ELECTRIC TRACTION. Although experimental electric motors were built more than a century ago electric traction is a modern development. Briefly described, an electric railway is a combination of a source of electric energy, means for transmitting it to vehicles along a right of way, including the raising and lower ing of electrical pressures and conversion of type of current, and motors on the several vehicles provided with means for collecting and controllably converting energy into mechanical power.
Some time elapsed before the remarkable characteristic of re versibility of function was known, with the natural corollary of the electric transmission of energy by the use of two similar ma chines connected in the same circuit, one generating and the other reconverting electricity. It is the fundamental of all modern power development of whatever character. It has been claimed that this principle was enunciated by Pacinotti in 1867, but certainly no use of it was made until about 1873, when Gramme and Fontaine demonstrated it at the Vienna Exposition.
The first public demonstration using the dynamo-electric ma chine was made at the Berlin Exhibition in 1879 by the Siemens firm. The transmission of electric energy for transportation was a natural sequence, and at this exhibition was installed and oper ated an equipment comprising a third of a mile of track, a small locomotive and three cars having a capacity of about 20 people. The current was supplied through a central rail, with running rails for a return. The motor was carried longitudinally, motion being transmitted through spur and bevel gears to a central shaft from which connection was made to the wheels. This exhibit was followed by others at Brussels, Dusseldorf and Frankfort, but the first regular line, a short one with one motor car, was installed at Lichterfelde, and opened for traffic in May 188i . At first both rails ' were used for conducting the current at low potential. The motor. was carried on a frame underneath the car between the wheels, the power being transmitted to the axles by steel cables, and a speed of about 3o m. per hour was attained. Some years later the rail distribution was replaced by overhead conductors. The Siemens firm also installed at the 1881 Paris Exposition a tram way about a third of a mile long. The overhead conductors con sisted of two slotted tubes, in which slid shoes held in contact by an underrunning wheel on a framework supported by the con ductors and connected to the car by flexible cables. The motor was placed between the wheels and the power transmitted by a chain.
About this same period various American inventors undertook experimental work. With the possible exception of one George Greene of Kalamazoo, Mich., who repeated some of the early primary battery experiments, apparently the first of these were Stephen D. Field and T. A. Edison. These inventors became involved in a patent interference with each other and with Siemens, all having filed applications within a few months in 1880. Siemens' early testimony was rejected under the existing rules and priority for limited features was awarded to Field, who filed a caveat in 1879, in February of which year he made plans for an electric railway to use current from a stationary generator through a con ductor carried in a conduit, with rail return.
In 188o at Menlo Park, Edison operated a small electric loco motive pulling a trail car. Two of his early lighting dynamos were used, one for generating the current and the other as a motor. The two rails, insulated from each other, were used for current supply through wheel contact, one wheel being insulated from the axle. The power was transmitted to the axle and at first the speed was varied by a friction drum or a belt with a tightener. Two years later, at the instance of Henry Villard, similar experiments were repeated on a larger scale but without material change. The system was impracticable because the use of the two rails as conductors was prohibitive on account of the impossibility of pre venting short circuits under commercial conditions. The method of transmitting and controlling power was likewise impracticable. Siemens meanwhile continued work, constructing experimental roads near Meran in the Tyrol and elsewhere.
At a somewhat earlier period F. J. Sprague, a midshipman in the U.S. navy, had constructed in 188i a series-parallel controlled dynamo and motor of novel design, this method of control having also been independently invented in England by Dr. John Hop kinson the year before. While acting as a juror at the 1882 Crys tal Palace Electrical Exhibition Sprague considered the possibility of operating the District Railway electrically, first planning the use of main and working conductors, the latter to be carried be tween the tracks with automatic means for maintaining tension; but to meet the complication of switches he later conceived the idea of a car moving freely between two contact planes, the ter minals of a constant potential generating system, for which in practice would be substituted the rails and switches, with wheel contact, and roof-supported conductors following the centre lines of tracks and switches, with under contact from a spring-mounted roller carried on the car over the centre of the trucks. This was the genesis of the present trolley in tramway and main line prac tice, but was not put into effect until four years later.
