armature shell is swung down by the use of a chain and
block placed in the car and the armature rolled out on a board.

The trucks of double truck cars are usually taken out from under the
car body when repairs are to be made. In this case the motor leads, the
sand box connections and the brake rigging are disconnected and the
car body either raised or the trucks lowered from it. Several methods
of raising the car body are in use. Where no special apparatus is at
hand, this is done by means of jacks, hydraulic or mechanical, placed
under the side sills of the car near the end to be raised. Sometimes an
overhead crane is employed to lift the car body. A special apparatus
to raise the body is employed by the St. Louis Transit Company. This
consists of four screw jacks located below the floor of the shop. An
I-beam extends over the tops of the two located on the same side of
the car. The jacks are motor driven by means of one sprocket chain so
that they rise at the same speed. When a car is to be raised it is run
on the track between the jacks, bars are placed under the car resting
across the I-beams and the jacks raise the car off the trucks. The
trucks are then rolled out from under the car and the repairs made.

Sometimes, as has been stated, the trucks are dropped from the car
body. In this case the car is so placed that the truck rests on an
elevator or section of track that drops to the floor below. After the
car is blocked up the trucks are dropped and the repairs made. This
method is also used in changing wheels in small shops. The old pair of
wheels is dropped by a hand-operated drop section of track. A new pair
is then elevated into position. This saves jacking up one end of the
car.

[Illustration: ONE OF THE SINGLE-PHASE LOCOMOTIVES ON THE NEW YORK,
  NEW HAVEN & HARTFORD RAILROAD CO.

  Note the two pantograph bow trolleys for collecting the current.]




                   THE SINGLE-PHASE ELECTRIC RAILWAY.


In no other line of electrical activity have developments during the
last few years been so rapid as in that of electric railway work, and
from all indications the limit has not yet been reached.

Until recent years all electric traction has been dependent upon direct
current as a motive power. This is due principally to the fact that the
series direct-current motor is admirably adapted for such work, and no
alternating-current motor had been developed which could be substituted
for it. One of the great advantages possessed by the direct-current
series motor is its large starting torque, which may be several times
greater than that required to propel a car at full speed. This type
of motor is also essentially a variable speed machine, and lends
itself very well to wide variations in speed control; consequently,
for many years, in this country at least, all advance was made along
direct-current lines.

The trolley voltage used at first was from 450 to 500 volts, this
being supplied directly to the cars by means of a trolley wire, the
rails being used for the return circuit. It is evident from the
outset that the comparatively low voltage, necessitating as it did a
correspondingly large current for a given amount of power, would place
a definite limitation on the use of such a system for anything other
than purely local distribution. To overcome this difficulty as far as
possible, the trolley voltage was gradually raised to 600 or 650. This
of course decreased the required current, thus increasing the scope
of the system accordingly. The limit of increase of direct-current
voltage on the trolley was reached at about this point, and the fact
was recognized that some means must be devised for using a still higher
voltage, since there are difficulties to increasing the trolley voltage
beyond 600 or 700, due to flashing of the motors, which seems to
increase directly with the voltage.

It may be mentioned in passing that one prominent electric traction
expert has stated that a direct-current trolley voltage of 1500 can
be used, but it remains to be proven whether or not he is correct. A
very satisfactory solution of the problem for large city street railway
systems and long interurban roads, consists in the use of a combination
alternating-current direct-current system in which three-phase high
tension alternating current is generated and distributed on high
tension lines to substations along the road. It is here stepped down
by means of transformers, and then changed to direct current by rotary
converters, and supplied to the trolley wire as direct current at the
usual voltage of say 600. This system has many advantages, as there is
but small loss in the high-tension lines, and these lines can be made
comparatively small, thus effecting a considerable saving in investment
for copper.

