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Bible Encyclopedias
Tramway
1911 Encyclopedia Britannica
or a track or line of rails laid down in the public roads or streets (hence the American equivalent " street railway "), along which wheeled vehicles are run for the conveyance of passengers (and occasionally of goods) by animal or mechanical power; also a light roughly laid railway used for transporting coals, both underground and on the surface, and for other similar purposes. The word has been connected with the name of Benjamin Outram, an engineer who, at the beginning of the 19th century, was concerned in the construction of tram roads, and has been explained as an abbreviation for " Outram way." But this is clearly wrong, since the word is found much earlier. It appears to be of Scandinavian origin and primarily to mean a beam of wood, cf. Old Swedish tram, tram, which have that sense. In a will dated 1555 reference is made to amending a "higheway or tram " in Bernard Castle, where a log road seems to be in question. In Lowland Scottish " tram " was used both of a beam of wood and specifically of such a beam employed as the shaft of a cart, and the name is still often given in England to the wheeled vehicles used for carrying coal in mining. " Tramway," therefore, is primarily either a way made with beams of wood or one intended for the use of " trams " containing coal (see Railway).
Construction
The first tramway or street railway designed for passenger cars with flanged wheels was built in New York in 1832. The construction of this tramway does not appear to have been a success, and it was soon discontinued. In 1852 tramways were revived in New York by a French engineer named Loubat, who constructed the track of flat wrought-iron rails with a wide, deep groove in the upper surface, laid on longitudinal timbers. The groove, which was designed for wheel flanges similar to those employed on railways, proved dangerous to the light, narrow-tired vehicles of the American type. To meet this difficulty a step-rail consisting of a flat plate with a step at one side raised about $ in. above the surface was designed and laid at Philadelphia in 1855. When tramways were first introduced into England by G. F. Train in 1860 a rail similar to that laid at Philadelphia was adopted. This rail (fig. r) was made of wroughtiron and weighed 50 lb per yard. It was 6 in. wide and had a step a in. above the sole. The rails were spiked to longitudinal timbers, which rested on transverse sleepers, and they were laid to a gauge of 4 ft. 82 in. Tramways of this type were laid at Birkenhead in 1860, at London in 1861, and in the Potteries (North Staffordshire) in 1863. The English public, however, would not tolerate the danger and obstruction caused by the step-rail, with its large area of slippery iron surface, and the tramway laid in London had to be removed, while those at Birkenhead and the Potteries were only saved by being relaid with grooved rails. Thus, while the step-rail became the standard form used in the United States, the grooved-rail became generally adopted in Europe. From the tramway point of view the step-rail has many advantages. A groove collects ice and dirt, and on curves binds the wheel flanges, increasing the resistance to traction. A grooved rail is, however, far less of a nuisance to the ordinary vehicular traffic, and it has come to be largely used in the principal cities of America.
After the passing of the Tramways Act of 1870 the construction of tramways proceeded rapidly in England. A flat grooved rail supported on a longitudinal timber and laid on a concrete bed was generally adopted. The paving consisted of stone setts from (Figs. 2 and 3 from D. K. Clarke's Tramways, their Construction and Working, by permission of Crosby Lockwood & Son.) FIG. 2.
Early Tramway Rails.
4 to 6 in. in depth, laid on a thin bed of sand and grouted with cement, mortar or a bituminous mixture. With the exception of the design of the rail and the manner of supporting it on the concrete foundation, which has continually changed, this method of constructing the track has varied but little to the present day.
The flat section of rail which was wanting in vertical stiffness soon proved unsatisfactory. A fillet or flange was then added to each side, which, bedding into the supporting timber, not only increased the vertical strength but also prevented horizontal displacement of the rail. With the addition of the side flanges a greatly improved method of fixing the rail to the sleepers was adopted. The old vertical spike, which was a crude fastening, was replaced by a " dog " or double-ended side spike, one end of which was driven through a hole in the flange of the rail (fig. 2). This fastening was very strong and proved a great improvement.
