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F1G . 8.–Half of See also:English See also:Double Track.
(fig. 9), where the over-hang of the See also:rolling stock is greater. The intervals between the sleepers are filled in level with See also:ballast,
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which less commonly is also heaped up over them, especially at the projecting ends.
Sleepers, called ties or See also:cross--ties in See also:America, are the blocks or slabs on which the rails are carried. They are nearly always placed transversely, 'across the direction of the lines, the See also:longitudinal position such as was adopted in connexion with the broad See also:gauge on the See also:Great Western in See also:England having been abandoned except in See also:special cases. See also: A great number of preservative processes have been devised. In that most largely used, known as " creosoting," dead oil of See also:tar, to the amount of some 3 gallons per See also:sleeper, is forced into the wood under pressure, or is sucked in by vacuum, both the timber and the oil being heated. In the See also:United States only a small percentage of the ties are treated in any way beyond seasoning in the open See also:air, timber, in the See also:opinion of the railway officials, being still too cheap in nearly all parts of that See also:country to justify the use of preservatives. Some railway companies, however, having a See also:long mileage in timberless regions, do " treat " their sleepers. Typical dimensions for sleepers on important See also:British railways are:—length g ft., breadth 10 in., and See also:depth 5 in. In America 8 ft. is the most See also:common length, the breadth being 8 in., and the depth 6 or 7 in. There are two See also:main ways of attaching the rails to the sleepers, corresponding to two main types of rails—the See also:bull-headed See also:rail A B and the Vignoles or flange rail. In the first method, which is practically universal in Great Britain and is also employed to 1 See a full See also:account of steel sleepers in a See also:paper read by A. Haarnann before the Verein der Deutschen Eisenhtittenleute on Dec. 8, £907, translated in the Railway See also:Gazette (London) on See also:April 3, 10 and 17, 1908.some extent in France and See also:India, the rails have rounded bases and are supported by being wedged, with wooden keys, in See also:cast-See also:iron chairs which are bolted to the sleepers. In the second method the rails have See also:flat flanged bases which See also:rest directly on the sleepers (fig. so). The chairs on the British See also:system weigh about 45 or 50 lb each on important lines, though they may be less where the See also:traffic is See also:light, and are fixed to the sleepers each by two, three or four fastenings, either See also:screw spikes, or See also:round See also:drift bolts entered in holes previously bored, or See also:fang bolts or wooden trenails. Sometimes a See also:strip of See also:felt is interposed between the See also:chair and the sleeper, and sometimes a serrated See also:surface is prepared on the sleeper for the chair. which is forced into its seat by See also:hydraulic pressure. The keys which hold the rail in the chairs are usually of See also:oak and are placed outside the rails; the inside position has also been employed, but has the disadvantage of detracting from the See also:elasticity of the road since the See also:weight of a passing See also:train presses the rails up against a rigid See also:mass of See also:metal instead of against a slightly yielding See also:block of wood. The rails, which for heavy main line traffic may weigh as much as roo lb per yard, or even more, are rolled in lengths of from 30 to 6o ft., and sleepers are placed under them at. intervals of between 2 and 3 ft. (centre to centre), Ix sleepers to a 30 ft. rail being a common arrangement. On the London & North-Western railway there are 24 sleepers to each 6o ft. rail. A small space is See also:left between the end of one rail and that of the next, in See also:order to allow for expansion in hot See also:weather, and at the See also:joint the two are firmly braced together by a pair of See also:fish-plates (fig.xx). These are flat bars of iron or steel from 18 in. to 2 ft. long, which are lodged in the channels of the rail, one on each See also:side, and secured with four bolts passing through the See also:web; sometimes, to give additional stiffness, they extend down below the See also:lower table of the rail and are See also:bent round so as to clip it. Occasionally the See also:joints thus formed are " supported " on a sleeper, as was the practice in the early days of rail- FIG. II.—British way construction, but they are generally Rail Rail " suspended " between two sleepers, which are set rather more closely together than at other points in the rail. Preferably, they are so arranged that those in both lines of rails come opposite each other and are placed between the same pair of sleepers. Flat-bottomed rails are fastened to the sleepers by See also:hook-headed spikes, the heads of which project over the flanges. In the United States the spikes are simply driven in with a maul, and the rails stand upright, little care being taken to prepare seats for them on the sleepers, on which they soon seat them-selves. The whole arrangement is See also:simple and cheap in first cost, and it lends itself admirably to fast track-laying and to See also:repairs and changes of line. On the See also:continent of See also:Europe the practice is common of notching the sleeper so as to give the rail a slight cant inwards—a result obtained in England by canting the rail in the chairs—and metal plates or strips of felt are put under the rail, which is carefully fastened to the sleeper by screwed spikes (fig. I2). This method of construction