Photograph of a trainFig. 12. Photograph of a train on the electrified section of the London, Brighton and South Coast Railway. The overhead wire is suspended from cables stretched between insulators, and current is conveyed from it to the trains through a 'bow' which slides along its lower side. The photograph is taken from the rear part of the train. The front and rear cars are both equipped with electric motors.
Fig. 12. Photograph of a train on the electrified section of the London, Brighton and South Coast Railway. The overhead wire is suspended from cables stretched between insulators, and current is conveyed from it to the trains through a 'bow' which slides along its lower side. The photograph is taken from the rear part of the train. The front and rear cars are both equipped with electric motors.
Fig. 12. Photograph of a train on the electrified section of the London, Brighton and South Coast Railway. The overhead wire is suspended from cables stretched between insulators, and current is conveyed from it to the trains through a 'bow' which slides along its lower side. The photograph is taken from the rear part of the train. The front and rear cars are both equipped with electric motors.
Where current has to be conveyed economically over long distances, it is generally done in the form of alternating current at high pressure. For instance, the transmission from a tramway power station to the sub-stations is almost uniformly by three-phase current at, say, 5000 volts. When it reaches the sub-station, it is 'transformed' down to the working pressure of 500 volts and 'converted' from alternating to continuous current by means of rotary machinery. The transforming is done by a stationary piece of apparatus similar in principle to the familiar induction coil. An induction coil takes current at a few volts from a battery into its primary circuit and transforms it, by induction in the secondary circuit, into current of high enough voltage to give a long spark. A transformer can be designed to 'step-up' or 'step-down' the pressure according to the requirements of the case.
So much explanation is necessary to give some account of the alternating current railways on the Continent and thence of the single-phase system on the London, Brighton and South Coast Railway. The Morecambe and Heysham section of the Midland Railway is also equipped on the single-phase system.
Most of the earliest electric railways on the Continent derived their power from waterfalls and had to transmit it for a considerable distance. Three-phase current at high pressure being adoptedfor this purpose, the Continental engineers set to work to find some means of utilising the high-pressure three-phase current directly. They did this by carrying the three wires on poles alongside the railway track, and using three 'bow' collectors (in place of trolley wheels) to convey the current to transformers on the motor cars or locomotives. In these transformers the current was brought down to working pressure and then led to motors designed for three-phase current.
An immense amount of technical ingenuity was exercised in developing this system; and when the Metropolitan Railway decided to follow the District in electrifying its lines, a three-phase system was proposed. As the Metropolitan and Metropolitan District companies share the working of the Inner Circle, it was necessary that both should adopt the same system. The result was that the question between three-phase and continuous current working had to go to arbitration. After a long discussion of masses of technical evidence, Mr Lyttelton, the arbitrator, decided that the direct current system was better suited to the conditions of traffic on an underground railway in London.
The wisdom of that decision will not be questioned now. Three-phase motors do not give the rapid acceleration which is so urgently required on suburban lines; there are complications in speed control;and the necessity of having three overhead conductors is also a serious drawback. For comparatively long-distance traffic with few stops, however, the three-phase system is quite suitable. That is to say, it is a possible solution of the main line problem.
The great simplicity and flexibility of the power supply arrangements in the case of alternating current traction encouraged engineers to find something better adapted to ordinary railway conditions than the three-phase motor. Their problem was to find an arrangement which required one overhead conductor instead of three, and also provided a motor with the high starting torque and easy speed control of the continuous-current motor. After much theoretical and experimental work, they found it in the single-phase system, using a motor which is similar in many respects to the continuous-current motor but capable of being operated by alternating current.
On the advice of Mr Philip Dawson, the London, Brighton and South Coast Railway Company decided to experiment with this system on the double line connecting London Bridge and Victoria stations, about 9 miles long. Power is supplied to each track by a single overhead conductor carrying current at 6000 volts. Transformers are placed on the trains to bring the pressure down to 300 volts; the current is then led through controllers to single-phase motors in much the usual way. The reason for using so higha pressure on the overhead line is not only economy in transmission. If lower pressures were used, the heavy currents required for train propulsion would require a thicker conductor and correspondingly heavier supports. At 6000 volts it is possible for two double sliding bows to collect sufficient current for a heavy train from a wire which is comparable in thickness to the ordinary trolley wire of a tramway.
