Journal of the Royal Society of Arts
April 22, 1887
Proceedings of the Society
Seventeenth Ordinary Meeting
Wednesday, April 20, 1887
The paper read was -
No less than seven papers bearing upon the subject of the transmission of power by means of electricity have been read and discussed in this room within the last six years, Mr. Alexander Siemens, in 1881, taking the lead with an interesting address on "Electric Railways and the Transmission of Power by Electricity." This gentleman again favoured us in April, 1883, with an account of the great progress made during an interval of two years by Messrs. Siemens on the Continent, and he was followed at the same meeting by Dr. Edward Hopkinson, who presented an equally interesting communication on “The Portrush Electrical Railway.” A few weeks later, Professor George Forbes enlightened us with his most instructive paper, entitled “Electricity as a Motive Power.”
The late Professor Fleeming Jenkin described, in 1884, an ingenious system of electric haulage called “Telpherage.” During the same session, I made an attempt to explain the principle of applying electricity to the propulsion of “Electric Launches;” and last year, on the 22nd of January, Captain Douglas Galton, in his excellent paper on the “Results of Experiments on Mechanical Motors for Tramways at the Antwerp Exhibition,” presented us with most valuable data concerning mechanical traction.
Yet, with all this vast amount of useful information before me, I have had little difficulty in selecting a point of view from which we may regard the subject to-night. The ground has been so well prepared on the various occasions enumerated, that there is now no necessity on my part to explain the principles involved in generating electricity, and transmitting or converting the same for the purposes of electric locomotion. I therefore beg leave to offer the following observations as an appendix to the aforementioned papers, and to bring forward fragmentary descriptions of details of construction, and also, where possible, of working expenses and the amount of traffic on several electric tramways in this country and on the continent of Europe.
Experiments with electric motors and their application to purposes of locomotion date as far back as 1834, when Professor Jacobi first investigated the principles involved. The history of these early attempts, as well as the work of subsequent inventors who helped to develop the ideas of Jacobi, Paccinotti, and others, up to the present day, would prove far more interesting than the present essay; but I trust that the facts and figures of this paper will in some measure compensate for omissions concerning historical data.
It has become the custom to distinguish between different systems of electric tramways, by the methods adopted in conveying the energy generated in the stationary dynamo to the electro-motor which moves along with the car, and we may divide these systems as follows :-
1. The system in which the ordinary rails serve as conductors of the electric current, the axles of the car being insulated from the wheel tyres, and circuit with the motor established through a contact brush, or roller, sliding along the rails.
2. The system of overhead conductors. In this a number of strong posts are placed alongside the line, carrying slotted tubes or rods of metal, upon which sliding or rolling contact-carriages are placed, and these communicate electrically with the car-motor by means of a flexible cable.
3. The system of the “third-rail conductor,” which is placed between the ordinary rails, or alongside the line, on insulators a short distance above ground.
4. The system of underground conductors enclosed in a channel, with a central slot for the free passage of the contact-carriage.
5. The system of well-insulated underground conductors, with no channel, temporary contact being made through short sections of surface contact-rails with the motor on the car during its passage over that particular section on which the car is moving at the time.
6. The system of applying secondary batteries within the car, carrying stored energy along with it, whereby the vehicle is rendered independent, so that it can run on any line of suitable gauge without alteration to the roadway.
7. The system of applying secondary batteries to a separate locomotive, which hauls an ordinary car or cars behind it.
Members of the Society of Arts, and readers of the technical journals, will recollect that on the 12th of May, 1881, an electric tramway between the Lichterfeld station of the Berlin-Anhalt Railway and the Central Military School, a distance of one and a half miles, was opened to the public. Not many weeks ago, I visited that district near Berlin in order to obtain some information concerning the working of the tramway, and I have the satisfaction of telling you that the electric cars, although in continuous operation for a period of six years, have exhibited no signs of deterioration, and there have been no mishaps worth mentioning. The rails, which serve as conductors, are laid along the high road principally, and a small portion of the line runs across fields. No special means of insulation were used, the rails being fixed in the ordinary way to wooden sleepers, laid transversely along one side of the road. Electrical contact between sections of rails is effected through flexible copper loops. With such short lines of comparatively little resistance, the electromotive force can be kept low, and, in the case of the Lichterfeld line, it amounts to only 90 or 100 volts, and is therefore not dangerous to the touch of man or beast. Several roads cross this line, and at such crossing places the rails are cut out of circuit by means of underground cables; contact boxes, with switches, are placed near the crossings, in order that the current may be sent through these insulated sections of rails if requisite. The house containing the steam-engines and generating dynamos is situated close to the rails, but at a distance of about one-third of a mile from the Lichterfeld terminus. There are two steam-engines, each of 6 horse-power nominal, and two Siemens dynamos; one is a horizontal engine, and this is generally in use when one car only is running; the other is a Dolgourouki high-speed rotary-engine, coupled direct to the dynamo, running at 700 revolutions per minute; this latter comes into requisition when the traffic demands the second car. According to the printed timetable, one car makes 24 journeys a day, between 7.47 a.m., and 11.21 p.m.
