Electric railway engineering

Preface

To students in technical universities who wish to specialize in the subject of electrical railway engineering and to those who understand the fundamental principles of electrical engineering and are interested in their application to electric railway practice it is hoped that this book may be of value.

While it is planned primarily for a senior elective course in a technical university, it does not involve higher mathematics and should therefore be easily understood by the undergraduate reader.

The volume does not purport to present any great amount of new material nor principles, but it does gather in convenient form present day theory and practice in all important branches of electric railway engineering.

No apology is deemed necessary for the frequent quotations from technical papers and publications in engineering periodicals, for it is only from the authorities and specialists in particular phases of the profession that the most valuable information can be obtained, and it is believed that a thorough and unprejudiced summary of the best that has been written upon the various aspects of the subject will be most welcome when thus combined into a single volume.

The author wishes to express his appreciation of the assistance of Mr. Emrick, instructor in electrical engineering at Purdue University, in preparing illustrations for the book and to those students who by thesis investigations hav.e added to its value.

LaFayette, Ind., September, 191 1.

PART I. Principles of Train Operation

I. History of Electric Traction 3

11. Traffic Studies (predetermined) 13

III. Traffic Studies (existing) 24

IV. Train Schedules 30

V. Motor Characteristics 35

VI. Speed Time Curves (components) 48

VII. Speed Time Curves (theory) 59

VIII. Distance, Current and Power Time Curves (theory) 66

IX. Speed, Distance, Current, and Power Curves (concrete examples) . 71

X. Speed Time Curves (straight line) 78

PART II. Power Generation and Distribution

I. Sub-station and Power Station Load Curves 87

II. Distribution System 91

III. Substation Location and Design 104

IV. Transmission System 131

V. Power House Location and Design 145

VI. Bonds and Bonding 170

VII. Electrolysis 178

VIII. Signal and Dispatching Systems 188

Chapter I

. History of Electric Traction.

Although it is not the purpose of this treatise to relate facts, but rather to study the engineering and economic problems encountered in electric traction, yet it seems advisable to review briefly the history of the development of the electric railway by way of introduction.

Two distinct epochs were encountered in the brief period in which electric traction has come to the front. The first was that in which the experimental designs were hardly more than models operated with primary batteries. Occasionally during this period, however, enthusiasts who did not realize the insuperable financial drawbacks of primary battery operation constructed and experimented with cars of considerable size operated in that manner. Such was the car constructed by Page in 185 1 for the Washington and Baltimore Railroad, which made use of a 16 h. p. motor supplied with power from two large Grove cells made up of platinum plates 11 in. square. This first epoch was soon brought to a close, however, partly by the foresight of the investigators who realized the limitations of the primary battery and partly by the failure of all attempts to commercialize the primary battery car by those who had continued to experiment therewith.

The second epoch opened, after a brief interval of inactivity, simultaneously with the development of the reversible dynamo. In the development of this machine progressive experimenters could foresee the beginnings of electric traction upon a practical basis. Bearing in mind the existence of these two periods, the history of electric traction will be considered, greatly abstracted, but as nearly as possible in chronological order.

Since electric traction has ever been dependent upon the electric motor and the latter upon the discovery by Faraday, in 1821, that electricity could be made to produce mechanical motion, the latter date rather indirectly and vaguely marks the birth of the subject under consideration. America has the honor of first applying the electric motor to a car, model though it was, while later developments vibrated from America to Europe and back to America with a rapidity difficult to follow with accuracy. A poor blacksmith of Brandon, Vt., by the name of Thomas Davenport has the honor of first making this application of electric motor to a car in 1835, the motor having been constructed by him several years previous. During the short period of six years it is said that Davenport constructed over a hundred electric motors of various designs. That which was described as having been exhibited by him upon a car at Springfield and Boston, Mass., consisted of a revolving commutated magnet which was caused to attract stationary armatures arranged around the periphery of its path of revolution. The car thus equipped was operated upon a small circular track.