The next change was the use of cast-iron chairs to support the rails, which were introduced by Kincaid in 1872. These led to a modification of the rail section, and instead of the two side flanges a rail with a central flange (fig. 3) which fitted into the cast-iron chairs was used. The chairs weighed about 75 lb each, and were spaced at intervals of about 3 ft. The Barker rail laid in Manchester in 1877 was somewhat similar to that shown in fig. 3, but a continuous cast-iron chair was used to support it.
The introduction of steam traction about 1880, with its heavier axle loads and higher speeds, was a severe test of the permanent way. The flat section laid on timber sleepers and the built-up rails of the Kincaid and Barker types began to be discarded in favour of the solid girder rail rolled in one piece. The solidity and depth of this section gave it great vertical stiffness, and its introduction materially assisted in solving the problem of providing a smooth and serviceable joint.
The merits of the girder rail soon caused it to be generally adopted, and although the design has been greatly improved it remains to-day the standard form of tramway rail used throughout the world. At first difficulty was experienced in rolling the heavier sections with thin webs and wide bases, but the introduction of steel and improvements in the rolling mills overcame these troubles. The early girder rails laid about 1880 usually weighed from 70 to 80 lb per lineal yard, and were 6 or 62 in. deep. The groove varied from I to 18 in., and the tread was about 14 in. in width. The fish-plates were not designed to give any vertical support, and were merely used to keep the rail ends in line. The girder rails were either bedded directly on the foundation or spiked to timber sleepers which were buried in the concrete.
The form of head adopted for tramway rails in Europe has almost universally been one with the groove on one side. With this section the wheel flange forces out the dirt clear of the tread. In a few isolated cases a centre grooved rail has been used. As with railways, the adoption of many different gauges has led to much inconvenience. This want of uniformity in the gauge is in some parts of the country a great obstacle to the construction of inter-urban lines. London and the larger provincial towns adopted the standard gauge of 4 ft. 82 in., but in many towns narrow gauges of 3 ft. or 3 ft. 6 in. were laid. Glasgow and a few other towns adopted the gauge of 4 ft. 74 in. with a view of making the narrow grooved rail of the tramways available for railway wagons, but without any real success.
With the introduction of electric traction the weight and speed of the cars greatly increased, and experience soon proved that only the most substantial form of permanent way was capable of withstanding the wear and tear of the traffic. The early electric lines were laid with girder rails weighing about 75 lb per lineal yard. These proved to be too light, and, at the present time, rails weighing from 95 to 11o lb per lineal yard are in general use. The large number of rail sections designed a few years ago gave considerable trouble to makers of rails. The issue in 1903 by the Engineering Standards Committee of a set of standard girder tramway rail sections was therefore generally welcomed. The sections comprise rails of five different weights. Modified sections for use on curves were also published, together with a standard form of specification. Fig. 4 shows the section of the loo lb. B.S. rail (No. 3).
Tramway rails are generally ordered in 45 ft. lengths. Rails 60 ft. long are sometimes used, but they are difficult to handle, especially in narrow streets. The rail joints still prove the weakest part of the track. Numerous patents have been taken out for fishplates and sole-plates of special design, but none has proved quite satisfactory. The " Dicker " joint, in which the head of the rail on the II fir, -- (Reproduced by permission of the Engineering Standards Committee) FIG. 4. - British Standard Tramway Rail, No. 3.
tread side is partly cut away and the fish-plate carried up so that the wheel runs on its top edge, and the " anchor " joint, in which a short piece of inverted rail is bolted or riveted to the undersides of the abutting rails, have been largely used. The latter makes a good stiff joint, but when buried in concrete it interferes with the bedding of the rail as a whole, often causing it to work loose in the centre. Various processes have also been introduced for uniting the ends of the rails by welding. Electric welding was first tried in the United States about 1893, and has since been considerably used in that country. In this process two specially prepared fish-plates are applied, one to each side of the joint. Each fish-plate has three bosses or projections, one in the centre opposite the joint and one near each end. By passing a heavy alternating current of low voltage between the opposite bosses the fish-plates are welded to the rail. The current is obtained from the line by means of a motorgenerator and static transformer. Another process which has been used considerably in the United States, and at Coventry and Norwich in England, is the cast-welded joint. To make this joint the rail ends are enclosed in an iron mould filled with molten cast-iron, which makes a more or less perfect union with the steel rails. The Inner Fish Plate.
a feet long,zaV,,Ibs.weight A Enlargement of A Outer Fish Plate.
feet iong,16ylbs.weight.
