Popular Science Monthly/Volume 37/July 1890/Telpherage in Practical Use
|TELPHERAGE IN PRACTICAL USE.|
By FREDERIK A. FERNALD.
A VAST field of application which electricity is only just entering upon is the transportation of freight and passengers. The use of electric motors for propelling passenger-cars on street railways may be said to have passed through the experimental stage into the domain of commerce. There are roads, using one or another of four or five different systems, in operation or in process of construction, in all parts of the United States, and new contracts are frequently being announced. Nothing, however, has been accomplished in this country in the direction of carrying freight by electricity. But a system, called "Telpherage," has been worked out in England, which is especially adapted to take the place of horses in carting, as they are already being displaced from the propelling of cars.
Telpherage may be regarded as a development of what is called in England the "wire-rope haulage" system, by which freight is conveyed in buckets suspended by a grip from an elevated wire cable. For distances of a few hundred feet, an inclined cable, down which loaded buckets suspended on traveling wheels move by their own weight, has also been used. The telpher system resulted from a union of the joint inventions of Profs. W. E. Ayrton and John Perry with those of Prof.Jenkin. Prof. Jenkin had had in mind for some time the idea of propelling electrically a continuous stream of light trains without attendants along an elevated single rope or rail, which should be also the conductor of the electricity. He had not solved the problem of preventing automatically these trains from running into one another, when he read an account of the plan for dividing electrically the rubbed conductor of electric railways into sections, devised by Profs. Ayrton and Perry, and described by the former in a lecture at the Royal Institution, London, toward the close of 1882. This plan, designed to prevent leakage of electricity, also furnished an absolute block, cutting off the power automatically from any train whenever it approached too close to the one in front of it. At Prof. Jenkin's suggestion, a partnership was entered into by these three gentlemen, and "The Telpherage Company was soon afterward formed, to bring their system into practical use. Experimental work was carried on for over two years on the estate of Mr. Melton R. Pry or, the chairman of the company.
Various details of construction were worked out in these experiments, and at the beginning of 1885 the scheme was were made with, the Sussex Portland Cement Company for building a telpher line to carry clay from the clay-pits on Lord Hampden's estate at Glynde, in Sussex, to the Glynde Railway station. While this work was in progress, Prof. Jenkin died, and was succeeded as engineer of the Telpherage Company by Prof. Perry, under whose direction the line was completed. It was put in operation October 17, 1885. The general appearance of the Glynde telpher line is shown in Fig. 1, and the following description of itdeveloped to be put in practical operation. Arrangements
Fig. 1.—Part of the Telpher Line at Glynde.
is based upon lectures delivered by Prof. Jenkin and Prof. Perry. The structure consists of a line of posts, eighteen feet high and sixty-six feet apart, with cross-heads eight feet long at the top. Instead of a cable, as used in the wire-rope haulage system, it was found better to have round steel rods, three quarters of an inch thick, running from post to post for the buckets, or "skeps," to travel on. The ends of the rods are fastened to cast-iron saddles. As the train of skeps runs on a single rail, a double track, or two lines of rods, can be supported at the two ends of the cross-heads on the single line of posts. As would be expected, these slender rods sag somewhat under the weight of the loaded skeps, but the trains are made of the length either of one span or two spans, so that the part of the train coming up out of the depression is helped on by the weight of the part just going down into it. The sagging makes the mechanical resistance but little more than is experienced in hauling a train of the same weight along a rigid track, while the use of flexible rods enables the road to be built much more lightly and hence much more cheaply than if stiff rails were used. On curves, sidings, and sections for loading and unloading, however, it is found better to employ the stiff rails, which are supported by posts thirteen feet apart. The form of
Fig. 2-A Telpher Train at the Railway Siding.
switch which has been devised for telpher lines consists of a hinged stiff blade of steel, which allows a train to run off on to a stiff siding, when it is lowered so as to rest on the main line.
At intervals along the line straining-posts are placed, each of which acts as an abutment for a number of spans on one side, and carries a compensation gear, by which an equal number of spans on the other side are kept up to the proper tension. The compensation gear consists of a chain attached to the end of a rod, which here is not bolted to the saddle, and running down to a lever and weight beneath the track. These gears keep the tension of the rods uniform in spite of varying loads and temperature; on the line at Glynde the tension is two and a quarter tons. While this line was being constructed, Prof. Perry discovered that the tension of a rod could be determined very simply, by setting it to vibrating, and counting the vibrations in a quarter of a minute.
A train on the Glynde line consists of an electric locomotive and either five or ten skeps, in the latter case the locomotive being in the middle of the train. The skeps, are spaced evenly and somewhat widely apart, being connected by poles fourteen feet long, in order to distribute the weight of the loaded train over a considerable length of the rail, which allows the track to be light and correspondingly cheap, and in order also to have the train of the proper length to make the necessary electrical connections as it passes from span to span. The poles are attached to the buckets by a hook-and-eye coupling, easily detached. Each skep weighs one hundred and one pounds, and holds about two hundred and fifty pounds of dry clay. The cross-piece connecting the two wheels is of wood, so that the bucket, being suspended from this by a hanger, is insulated from the line, and may be handled without any shock being felt. An empty train at Glynde will travel to the clay-field where the track slopes down so as to bring the skeps nearly to the level of the ground. A laborer touches a key and stops the train, the skeps are then filled, the key is touched again, and the train starts off.