I have not been able to ascertain the working costs of this line, but it must be very low, since the engines and dynamos are in the house, which also contains the pumping machinery of the district waterworks; one engineer and one stoker attend to both the hydraulic and the electric apparatus, the same boiler serving both purposes, and these men find time to attend to minor repairs. On the car is a driver, but no conductor. Each vehicle carries 24 passengers; it weighs, when empty, but including motors and gearing, 3.2 tons. The average speed is 12 miles an hour, and one journey occupies nearly eight minutes, for which a passenger has to pay 20 pfennige; this is nearly 2 1/2d. About 100,000 passengers are carried annually. One remarkable fact in connection with this successful enterprise is, that the cars, although identical in every other respect, are fitted with different kinds of gearing, with a view of ascertaining practically the efficiency of each. Those who have devoted their attention to the subject of electric locomotion are well aware that the choice of the mechanical transmission between the fast running motors and the comparatively slow motion of car wheels is one of considerable difficulty. To the uninitiated it seems the easiest thing in the world to reduce, for instance, 800 revolutions of one shaft to 80 revolutions of another shaft; but when the arrangement has to be applied to a tram-car, where space is limited, noise objectionable, dirt and dust in abundance, then one obstacle after another seems to appear. This branch of our subject really deserves a separate and exhaustive treatment, if we had sufficient time at our disposal; but as I have chosen such a sweeping title, I shall have to confine my remarks on mechanical gearing within very narrow limits. With regard to the Lichterfeld cars, the one which ran some 13,000 miles per annum, or nearly 76,000 miles since the opening of the line, is fitted with a peculiar kind of transmission, little known in this country. The motor, in this case, is fixed underneath the floor, in the middle of the car, with the shaft of the armature parallel to the axles. The motor shaft carries a pulley of small diameter with 27 V-grooves cut upon its rim; one of the car axles has a large pulley with 13 grooves, and the other car axle carriesa similar pulley upon which 14 V-grooves are cut. The wheel-base is 5 feet 9 inches, consequently the centres of the pulleys are only 2 feet 10 1/2 inches apart. Within the grooves run 27 cords of spiral steel wires, so that one driving axle is worked by 13 and the other by 14 cords from one common pulley on the motor. The steel cords, a sample of which is on the table, are made of a pair of wires wound closely upon a mandril rather less than one-eighth of an inch in diameter; the mandril is afterwards withdrawn, so that a stiff and yet flexible spiral is left with an external diameter of barely 7/32 of an inch. The ends of each spiral cord have steel eyes screwed into them and soldered, and when placed in position these eyes are connected by a steel wire link. One curious fact about these spirals is, that they stretch very little, and experiments have shown that one single cord will suffice to draw the empty car on a clean level line, whilst 8 cords were used for a car full of passengers; therefore, with 27 there is a good margin of safety. As may be expected, this mechanical arrangement works without noise or vibration. Some experience is required in putting the cords upon the pulleys, for, I am told, if stretched too tightly, they are liable to break at the joints, and if too loose they will slip when starting; but with careful attention on the part of the engineer in charge, very few breakages occur. There are only moderate gradients on this line, the worst, of 1 in 100, is about 460 yards in length; the question, therefore, remains whether this kind of gearing would suit a more difficult line. The second spare car belonging to this tramway is fitted with pitch-chain gearing; as in the former case, the motor is placed centrally underneath the floor, with its shaft parallel to the car axle, but only one of the pair of axles is connected by means of the chain to the toothed wheel of the armature. There is some noise and vibration with this arrangement, more current is required, and slightly less speed is obtained with this vehicle than with the other; consequently, chain-gearing must be less efficient than steel cords, the motors and all other conditions being similar.
Another line on which the ordinary rails serve as conductors of the electric current is that of Mr. Magnus Volk, at Brighton. When opened by the Mayor of Brighton, on August 2nd, 1883, the line was only a quarter of a mile long, running from the Aquarium entrance to the Chain Pier; 30,000 passengers having used it during the first five months of its existence, Mr. Volk obtained permission to extend it as far as Kemp town, a distance of nearly a mile from the Aquarium. The rails are fastened to wooden sleepers which rest upon the shingle along the beach, and no special insulation is employed; the necessity of passing under the Chain Pier involved a gradient of 1 in 28 on the west side and 1 in 14 on the east side of the pier. Two cars connected together, and containing 60 passengers, mount these inclines without difficulty. Each car, when empty, weighs 1 1/4 tons, and with 30 passengers about 3 1/4 tons; the speed is limited to eight miles an hour. The motive power in this case is a 12 horse-power gas-engine placed at one end of the line, driving a Siemens compound-dynamo, which generates a current of about 20 ampéres at 160 volts when one car is running. As a rule, only one car is used, but on bank holidays and special occasions, when the traffic is great, the second car is put upon the line. The average distance made by each car last year, I am told, was 23,475 miles, and the expenses per car mile amounted to only 2d. This is remarkably low, considering that gas is used in the prime mover, costing 3s. 3d. per 1,000 cubic feet, and this item alone amounted to 1.11d. per mile; for wages .7 of a penny was expended; oil, waste, &c., .07 of a penny, and the repairs to machinery came to .12 of a penny per car mile. The number of passengers last year averaged 8.51 per car mile, and the total expenses amounted to 55 per cent. of the gross receipts. On the Brighton cars leather link belts are employed for transmitting the power of the motor to the driving axle; the armature shaft is provided with a 5-inch pulley; this gears into a 24-inch pulley, on a countershaft fixed under the car. Mr. Volk used plain leather straps at first, but found them unsatisfactory, whilst the linkbelts proved quite practical, after an experience reaching over a period of nearly three years. A sample of a worn-out belt of this description has been sent to me by Mr. Volk. The belts slip a little at starting, but this is not considered a disadvantage, since it eases the motor; the bearings of the countershaft are adjustable by means of a slide, so that any slack caused by stretching of belts may be readily taken up. No protection is provided for the gearing, there being no mud to contend with, but I fear that this arrangement would hardly be suitable for the ordinary street cars. Judging by the large traffic which the Brighton line enjoys, one would think that it is highly popular; it is so with the public, but a section of the Town Council is opposed to the enterprise. The line was severely damaged by storms, in September, 1883, December, 1884, and October, 1886, involving a large outlay for repairs, to the anything but “permanent way." That it is a success in every way, excepting the storms from within the Town Council, and storms from across the sea, may also be gathered from the fact that a million passengers have already been carried, without injury or mishap to one of them.