Enlargement of B. '.I.
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FIG. 3.
great drawback to these two processes is the costly and cumbersome apparatus required. The " thermit " process (see Welding) does not require any large initial outlay, and has been applied to welding the joints on both old and new tracks. The cost of making each joint is about £1.
Points and crossings are used on a tramway to deflect a car from one road to another. In the days of horse traction no movable switch was used, the car being guided by making the horses pull the leading wheels in the required direction. With the introduction of mechanical traction a movable switch was fitted in one of the castings to act as a guide to the wheel flanges. On modern tramways the points consist of a pair of steel castings, one being a fixed or dummy point, and the other containing a movable switch. On a single track at passing places the cars in Great Britain always take the lef thand road, and a spring is fitted to hold the movable switch to lead in that direction. The bottom of the grooves at open points and crossings are raised so that the car wheel runs on its flange over the break in the tread of the rail. Double switch points in which the two tongues are connected are sometimes laid. In recent years the size and weight of the castings and the length of the movable switches have considerably increased. Manganese steel is very generally used for the tongues and sometimes for the whole casting. Ordinary cast steel with manganese steel inset pieces at the parts which wear most quickly are a feature of the later designs. At some junctions the points are moved by electric power.
While the form of concrete foundation remains the same as that laid at Liverpool in 1868, far greater care is now given to the bedding of the rails. After the excavation has been completed the rails are set up in the trench and carefully packed up to the finished level. The concrete is then laid and packed under the rail, generally for a depth of 6 in. When the surface is to be paved with stone setts bedded on sand the concrete may be left rough, but where wood is to be laid the surface must be floated with fine mortar and finished to a smooth surface. Both hard and soft wood blocks are used for paving. Wood should not be used unless the whole width of the carriage-way is paved. Many different qualities of stone setts have been laid. Hard granite such as that supplied from the quarries near Aberdeen is the most suitable.
In urban districts the road authorities almost always require the tramway surface, i.e. between the rails and for 18 in. on either side, to be paved. In country districts many tramways have been laid with only a sett edging along each rail, the remainder of the surface being completed with either ordinary or tarred macadam. This construction, however, is only suitable on roads with very light traffic. After a tramway is laid, especially in a macadamized road, the heavy vehicular traffic use the track, and the wear is very much greater than on other parts of the carriage-way.
Steam and Cable Tramways
Horse traction, especially in hilly districts, has many limitations, and early in the history of tramways experiments were made both with steam cars and cable haulage. Although experimental steam cars were tried in England in 1873 the first tramways which regularly employed steam engines were French, though the engines were supplied by an English firm. About 1880 many improvements were made in the design of the engines employed, and this form of traction was adopted on several tramways in England. Beyond - - - 8'O width orSmgleTrack formed of concrete, with cast-iron yokes spaced at intervals of 4 ft. to support the slot beams. The conduit was 19 in. deep by 9 in. wide. The slot was 4 in. wide. The running rails were of the ordinary girder type bedded in concrete. Fig. 5 shows a cross-section of the track at a yoke. This form of construction is very similar to that employed in forming the tube on a modern electric conduit tramway. At Edinburgh and other places where a shallow conduit is used the supporting pulleys are placed in pits sunk below the general level of the tube. On the Birmingham cable tramway, where the tube is 2 ft. 8 in. deep, pits are not required at the supporting pulleys. This reduces the difficulty of draining the conduit. The yokes in this case are made of steel T-bars spaced 4 ft. apart.