The power distribution arrangements, it will be noticed, are very much simpler than with continuous current on the third-rail system. There are no sub-stations with rotary machinery. Power is supplied direct from the generating station to the overhead line and is transformed down by stationary plant on the train itself. Single-phase traction represents, in fact, power transmission for railway purposes reduced to its simplest elements.
The overhead construction differs, however, in some important points from the tramway standard. The supports, which are in both bridge and bracket form, are stronger; the insulators are, owing to the much higher pressure employed, more massive; and a different means of suspension has been adopted. Each conductor is hung by links from two steel cables stretched chain-wise between the supports. This method of 'catenary suspension' enables the bow to slide along the wire without the jolts which are noticeable with a tramway trolley. Such smoothrunning keeps the bow continuously at an even pressure on the wire—an advantage which is of great importance at high speeds. The trains are arranged on the multiple-unit system.
The full financial results obtained on this railway have not so far been made public; but it is sufficient for our purpose to note that the Company, after more than a year's full trial, extended the system to the Crystal Palace and to Croydon. Further extensions are, it is understood, contemplated over the suburban lines to Sutton and elsewhere; and in course of time the conversion of the main line to Brighton will be undertaken.
Here we touch upon the most interesting aspect of this demonstration of electric traction on the single-phase system. The system was adopted in the first instance because the third-rail system would lead to complications and dangers which could not be permitted at crowded railway termini shared by all kinds of traffic, suburban and main line. But the advisers of the Company had also in view the possibility of development beyond the range of suburban traffic. They therefore sought a system which, while comparable to the third-rail continuous current in the handling of suburban business, would be adaptable to main line conditions, where infrequent stops and long runs at high speeds are the rule.
The adoption of electric traction on such a routeas 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. It would also lead to a more frequent service, as the electric system is free from the conditions which force a steam railway to try to concentrate traffic on a limited number of long trains. Further, it would, by reducing the time lost in stopping and starting, bring the average speed of stopping trains much closer to that of express trains. All these improvements—assisted, probably, by lower fares—should lead to a great increase in the volume of traffic, thus reproducing the characteristic results of electric traction on suburban lines.
[1]An admirable explanation of alternating currents will be found in Mr Frank Broadbent'sChats on Electricity. (Werner Laurie, 1910.)
[1]An admirable explanation of alternating currents will be found in Mr Frank Broadbent'sChats on Electricity. (Werner Laurie, 1910.)
Like many other industries, electric traction has had its history brightened and made picturesque by curiosities of invention. Locomotion has, in fact, been a favourite field for the freak inventor; and some of his efforts with electric cars have been as weird and as fatuous as the most remarkable of perpetual motion devices.
One of these electrical monstrosities was, indeed, a kind of perpetual motion arrangement. It was invented about the year 1890 and consisted of a car equipped with accumulators which supplied power to a motor which drove a hydraulic pump, which in turn worked a dynamo supplying current to motors driving the axles of the car, and also to the accumulator for re-charging purposes. The inventor was so sure that he had got the better of the law of the conservation of energy that he provided his car with pointed ends, fitted with revolving fans to break down the air-pressure, in order that a speed of 125 miles per hour might be achieved. His name was Amen; and it provides a fitting comment upon his scheme.
Elberfeld-Barmen hanging electric railwayFig. 13. Illustration of Elberfeld-Barmen hanging electric railway. FromThe Electrical Industry(Books on Business), published by Messrs Methuen.
Fig. 13. Illustration of Elberfeld-Barmen hanging electric railway. FromThe Electrical Industry(Books on Business), published by Messrs Methuen.
Fig. 13. Illustration of Elberfeld-Barmen hanging electric railway. FromThe Electrical Industry(Books on Business), published by Messrs Methuen.
Several electric flying-machine ideas found their way on to the patent records. In 1893 a Frenchman registered a design for an air-ship with a cigar-shaped body and electrically-driven propellers. There was, however, more originality in an American idea that the progress of trains on the overhead railway might be assisted by the action of balloons in taking the weight of the cars off the rails. Curiously enough, other original inventors tried to get the opposite effect, by devising magnetic arrangements to increase the adhesion of the wheels to the rails.
More plausible forms of super-ingenuity have been exercised in connection with established modes of electric traction.