The above mentioned system of distribution is very generally used, and
has been found quite satisfactory. The substations can be located at
frequent intervals, and the distance that the 600-volt current must be
conducted to supply the cars is not great. By this means current can
be distributed over wide areas with a small loss, where it would be
impossible to use the straight direct-current system of distribution.

While, as stated, this furnishes a fairly satisfactory solution of the
problem, it is far from perfect, as it necessitates the intervention of
the rotary converter substation, in which the investment must be large;
and moreover the cost of operation is high, as such a station requires
skilled attendance on account of the somewhat intricate nature of the
rotary converter. The ideal system, therefore, is one which does away
altogether with the use of direct current, the power being generated,
distributed, and utilized by the motors, as alternating current.

Three-phase induction motors have been used quite extensively and with
considerable success in Europe for many years past. The three-phase
motor, however, is not entirely adapted for railway work, since it
possesses the characteristics of the shunt rather than of the series
motor, being a constant speed, not a variable speed machine. Moreover,
two trolley wires are necessary instead of one, and still another
disadvantage consists in the low power-factor of the three-phase
induction motor at starting.

The recent application of the single-phase alternating current to
railway work has opened up a new field, which bids fair to supplant all
other forms of distribution to a great extent at least, and it is
impossible to predict at the present time just what its limitations may
or may not prove to be. This has been made possible by the development
of a _practical commercial_ single-phase motor, which permits of the
use of alternating current on the trolley wire with all its advantages,
and yet sacrifices few, if any, of the advantages of the direct-current
series motor on the car.

[Illustration: INTERIOR OF SUB-STATION SHOWING ROTARY CONVERTER AND
  TRANSFORMERS.

The three-phase current is delivered to the transformers where it is
stepped down to the voltage required for the rotary converter. In
this machine it is transformed to direct current and delivered to the
trolley wire.]

This motor, which is the latest and most important development in the
electric railway field, is of the series commutator type, and does
not differ in principle from its direct-current contemporary. It is
called the _commutator type single-phase motor_, and is the one type of
alternating-current motor which has the same desirable characteristics
for railway work as the direct-current series motor.

[Illustration: Compensating Alternating-Current Railway Motor.]

At first thought it may seem strange that a motor built fundamentally
on the same lines as a direct-current machine would operate on an
alternating current, as it might appear that the motor would tend to
turn first in one direction and then in the opposite direction with no
resultant motion. This, however, is not the case, because the direction
of rotation of a motor depends upon the relative direction of its field
and armature currents. If now the field were maintained in a constant
direction and the armature supplied with alternating current, then the
tendency would be to rotate first in one direction and then in the
other, it is true, but as a matter of fact the alternating current
is supplied to the field in series with the armature, so that when
the direction of current in the armature changes it also reverses
in the field. The result is that the relative direction of current
in the field and armature is constant and the motor has, therefore,
a tendency to turn continuously in one direction as long as the
alternating-current power is supplied.

This being true, the question may arise as to why the single-phase
motor was not brought to the front for railway work long ago. The
answer is that there were certain inherent difficulties to be overcome,
and the development of the single-phase motor has been simply the
removal of these difficulties, rather than the design of an entirely
new type of machine.

The most serious obstacle to overcome is the sparking at the
commutator, due to the fact that when the terminals of a coil are
bridged by a brush, the coil acts like the short circuited secondary of
a transformer of which the field winding constitutes the primary. Also
there is an iron loss due to the alternating magnetic flux through the
magnetic circuit; while another objectionable feature is the counter
E.M.F. induced in the field coils.

[Illustration: Alternating-Current Railway Motor Field.]

In order that it may overcome these difficulties, to some extent, at
least, the single-phase motor presents certain modifications from the
direct-current type, in that it has more field poles, and the entire
magnetic circuit of field frame, cores, and pole pieces, is carefully
laminated. The number of commutator segments is also increased, thus
reducing the number of armature turns per coil, and there are special
features introduced to prevent sparking, such as compensating windings
which neutralize the effect of armature distortion; the use of narrow
brushes; a type of armature winding which gives a low reactance per
coil; the use of high resistance leads between the armature coils and
commutator segments, etc.