At the railway siding the train does not stop. The buckets pass above the middle of the cars, into which the clay is dumped automatically by the handle at the bottom of each bucket striking an arm projecting from a post. Any kind of a load, such as bags of grain or logs, may be hung from the hangers by replacing the buckets by bands, or a seat holding two passengers may be substituted for the bucket, which would allow of twenty passengers being drawn by one locomotive. For passenger lines, however, Prof. Perry says that it would be found probably more convenient to use a stiff rail rather than the flexible rod. A single-wheeled skep, suggested by Mr. Horace Darwin, has been given practical form by Mr. Gordon Wigan. A train of these skeps moves with less friction and is more flexible, so that it goes round curves more readily than a train of the two-wheeled skeps. Mr. Wigan has also designed a one-wheeled locomotive.
An end view of the "tandem locomotive," which is the form used at Glynde, is shown in Fig. 3.
This consists of a Reckenzaun motor, with the necessary gearing, driving-wheels, etc. The locomotive is suspended by two wheels, Q, which have rubber tires. The electrical current passing through the motor drives it at the rate of sixteen hundred to seventeen hundred revolutions a minute, and the power is transmitted by the cog-wheels A and B to a second horizontal shaft on which is a chain-wheel, F. A chain going round this wheel, and round two chain-wheels at C, C, causes the two driving-wheels of the locomotive to rotate.
Various forms of grip and friction-gearing locomotives have been devised by the staff of the Telpherage Company, but it was found that the simple locomotive represented in the figure could go quite readily up inclines as steep as one foot rise in thirteen; no grades so steep as this were needed at Glynde, hence the more elaborate machines were not put in use there. Prof. Perry is confident that the simple locomotive would be effective on grades as steep as one in ten, if the rail be kept quite dry. It was found that the weight of the locomotive, which is not much greater than that of one of the loaded skeps, with the aid of the rubber tires produces enough friction on the rail for the propulsion of the train. In the wet season of the year the rubber tires will last only a fortnight, but in dry weather their life is much longer. Still, even on the wettest days the locomotive performs its work quite well.
It was feared at first that trains near the engine-house would move much faster than those which were farther away. But this difficulty is prevented by an electrical governor attached to each locomotive. In Fig. 4, D is the second shaft, and W' W' are the two weights of a centrifugal governor, which are held ordinarily in position near the axis by means of the spring S. When the weights fly apart to the dotted positions W' and W', they draw the lever into the dotted position and break the metallic contacts at c, so that no electricity can be received by the motor. But no spark is made at c, because, after the contact is broken there, a connection of small resistance is continued for a short time at a, between two carbons, or a piece of carbon and a piece of iron, one of which is compelled by a spring to follow the other for some distance. If the contact be suddenly broken when the motor is making seventeen hundred revolutions a minute, the electric current will remain cut off until the speed of the motor has become reduced to about fifteen hundred. The position of the governor on the locomotive may be seen in Fig. 3, under the motor. While ascending a steep grade the current will be on for almost the whole time; while descending such a grade it will be off altogether; on level stretches it may be on for, say, a quarter of the whole time of running. This plan avoids all waste in switches or interposed resistances, and the current cut off by each governor is too small to injure the dynamo.
But since a train when going down a steep incline is liable to get up too great a speed, even without its motor receiving any
Fig. 4.—Electrical Governor.
electricity, the locomotive is provided also with a brake, shown in Fig. 5. This is placed on the shaft of the motor, and the edge of it may be seen in Fig. 3, beside the cog-wheel A. In Fig. 5, W W are two weights whose centrifugal force, up to a speed of eighteen hundred revolutions of the shaft A per minute, is balanced by the springs S S, but above that speed the weights draw outward and press the wooden brake-blocks B B against the metal ring C, which is fixed to the frame of the locomotive, thus retarding the motion of the train.
The method of working telpher trains employed at Glynde is what the inventors call the "Cross-over Parallel System." Fig. 6 is a diagram showing the electrical connections according to this system, where an up and a down track are used. Each track is divided into sections, each span of the ordinary length being a section. Alternate sections of each track, A1, B2, A3, B4, etc., are electrically connected together and to one pole of the generator of electricity D; the other sections are also connected together, and to the other pole of the generator. The two sets are well insulated from each other. Only two wheels of a train are employed for making contact, and these wheels are just the length of a section apart. When the leading wheel L is on a negative section, as A2, the trailing wheel T is on a positive section, A1, and vice versa, so that a circuit is made between the poles of the generator through the rails, the two contact wheels of a train, and a wire connecting these wheels through the motor M on the locomotive, which thus receives its supply of electric energy. Of course, the current through the motor is stopped and reversed each time the contact wheels pass from a positive to a negative or a negative to a positive section, but this makes no difference with the direction in which the motor runs, nor does it injure the dynamo. We can cause the locomotive to run backward, however, by altering the positions of the commutator-brushes on the motor. In the case of a single track, the positive sections A1, A3, etc., would have to
Fig. 6.—Diagram of the Cross-over Parallel System.
be connected by a long wire instead of through the sections of rail B2, B4, etc. This system requires that the sections shall all be of equal length, which is sometimes inconvenient, as when broad gorges have to be crossed, and at curved parts of the line. But this difficulty can be overcome to some extent by employing a "gravitation section" longer than the distance between the contact wheels of a train. This section is constructed with a downward slope, so that the weight of the train will propel it over the part in which it receives no electric energy.