For the conduit system one inventor suggested a kind of reversion to the 'continuous valve' of the old atmospheric railway. The slot of the conduit was closed by a continuous series of springs which would be opened in succession by the plough as it passed along. This arrangement was actually tried on an experimental track in London. Another inventor proposed a novel plan for keeping the conductor in a conduit free from damp. The conductor was to be made hollow, so that hot air could be pumped through it to dry off any accumulated moisture.
Heilmann electric locomotiveFig. 14. The Heilmann electric locomotive—a generating station on wheels. The general arrangement of this locomotive should be compared with that of the modern electric turbo-locomotive described onp. 130and illustrated inFig. 15.
Fig. 14. The Heilmann electric locomotive—a generating station on wheels. The general arrangement of this locomotive should be compared with that of the modern electric turbo-locomotive described onp. 130and illustrated inFig. 15.
Fig. 14. The Heilmann electric locomotive—a generating station on wheels. The general arrangement of this locomotive should be compared with that of the modern electric turbo-locomotive described onp. 130and illustrated inFig. 15.
The most entertaining freak in connection with the trolley system was a device to enable two lines of car to use a single trolley wire. Cars going in one direction were to carry a double-ended inclined plane which would lift the trolley wheels of passing cars off the wire and let them slip back again. The only drawback to this arrangement was that it would not work.
Another inventor who was apparently impressed with the noise of trolley wheels on the wires designed a trolley head fitted with a pneumatic tyre. If he could have persuaded indiarubber to be anything but one of the best of insulators, he would have been completely successful.
One of the best known of electrical freaks—the Heilmann locomotive (Fig. 14)—is a very good example of the way in which an invention may be tried with enthusiasm, rejected with contumely, and revived at a much later date in an improved and more promising form. The Heilmann locomotive was practically a generating station on wheels. It carried a boiler and engines, which drove a dynamo, the current from which was led through controllers to motors coupled to the wheel axles. It was an enormous affair, over 18 metres long and running on sixteen wheels; extensive trials were made with it on the Western Railway of France in the early nineties. Some advantage was gained in smoothness of running, ease and uniformity of control, and improved acceleration; but its great weight, cost, and complexity were against it. In spite of the cordial support given to it by railway engineers, it was soon relegated to the scrap-heap.
Electro-turbo-locomotiveFig. 15. Electro-turbo-locomotive built by the North British Locomotive Company for experimental purposes. This locomotive is a 'generating station on wheels.' It carries a steam turbine driving a dynamo which supplies current through a controller to motors geared to the axles.
Fig. 15. Electro-turbo-locomotive built by the North British Locomotive Company for experimental purposes. This locomotive is a 'generating station on wheels.' It carries a steam turbine driving a dynamo which supplies current through a controller to motors geared to the axles.
Fig. 15. Electro-turbo-locomotive built by the North British Locomotive Company for experimental purposes. This locomotive is a 'generating station on wheels.' It carries a steam turbine driving a dynamo which supplies current through a controller to motors geared to the axles.
The Heilmann locomotive, it will be noticed, is similar in principle to the petrol-electric systems of propulsion now in use for road traction. But it is probable that the idea would never have been heard of again in connection with railway work had it not been for the appearance of the steam turbine. It was natural that the locomotive engineer should consider how the turbine could be applied to his purposes; and the first step in this inquiry made it plain that some electric method of control was necessary between the high-speed turbine and the driving axle.
Consequently, when the engineers of the North British Locomotive Company set to work in 1909 to design an 'electric turbo-locomotive,' they produced something not at all unlike the Heilmann locomotive. The equipment consists of a steam turbine, with elaborate condensing plant, a generator, and a group of driving motors (Fig. 15). The turbine runs at 3000 revolutions per minute and drives a continuous-current dynamo, the current from which passes through controllers to four motors which can be run in series, or two in series and two in parallel, or all in parallel, according to the draw-bar pull required. Trials with this locomotive were begun early in 1910, but it is yet too early to say whether it will be more fortunate than the Heilmann locomotive, and whether it is likely to delay the advance of the electric locomotive proper, fed with power by overhead wires from a central power station.
Behr electric mono-rail carFig. 16. Diagrammatic sections of the Behr electric mono-rail car. The car is balanced on the summit of a continuous trestle and is designed for speeds up to 120 miles per hour.
