Electric traction

“ The adoption of electric traction on such a route [Pg 123] as the Brighton main line would be a benefit in several ways. It would lead to a faster express service, as the high overload capacity of the electric motor enables it to take small account of gradients. ”

“ Electric traction by storage batteries.In all the instances which have been referred to above, electricity is employed as a means of transmitting power as it is wanted from a generating station to the cars, through a conductor extending along the track. Another method of effecting electric traction is to carry a store of energy on the car or on a special locomotive, by using secondary batteries which are charged from time to time at the generating station. ”

“ Commercial Results.—Interest in the commercial results of tramway enterprise is practically limited to electric traction, since other forms of traction have been almost entirely superseded owing to their economical inferiority. The main advantages of electric traction over horse traction lie in the higher speed, greater carrying capacity of cars, and the saving in power over a system in which only a small proportion of the power source is available at one time. ”

“ A further rival to the electric tramway is arising in the system of railless electric traction, the fundamental principle of which is the application of electric power, derived from overhead wires, to electric cars, resembling motor-omnibuses (or alternatively, to goods lorries and vans) , driven on ordinary roads without rails, and capable of being steered in and out of the traffic over the whole width of the roadway. ”

“ Before going on to discuss the 'accumulator' or 'storage battery' system of electric traction, reference should be made to an invention which holds the germ of great economies in electric traction. This invention is known under the name of 'regenerative control.'
It has already been explained that the dynamo is reversible—that is to say, a dynamo may act as a motor, or a motor as a dynamo. This fact is usefully applied in braking tramcars. When a car has gained speed, its momentum represents a certain amount of stored energy. ”

“ Those forms of electric traction in which the power is supplied to the cars from an outside source have many advantages. Only the weight of the. motors has to be carried. These are efficient over a wide range of speed, accelerate quickly, have a large reserve of power and are clean and silent. The electric conduit and surface contact tramways do not require any disfiguring overhead wires. They have, however, troubles of their own. The construction of the electric conduit is so expensive that its choice must necessarily be limited to large cities. ”

“ As a means of city transit, and of rapid, convenient, and economic intercourse between suburban localities and rural towns and villages, the electric traction system ranks as one of the greatest wonders of the century. The speed with which it found favor, the enormous capital it provoked to activity, the stimulus it gave to further study and invention, the surprising number of passengers carried, go to make one of the most interesting chapters in electric annals. ”

“ There never has been any question as to the value of electric motors for traction service. Wherever a current of electricity can be distributed and transmitted to a motor, it is the most satisfactory method of moving vehicles, as has been shown in street railways.
Requirements.—But on individual cars, incapable of getting current from a system of wiring, the matter presents an entirely different aspect, and brings forth new problems, hence storage batteries must be resorted to, and this involves the consideration of many elements that may be ignored with the usual traction system. ”

“ As already mentioned, it costs about as much to work a horse tramway when the cars are empty as when they are full, since the main item is the maintenance of the 'vital principle' of a certain number of horses independently of the traffic. But with electric traction the motors require less power when the cars are running light. And less current for the motors means less current generated at the power station—that is to say, less steam, less oil, less coal, less wear and tear. If more current is demanded, it is because more passengers are being carried and more revenue earned. ”

“ Among the industrial applications of electricity none have attained greater commercial importance in recent years than electric traction. Although experimental work in this field had been carried on both here and abroad for many years, it was not until the great electric revival of a dozen years ago that the subject began to have importance. Even then this form of traction did not take a commercial place comparable with the other applications of electricity. ”

“ Anyone who glances over the history of electric traction will be struck by the absence of outstanding names. There is no man who occupies the same position in the sphere of electric locomotion as Watt does in the world of steam, or Stephenson in the world of railways. As a pioneer, Dr. Wernher von Siemens perhaps deserves more honour than any other. But the leading ideas embodied in electric traction systems were contributed by engineers who worked in the general field of electrical engineering ”

“ But by 1890 electric traction had become practical, and the issuing of patents for cable lines ceased as abruptly as it had begun. Before the close of the century practically every important cable line in the United States had changed its motive power to electricity. Thus in a brief quarter of a century this method of street-car traction had come into existence, revolutionized all hitherto known methods, and become obsolete. ”

“ There has been a steady improvement in the power and efficiency of locomotives, but progress has reached a point at which further increases in speed and accelerating power (a very important matter) are not attainable without a prohibitive increase in the consumption of coal and a costly strengthening of the railway track to stand the strain of heavier engines pounding along at very high speeds. Electric traction, which is a reversion in part to the stationary engine system, offers a means of escape from the limitations of the locomotive. ”

“ The electric and power equipment, which embodied in itself the latest results of American practice, was also manufactured in America to suit the needs of the road. Other similar railways are in contemplation in London and in other cities of Europe. As on the elevated roads in New York City, the replacement of underground steam traction, where it exists, by electric traction is evidently only a question of a few years. ”

“ It is not a question of engineering but of finance, and high-speed, heavy electric roads are likely to come when the traffic will support trains at short intervals. The application of electric traction to trains of more than several cars requires a large electric locomotive or a special system of control, so that the motors on each can be controlled by one motorman. The only system in use to-day is the Sprague multiple-unit system, a most ingenious system. (See Street Railway Journal, May, 1901.) ”