Fig. 7 shows how the ends of the steel rods are fastened and insulated from each other. The end of one rod is turned down and fastened to the cast-iron saddle with a nut, as shown at the right of the figure. The end of the next rod, A, is bolted to the cast-steel cap C, which is insulated from the saddle by an insulator of vulcanite, V; and, in order that the tension of the rods may not break the vulcanite, melted lead is run in between the
Fig. 7.—Ordinary Saddle.
saddle and the insulator, and between the insulator and the cap. To prevent the metallic wheels of the skeps from short-circuiting the two sections as they cross the tops of the posts, there are insulated gap-pieces, as shown in this figure, on the saddles between each rod and the next.
Each of the motors at Glynde receives a power of about fifteen hundred watts, or about two horse-power, and as the potential is about two hundred volts everywhere on the line, each motor receives about eight ampères when a train is running at about four and a half miles an hour. The dynamo used on this line is a Crompton six-unit "shunt-wound" machine of the Gramme type driven by a steam-engine. It is evident that a telpher line could be run with water-power, where this is available, even if the source of power is several miles from the track.
The line at Glynde is a little under a mile in length. On long lines it is expected that a source of power would be needed every ten miles, working the trains for five miles in each direction.
The advantages claimed for telpher lines over surface railroads using steam locomotives are, first, the much less cost of the road and equipment. Thus, as the result of the experience gained in constructing the Glynde line, it was estimated that a similar line could be erected for a total cost equal to about six thousand dollars, including engine, dynamo, track, and five trains, with locomotives to carry one hundred tons a day. Where rivers and gorges have to be crossed and very uneven ground is to be passed over, no expensive bridging or grading has to be done. It is not necessary to buy the land over which the line runs; only a right of way need be acquired—for the tracks being elevated, the road does not interfere with the use of the ground for agricultural or other purposes. At Glynde this consideration was an important one, and the fact of the tracks being elevated was also important for the reason that sometimes in winter some of the fields over which the line passes are several feet deep in water. The presence of an electric line of conveyance may be an actual convenience for agricultural operations; for a root-cutter, a shearing-machine, a thrashing-machine, a circular saw, or any other agricultural machinery, may be driven by attaching a small electro-motor to the machine, and connecting it by wires with the rods of the line.
A train of ten loaded skeps, on a road of flexible rods such as has just been described, weighs about two tons, yet lines can be designed, especially when stiff rails are used, that will carry almost as heavy loads as desired. Yet telpher lines are especially applicable where the traffic is not large enough, or the difficulties of construction are too great, to make an ordinary railroad profitable, and where the goods would be conveyed in carts or on pack-horses. Prof. Perry estimates that on a railway the cost of transporting freight is about 1d. per ton per mile, if there is a sufficient amount of traffic; that on a telpher line the cost is from 2¼d. per ton mile to 3½d.; whereas cartage can not be performed at much less than 1s. per ton mile, and even at this high price the cost of constructing the cart-road and keeping it in repair is left out of account. Telpherage is claimed to be superior to the wire-rope haulage system in its power to turn sharp corners with ease.
It was reported in the spring of last year that the Glynde line had given every satisfaction under continuous working for over three years, and that negotiations were in progress for the erection of telpher lines both in England and abroad. Among the contracts then recently made was one for two lines in Cornwall, for the carriage respectively of one thousand and five hundred tons of tin ore a week.
In regard to possible applications of telpherage Prof. Perry has said: As we have it at present, it will not only be very useful in bringing ore from mines, but it is easy to arrange for a telpher line which will load or unload a vessel which is unable to come close to shore on account of the shallowness of the water, and we can imagine these trains of skeps running out over the sea, running down into the hold of a vessel, running up again, and coming back to land .... We have at present very modest aims. I should prefer for some time to simply develop lines like the one at Glynde; but I am quite sure that in future, when more capital than we have had at our command is employed to develop the system, we shall have trains of skeps passing down empty into coal-mines and along the workings, to be filled by the men as they dig the coal from the face, coming back to the bottom of the pit, and, moving up a vertical rod, passing on to the ordinary lines at the surface, and then without stopping, except perhaps to be labeled, traveling along, shunted from point to point by men properly stationed, who will know what to do with each train by the ticket upon it, until they will eventually reach the door of the customer who is to use the coal. The immense amount of worry which there has been in the development of telpherage, even as we now see it, shows me that its grandest developments can not come in my own time; but that it must come in the long run; and that telpherage will be a general system of distribution of goods is a fact which is fixed in my mind so securely that no amount of disappointment or worry can remove it."