Coming now to lines worked by means of overhead conductors, on the plan of Messrs. Siemens and Halske, the most carefully constructed, if not the most important, is that of Moedling, near Vienna. This is the property of the Austrian Southern Railway; the rails wind through a lovely country district for a distance of 2.8 miles, and terminate in that beautiful spot with the ugly name -Hinterbruehl.
I am indebted to Mr. C. Jenny, Engineer of the Southern Railway, and to Dr. Dolinar, electrician of the Moedling tramway, for their extreme courtesy in conducting me over the line and stations, and for allowing me to inspect every detail concerning the working of the same. Like most of the existing electric tramways, this has a large traffic during the summer months, but a comparatively small one in winter. The number of passengers carried during the year 1886 was 342,257, of these 320,000 came between the 1st of April and the 31st of October, whilst in the five remaining months only 22,257 persons availed themselves of this mode of transit. The month of August, with 72,600 travellers, stands highest in the list, and January, with 2,557 passengers, stands lowest of all. The revenue of seven months of the milder seasons is fifteen times as great as the revenue of the remaining five months, but the working expenses were not at all proportional, barely as five to one, and with all that the average cost did not amount to 3 1/2d. per car mile, inclusive of every item of expenditure, the sum of which came to £1,700 for the year ending December 31st, 1886. The number of car miles was 91,002, with a consumption of 545 tons of coal, at 7s. 6d. the ton. This was a very inferior “brown coal,” with an evaporative power of barely one-half that obtained with anthracite. The cost of fuel, therefore, came to .54 of a penny per mile, representing a consumption of 13.4 lbs. per car mile. With coal of the best quality, 7 lbs. per mile would suffice, but the price of this, in Vienna, is more than double that of “brown coal.”
The generating station is situated at the Moedling terminus; it contains three portable engines of 12 h.p. (nominal) each, and six Siemens compound dynamos, each capable of producing 500 volts and 50 amperes. When two loaded cars are running, i.e., one electric car, to which an ordinary car is attached, the indicated power of one engine varies between 12 and 20 h.p., according to the position of the vehicles relatively to the line during the outward journey. From the plan on the wall, it will be observed that the track is not an easy one; it consists almost entirely of curves, with radii of from 60 feet and upwards. Moreover, the terminus of Hinterbruehl lies 120 feet higher than that of Moedling; thus the line consists of a series of gradients, so that for the outward journey a considerable amount of tractive power is necessary, whilst on the return journey the cars run almost entirely by the force of gravity, and the driver touches the switch only when starting and at the sharpest curves. During the winter months one electric car suffices, and then one engine and one dynamo are used, attended by an engine driver and a stoker. In summer, when three engines, six dynamos, and six double cars are running, three stokers are required. The maximum number of journeys, each of 2.8 miles, last summer was 180 a day, with six electric and six ordinary cars coupled in pairs, and the minimum number of journeys in winter with one car was 24 per day; the time allowed for one journey is 20 minutes. There are four stopping-places along the line, and the average speed allowed is 9 1/2 miles an hour. The conductors - the metal ones, not the animate being on the car - are carried on posts 18 feet high and 90 feet apart, except on sharp curves, where they stand at a distance of 45 feet from each other. These conductors are made of slotted tubes, in lengths of 15 feet each, and soldered together when placed in position. To prevent them from sagging, stout wires are stretched over brackets on the tops of the posts, and fastened to the tubes half way between the posts. The bore has to be made perfectly smooth and clean, so that neither mechanical nor electrical resistance is offered to the contact carriage sliding within. The diagram shows the arrangements on an enlarged scale; the actual diameters of the tube are 1 inch internally and 1 5/8 inches externally. The contact carriage consists of a flexible piece of flat steel, upon which three gun-metal pistons are fastened. These pistons, which have to be renewed every two months, are made in two halves, with springs in the middle, whereby a slight pressure is produced between the surfaces in contact. The resistance of the conductors is 2 ohms, and the insulation in damp weather never falls below 6,000 ohms. Measurements gave a difference of potential of 500 volts at the dynamo, and 390 volts at the furthest end of the line when three electric cars were running, and this would correspond to a current of about 18 ampéres per car. All the electric cars on this tramway are fitted with spur gearing; but I will reserve any remarks on this mode of transmission until I am describing another line worked on the same principle. The Moedling-Hinterbruehl Tramway has been working successfully since 1884, at an average cost of 3.42d. per car mile, inclusive of every item of expense.
The second line, almost identical with the last one, as far as electrical details are concerned, is that of Frankfort-on-Main, in Germany. It leads from the “Roemerbruecke,” in Frankfort, through the villages of Sachsenhausen, Oberrad, and through the town of Offenbach; its total length is 4.1 miles; it has a double track laid with ordinary tram rails, thus differing in this respect from the Moedling line, which has a single track with three passing places, and ordinary railway rails of a light construction. Single cars, as well as trains composed of one electric and one ordinary car, run between Frankfort and Offenbach every twenty minutes, from six in the morning until eleven o’clock at night. The entire rolling stock consists of fourteen vehicles, ten of which are fitted with electric motors. All are constructed to carry twenty-four passengers; but the weight of the electric cars is four tons, empty, and that of the others about two and a half tons. The engine-house is situated at Oberrad, nearly half way between the termini. It contains two horizontal steam-engines of 120 horse-power each, and four vertical Siemens dynamos, each capable of generating a current of 70 amperes and 300 volts. Ordinarily on weekdays, four pairs of cars are running, when one engine, working at half-power, is used for driving two dynamos. With eight electric cars and four ordinary cars on the road, the engines indicated 164 horsepower. The average speed allowed on this line is seven and a half miles an hour, and one journey occupies forty minutes, inclusive of stoppages at eight stations.