About the year 1838 Robert Davidson of Aberdeen, Scotland, built a much larger motor placed upon a battery car 16 ft. by

5 ft. in dimensions of the gauge then standard and operated same with 40 cells of battery consisting of iron and amalgamated zinc plates immersed in dilute sulphuric acid. It is of interest to note -that after several successful trips over Scotland railways this car was purposely wrecked by steam railway engineers who were afraid it would supersede types in use at that time.

Two rather fundamental patents were issued in England about this time, one in 1840 to Henry Pinkus involving the use of the rails for current conductors and another in 1855 to Swear which, although applied to telegraphic communication with moving trains, comprised the basis of the present current collecting trolley. Patents were also granted in 1855 by both France and Austria to Major Alexander Bessolo which covered the same fundamental principles but which described more in detail the third rail conductor, the insulated trolley, and even suggested central station supply.

The experimental work in this country of Prof. Moses G. Farmer in 1847 and Thomas Hall in 1850 might be considered in particular because of the use for the first time of the rail as a conductor and the adoption of a geared speed reduction between motors and driving axle. The work of Page, previously men-

HISTORY OF ELECTRIC TRACTION. 5

tioned, deserves prominent mention at this time. For many years after these experiments investigations in electric traction seemed to be dormant, largely due to the general realization of the impracticability of the battery as a source of energy.

The second era of electrical railway development opened about the year 1861 when Pacinotti invented the reversible continuous current dynamo. From this invention may be said to have arisen all modern generators and motors. While these were gradually developed by Gramme and Siemens, Wheatstone and Varley, Farmer and Rowland, Hefner-Alteneck and others, Wheatstone and Siemens having almost simultaneously developed selfexciting generators equipped with shunt and series winding, respectively, yet a considerable period of time elapsed before these developments were effectively applied to traction.

The work of George F. Green, a poor mechanic of Kalamazoo, Mich., has been quoted as the connecting link between the two eras. Although he began his experiments as late at 1875, after the development of the dynamo, his first model road reverted to the battery delivering current to the car over the operating rails. Although Green proposed the trolley for his experimental track, he did not make use of it. The following work of this man is rather pathetic, in that he constructed a car about the year 1878 large enough for two people and realized the advantages of the dynamo for supplying energy for same. He did not understand how to construct this machine himself, however, and was not financially able to procure one of the few being constructed abroad at that time. He applied, in 1879, for. patents which would probably have been of considerable value at that time, but because of limited funds and the fact that he was obliged to act as his own patent attorney, his claim was rejected and only finally granted in the year 1891 after a belated appeal to the circuit court of the District of Columbia.

The first electric road operating on a practical scale was the one exhibited by Siemens and Halske at the Berlin Exposition in 1879. This consisted of an oval track about 1/3 mile in length upon which an electric locomotive was operated with three small trailers accommodating from 18 to 20 passengers. The motor was mounted with its axle lengthwise of the car and power was transmitted to the car axle through a double bevel gear speed reduction. A speed of about 8 miles per hour was attained. The current was supplied by means of a third rail located between the running rails.

The year 1880 in Europe marked the exhibition of another model electric railway at Vienna by Egger which used the running rails for conductors. In this year also the study of a method of replacing the pneumatic dispatch system of Paris by miniature electrically propelled carriages was carried on. Siemens proposed at this time a commercial road for Berlin and endeavored to obtain a franchise for same.

The first electric road to be installed apart from an exposition was that at Lichterfelde, near Berlin, which was opened in 1881. A single motor car using cable drive between motors and axles operated upon this road which was i i /2 miles in length, at a speed of about 30 miles per hour. It was sufficiently large to accomodate 36 passengers. Although a third rail road when installed, it was changed over 12 years later to a double trolley system. This road has remained in continuous operation. During this year, also, the horse railroad between Charlottenburg and Spandau was changed to electric traction.