Fig. 16. Diagrammatic sections of the Behr electric mono-rail car. The car is balanced on the summit of a continuous trestle and is designed for speeds up to 120 miles per hour.
Fig. 16. Diagrammatic sections of the Behr electric mono-rail car. The car is balanced on the summit of a continuous trestle and is designed for speeds up to 120 miles per hour.
The possibilities of high speed on a mono-railway, and especially an electric mono-railway, have acted like a will-o'-the-wisp to the imaginations of many engineers. Of the various systems suggested, only one—the gyroscopic mono-railway invented by Mr Brennan—seems likely to survive; and even in that case victory under practical conditions is not yet certain.
At Ballybunnion there is a steam mono-railway which has been at work since 1888. It has had, so far as I am aware, no imitators; but its engineer, Mr Behr, retained so much faith in the principle that he decided to apply it to the problem of high-speed electric traction. During the 1900 session he promoted a Bill for the construction of a mono-railway between Liverpool and Manchester. There was tremendous opposition from the existing railway companies, which brought experts to prove that Mr Behr was a vain dreamer; but the Bill succeeded. The promoters, however, found it much harder work to raise capital for the project. They needed close upon £3,000,000, but the public response to the first invitation was so small that the scheme was abandoned.
The line, as projected, was nearly 35 miles long; and a speed of 100 miles per hour was intended, reducing the time of the Liverpool-Manchester journey to twenty minutes. At each end of the line (which was a double one) a steep gradient was arranged to facilitate starting and stopping—an arrangement, by the way, which is adopted to a certain extent on London tubes. The track itself was shaped like an invertedV, and practically the whole of the weight of the cars was borne upon a rail at the top. The wheels, therefore, were right in the centre of the car, which balanced itself on the trestle with its centre of gravity below the rail. Each side of the trestle carried two guide-rails which bore against free-running horizontal wheels on the car to prevent any undue lateral movement. Each car was designed to carry four motors with a total normal capacity of 160 horse power and an overload capacity up to 320 horse power. The rails for carrying the current were placed on the track in very much the same position as the ordinary rails occupy on a normal railway.
In another form of mono-railway—the Kearney high-speed railway—the wheels are placed below the car and run on a single rail laid direct on sleepers. The cars are held upright by flanged wheels on the top, running on a rail fixed to the roof of tunnels or to standards not unlike those of an overhead trolley. This railway has been exhibited in the form of a model.
The Brennan gyroscopic mono-railwayFig. 17. The Brennan gyroscopic mono-railway.—The car is electrically driven, and its equilibrium is maintained by the action of two gyroscopes, also electrically driven.
Fig. 17. The Brennan gyroscopic mono-railway.—The car is electrically driven, and its equilibrium is maintained by the action of two gyroscopes, also electrically driven.
Fig. 17. The Brennan gyroscopic mono-railway.—The car is electrically driven, and its equilibrium is maintained by the action of two gyroscopes, also electrically driven.
Mr Brennan's gyroscopic mono-railway was first shown, in a small size, at a conversazione of the Royal Society in 1907. Full-sized cars were constructed later, and one was seen at work during the Japan-British Exhibition of 1910. The distinguishing feature of the vehicle is the use of two gyroscopes (electrically driven), one horizontal and the other vertical, to maintain the car upright on a single rail, even when loaded unevenly and running at a fair speed round sharp curves. From one point of view, the gyroscopic car is no more wonderful than a spinning top, but the spectacle of a vehicle running steadily on a single rail was so extraordinary that the interest of the whole world was immediately aroused. Support was given to Mr Brennan's experiments by the India Office and the Colonial Office, on the ground that a railway which required only one rail, and was more or less independent of both curves and gradients, would be of great value in districts where the ordinary two-track railway might be both inconvenient and too costly. One drawback to the arrangement is the necessity of fitting each vehicle with gyroscopes, which are expensive and delicate pieces of apparatus. But the ingenuity of the invention is so great that Mr Brennan ought to reap the reward of seeing a gyroscopic railway in full operation before long.
'Telpher' systemFig. 18. The 'Telpher' system of electrical locomotion adapted to the transport of materials in a factory. The 'car' is suspended from a girder and is operated by the driver in the same way as an electric car. (FromElectrics.)