The Frankfort Offenbach Tramway has been in operation since April, 1884; last year, 990,238 passengers were conveyed, and 292,269 car miles were run, at a cost of 3.83 pence per mile, including the following items :
Wages and salaries of directors,
clerks, &c..................................... 2.23d.
Fuel (7.54lbs. of coal per mile)........ 0.65d.
Repairs of machinery, cars, and per-
manent way................................... 0.82d.
If we could deduct the directors’ fees, repairs to roadway, and such items, which do not really belong to the costs of motive power and maintenance of the same, then the expenses per car mile might come to less than 3.5d.
With reference to the overhead conductor, I need only mention that the slotted tube is used in the same manner as at Moedling, with the exception that its resistance in the present case is only 1.6 ohms, and the contact carriage is somewhat differently constructed, as will be seen in the diagram on the wall. Instead of three gun-metal pistons made in halves, there are two solid iron pistons without expansion springs. These parts have to be renewed every three or four weeks, at the cost of 1s. for each carriage.
A skeleton plan of this line is shown on the upper diagram on the wall; the lower represents the Moedling track. There are several gradients, the stiffest of which is 1 in 32 for a distance of 100 yards; another of 1 in 45, 150 yards long, with a curve of 110 feet radius upon it; and a third incline of 1 in 80, 300 yards in length. To those that study the subject of mechanical traction, the following data relating to the tramway under discussion may be interesting. The energy expenses was measured on the car as well as on the generating dynamo, simultaneously, when the total weight, propelled at the normal speed, was 8.35 tons, comprising one electric car hauling an ordinary car and passengers:-
.........................................on car...at Dynamo
Running on a level road......... 3.87 .... 6.47
Running up gradient 1:45
without curve........................ 8.00 .... 13.5
Running up gradient 1:45
with curve............................. 9.70 .... 16.7
Starting up gradient 1:150..... 10.20 .... 26.4
I have already stated that spur gearing is used on the Moedling cars as well as on those of Frankfort; concerning the working of the latter I will now submit a few particulars. The train of wheels on one of these cars consists of a pinion on the motor shaft having 17 teeth which gears into a spur-wheel of 56 teeth keyed upon a countershaft. On this counter-shaft is the second pinion of 26 teeth, and this drives the spur-wheel of 52 teeth fixed to the car axle. We get thus a ratio of 1 to 6.6, nearly, between the motor and the car wheels; the whole set of wheels weighs 4 cwt., the electric motor, also, is very heavy, so that the driving apparatus of one car comes to about 26 1/2 cwt. It must, however, be noted that the motor runs at the comparatively low speed of 500 revolutions. A considerable amount of noise is produced by this gearing, so that the sensation felt inside the electric car is anything but agreeable. As regards the economy of spur gearing for tram-cars of this description, the experience gained is not at all favourable; the pinion of the motor, for instance, which is made of hard gun-metal, wears out in a month; the diagram on the wall shows the teeth of one of these pinions in full size when new and after four weeks'work. The second sketch on the same diagram is a copy of the teeth of one of the cast steel spur-wheels on the driving axle, their shape when new, and after ten months'wear. One of the cars is now being fitted with wheels having double helical teeth, and it is expected that these will work more smoothly, and be more durable. I am indebted to Mr. Prins, the manager, and to Messrs. Dill and Strauss, of Frankfort, for their kindness in conducting me over the line and premises, and for affording me every facility in studying the whole arrangements. Overhead conductors of a different form to those just described were constructed by Messrs. Siemens and Halske for the electric railways in the mines of Zankerode, in Saxony, and the Hohenzollern colliery, in Upper Silesia. The Zankerode line has been in operation since the autumn of 1882, and the Hohenzollern was started in August, 1883; another is now being constructed for the salt mines of Stassfurt. In all these, the conductors are made of bars in the shape of an inverted T fixed along the roofs of the mines. Sliding contact pieces grip the edges of the lower flanges of these bars, and insulated wires lead from the slides to the electrical switch on a small electric locomotive which hauls a number of trucks. An interesting description of the Zankerode line is given in Mr. F. J. Rowan's paper, recently read before the Mining Institute of Scotland. Mr. Rowan states that the cost of haulage, including 15 per cent. for depreciation of plant, came to only .77 of a penny per ton, when 660 waggons were drawn per day of sixteen hours.
Concerning the Hohenzollern line, Mr. Zacharias, of Berlin, has kindly placed his notes, which contain many details of its construction and working, at my disposal, but unfortunately our time is limited, and I can therefore give very few particulars at present. Two sets of rails are laid underground, for a length of 820 yards, and there are several curves of from 15 to 30 feet radius; about forty trains run daily, with one locomotive and fifteen waggons; each Waggon carries nearly half a ton of material, and the cost of haulage is said to be about 1/2d. per ton.
The steam-engine and dynamo are placed near the top of the shaft, 250 yards above the working level; when running at 277 revolutions per minute, the generator gives 350 volts and 37 amperes. Each waggon weighs when empty 1,210 lbs., and when loaded, a little over a ton; the electric locomotive weighs 2.1 tons, and the whole train of fifteen waggons 17.8 tons, running at an average speed of seven miles an hour. For transmitting the motion of the motor to the driving wheels, two pairs bevel wheels, one pinion, and two spur wheels are employed.
