Two handholes are usually provided in the bottom shell for o_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

American School of Correspondence+

Entered at Stationers’ Hall, London

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.

========+======+=====+=====+======+======+======+======+========+=========+=======+==========+=========+=====+=======

--------+------+-----+-----+------+------+------+------+--------+---------+-------+-----+----+----+----+-----+-------

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 | |

--------+------+-----+-----+------+------+------+------+--------+---------+-------+-----+----+----+----+-----+-------

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

A A₁, and from finger 15 to finger A A₂. 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.