In the fall of 1882 Dr. Finney of Pittsburgh proposed operating omnibuses electrically with current from overhead wires carrying a small trolley connected to the vehicle with a flexible cable, while in England Profs. Ayrton and Perry read a paper on automatic railways before the Royal Institution, and Dr. Fleeming Jenkin, the distinguished Scotch scientist, proposed a telepherage system, or automatic overhead railway for carrying merchandise. The de velopment by Faure and Brush of the storage battery was followed by experiments in London and Berlin in 1883 by Reckenzaun. Here the car body was carried by two trucks, each equipped with a motor and worm gear drive. Two sets of brushes were used and speed varied by using the batteries in series or parallel, with resis tances to reduce sparking in changing.
Following their experiments in the United States the Field and Edison interests were combined in a corporation, which first oper ated a small locomotive equipped with a Weston machine at the Chicago Railway Exposition in 1883. The motor was connected by bevel gears to a shaft from which power was transmitted by belts to one axle, and the current was taken from a centre rail with track return. A lever operated clutches on the driving shaft and the speed was varied by resistances. Reversal of movement was effected by two movable brushes, only one of which could be thrown into the circuit at a time. A short experiment was made by Field at Stockbridge and another on the 34th street branch of the New York Elevated, but no commercial installations were made by the company. Field later joined with Eickemeyer in the devel opment of a side-rod driven equipment but this was short-lived.
The use of the conduit for carrying the conductors was under taken by Bentley and Knight, who in 1884 installed a 2 m. section and two cars on the tracks of the East Cleveland Railway Com pany, the wooden conduits being laid between the tracks. The motors were carried under the car bodies and power transmitted by cables. This installation was operated during the following winter and abandoned later. At this period J. C. Henry entered the field and installed a small line in Kansas City, using two over head conductors on each of which travelled a trolley connected to the car by a flexible cable. The motor was mounted on a frame supported on the car axle, with power transmitted through a clutch and a nest of gears. Experiments conducted on another section of the road included use of the rails as a return circuit. The col lectors were of different types but the preferred one was a trolley carried by and gripping the sides of the wires.
In the next two years Prof. Short of Denver began experiments on a short track, and the construction with Nesmyth of a section for conduit operation. The series system was used, a constant current being sent through all the motors on the line by automatic sectionalizing of the conductors, the total potential varying accord ing to the number of motors. Speed and direction were varied by shifting the commutator brushes or diverting a part of the cur rent around the motor. The experiments were continued into the following year and repeated at Columbus but failed because of the principle involved.
Daft and Van Depoele meanwhile were continuing work, the former making an installation on the Union Passenger railway of Baltimore, the first in the United States to regularly operate for fares. Here were installed four dummies which pulled regular street cars. Centre and running rails were used for the normal current supply, and at crossings an overhead conductor with under running contact. Daft's most ambitious project was the equipping of a 2 m. section of track on the Manhattan Elevated, on which tests were conducted in 1885 with the "Benjamin Franklin," oper ated by a motor mounted on a platform and pivoted at one end, the drive being through grooved friction drums held in close con tact. Then followed installations in Los Angeles and elsewhere, using double overhead wires carrying a trolley carriage with flexible connection to the cars.
Van Depoele's work in this period was the equipping of a loco motive, current being taken from an underground conduit, to pull a train at the Toronto Exhibition. In the following year he used an overhead wire and a weighted under-contact arm at the end of the car. His next installations were on the South Bend railway with several cars, and in Minneapolis, where an electric car took the place of a steam locomotive. The next year he equipped a road at Montgomery, Ala., first using a travelling trolley connected to the car by a flexible conductor, but later a non-reversible under running contact mounted at one end of the car. Other small installations were made in Windsor, Ont., Detroit, Mich., Apple ton, Wis., and Scranton, Pa. In these equipments the motor was carried on the platform and connected to the wheels by belts or chains. The cars operated from one end only.