Among the lines on which the “third rail" system of conductors is used, the electric tram-way of Portrush and that of Bessbrook, both in Ireland, must be considered the most important. The Portrush line, which was described in this room four years ago, is the longest electric tramway in the world; its rails traverse the country a distance of six miles, between the terminus of the Belfast and Northern Counties Railway and Bushmills. Since the reading of Dr. E. Hopkinson’s paper, important additions have been made by the installation of two 50 horse-power turbines, driven bya 26-feet water-fall on the river Bush, which is 1,600 yards away from the nearest point of the tramway. The electric resistance of the line is 1.9 ohms; the generating dynamo gives a maximum current of 100 ampéres, with 250 volts E.M.F. Since water-power has been applied to produce the electric energy, the working expenses have not amounted to three-pence per car mile. The cars are fitted with pitch chain gearing. Mr. Traill, the managing engineer, informed me that he is satisfied with the working of this gear. An extension of this line is in contemplation. The Bessbrook-Newry Tramway is three miles in length, single rail of 3 ft. gauge, with gradients averaging 1 in 85, the maximum being 1 in 50. In this case also, water-power is available, there being a constant supply of three million gallons a day, with a fall of 28 feet, and part of this is utilised in a turbine which developes 62 h.p., and actuates two dynamos of the Edison-Hopkinson type, each capable of transforming the mechanical energy of 30 h.p. into electrical energy equivalent to 25 h.p., with an E.M.F. of 250 volts. Two electric cars, each capable of carrying 38 passengers, and weighing, when fully loaded, eight tons, run on this line; besides these, there are six goods waggons, with a capacity of two tons of freight per waggon. A train consists of one passenger-car and several waggons, generally three of the latter. The maximum speed attainable is 15 miles an hour, but, to conform to established rules, only 8 to 10 miles an hour are actually made. The line was passed on behalf of the Board of Trade in September, 1885, and from that time to the commencement of the present year, 30,000 train miles were run, 150,000 passengers carried, and 15,000 tons of goods were hauled. The cost of propelling a train containing the full complement of passengers and six loaded waggons is said to be fourpence per mile, including wages, repairs, and rental of water-power. Chain-gearing is employed for the purpose of transmitting the power of the motor to the car-axles. These particulars were kindly given to me by Dr. E. Hopkinson.
Mr. Holroyd Smith has devised an underground conductor contained in a channel, which is provided with a slot for the free passage of the electrical contact slide. The most important application of this system on a large scale is that at Blackpool, where it is worked on a line nearly two lines in length. Descriptions of this tramway have appeared in most of the technical journals, and Mr. Smith having read several papers before scientific societies, I need not dwell upon the details of construction, but will confine myself to a few general remarks. The roadway runs along the coast; ten cars of various sizes comprise the rolling stock, the largest having a seating capacity for 56 passengers, and the smallest carry 30 persons. At the generating stations there are two steam-engines, each of 25 horsepower nominal, driving four shunt wound Elwell-Parker dynamos, which give a maximum current of 180 ampéres, with 300 volts. The E.M F. ordinarily employed is 220 volts, which is reduced to 168 volts at one end, and 185 at the other end of the line, the generating station being situated near the middle of the tramway. From all accounts this line has proved quite successful. It was opened in September, 1884. I have not been able to obtain particulars as to the number of car miles run and passengers carried, consequently I cannot establish the relative cost, but Mr. Smith informed me that the expenses do not reach 4d. per car mile. VVhilst on the Moedling and the Frankfort tramways the resistances of the conductors are 2 ohms and 1.6 ohms respectively, the calculated resistance of the underground copper tubes at Blackpool is only .041 of an ohm. We do not know the actual resistance of these conductors, but I should think it must very much exceed that found by calculation, considering the great fall of potential at different points of the line. In one of the papers read by Mr. Holroyd Smith, we find some extraordinary statements with regard to insulation, and consequently leakage, in his system of underground conductors :—
“Measurements were taken of the insulation of the line during construction, and 150 yards’ length was found to give 4.490 ohms. The average working loss, through leakage, may be taken at 25 amperes, which, at an electromotive force of 200 volts, is equal to 7.2 h.p.”
Professors Ayrton and Perry have devised a system of conductors which is said to overcome the objections against losses arising from bad insulation. Instead of supplying electricity to one very long, perhaps imperfectly insulated, rail, they lay by the side of the railway a well insulated cable which conveys the main current. A third rail, which is rubbed by the moving train, is divided into a number of sections, each fairly well insulated from its neighbour and the ground; but at any moment only that section which is in the immediate proximity of the train is connected with the main cable, the connections being made automatically by the moving train. The loss of power by leakage is very much lessened through this arrangement, since any possible electrical contact between rails and earth is confined to that particular section upon which the train moves at the time, and connection from the surface rail to the insulated cable is made automatically by the pressure of the vehicles upon springs underneath the conducting sectional rails. Such an arrangement could scarcely be applied to ordinary street tramways, for if the sectional rails were laid flush with the roadway, then any other vehicle would, by its weight upon the rails, cause connection with the main cable.
In order to prevent the possibility of any extraneous force, other than that provided by the electric car, from making contact between surface rail and underground conductor, Messrs. Pollak and Binswanger have devised an ingenious plan, illustrated in a diagram on the wall. Underneath each electric car is a powerful magnet, and underneath each rail section, within a thoroughly insulated trough, is an armature of iron, which, when attracted by the influence of the passing magnet, makes contact between the cable and the surface rail, and through the latter with the switch of the car motor. No external force but that of a strong magnet, therefore, can draw electrical energy from the insulated underground conductor, and since the surface rail sections are each very much shorter than a car or train, no other vehicle following or preceding in the same track will be influenced by the current. Neither the Ayrton and Perry system nor that of Pollak has been tried on any tramway, therefore no opinion as to efliciency can be formed at present, but these systems seem worthy of an extended trial.