The single-phase motor is then a refined and highly perfected type of
direct-current motor, and this explains the fact that it will operate
on either alternating- or direct-current circuits. In fact some claim
that it will operate even more efficiently on direct current than the
regulation direct-current motor itself.

[Illustration: Single-Phase Armature, Unmounted.]

The field for which the single-phase motor seems particularly adapted
is that of heavy service and interurban work, where it has many
distinct advantages, among which may be mentioned the following:

The alternating current on the trolley allows the use of a high voltage
and correspondingly smaller current, which reduces the line loss and
permits of the use of smaller wire, which of course means a saving
in the investment for copper. Moreover, the difficulty of collecting
a large current from the trolley wire is overcome. Rotary converter
substations are eliminated, being replaced by simple and cheap
transformer substations, which require no attendance. The capacity
can be easily increased by merely increasing the number of these
transformer substations.

The efficiency of speed control is a point particularly worthy of
mention. In direct-current speed control, the series-parallel method
is used almost exclusively. This consists of putting the motors in
series for low speed and in parallel for high speed. This permits of
two, and only two, economical running points; the one at full speed,
and the other at approximately half speed. All intermediate points must
be obtained by the insertion of dead resistance in which the voltage
is simply wasted as heat, thus causing a large loss particularly at
starting.

With the single-phase motor the current is supplied to the car with a
voltage of say 3300. It is then stepped down by means of transformers
on the car to the voltage of the motors, which may be 200 or 250
volts. The speed is, of course, dependent upon the voltage applied to
the motors, and this voltage is cut down from the maximum, to obtain
various gradations, by means of an induction controller, or by taps
from an auto-transformer. Thus the motor takes from the trolley only
slightly more power than is actually required to operate it at any
given speed, instead of taking full voltage from the line and absorbing
part of it in dead resistance.

[Illustration: Auto Transformer.]

The effect of electrolysis upon neighboring water pipes paralleling
an electric road, which is the cause of so much trouble with direct
current, is entirely eliminated, as electrolysis evidently will not
take place with alternating current.

In connection with this system a sliding contact device or bow trolley
has in many cases been substituted with considerable success for the
ordinary current collecting device, or trolley wheel, one advantage
of this being that the car can be run in either direction without
reversing the contact device. Another very satisfactory form of trolley
is of the pantograph type with sliding shoe, shown on the New York, New
Haven and Hartford locomotive.

A new form of trolley suspension known as the catenary has been
developed to meet the demand for more substantial construction
necessitated by the high trolley voltage. This consists of a stranded
galvanized steel messenger or supporting cable, from which the trolley
wire is suspended at intervals of about 10 feet, thus keeping it at a
uniform distance above the track.

[Illustration: Master Controller Used in Connection with the
  Multiple-Unit System as Applied to Single-Phase Work.]

The multiple-unit system of control can be used in connection with
single-phase motors, this being the scheme which has been in use for
a long time on elevated and other roads using direct current, whereby
several cars can be operated in a train from a single point, each car
being equipped with its individual motor and controlling apparatus.
The entire system is then controlled as one unit by a single motorman
stationed usually in the front of the first car. This method of control
has become of such tremendous importance that any system to which
it cannot be applied would be seriously handicapped. Cars equipped
with single-phase motors can be operated on either direct-current or
alternating-current lines, with high or low tension, with trolley or
third rail.

It must not be supposed, however, that with all the above mentioned
advantages, the single-phase system has no disadvantages, as such is
not the case. The car equipment, due to the transformers and the nature
of the motors, is considerably heavier. The motors themselves are more
expensive on account of their special construction. The equipment is
not always adapted for operation on existing lines. There is a slight
increased “apparent” resistance of the trolley line and a considerable
increased “apparent” resistance of the rails, due to reactance caused
by the alternating nature of the current. There is also an active
electro-motive force between the field coils, which is objectionable,
and there is a possibility of interference with neighboring telephone
lines. Furthermore, there is slight loss in power in the transformers
on the car, while the power-factor of the motors is less than unity.