“ In the railway world there is a growing conviction that the adoption of electric traction on all suburban and inter-urban railways must be simply a matter of time. For main line traffic the possibilities of using electricity are as yet only an article of faith among electrical engineers. ”

“ Electric Street Cars—Suburban Cars—Electric Third-rail from Utica to Syracuse—Some Railroads Partially Adopt Electric Power—The Benefit of Electric Power in Tunnels—Also at Terminal Stations—Conditions Which Make Electric Traction Practical and Economical—Hopeful Outlook for Electric Traction—The Monorail and the Gyroscope Car, Invented by Louis Brennan—A Similar Invention by August Scherl.
It is barely more than a quarter of a century since electricity first became practical for use as a motive power upon railroads. ”

“ If the advance of electric traction on railways must be slow, it is because financial and not engineering considerations govern the speed of conversion. No railway company can take a step involving hundreds of thousands of pounds, and a revolution in working methods, without prolonged consideration and elaborate preparation. ”

“ There is still some doubt in the minds of railway engineers whether electric traction is really superior to the steam locomotive on the main railway lines, where distances are great and train loads heavy. ”

“ The system is very simple and inexpensive, and the amount of traction secured is entirely within the control of the motor man, as in the electric system. It will be seen that the car here will not, with the traction circuit open, propel itself up hill when one end of the track is raised more than 5 inches above the table; but with the circuit energized it will readily ascend the track as you now see it, with one end about 131⁄2, inches above the other in a length of three feet, or the equivalent of a 40 per cent. ”

“ Some of the London railway companies have spent enormous sums in enlarging their terminal accommodation and have found that it is still inadequate to the demands of the 'rush' traffic. Electric traction therefore offers them an improvement of enormous value without the expenditure of a penny on station alterations. ”

“ Wherever traffic is dense and the distance to be traversed not too great, the conditions are already present for the advent of this form of locomotive; and when we recall the rapidity with which city and suburban railways have spread, we can not doubt that once the problems of electric railway engineering are worked out, and the necessary preliminary work of demonstration gone through with, we will witness an equally rapid extension of electric traction to the steam highways of the world. ”

“ By the end of 1903 it is hoped that the work will be sufficiently advanced for some trains to be run by electricity. Finally, as the Metropolitan’s engineer-in-chief remarks, there will be no marked novelties, but “the very conversion from steam to electric traction will prove a great novelty and an attraction. New cars of the latest type will be introduced, the stations will be bright and cheerful, the atmosphere pure; travel will be undertaken with a greater degree of comfort, and freedom from disagreeable odours. ”

“ As a rule, the cars used for electric traction have varied but slightly from the type of tramway car prevalent in different localities. The tendency, however, has been to increase their size.Cars. For electric railway work, as distinguished from tramway work, the cars generally follow the pattern that is standard on American steam lines. The trucks used for electric cars are made of steel, with heavy axles and suspension bars for carrying the electric motors. ”

“ Mining men insist upon the caution that where this length of distance has to be exceeded in the haulage of ore from the mine over wire-rope tramways, there is need for two installations, the loaded trucks being passed along from one to the other by means of suitable appliances at the termini.
Electric traction must, in the near future, displace such a cumbrous system, and the plan upon which it will be applied will probably depend upon the use of a steel cable along which the motor-truck must haul itself in its progress. ”

“ All electric roads do not use direct current. Certain simplifications in the use of single-phase alternating currents in traction motors have increased the number of roads using a system of alternating-current power supply. ”

“ The operation of our ordinary electric railways is very simple: the current is taken from an overhead, side, or underneath wire, directly through the air, without the intervention of a trolley, and the fast cars, for they are no longer run in trains, make five miles a minute. The entire weight of each car being used for its own traction, it can ascend very steep grades, and can attain high speed or stop very quickly. ”

“ Hence most urban stations now supply current not only for electric lighting but for running the town tramway system, and this traction load being chiefly a daylight load serves to keep the plant employed and remunerative. It is usual to furnish a continuous current supply for traction at 500 or 600 volts, although some station engineers are advocating the use of higher voltages. ”

“ In stopping the car, this energy has to be absorbed or dissipated in some way or other. One method is to utilise the friction of brake blocks on the wheels, or of skids on the rails themselves. With the electric car, however, it is possible to absorb the energy by making it drive the motors as if they were dynamos. The moving car drives the wheels, which in turn drive the motors; and the current so generated may either be absorbed in electrical [Pg 68] 'resistances' or led to electro-magnets which are so placed that they exercise a retarding pull on the rails. ”

“ So some of these, with the aid of the electrical manufacturers, experimented and developed the alternating current of high voltage and low amperage, which is capable of being carried to distant transforming or sub-stations and there reduced to low voltage and high amperage. This alternating [Pg 438] current system, because of its great operating economies, is rapidly becoming the standard for the city railroad systems of metropolitan communities, as well as for the great trunk-line interurban electric roads that are beginning to gridiron the country. ”