The idea of employing secondary batteries, the stored energy of which sets the motor in motion, and with it the car, suggested itself to the earliest inventors; indeed, the principle of applying batteries to the propulsion of a vehicle containing them was actually demonstrated in the year 1839, by a Scotchman named Robert Davidson; he used primary batteries, which proved a very expensive mode of generating electric currents; the method of storing energy in accumulators was unknown at that time. Today, we are able to convert the energy of a waterfall or of coals into electricity by means of dynamo machines having an efficiency of 90 per cent., and more. The current thus produced can be made to decompose the acidulated water in the secondary cells which contain electrodes, or plates, capable of absorbing the oxygen and hydrogen resulting from the decomposition of water; and finally, the gases thus stored re-combine whenever we desire it, and manifest themselves in the form of electric energy capable of doing mechanical work through an electric motor. As transformations of energy always involve some loss, so there is a loss in this electro-chemical conversion, amounting to from 25 to 30 per cent. In order to establish a comparison between a system having conductors and one having accumulators carried in the cars, we have, in the first place, to ascertain the efiiciency of the conductors in the one case and that of the secondary battery in the other. The efficiency of a conductor depends upon its resistance and the current transmitted. Let us take for an example a tramway similar to the one at Moedling, with a conductor of 2 ohms resistance, 20 amperes of current for each car, and 500 volts E.M.F. at the terminals of the charging dynamo. Supposing that only one car was running on this line, then the waste of energy would be practically nil at the commencement of its journey from the generating station, but it would be 20(squared) X 2 when it approaches the furthest end of the line; the average resistance, or that due to half the length of the conductor is 1 ohm; therefore the average loss is only 20(squared) X 1 = 400 watts, against 500 X 20 = 10,000 watts generated by the dynamo; consequently the efficicncy of the conductor comes to 96 per cent., since we lose only four per cent. With six cars on the line equally distributed, and using, together, 120 ampéres, the loss will be 14,400 watts out of 60,000 produced at the station, and then the efficiency is only 73 1/3 per cent., and so on, by increasing the number of cars, and with it the current, the efficiency gets less and less. With the accumulator system, on the other hand, we have a constant loss, no matter how long the line, provided that the quantity of energy stored is sufficient for the time, and it matters not how many cars run at any time on the same tramway. If the cars at Moedling were fitted with accumulators, then the weight to be propelled would have to be increased by, at least, 20 per cent , and this would entail a corresponding augmentation of power, in order to keep up the same speed, therefore a greater consumption of fuel would be the result. But we have seen that the item of fuel really plays a minor part in the total expenditure, in fact, it is only about 16 per cent. of the whole, hence we need not look upon the question of the loss of energy with too critical an eye. According to the report issued by the jury of the Antwerp Exhibition, a resume of which has been presented to this Society by Captain Douglas Galton, the consumption of fuel with the accumulator car came to 6.16lbs. per mile, which, at 16s. the ton, costs little more than 1/2d. This car, however, carried only 34 passengers, and the line was practically level. On the other hand, the steam-engine employed was an old portable engine, which did other work besides charging the accumulators of the tram-car. From practical tests made with cars of my own design, here and on the Continent, I have ascertained that the consumption of fuel need never exceed 8 lbs. per car mile on ordinary tram-lines in towns, provided that the weight of the accumulator carried on the car does not exceed 25 cwts.
Viewed from the standpoint of convenience, the propulsion of tram-cars through the medium of secondary batteries must be conceded to be second to none. The battery occupies no valuable space when stowed under the seats, while the motor, with its attachments, can be placed underneath the car. There is no interference with the permanent way, and for city trafiic such a service ought to be found eminently practicable.
The last system on our list is that of the separate locomotive, carrying accumulators within, and hauling an ordinary car behind it, I have placed this at the bottom of the list because it is the latest, but, from all appearances, it will be the first electric system to be adopted on a tramway in London. The early adoption of electric locomotives is partly due to the progressive spirit, the energy, and perseverance of the North Metropolitan Tramway Company, but mainly, perhaps, to the vigorous enterprise of the Electric Locomotive and Power Company, who work the patents of Mr. Elieson, their energetic manager. I have recently had the privilege of witnessing trial trips with six of these locomotive engines. It was a pretty sight to see these vehicles running along Romford-road, one after another, on a dark night, each brilliantly illuminated by its own electric light. Mr. Elieson has prepared a diagram now on the wall, from which the details of construction can be seen. The mechanical connection of the motor with the axles is very ingenious. Instead of the electro-motor being a fixture, it turns round upon a vertical pivot. The horizontal armature shaft carries on its end a bevel wheel, which gears into a large circular rack. At the lower end of the pivot there is mitre gear connected to the driving axle. Reversal of motion can be effected by a clutch which brings one or the other mitre wheel of the axle into gear with that fixed to the pivot. Each of these locomotives weighs nearly seven tons, and this is the only disadvantage one can think of when examining the system. These engines have been ready for some time, they would have been earning money long before now, but for red tape and Acts of Parliament. Before we can run electric cars in this country we must have an Act of Parliament. To obtain one takes a year or more. It causes an immense amount of trouble and expense to get an Act of Parliament, and the worst of it is that each company has to apply separately for it; it is this awkward circumstance which retards the progress of electric locomotion on tramways in this country. Whereas, on the Continent of Europe and in the United States of America, there are dozens of electric tramways at work to the satisfaction of everybody, here in England, the home of the dynamo machine, the country where the electric motor has found its highest development, we have so few opportunities to demonstrate their advantageous applications. With regard to America, there are electric tramways at work in New York, Philadelphia, Baltimore, Saratoga, Califomia, New Orleans, Toronto, Detroit, Windsor, Chicago, Cleveland, Montgomery, Denver, and in other parts. The American capitalist encourages electrical enterprise because it is worthy of every encouragement when untrammelled by unnecessary legislation. I have made out a strong case in favour of electric traction. Any electrician sitting at home in his arm chair can reckon out upon paper what electric locomotion ought to cost, but I have made it my business to travel from place to place and examine into the details of the actual working electric tramways. Practical men want figures based on facts, not estimates. Through the courtesy of the engineers of the oldest lines I have obtained data which render the question of cost beyond doubt, and we have seen that the entire working expenses of those lines do not exceed - or need not exceed - 3 1/2d. per car-mile. There is no reason why these expenses should exceed 3d. per mile, when the most efficient machines of the present day will be applied.