Summing the matter up as a whole, however, the advantages seem to
overbalance the disadvantages, at least for many kinds of work, and it
is safe to predict that this new system of operation will have a very
wide and increasing application in the near future.

As to the operation of the system in general, the current may be
developed by single-phase, two-phase, or three-phase generators,
and supplied to the transformer substations just as it was formerly
supplied to the rotary converter substations. Only a single phase
is used on any section of the trolley line. The voltage on this
transmission line will depend upon the existing conditions, and can be
figured out like any other problem in power transmission.

[Illustration: Truck Complete with Single-Phase Motors and Contact
  Shoes.]

Three-phase generators would ordinarily be used, as less copper is
required to supply a given amount of power. The common frequency is 25
cycles per second. At the transformer stations, the voltage is then
stepped down to that required on the trolley, which may be 2,000,
3,300, 6,600, or even 11,000 volts. While we cannot speak yet of a
standard voltage, 3300 seems to be finding considerable favor. The
voltage for which the motors are wound is 200 or 250, the General
Electric motors using the former voltage, and the Westinghouse the
latter. When operating on alternating current the motors are connected
in parallel, and when running on direct current they are connected
in series. Motors have been constructed from 50 to 225 horsepower,
and there is no apparent reason why larger ones could not be made to
operate with equal satisfaction.

[Illustration: Magnetic Speed Indicator.]

Among the roads in this country which are either using, or planning to
use single-phase current, may be mentioned the Ballston-Schenectady
line, which was one of the first systems to be equipped and has
been in successful operation for some time. This road uses the
alternating-current motor developed by the General Electric Co. The
motors are adapted for operation on the 2,000-volt alternating-current
trolley between cities, and on the standard 600-volt direct current
in Schenectady. They are wound for 400 volts, and are operated in
series on the 600-volt direct current. The frequency used is 25 cycles.
Current is supplied by an overhead trolley, no feeders being used.

A second road of importance is one in Georgia between Atlanta and
Marietta, which is 15 miles in length. This uses the Westinghouse
equipment. The current on the trolley is 2,200 volts and 25 cycles. It
is transmitted at a voltage of 22,000.

Another road of importance is the Indiana and Cincinnati interurban
line, 41 miles in length, which has been in operation on regular
schedule since July 1st, 1905. For 37 miles the road is operated
from alternating current, and for 4 miles, from direct current. Four
75-horse power motors per car are used, capable of a maximum speed of
65 miles per hour.

[Illustration: Armature Quill.]

The Bloomington, Pontiac and Joliet Electric Railway is a single-phase
road equipped with General Electric apparatus, and has maintained a
regular schedule over a distance of more than 10 miles since March,
1905.

The plans are now being laid for a single-phase road, which will run
south from Spokane, Washington, a distance of 150 miles. The current
on the transmission line is 45,000 volts, which is stepped down to
6,600 on the trolley. The car will be capable of operating on current
from a 6,600-volt alternating, a 700-volt alternating, or a 575-volt
direct-current supply.

Perhaps the most important move which has been made in the direction
of single-phase traction thus far is the decision of the New York, New
Haven, and Hartford road to establish a long-distance passenger traffic
on the single-phase system. According to the latest plans this road
will operate between the Grand Central Depot and Woodlawn, N. Y., over
the terminal tracks of the New York Central road, on direct current
taken from the trolley. From Woodlawn, N. Y., to Stamford, Conn., the
road will be operated on the single-phase system.

[Illustration: A Pair of Drivers with Single-Phase Motor Mounted upon
  Quill.]