is more expensive than the American in first cost, but it gives a more durable and See also:stable track. Such metal plates, or " tie-plates," have come into considerable use also in the United States, where they are always made of rolled steel, punched with rectangular holes through which the spikes pass. They serve two See also:principal purposes: they diminish ; the See also:wear of the sleeper under the rail by providing a larger bearing surface, and they help to support the spikes and so to keep the gauge. On all the accepted forms there are two or more flanges at the bottom, See also:running lengthwise of the See also:plate and crosswise of the rail; these are requisite to give proper stiffness, and further, as they are forced into the tie by the weight of passing traffic, they help to See also:fix the plate securely in See also:place. The joints of flanged rails are similar to those employed with bull-headed rails. Various forms, mostly patented, have been tried in the United States, but the one most generally adopted consists of two symmetrical See also:angle bars (fig. 13), varying in length (from 20 to 48 in.), in weight and in the number of bolts, which may be four or six. The substitution of steel for iron as the material for rails which made possible the See also:axle loads and the speeds of to-See also:day, and, by reducing the cost of See also:maintenance, contributed enormously to the economic efficiency of railways, was one of the most important events in the See also:history of railways, and a scarcely less important See also:element of progressive See also:economy has been the continued improvement of the steel rail in stiffness of See also:section and in toughness and hardness of material. See also:Carbon is the important element in controlling hardness, and the amount See also:present is in general higher in the United States than in Great Britain. The specifications for bull-headed rails issued by the British See also:Engineering See also:Standards See also:Committee in 1904 provided for a carbon-content ranging from o•35 to 0.50%, with a See also:phosphorus maximum of 0.075%. In the United States a committee of the American Society of See also:Civil See also:Engineers, appointed to consider the 'question of rail manufacture in consequence of an increase in the number of rail-failures, issued an See also:interim See also:report in 1907 in which it suggested a range of carbon from 0.55 to 0'05% for the heaviest sections of See also:Bessemer steel flange rails, with a phosphorus maximum of o•o85 %; while the specifications of the American Society for Testing Materials, current at the same See also:period, put the carbon limits at 0.45 to 0.55%, and the phosphorus limit at o•10. For rails of basic open-See also:hearth steel, which is rapidly ousting Bessemer steel, the Civil Engineers' specifications allowed from o•65 to 0.75% of carbon with 0•o % of phosphorus, while the specifications of the American Railway Engineering and Maintenance of Way Association provided for a range of 0.75 to 0'85% of carbon, with a maximum of 0.03% of phosphorus. The rail-failures mentioned above also See also:drew renewed See also:attention to the importance of the thermal treatment of the steel from the See also:time of melting to the last passage through the rolling See also: Ir1 Great Britain the See also:Board of See also:Trade requires facing points to be avoided as far as possible; but, of course, they are a necessity at junctions where running lines diverge and at the See also:crossing places which must be provided to enable trains to pass each other on single-track lines. At stations the points that give See also:access to sidings are generally arranged as trailing points with respect to the direction of traffic on the main lines; that is, trains can-not pass See also:direct into sidings, but have to stop and then run backwards into them. See also:IIt shunting yards the points are commonly set in the required direction by means of See also:hand levers placed See also:close beside the lines, but those at junctions and those which give access from the main lines to sidings at wayside stations are worked by a system of rods from the See also:signal See also:cabin, or by electric or pneumatic See also:power controlled from it and interlocked with the signals (see SIGNAL: § Railway). Crossings are inevitable adjuncts of points. Where a branch diverges from a main line, one rail of the one must cross one rail of the other, and a V-crossing is formed (V). Where, as at a double-line junction, one pair of rails crosses another pair, " See also:diamond" crossings (D) are formed. At both types of crossing, check rails (c) must be provided to See also:guide the See also:wheel-flanges, and if these are not accur' ately placed the safety of the trains will be endangered. At double-line junctions trains passing over the diamond crossings evidently block traffic going in the opposite direction to that in which they are travelling. To avoid the delay thus caused the branch line which would occasion the diamond crossing if it were taken across on the level is sometimes carried over the main line by an over-See also:bridge (" flying junction ") or under it by an under-bridge (" burrowing junction"). Railway Stations.