At the Paris exposition of 1881, Siemens and Halske demonstrated the use of the overhead trolley for current distribution to cars, the conductors consisting of metal tubes slotted on the underside, mounted upon wooden insulators; in which tubes, metal contactors, electrically connected with the car, were allowed to slide. In 1883, a 6-mile third rail road was opened at Portrush, Ireland, which was worthy of note because of its operation from a central station driven by water power.

Referring back to this country, Thomas Edison and Stephen D. Field began experimenting about the year 1880. Edison was principally interested in the development of the incandescent and arc lamps at this time and aside from building a short road at his laboratory at Menlo Park and taking out a few patents, he did little in this line. Field did considerable pioneer work, having made plans in 1879 for a railway to be supplied with power by means of a conductor enclosed in a conduit and using the rails as a return circuit. In 1880-81 he constructed and put into

HISTORY OF ELECTIRC TRACTION. 7

operation an experimental electrical locomotive at Stockbridge, Mass. Patents were applied for by Field, Siemens, and Edison within 3 months of each other early in 1880. Since Field had filed a caveat, however, the year before, his papers were given priority. Field's plans, however, remained on paper until the latter part of the year 1880 which was a year later than the installation of the Berlin road.

Little more was accomplished in the United States until 1883, when the interests of Edison and Field were united and the Electric Railway Company of the United States was organized. This company exhibited an electric locomotive at the Chicago Railway Exposition in 1883, which operated on a track about I /3 mile in length in the gallery of the exposition building. The motor operated a central driving shaft by means of bevel gears, this shaft being belted to one of the axles. The speed was varied by the use of resistances. Reverse motion was accomplished by throwing into service an extra set of brushes by means of a lever, only one set of brushes, of course, being upon the commutator at any one time.

Charles J. Van Depoele, a Belgian sculptor, who was destined to play an important part in the later development of electric traction, entered the field in 1882-83 when he operated a line in connection with the industrial Exposition at Chicago. After installing equipments at the New Orleans Exhibition and at Montgomery, Ala., and putting roads in operation at Windsor, Ont., Detroit, Mich., Appleton, Wis., and South Bend, Ind., the company which Van Depoele had formed was absorbed in 1888 by the Thompson Houston Co., which had recently been organized. The name of Leo Daft was one that cannot be neglected in the development of this period, for after considerable work with stationary motors in 1883 he constructed a locomotive capable of hauling a full sized car. The control in this car was brought about by varying the resistance of the motor field for which purpose some of the coils were wound with iron wire in place of copper. The company organized by Daft at Greenville, N. J., installed roads at Coney Island, N. Y., and the Mechanic's Fair in Boston, and in 1885 equipped the Baltimore Union Passenger Ry. Co. with electric locomotives. During this year electric traction was applied by this company to the Ninth Avenue lines in New York, but after a few experimental runs of the locomotive termed the "Benjamin Franklin" the experiment was abandoned.

In 1884 Bentley and Knight installed a system in Cleveland, Ohio, which was probably the first to come into active competition with a horse car line. Two miles of track were operated with under ground conductor in wooden slotted conduit. Motors were connected with car axles through the agency of wire cables.

The railroad installed in Kansas City, Mo., in 1884, by J. C. Henry was noteworthy for its departure from other designs and its adoption of features which have since become standard practice in electric railroading. Henry claims to have introduced the use of the overhead trolley. Whether this be true or not, the word "trolley" was first coined by the employees upon this road as a contraction for "troller" the word first applied to the four wheeled carriage which was used on the overhead wire as a current collector and connected with the car by means of a flexible cable. The use of the trolley rope for replacing the trolley was of much more significance than it would at first appear because of the fact that it was formerly customary to hire a boy to ride on top of the car to keep the trolley on the wire. The present system of span construction and feeder installation was first developed by Henry on this road. His overhead conductors consisted of two No. I B. & S. bare copper wires spliced every 60 ft., for this was the greatest single length procurable at this time. The rails used were those which had been installed 12 years before for horse car service and weighed but 12 lb. per yard. They were at first bonded by driving horse-shoe nails between the fish plates and the rails. The motor was a 5 h. p. Van Depoe e type connected with the axles by means of a clutch and a five speed differential gearing. The generator was a series arc machine of 10 h. p. developing a voltage up to 1000 volts. Although Henry was able to mount 7 per cent, grades without difficulty, the Cleveland road was the only other practical road operating in America at that time and it was extremely difficult to gain the confidence of the public.