Electric locomotion includes numerous other applications of the motor besides tramways, but I must stop short at this stage of the subject, having already trespassed beyond the usual limit of time.
The CHAIRMAN said they had never had in that room within his recollection any paper on this subject in which the facts were more clearly enunciated than they had been in this case. It had hitherto been very generally the practice for those who brought forward papers on electrical matters to trust very much to their imagination and to their hopes for that future when those restrictive Acts of Parliament to which reference had been made had been swept away; but Mr. Reckenzaun had not given vent to the promptings of his imagination. One fact had struck him very much on making a very rough estimate of the cost, namely, that while the early lines established by Siemens and Halske showed a cost of about 1d. per ton per mile, in all the later lines the estimate came out about half of that, which showed a very great advance in the practical application of electricity. The cost of horses on tramways came to from 7d. to 10d. per car mile, which was probably about 3d. per ton per mile, so that there was a considerable difference between the cost of electrical haulage and that of horse power.
Mr. M. Holroyd Smith said this paper could not be called an exhaustive one, because it would take several days to treat exhaustively so large a subject, but it was more comprehensive than he thought it could have been in the time, and he complimented the author on having given so much information in so short a time. He might also be praised for having said so little about his own particular work. Considering he was one of the first to use secondary batteries for the propulsion of tram-cars, and that his work has been taken advantage of by more than one, who were now making a profitable employment of his skill, it was certainly very commendable that he had not said more on that point. He agreed with him that secondary batteries would be very advantageous on certain lines, but he did not agree with him as to their efficiency compared with that of direct working. There were two strong lines of demarcation in this matter -direct driving and batteries. Either primary or secondary batteries might be employed, and when using the direct current, it might be done with the actual rail, by overhead or side bars, or underground conductors. On going into the calculation, he should be able to show that, taking a line five miles in length, and working one car an hour over it, it would be cheaper to run it by secondary batteries; but if the lines were working a quarter of an hour service - and tramways did not as a rule pay unless the service was more frequent than that - it would be much cheaper to use direct driving. Even with a central channel constructed in the same manner, and at the same cost, as he had laid in Blackpool, it would cost less to construct a five-mile line, and equip it with channel, motors, gear, engines, dynamos, &c., when driving direct, than to equip all the cars and provide the surplus batteries, &c., for the secondary battery method. He should also say that the cost of the construction of the central channel at Blackpool was not to be taken as the standard for the future. As had been said, the resistance of these conductors was very low, and it was purposely so arranged, because he saw it would be better to spend a few hundred pounds more than was absolutely necessary on the copper tubes which formed the conductors, and on the structural details of the central channel, than to run any risk of failure, and therefore, in every item he had erred on the side of safety. It would be quite possible to construct a line at a little more than half that cost, and making that important alteration to the calculation, it would be found that direct driving would compare still more favourably with secondary batteries. In towns like London, where there were busy thoroughfares, tramway directors found the rail their greatest trouble, and omnibus and cab drivers were always using bad language about the groove which would form along side the rail, they did not want another rail, until further advance was made in public opinion, and it was possible that tramway companies in such a situation would adopt secondary batteries; but as he had pointed out in that room before, he regarded secondary batteries merely as a means of educating the public mind. One point which would be very interesting to discuss at greater length than was then possible was that of gearing, and he would again compliment Mr. Reckenzaun in not having brought forward his claim as being the first to use worm gearing on large tram-cars, although he (Mr. Smith) had used it on a small experimental car before, but he did not venture to adopt it for large cars until he saw Mr. Reckenzaun was successful. He said most unhesitatingly that he found it the most effective mode of transmitting the power from the motor spindle to the axle, taking all points into consideration. He might mention that the reason he could not give more detailed information to Mr. Reckenzaun, was that his directors had special reasons at the time for not desiring the details of their results to be made public, but he might say that the practical working at Blackpool was more economical than any of the figures given in the paper. He must take exception to one calculation put forward tending to show that by increasing the number of cars on a line the efiiciency would decrease very rapidly. That was entirely contrary to his experience. He found that during the winter months, when only three cars were running, and the number of passengers per week was under 3,000, the total working expenses were about £20; in the summer months, when the passengers were 45,000, and there were ten instead of three cars, crowded instead of empty, the total working expenses were only £45. He was also struck with the figures given as to the number of passengers carried, and the car accommodation on other lines. On none of the lines had they cars which would seat 56, as they had in Blackpool - and very often they carried from 60 to 70; and instead of reckoning the people by tens of thousands, or even hundreds of thousands, they were now in the second million, and not one single accident had happened to anyone. With regard to the diagram with Messrs. Pollak and Binswanger’s name upon it, illustrating a magnetic system of making contact between an underground conductor and a sectional surface rail, it was evident to him that no working test had been made, because he knew from his own numerous experiments in the same direction that the details there shown would not be successful in practice.
The CHAIRMAN inquired if the Blackpool Company had paid a dividend.
Mr. M. Holroyd Smith said it had, and not only so, but having, at the request of the directors, taken some fees due to him in shares instead of cash, he had sold them at 10 per cent. premium, and was, therefore, better off in consequence.