—Railway stations are either " terminal or " intermediate." A terminal station embraces (1) the passenger station; (2) the goods station; (3) the See also:locomotive., See also:carriage and waggon depots, where the engines and the carrying stock are kept, cleaned, examined and repaired. At many intermediate stations the same arrangements, on a smaller See also:scale, are made; in all of them there is at least See also:accommodation for the passenger and the goods traffic: The stations for TP =Trailing points. a=Stock rail. b = Switch rail. V=Single or V-crossing. D= Diamond crossing. c= Check rails. d =Wing rails. e = Winged check rails. f = Diamond points. passengers and goods are generally in different and sometimes in distant positions, the place , selected for each being that which is most convenient for the traffic. The passenger station abuts on the main line, or, at termini, forms the natural See also:terminus, at,a place as near as can conveniently be obtained to the centre of the, See also:population which constitutes the passenger traffic; and preferably itsilatforms should be at or near the ground level, for convefnce of access. The goods station is approached by a s ding or See also:fork set off from the main line at a point See also:short t' the passenger station. In order to keep down the expense of shunting the empty trains and engines to and from the platforms the carriage and locomotive depots should be as near the passenger station as possible; but often the See also:price of See also:land renders it impracticable to locate them in the immediate vicinity and they are to be found at a distance of several See also:miles. In laying out the approaches and station yard of a passenger station ample width and space should be provided, with well- defined means of See also:ingress and See also:egress to facilitate the Passeionngers. circulation of vehicles and with a long setting-down stat See also:pavement to enable them to See also:discharge their passengers and luggage without delay. The position of the main buildings —ticket offices, waiting and refreshment-rooms, parcels offices, &c.—relative to the direction of the lines of rails may be used as a means of classifying terminal stations. They are placed either on the departure side parallel to the See also:platform (" side " stations) or at right angles to the rails and platforms (" end " stations). Many large stations, however, are of a mixed type, and the offices are arranged in a fork between two or more See also:series of platforms, or partly at the end and partly on one side. Where' heavy suburban traffic has to be dealt with, the expedient is occasionally adopted of taking some of the lines round the end in a continuous See also:loop, so that incoming trains can See also:deposit their passengers at an underground platform and immediately proceed on their outward See also:journey. Intermediate stations, like terminal ones, should be convenient in situation and easy of approach, and, especially if they are important, should be on the ground level rather than on an See also:embankment or in a cutting. The lines through them should be, if possible, straight and on the level; the British Board of Trade forbids them being placed on a gradient steeper than r in 26o, unless it is unavoidable. Intermediate stations at the surface level are naturally constructed as side stations, and whether offices are provided on both sides or whether they are mainly concentrated on one will depend on See also:local circumstances, the amount of the traffic, and the direction in which it preponderates. When the railway lies below the surface level the bulk of the offices are often placed on a bridge spanning the lines, access being given to the platforms by staircases or lifts, and similarly when the railway is at a high level the offices may be arranged under the lines. Occasionally on a double-track railway one platform placed between the tracks serves both of them; this " See also:island " arrangement, as it is termed, has the See also:advantage that more tracks can be readily added without disturbance of existing buildings, but when it is adopted the exit from the trains is at the opposite side to that which is usual, and accidents have happened through passengers alighting at the usual side without noticing the See also:absence of a plat-See also:form. At stations- on double-track railways which have a heavy traffic four tracks are sometimes provided, the two outside ones only having platforms, so that fast trains get a clear road and can pass slow ones that are See also:standing in the station. In Great Britain, it may be noted, trains almost invariably keep to the left, whereas in most other countries right-handed running is the See also:rule. The arrangement and See also:appropriation of the tracks in a station materially affect the economical and efficient working of the traffic. There must be a sufficient See also:provision of sidings, connected with the running tracks by points, for holding spare rolling stock and to enable carriages to be added to or taken off trains and engines to be changed with as little delay as possible. At terminal stations, especially at such as are usedby short-distance trains which arrive at and start from the same platform, a third track is often laid between a pair of platform tracks, so that the See also:engine of a train which has arrived at the platform can pass out and place itself at the other end of the train, which remains undisturbed. At the new See also:Victoria station (London) of the London, See also:Brighton & See also:South See also:Coast railway—which is so long that two trains can stand end to end at the platforms—this system is extended so as to permit a train to start out from the inner end of a platform even though another train is occupying the outer end. One of the advantages of electric trains on the multiple See also:control. system is that they economize terminal accommodation, because they can be driven from either end indifferently, and therefore avoid the necessity for tracks by which engines can See also:change from one end of the train to the other. The platforms on British railways have a standard See also:elevation of 3 ft. above rail level, and they are not now made less than 21 ft. in height. In other countries they are generally lower; in the United States they are commonly level with, or only a few inches higher than, the See also:top of the rails. They may consist