Following motor exhibits at the Philadelphia Electrical Ex hibition in 1884, Sprague in the following year essayed a major project, the equipment of the New York elevated system with motors carried on the regular car trucks, beginning actual con struction of a test equipment that was transferred to the 34th street branch of the "L" where regular tests began in May 1886. These motors were the parent models of modern equipment. They were centred on the driving axles, connected to them by adjustable single-reduction gears, and the free ends were carried by springs from the transom, now known as the "wheelbarrow suspension." One set of brushes was used for both directions of movement, and the motors were used not only for propulsion but for braking. A shunt field coil was supplemented by a coil in series with the armature at right angles to the normal field, to prevent shifting of the neutral brush point, this being the first "interpole" winding used on railway motors. They were operated at 600 volts, at each end of the car by similar switches, and variation of speed was effected by inverse changes of resistances and field strength. This control provided the means for regeneration, energy being first returned to the line when slowing down from high speed and the motor circuit then closed on itself. Then construction began of a locomotive car of 30o h.p. capacity, all axles to be equipped. Later followed motors for experiments with storage batteries in Philadelphia, New York and Boston in 1886.
In Europe a short road was installed at Bessbrook-Newry under the direction of the Messrs. Hopkinson in 1885, and one at Ryde in 1886, in which year Holroyd Smith equipped the Blackpool road, using a conduit with a complete metallic circuit, the first of this type abroad. The motor was carried under the car between the axles and connected by chain gearing. Fixed brushes with end contact were used for both directions in running.
The Richmond contract called for completion in 90 days of an installation for a road with i 2 m. of track, at that time unlaid and with route undetermined, of equipment for a complete steam and electric central-station plant and 8o motors on 4o cars, with all the appurtenances necessary for operation. This was nearly as many motors as were in use on all existing installations. Thirty cars were to be operated at one time and many heavy grades and curves negotiated. Finally, the payment was to be $120,000 "if satisfactory." Experimental operation began in the fall of 1887 and regular service in Feb. i 888. The difficulties met were numerous, but after many vicissitudes which taxed the technical and financial resources of the company, success was achieved, and the Richmond road is now recognized as the first of the modern systems in which a large railway was equipped and operated under service conditions by electricity, and as the pioneer of com mercial electric traction.
Its features included distribution by an overhead line over the centre of the track, reinforced by a main conductor in turn sup plied at central points from a constant potential plant operated at 45o volts, and with reinforced track return. Current was taken from the overhead line, at first by fixed upward pressure contacts and later by a wheel carried on a pole supported over the centre of the car and having free up and down and reversible movement. Series-wound motors, one to each axle, were centred on and geared to them on the "wheelbarrow" suspension method, first by single adjustable and then by double reduction gears. All the weight was available for traction and the car could be operated in either direction from either end of the platform. Control was at first by variation of the field coils from series to multiple relation and series-parallel grouping of armatures by a separate switch. Motors were run in both directions with fixed brushes, at first laminated ones placed at an angle, then solid metallic ones with radial bearing and finally carbon ones as proposed by Van Depoele.
Prior to this time the cable system had been adopted on several roads and was under consideration for the West End road of Boston, but was abandoned by its president, Henry M. Whitney, in favour of Sprague equipment. Soon afterwards the cable road in Minneapolis was abandoned. Meanwhile the Van Depoele interests had been absorbed by the Thomson-Houston Electric Company and there followed a period of extraordinary activity in the United States. in which this company and the Sprague Electric Railway and Motor Company were the principal competi tors. It resulted in contracts for over 200 railways within two years. There followed continuous improvement and increase in the size of apparatus. Form-wound armatures, proposed by Eicke meyer, replaced irregular windings, and metallic brushes gave way to carbon, this single change initiated by Van Depoele being of prime importance. Cast and wrought iron yielded to steel, two pole motors to four-pole, double reduction gears to single, and open motors to closed, protected by their own castings. In 1892 the Reckenzaun-Condict single movement series-parallel and resist ance control was adopted and the Thomson magnet blow-out suc cessfully applied to controllers by Potter.