Of the roads that were installed during the next few years,

HISTORY OF ELECTRIC TRACTION. 9

the one which gave the greatest impetus to electric traction and the one often quoted as the first electric road in the United States was that in Richmond, Va., equipped in the year 1888 by Frank J. Sprague. At this time Mr. Sprague was already prominent in the railway field, although much of his time had been given to the development of the stationary motor. In a paper befoie the Society of Arts of Boston in 1885 he had advocated the equipment of the New York Elevated Railway with motors carried upon the trucks of the regular cars. In 1886 a series of tests were carried on upon the tracks of the 34th street branch of this road. These experiments, like many previous ones, however, were finally suspended because of the impossibility of interesting the railway management sufficiently to launch out upon a commercial installation.

The motor design and suspension used by Sprague in these tests were the forerunners of present construction and therefore worthy of a brief description. The motor frame contained bearings mounted upon the car axle, thus permitting the former to swing slightly about the axle as a center keeping the gear and pinion always in mesh on rough track. The other side of the motor frame w^as hung from the truck frame by means of springs. Single reduction gearing was used. Two motors were used on each truck but they were open to the weather. The first designs were shunt wound but later types made use of a series compensating winding. Control was obtained by resistance in both armature and field circuits. The motors were used for returning energy to the line as well as for braking.

Before considering further the rather important installation at Richmond, it is well to consider a census of electric traction development early in 1887. In Europe at this time there were but nine installations including but 20 miles of track taking into consideration every type of electric traction including that in mines. In the United States there were 10 such installations involving 40 miles of track and 50 motor cars. Public prejudice had not been overcome and no system of any size had been operated commercially.

The Sprague Electric Railway and Motor Company, contracted for installations at St. Joseph, Mo., and Richmond, Va., during lO ELECTRIC RAILWAY ENGINEERING.

the year 1887, the latter contract covering a complete new road including generating station, overhead lines, and the equipment of 40 motor cars with two 7 i /2 h. p. motors each. It was placed in operation in February, 1888, and many were the new experiences and amusing anecdotes connected with this installation. The distribution system consisted of an overhead conductor mounted over the center of the track with a second parallel conductor on the pole line supplied with feeders from the power station and extending to various distributing points. The power station was equipped with six 40 k. w. 500 volt Edison generators driven by three 125 h. p. engines. Upon each axle of the car was mounted an exposed motor in the manner previously described. The single reduction gearing employed at first was later replaced by the double reduction type. The speed control was effected by two separate switches, one changing the field connections from series to parallel and the other making similar changes in the armature circuit. The cars could be operated in either direction from either end and the entire weight of the car was available for traction. Motors were operated in both directions, at first with laminated brushes fixed at an angle and later with radial solid metallic brushes. The success of this road at Richmond, in the face of many reverses and new engineering problems which had to be overcome, was probably largely due to the fact that Mr. Sprague was the first man with a competent education to enter the field. With this technical training together with his familiarity with the failures of other experiments and the development of the stationary motor with which he was closely allied, he was able to solve the many difficult problems which arose and place this road on a practical operating basis.

From this date electric traction became firmly seated and its future development was rapid, the natural tendency being toward heavier equipment. After investigation of the Richmond system the West End Railway of Boston soon adopted electric traction. In 1890 the South London road was equipped with electric locomotives and three years later the Liverpool overhead electric railway was put in operation. Third rail trains of four motor cars, equipped with hand control, hauling three trail care were used at the Chicago World's Fair in 1893 and in 1896 the

HISTORY OF ELECTRIC TRACTION.