of See also:earth with a retaining See also:wall along the tracks and with the surface gravelled or paved with stone or See also:asphalt, or they may be constructed entirely of timber, or they may be formed of stone slabs supported on longitudinal walls. They should be of ample dimensions to accommodate the traffic—the British Board of Trade requires them to be not less than 6 ft. wide at small stations and not less than 12 ft. wide at large ones—and they should be as free as possible from obstructions, such as pillars supporting the roof. At intermediate stations the See also:roofs are often carried on brackets fixed to the walls of the station buildings, and project only to the edge of the platforms. At larger stations where both the platforms and the tracks are covered in, there are two broad types of construction, with many intermediate See also:variations: the roof may either be comparatively low, of the " See also:ridge and furrow " See also:pattern, See also:borne on a number of rows of pillars, or it may consist of a single lofty span extending clear across the See also:area from the side walls. The advantage claimed for roofs formed with one or two large spans is that they permit the platforms and tracks to be readily rearranged at any time as required, whereas this is difficult with the other type, especially since the British Board of Trade requires the pillars to be not less than 6 ft. away from the edges of the platforms. On the other hand, wide spans are more expensive both in first cost and in maintenance, and there is the possibility of a failure such as caused the collapse in See also:December 1905 of the roof of Charing Cross (S.E.R.) station, London, which then consisted of a single span. , Whatever the pattern adopted for the roof, a sufficient portion of it must be glazed to admit light, and it should be so designed that the ironwork can be easily inspected and painted and the See also:glass readily cleaned. For the See also:illumination of , large stations by See also:night electric arc lamps are frequently employed, but some authorities favour high-pressure incandescent See also:gas-See also:lighting. At busy stations See also:separate tracks are sometimes appropriated to the use of light engines and empty trains, on which, they may be run between the platforms and the locomotive and L.., carriage depots. A carriage See also:depot includes sheds in moue which the vehicles are stored, arrangements for See also:wash- depots; See also:ing and cleaning them, and sidings on which they are marshalled into trains. At a locomotive depot the See also:chief See also:building is the " running See also:shed " in which the engines are housed and cleaned. This may be rectangular in shape (" straight " shed), containing a series of parallel tracks on which the engines stand and which are reached by means of points and crossings di-verging from a main track outside; or it may take a polygonal or circular form (round See also:house or rotunda), the lines for the engines radiating from a turn-table which occupies the centre and can be rotated so as to serve any of the radiating lines. The second arrangement enables any particular engine to, enter or leave without disturbing the other; but on the other hand an See also:accident to the turn-table may temporarily imprison the whole of them. In both types pits are constructed between the rails on which the engines stand to afford easy access for the inspection and cleaning of their mechanism. See also:Machine shops are usually provided to enable See also:minor repairs to be executed; the tendency, both in England and America, is to increase the amount of such repairing plant at engine sheds, thus lengthening the intervals between the visits of the engines to the main repairing shops of the railway. A locomotive depot further includes stores of the various materials required in working the engines, See also:coal stages at which they are loaded with coal, and an ample See also:supply of See also:water. The quality of the last is' a See also:matter of great importance; when it is unsuitable, the boilers will suffer, and the See also:installation of a water-softening plant may See also:save more in the expenses of See also:boiler maintenance than it See also:costs to operate. The water See also:cranes or towers which are placed at intervals along the railway to supply the engines with water require similar care in regard to the quality of the water laid on to them, as also to the water troughs, or track tanks as they are called in America, by which engines are able to pick up water without stopping. These consist of shallow troughs about 18 in. wide, placed between the rails on perfectly level stretches of line. When water is required, a See also:scoop is lowered into them from below the engine, and if the See also:speed is sufficient the water is forced up _it into the See also:tender-tanks. Such troughs were first employed on the London & North-Western railway in 18i7 by See also: In general, however, the conditions are less simple. Though a busy colliery may send off its product by the train-load to an important See also:town, the wagons will usually be addressed to a number of different consignees at different depots in different parts of the town, and therefore the train will have to be broken up somewhere short of its destination and its trucks rearranged, together with those of other trains similarly constituted, into fresh trains for See also:conveyance to the various depots. Again, a station of moderate size may collect goods destined for a great variety of places but not in sufficient quantities to compose a full train-load for any of them, and then it becomes impossible, except at the cost of uneconomical working, to avoid despatching trains which contain wagons intended for many diverse destinations. For some distance these wagons