The rapid spread of electric railway in the United States resulted in installations in Europe at Florence-Fiesole, Halle and elsewhere, but it was not until some time later that there was any general adoption of the electric railway. Meanwhile the Sprague Com pany was absorbed in 1890 by the Edison General Electric Com pany, which later combined with the Thomson-Houston Company and others in the General Electric Company, and the Westing house Company also entered the field.
The electrification of the standard main line railroads, al though slow in beginning, has already made great progress and may be expected to continue. At first, on account of the high capital costs installations were confined to special conditions, as the operation of city terminals and tunnels. For a general solution the use of high electrical pressure is vital, and before the increased possibilities of the direct current motor were demon strated this need led to attempts to use both polyphase and single phase alternating currents without intermediate moving wayside apparatus. One of the earliest undertakings of this kind was the high speed test on the Zossen Military line in 1903, where a car was operated at 126 m. per hour, current being supplied on the polyphase system from three overhead wires through sliding con tacts at 14,000 volts pressure. The Valentina line, equipped by Ganz, also used the polyphase system, but with the rails as one conductor and at a lower pressure of 6,000 volts. In the United States a like equipment was installed on the Great Northern rail way, but this has been abandoned in favour of the single phase system. The multiplicity of conductors militates against the poly phase system, and where used directly alternating current is now generally supplied through a single overhead trolley line supported by a catenary.
An outstanding example of high-voltage, single-phase electrifica tion is that of the Pennsylvania railroad. Including branch lines and sidings a total of more than 2,000m. of track have been elec trified on this system. Both passenger and freight trains are op erated by electric locomotives from New York to Harrisburg, a distance of 184m., and from New York to Washington, a distance of 226 miles. Local trains of multiple-unit cars are operated in suburban service out of New York and Philadelphia. Other im portant single-phase electrifications in the U.S. are those of the New York, New Haven and Hartford, the Virginian, and the Nor folk & Western railroads. The last two are heavy coal-carrying roads which operate with electric locomotives.
Among the direct current electrifications the largest is that of the Chicago, Milwaukee, St. Paul & Pacific railroad. Nearly 9oom. of track have been electrified at 3,00o volts on this system. At the same voltage the Lackawanna railroad operates suburban serv ice with multiple-unit cars over 16om. of track in northern New Jersey, and the Cleveland Union Terminals Company operates in the metropolitan area of that city.
Suburban service with multiple-unit cars is operated in Chicago at 1,500 volts direct current by the Illinois Central railroad. At 600 volts direct current the New York Central railroad operates a terminal zone for some 3omi. outside of New York, using both electric locomotives and multiple-unit cars. The Long Island railroad also operates at this voltage over some 45omi. of track serving Long Island suburban towns. Both of these systems use a third rail for current collection as do all of the subways and elevated railway lines. The high voltage systems, both direct current and alternating current, have overhead current col lection systems.
Railroad electrifications in England and foreign countries show about the same diversity of types as in the U.S. Direct current opera tion at 600 volts is the usual practice in England, although there has been some electrification at 1,500 volts direct current. Other countries using direct current systems at voltages ranging from 600 to 3,00o in clude Argentina, Australia, Belgium, Brazil, Chile, India, Italy, Japan, New Zealand, the Netherlands, Poland, Spain, and the Union of South Africa. High voltage single phase alternating current installations are found in Germany, Hungary, Norway, Switzerland, and Sweden. Earlier electrifications in Italy were of the three-phase type, but the more recent installations have been 3,00o volts direct current.