II

Nantasket branch of the New York and New Haven Railway was electrified. September of the same year saw the Lake Street Elevated of Chicago begin electrical operations and two months later electric service was begun on the Brooklyn Bridge. Since it is impossible to further list the new electric roads coming into existence the following table will be of value in pointing out the remarkable growth of the electric railway in the United States.

TABLE I.

Growth of Electric Traction in United States.

Year.

No.

electric roads.

Miles track.

10863

22000

Note. — The decrease in the number of companies from 1895 to 1902 is probably due to the large amount of consolidation going on during this period.

The most important changes in motor design that came with this progressive movement of the electric railway were the enclosing of the frame to protect the motor from the weather, the replacing of cast iron by steel, the change from two to four poles, the use of form wound coils and carbon brushes and the return to the old single gear reduction between motor and axle. The control system of 1892 made use of the combined resistance and series parallel connection, which is recognized as good practice to-day while the introduction of the blow out magnet was a long step forward in controller design.

The more recent developments in electric traction comprise the use of alternating current for transmission to substations, the multiple unit control of the various cars of a train from a single master controller, the use of alternating current motors on the car, the electrification of steam roads with the more powerful electric locomotives, and the use of high voltage direct current system. These problems are of such a broad nature and so important in the study of modern practice that they will be taken up more in detail elsewhere. Suffice it to say, by way of historical comment, that the rapid introduction of interurban railways beginning about the year 1894, together with the advances made in transformer design by Stanley, in polyphase transmission by Ferraris and Tesla and in the synchronous converter by Bradley and others brought about the first of the above mentioned changes, i.e., the use of alternating current for transmission purposes. Probably the first proposal to use such a system with substations was the one made by B. J. Arnold in 1896 for an interurban road to run out of Chicago. Although this particular line was not built, a similar system was installed about two years later. The multiple unit system was developed by F. J. Sprague who proposed its application to the New York Elevated Railway in 1896. After several vain endeavors to secure its adoption it was finally installed the following year by the South Side Elevated Railroad of Chicago and is now in common use on elevated systems and is used to some extent in interurban traction.

Summarizing briefly, the most prominent names in the development of the electric railway are found to be those of Faraday, Davenport, Farmer, Hall, Pacinotti, Siemens, Green, Field, Van Depoele, Daft, Bentley, Knight, Henry, and Sprague. While gradual developments have been going on more or less irregularly since 1835, the practical electric railroad, operating upon a commercial scale, dates back to about the year 1888. Vast strides have taken place since that date, however, until at the present time electric traction is the recognized transportation system in practically all cities and towns. It has tied together the larger cities with facilities for rapid passenger transit and for the transportation of both express and freight. It has opened up the city markets for the farmer of the small town, and the country suburbs for the residences of the city business man. It has competed successfully with the steam roads on interurban lines; it has found a foot-hold in the city terminals of the former, and is at present being seriously considered and in some particular cases has been adopted and successfully tried out for trunk line ser\dce. Rightly has it been said that its growth is without a parallel in the history of American invention and industrial progress.

CHAPTER II. Traffic Studies (Predetermined

One of the first considerations in connection with the planning of a new railroad or of an extension to an old system, whether it be within the limits of a city or an interurban line, is the study of probable traffic. Upon such a study is based the predetermination of gross income, train schedules, and power station demand. The importance, therefore, of an accurate and detailed study of all the factors which may affect the traffic upon a given road need not be emphasized further.

Population. — A study of the railway census will disclose the fact that there is a fairly dependable relation between passenger traffic and population for both urban and interurban railroads. In the latter case, of course, the population under consideration must be that of the two terminal cities and, in most cases, a portion of the intermediate population which may be considered as tributary to the line. The determination of this tributary population is rather difficult, being largely dependent for its accuracy upon the experience and judgment of the engineer. In general, however, it is usually taken as the population of a strip of territory from i 1/2 to 2 miles in width on either side of the proposed railroad and parallel thereto. The population of such a strip may be determined by actual canvass or it may be assumed that the township or county through which the road extends is evenly populated throughout the rural districts. If this be true, the tributary population may be found from the following proportion.