will all travel over the same line, but sooner or later they will reach a junction-point where their ways will diverge and where they must be separated. At this point trains of wagons similarly destined for different places will be arriving from other lines, and hence the necessity will arise of See also:collecting together from all the trains all the wagons which are travelling to the same place. The problem may be illustrated diagrammatically as follows (fig. 15) : A may be supposed to be a junction outside a large C seaport where branches from docks a, b, c and d converge, and where the main line also divides into three; 'going to B, G and D respectively. A train from a will contain some wagons for B, some for C and some for D, as will also the trains from a, b, c and d. At A therefore it becomes necessary to disentangle and See also:group together all the wagons that are intended for B, all that are intended for C, and all that are intended for D. Even that is not the whole of the problem. Between A and B, A and C, and A and D, there may be a See also:string of stations, p, q, r, s, &c., all receiving goods from a, b, c and d, and it would manifestly be inconvenient and wasteful of time and trouble if the trains serving those intermediate stations were made up with, say, six wagons from a to p next the engine, five from b to p at the See also:middle, and four from c to p near the end. Hence at A the trucks from a, b, c and d must not only be sorted according as they have to travel along A B, A C, or A D, but also must be marshalled into trains in the order of the stations along those lines. Conversely, trains arriving at A from B, C and D must be broken up and remade in order to distribute their wagons to the different See also:dock branches. To enable the wagons to be shunted into the desired order yards containing a large number of sidings are constructed at important junction points like A. Such a yard consists essentially of a group or See also:groups of sidings, equal in length at least to the longest train run on the line, branching out from a single main track and often again converging to a single track at the other end; the precise design, however, varies with the amount and character of ;the See also:work that has to be done, with the configuration of the ground, and also with the mode of shunting adopted. The See also:oldest and commonest method of shunting is that known as push-and-pull," or in America as " See also:link-and-See also:pin " or tail " shunting. An engine coupled to a batch of wagons runs one or more of them down one siding, leaves them there, then returns back with the See also:remainder clear of the points where the sidings diverge, runs one or more others down another siding, and so on till they are all disposed of. The same operation is repeated with fresh batches of wagons, until the sidings contain a number of trains, each intended, it may be supposed, for a particular town or See also:district. In some cases nothing more is required than to attach an engine and See also:brake-See also:van (" caboose ") and despatch the train; but if, as will happen in others, a further rearrangement of the wagons is necessary to get them into station order this is effected on the same principle. Push-and-pull shunting is simple, but it is also slow, and there-fore efforts have been made at busy yards where great See also:numbers of trains are dealt with to introduce more expeditious methods. One of these, employed in America, is known as " poling." Alongside the tracks on which stand the trains that are to be broken up and from which the sidings diverge subsidiary tracks are provided for the use of the shunting engines. These engines have a See also:pole projecting horizontally in front of them, or are attached to a " pole-See also:car " having such a pole. The method of working is for the pole to be swung out behind a number of wagons; one engine is then started and with' its pole pushes the wagons in front of it until their speed is sufficient to carry them over the points, where they are diverted into any desired siding. It then runs back to the train to repeat the operation, but while it is doing so a second engine similarly equipped has poled away a batch of wagons on the opposite side. In this way a train is distributed with great rapidity, especially if the points giving access to the different sidings are worked by power so that they can be quickly manipulated. Another method, which was introduced into America from Europe about 189o, is that of the See also:summit or " hump." The wagons are pushed by an engine at their See also:rear up one slope of an artificial See also:mound, and as they run down the other slope by gravity are switched into the desired siding. ,Sometimes a site can be found for the sorting sidings where the natural slope of the ground is sufficiently steep to make the wagons run down of themselves. One of the earliest and best known of such " gravity " yards is that at Edgehill, near See also:Liverpool, on the London & North-Western railway, which was established in 1873. Here, at the highest level, there are a number of " upper reception lines " converging to a single line which leads to a group of " sorting sidings " at a lower level. These in turn converge to a pair of single lines which See also:lead to two groups of marshalling sidings, called " gridirons " from their shape, and these again converge to single lines leading to " lower reception and departure lines " at the bottom of the slope. The wagons from the upper reception lines are sorted into trains on the sorting sidings, and then, in the gridirons, are arranged in the appropriate order and marshalled ready to be sent off from the departure lines. (H. M. Additional information and CommentsThere are no comments yet for this article.
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