Sir John Jenkins said he was connected with a tramway or short railway, from Swansea to the Mumbles, one of the oldest in the kingdom, the Bill for which was originally for a canal, but though it passed as such on the second reading, it came out of the House of Commons as a railway, in 1804. The cost of running on this was less than on ordinary tramways, and the question in all these cases was really which was the cheapest motor. As Mr. Holroyd Smith had said, there was a great objection to electricity on account of the third rail, but independently of that, he did not think the time had yet arrived when electricity could compete with steam power, where it was practicable to use it. Still they were much indebted to the scientific gentlemen who occupied themselves with this subject, and who, he trusted, would ultimately achieve a success which would be beneficial not only to themselves, but to the nation at large. The cost of Mr. Reckenzaun’s mode of working would be about 3 1/2 d. per train-mile, but the cost of the small line he referred to was not more than half that. It ran not upon the road, but parallel to it. Of course, on great railways, he knew the cost was much higher, and horse-power, as the Chairman had said, came to about 7d. or 8d., and, in some places, 9d. per train-mile. On the railway he referred to almost every possible motive power had been tried, including sails, but nothing was so economical as the steam-engine.
Mr. Magnus Volk thought the spiral wires referred to in the paper, running at a very high velocity, would wear considerably, and would not be successful. A somewhat similar plan was tried at Shoreham, and it seemed as if the whole thing would be torn to pieces in a few days, but possibly that might be due to faulty construction. Pitch chains were used on the Ryde pier railway, which he lately visited, and he was informed that they suddenly gave way, without any warning, causing considerable delay. Spur gearing had been used in Ireland, but though when first fitted it was tolerably silent, when he was there, it made so much noise that conversation in the car was almost impossible. He had found leather-link belts the best of all. He first tried single leather, but this broke every day or two, then double belts, which did not last much longer, as one lap slipped off the other. The leather-link belts had now been in use three years, and the portion shown had helped to drive a car over 50,000 miles. It was not worn out, but was a piece taken out to shorten the belt, which would have to do the next season’s work. They stretched a little on being first put on, but there was an arrangement for taking up the slack. Toothed gear he found caused a great deal too much vibration in the car to be pleasant, though some people liked it, thinking it was spare electricity given off which did them good. The Brighton line was not perfect by any means, but he had from time to time made various improvements, and he had a great deal of opposition to contend with. Still, next August, he should have kept the line open for four years; he had run about 100,000 car-miles, and carried about a million passengers, the cost being just under 2d. per car-mile. All repairs were paid for out of revenue, but he put aside nothing for depreciation, for he never knew during the winter whether he should find the line there at all in the morning. Apart from damage by storms, it had paid a dividend of 20 per cent. With regard to light railways running through a poor district, he would remark that if steam were employed you must carry a considerable number of passengers to make it pay at all; but with electricity you could run a small car, seating five or six people, at almost the proportionate expense that you could carry thirty or forty, and thus, where it would not pay to run half-hourly, you might run a car every five minutes, and so work up a traffic. He agreed with Mr. Holroyd Smith as to the comparatively small extra cost of working extra cars. Last summer, for the first time, he worked a second car, and when his quarter's gas bill came in he found it was only increased by £3. Great pains had been taken at Blackpool to secure a very low resistance in the conductors; but if more pains had been taken in the insulation, he thought a better result would be attained, for he found that Mr. Smith’s loss by leakage was just about the same as his own, where there was no attempt at insulation at all except by the sleepers. He should like to know Mr. Smith’s experience as to the electrolytic effect of the current that escaped. He had found some 3/4 in. bolts, which he put in last October, were last week reduced to about 3/8 in. He did not think the magnetic system would be practicable, for a car going at anything like a fair speed would not have time to act on the armatures so as to pick up the current. The idea was very pretty and clever, but he did not think it would work.
Mr. Kapp said he had had no experience of electric tram-cars, but he knew something about gearing, and he did not think the spur gearing had yet had a fair trial. Mr. Reckenzaun’s worm gearing had been very successful, but that was probably because it was well adapted to the work it had to do, and other gearing equally well designed might also answer as well. The noise could be avoided in various ways; you might have slanting teeth, or might split up the width of the wheel into narrow portions, so as virtually to have several wheels side by side, and shift them by a small angular distance, less than the pitch of the wheel, and so obtain a tooth consisting of several steps. In this way the violence of the blow of two teeth coming into contact would be very much reduced, and it was this blow which caused the noise. He had seen a very large spur gear on this principle on one of the large steamers of the Messageries Maritimes, the propeller shaft being geared to the engine shaft in this way, and the noise was hardly more perceptible than that of a shaft directly driven.
Mr. R. Capper said the question after all, with regard to the application of electricity to tramway working, was whether it would pay. He was interested in the railway mentioned by Sir J. Jenkins, which was now 84 years old, and naturally, having to carry three-quarters of a million of people a year, they looked at all these things very closely, but he had never yet come across any instance of an electric motor, as applied to tramways, which it would answer their purpose to adopt. There was still a field open to anyone who could show them how to make that six miles of line pay better by electricity than it did at present with locomotives.
General Brine thought electricity would never pay as a motive power, or take the place of steam, which could hardly be surpassed. If anything were likely to interfere with it, it would be petroleum. Electricity might do very well on the Thames, or in tram-cars, going at the rate of seven to ten miles an hour, but anything beyond that was out of the question.
Mr. Binswanger said he thought the system invented by Mr. Pollak and himself, had been rather severely criticised. Seeing that it had only been completed a few months, there had been no opportunity to try it practically, but gentlemen of quite as high standing, and as large experience, as Mr. Holroyd Smith, had spoken very favourably of it, and the models which had been constructed worked very well. In an ordinary street you could not use an open channel, which would become full of water and clogged with dirt, and if the conductors were enclosed, he did not think any other mode of making contact would be so good as a magnet.
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