Tributary population Area strip.

Township population Area township The township population may be obtained from the census

reports and the required areas scaled from a map of the territory

in question.

While it will be found advisable t.n make an analysis of the

ELECTRIC RAILWAY ENGINEERING.

relation between population and passenger traffic per year, mileage of track economically operated, gross income, etc., for the entire country, a table or series of curves covering such data obtained from the particular locality in which the proposed road is to be operated will be found of more value. The nearer the conditions of installation and operation of these roads approach those of the proposed road, the more dependable will be the results based thereon.

A table giving data of value in predetermining the traffic and gross income for a proposed road is given herewith for cities of the middle west under 25,000 population.

TABLE II.

Electric Railway Statistics.^

City,

Population.

Total.

No. passengers per unit population.

Total.

Miles track population.

Alton, North Alton, Up- |, 17,487

per Alton, 111.

Kankakee, Bradley, Bour- 15,708

bonnais, 111.

Vincennes, Ind

Burlington, la

Ashtabula, O

Lima, O

Tiffin, O

Zanesville, O

10,249 23,201 12,949

21,723 10,989

23,538

1,497.130

870,838 714,769

450,000 1,600,000

999,857 1,375,979

482,000 1,800,000

43 69

77 63

43 76,

.6

12.25 ;

•3

9.67

•5

12.78 1

•9

8.00

.0

14 50 !

.2

5-75 !

•3

18.55

•9

7-33

•5

10.00

i

0.70

0.77 0.81

0.78

0.62

0.44

0.85

0.67 0.42

Whereas such a table offers more opportunity for the correct comparison of traffic, etc., for an urban road or for extensions to such a system than for the predetermination of interurban traffic, yet the methods outlined may be used to advantage in interurban developments providing they are applied with conservative judgment based upon successful interurban experience. As an example of such adaptation of data to interurban practice it should be noted that a different proportion of terminal population will be tributary to the traffic of the proposed road in each

^ Taken from Railway Census, 1902.

case under consideration. In the case of the road being the first to enter a relatively small terminal city, a large portion of the population of the city will avail itself of the road, but if the road is the fifth or sixth to enter such a city, as Indianapolis or Chicago, a relatively small portion of the population of the terminal city can be counted upon for passenger traffic. It follows directly from this, therefore, that with a large terminal city, the earnings of the road per capita of terminal population willbe small and the earnings of a successful road per mile of track will be relatively large and vice versa.

Growth in Population. — It is necessary, however, to know more than the present terminal and tributary population. The growth of both for several years to come must be predicted. In order to do this intelligently it is necessary to know the growth in the past not only, but to study the causes of any eccentricities in the growth curve. It is only after such a detailed study that the population curve may be accurately extended to determine the population to be expected forty or fifty years hence.

Bion J. Arnold, consulting engineer of Chicago, in his "Report on the Chicago Transportation Problem," points out very clearly the fallacy of predicting the population for any considerable term of years by any rate of growth which has existed in the past, if the law of "Yearly decrease in the rate of increase" be neglected. If, by way of illustration, we refer to the curve of Fig. I which represents the population of the city of Philadelphia during a long term of years, we shall see at once that had the future population of that city been predicted in i860 from the rate of increase during the previous decade, the result would have been far from the fact. As a matter of fact, the rate of increase in population of Philadelphia dropped in five years from 1^7, per cent, per annum to 9 . 7 per cent, and, in another five years, to 2 . 9 per cent. Although this marked change in the rate of increase of population is exceptional in the case of Philadelphia, x\rnold found that in the cases of the eight largest cites of the world which he studied the average rate of increase in population is gradually decreasing. It is obvious, therefore, that even if the average rate of increase in population over a long term of years were applied to the future growth of a city.