The equipment is being supplied by the Westinghouse Co. The current
is generated by revolving-field type turbine-driven alternators.
The armatures are designed for either three-phase or single-phase
connection. The current is generated at 25 cycles and 11,000 volts,
being delivered directly to the trolley, and thence to the cars,
without the intervention of any transformers. The double catenary
suspension from messenger wires is used to support the trolley. The
locomotives are each equipped with four 200-H. P. gearless motors,
designed to operate on 235-volt alternating current and 275- to
300-volt direct current. The armature is not mounted on the shaft
direct, but is built upon a quill through which the axle passes with
about ⅝-inch clearance all around. There is a flange at each end of
the quill from which seven pins project and fit into the hubs of
the driving wheels. On the direct-current part of the line, current
is delivered to the car through eight collecting shoes from a third
rail. On the alternating-current section, current is delivered through
two pantograph bow trolleys. On the direct-current section the
series-parallel method of speed control is used, current being fed
directly to the motors which are connected two in series permanently
and the series-parallel control is applied to the motors in groups of
two. The alternating-current speed control is accomplished by six taps
from an auto-transformer for the corresponding running points. The cars
weigh 78 tons and are capable of a speed of 60 to 65 miles per hour.
The electro-pneumatic unit-switch type of control is used. At each
end of the cab is a master controller from which the main controller
is operated. Several locomotives can be operated together on the
multiple-unit system, if desired.

[Illustration: Six-Unit Switch Group, Single-Phase System.]

The Washington, Baltimore and Indiana single-phase road is the latest
in the field, contracts having been placed very recently. The current
will be transmitted at 33,000 volts and 25 cycles, then being stepped
down to 6,600 volts on the trolley. The road will be 60 miles long and
will be equipped with General Electric apparatus. Four 125-H. P. motors
capable of operating on either alternating current or direct current
will be used, and the cars will be capable of a speed of 60 miles per
hour.




                                  INDEX


      Air brakes, 56

      Air compressors, 57
        automatic governor for, 57
        Westinghouse, 58

      Alternating-current generators, 105

      Alternating-current switchboards, 110

      Alternating-current systems, 113
        single-phase motors, 114
        three-phase motors, 113

      Alternating-current transmission, 99

      Armature coils, 8

      Armature leads, 9

      Armature tests for grounds, 133

      Armature winding, 5
        defects of, 124
        mistakes in, 126

      Automatic governor for air compressors, 57


      Ballast, 85

      Bearings of railway motors, 13

      Block signals for electric railways, 94

      Bond testing, 120

      Bonding and return circuits, 88

      Booster feeder, 98

      Brackets, 75

      Brake leverages and shoe pressure, 54

      Brake rigging, 53

      Brake shoes, 64

      Brush holders, 10

      Brushes, 10

      Burn-outs, 123


      Canopy switch, 39

      Car, failure of to start, 127

      Car bodies, 67

      Car circuit breaker, 39

      Car construction, 67

      Car equipment, 3

      Car heaters, 34
        electric, 34
        hot-water, 36

      Car painting, 72

      Car repair shops, 134

      Car weights, 72

      Car wheels, 51

      Car wiring, 37

      Cast-welded joints, 87

      Coefficient of friction, 65

      Common T-rail, 84

      Commutator type single-phase motor, 139

      Compressors, 57

      Conductivity of steel rail, 80

      Conduit systems, 81
        contact plow, 82
        cost of, 82
        current leakage, 83

      Contact plow, 82

      Contact shoes, 45

      Controller construction, 19

      Controller notches, 27

      Controller wiring, 20

      Controllers, 16

      Cost of power, 119

      Couplers, 66

      Current required to heat cars, 35

      Current leakage, 83


      Defects of armature windings, 124

      Direct-current feeding, 98

      Double-current generators, 105

      Drawbars, 66


      Economy in power, 118

      Electric car accessories, 39
        canopy switch, 39
        car circuit breaker, 39
        contact shoes, 45
        fuses, 41
        lamp circuits, 43
        lightning arresters, 41
        trolley base, 44
        trolley poles, 44
        trolley harp, 45
        trolley wheels, 44