Fig. 18. The 'Telpher' system of electrical locomotion adapted to the transport of materials in a factory. The 'car' is suspended from a girder and is operated by the driver in the same way as an electric car. (FromElectrics.)
Fig. 18. The 'Telpher' system of electrical locomotion adapted to the transport of materials in a factory. The 'car' is suspended from a girder and is operated by the driver in the same way as an electric car. (FromElectrics.)
The only electric mono-railway actually at work is the 'hanging railway' at Elberfeld in Germany (Fig. 13). This railway is an evolution from the system of 'telpherage' which was devised in the very infancy of electric traction for the transport of goods. The root idea is to make the overhead wire carrying the current the track rail as well, the whole contrivance—rails and cars—being suspended from girders orcables supported by a series of standards or bridges. At Elberfeld the cars pass over streets and also over canals. There are no signs, however, that the 'hanging railway' will have any imitators. In appearance and in cost of construction and operation it does not seem to have any conspicuous advantages over a double-track overhead railway. The system of telpherage is therefore likely to be confined to the carriage of goods from one part of a factory to another, and (in the form of cable-ways) to the handling of materials in mines and other extensive engineering works. For such purposes it is having an increasingly extended application.
Nothing irritates an electrical engineer more readily than the repetition of the phrase, 'Electricity is in its infancy.' The words have been used by countless mayors and aldermen while 'inaugurating' tramway or electric lighting schemes; they have been echoed by innumerable journalists who persist in maintaining a Jules-Verne attitude towards the electrical industry. And what disturbs the electrical engineer is not only the banality of the phrase but the use of it as a comment upon the achievements to which he has devoted his life.
Nevertheless it will be admitted, from the rapid survey which we have taken of electric traction, that the potentialities of electricity in locomotion make an even stronger appeal than the actualities. Except in one field—the tramway field—engineers have only touched the fringe of possible developments in electric locomotion.
Even in tramway work we may, if legislative conditions improve and if current becomes much cheaper, see a considerable development in passenger and also in agricultural lines. Meanwhile the trolley omnibus offers a prospect of extension in electric road traction; and there is a great deal yet to be done with petrol-electric vehicles and with electric automobiles in certain classes of transport.
The great field, however, lies in railway traction. There are 200 miles of electric railway in the United Kingdom; and there are nearly 13,000 miles of steam railway. Not even the most sanguine electrical missionary will believe that this difference can be materially altered within the next decade, but there is ample ground for faith in the steady increase of the electrical figure. 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.
On roads, on tramways, and on railroads, the future lies with electricity—wholly on railroads and tramways, perhaps not wholly on roads. There is scope for it also at sea; and if our canals are worth the cost of reconstruction on modern lines, electric haulage will be used there on the model of the canalhaulage installations which exist here and there on the Continent. For marine work the advantages of electricity have yet to be confirmed by practical experience; but on land it has already proved that it supplies a means of locomotion which is more efficient, cleaner and more attractive, and more closely adapted to the needs and distribution of modern population than any other.
The fashion for devising Utopias is not so popular as it used to be, but in every ideal world which is more than a spiritual vision, and in every intelligent forecast of an advanced civilisation, universal electric transport is taken for granted. Electrical engineers are ready to prove that this standard element in Utopia is available at the present day on the basis which is the ultimate justification of all engineering projects in this workaday world—the basis of profit.
Their confidence will be intensified when we approach the 'all-electric' age prophesied by Mr Ferranti in his Presidential Address to the Institution of Electrical Engineers in 1910. Mr Ferranti looks forward to a national scheme for the supply and distribution of electric power. Under this scheme, the production of electricity would be concentrated in one hundred huge power stations, using engines of enormous capacity and acting as wholesale suppliers of electrical energy to towns, railways, tramways, and factories. The price of electricity would then be afraction of what it is now; and all the economies of electricity in action would be multiplied accordingly. Technically, the scheme is quite feasible; and it could be realised in the near future if capitalists and the Government could be brought to appreciate the tremendous stimulus it would offer to industrial activity and the effect it would have in conserving the power which is latent in our coal measures.
Cambridge:PRINTED BY JOHN CLAY, M.A.AT THE UNIVERSITY PRESS