      Electric cars, road tests of, 117

      Electric heaters for cars, 34

      Electric railway, 1

      Electrically welded joints, 87

      Electrolysis, 95
        prevention of, 97


      Feeder panel, 110

      Feeder systems, 92

      Feeders, 75

      Field coils, 8

      Field tests for grounds, 133

      Four motors, 19

      Fuse blows, 130

      Fuses, 41


      Gearing, 12

      G. E. electric brake, 61

      G. E. train control, 29

      Generator, starting up, 108

      Generator D. C. panels, 106

      Generators, 105

      Girder rail, 83

      Grounds, 123


      High-tension lines, 77

      High-tension oil switches, 111

      Highway crossings, 80

      Hot-water heaters for cars, 36


      Insulators, third rail, 79

      Interurban railway, system of distribution for, 101


      Joints for rails, 86


      Lamp circuits, 43

      Lightning arresters, 41

      Locating defects in motor and controller wiring, 128

      Location of
        power houses, 101
        third rail, 79

      Lubrication of railway motors, 13


      Magnetic blow-out, 26

      Maximum traction trucks, 51

      Momentum brakes, 59

      Motor leads, 9

      Motor suspension, 14

      Motor-coil testing, 121

      Motors, 3
        as emergency brakes, 63
        of the New York Central electric locomotive, 15

      Multiple-unit control, 29


      Oil switches, high tension, 111

      Open-circuit tests, 128

      Opening cases for inspection, 10

      Overhead construction, 73
        brackets, 75
        feeders, 75
        high-tension lines, 77
        section insulators, 76
        span wires, 74
        trolley wire, 73
        trolley-wire clamps and ears, 73


      Potter third-rail shoe, 46

      Power
        cost of, 119
        economy in, 118
        taken by cars, 115

      Power house location, 101

      Power stations, general plan of, 105

      Power supply and distribution, 98


      Railway motors
        bearings, 13
        brushes, 10
        characteristics of, 3
        gearing of, 12
        lubrication of, 13

      Rate of retardation in braking, 66

      Resistance of track, 91

      Resistances, 38

      Return feeders, 92

      Reversal of motor, 26

      Reversed fields, 133

      Rheostat control, 17

      Road tests of electric cars, 117


      Sectional insulators, 76

      Series-parallel control, 17

      Shanghai T-rail, 84

      Short-circuit tests, 130

      Single trucks, 48

      Single-phase electric railway, 136

      Single-phase motors, 114, 139

      Sleet on trolleys and third rails, 46

      Sliding and spinning wheels, 119

      Span wires, 74

      Sparking at the commutator, 127

      Sprague multiple-unit system of control, 29

      Steel car framing, 71

      Storage air brakes, 58

      Storage batteries in stations, 113

      Street railway motors, general data on, 6

      Supplementary return feeders, 92

      Swing bolster trucks, 49

      Switchboards, 106
        alternating-current, 110

      Switches, third rail, 79

      Swivel trucks, 48


      T-rail, 84

      Thermit welding, 88

      Third rail, 79
        advantages in operation, 80

      Third rail
        conductivity of, 80
        cost of, 80
        highway crossings, 80
        insulators for, 79
        location, 79
        switches, 79

      Three-phase motors, 113

      Track brakes, 63

      Track construction, 83

      Track resistance, 91

      Track sanders, 65

      Track support, 85

      Transmission systems, efficiency of, 101

      Trilby groove rail, 84

      Trolley base, 44

      Trolley harp, 45

      Trolley poles, 44

      Trolley wheels, 44

      Trolley wire, 73

      Trolley-wire clamps and cars, 73

      Trucks, 46
        maximum traction, 51
        single, 48
        swing bolster, 49
        swivel, 48

      Type L controllers, wiring of, 24




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