Electric Tramways. - Electricity is now the standard motive power for tramway service, and is applied in three main ways: (I) the overhead or trolley system; (2) the open conduit system; and (3) the surface contact or closed conduit system. (See also Traction.) On a tramway worked on the overhead principle current is supplied to the cars by two overhead conductors or wires. Round copper wires varying in size from o (0.324 in.) to 0000 (0.40 in.) S.W. gauge are generally used. With feeding points at every mile, the o wire is electrically sufficient on most Trolley. roads, but from a mechanical point of view oo wire is the smallest it is desirable to erect. Wires having figure 8 or elliptical grooved sections have been employed, and have the advantage of allowing the use of a mechanical clip ear which is clear of the trolley wheel. The ordinary round wire is usually supported by a gun-metal or gun-metal and iron ear grooved to fit the wire, which is soldered or sweated to it. In Great Britain the overhead conductors are required by the board of trade to be divided into half-mile sections. The wires on adjoining sections are connected by section insulators. These consist of gun-metal castings in two parts, insulated from each other. The line wires are clamped to the metal ends. The continuity of the path of the trolley wheel is provided for on the underside of the insulator by fixing a hardwood strip between the ends or by the ribs on the castings with air gaps.
The trolley wires are supported by ears either from span wires which extend across the roadway between two poles or from bracket arms carried on a pole on one side only of the road. The span wires and short bracket suspension wires are also insulated, so that there is double insulation between the conductor and the pole. The overhead conductors are usually hung about 21 ft. above the rails. (For catenary suspensions see Traction.) The poles which carry the span wires and the bracket arms are placed not more than 40 yds. apart and are generally placed at the edge of the kerb. They are built up of three sections of steel tubes, one overlapping the other; the joints are shrunk together while hot. A cast-iron case is used to improve the appearance of the pole, and cast-iron collars hide the joints. Standard specifications for poles have been issued by the Engineering Standards Committee.
When permission can be obtained the span wires are sometimes supported by rosettes attached to the walls of the houses on either side of the street. This method has been largely adopted in Germany, ..?¦.? }?? ??i "?FC?eO;.i?i?
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Permanent Way for Tramways and Street Railways, by permission of The Railway Engineer.) FIG. 5. - Section Edinburgh Cable Conduit.
requiring a better constructed track it does not necessitate any modifications in the general design of the permanent way. The first cable tramway was constructed at San Francisco in 1873. In England the first cable system was a short length at Highgate in 1884. Cable tramways were also laid down at Edinburgh, Birmingham, Matlock and Brixton (London). Cable traction, with the expensive track construction it necessitates, and the limited speed of haulage, belongs to the past. Only gradients too severe to be worked by ordinary adhesion will in the future justify its use. The construction of the conduit or tube in which the cable runs adds very considerably to the cost of the permanent way. On the Edinburgh system the conduit was XXVII. 6 and by dispensing with the poles in the roadway it improves the appearance of the street.
Overhead conductors will not be tolerated in some cities, and to avoid the use of them open conduit and surface contact tramways have been introduced. In the conduit system the conductors are carried in a conduit or tube beneath the surface of the track, and the electric current is picked up by means of a plough carried by the cars. Modern conduit tramways are divided into two kinds: those which have the conduit at the side under one running rail, and those which have it under the centre of the track. The only example of the former to be found in England is at Bournemouth, but it is used at Vienna, Brussels, Paris, Berlin and Budapest. Centre conduit construction has been adopted in London, Nice, Bordeaux, New York, Washington, &c. The advantages of the side slot system are the reduction in the amount of metal in the roadway, less breaking up of the pavement, and slightly cheaper cost of construction. Its chief disadvantage is the difficulty it introduces in connexion with points and crossings. It is also objected that if the side slot is made the same width as the rail groove 6 ,.
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-- aJ (From The Tramway and Railway World.) FIG. 6. - Section of Side Conduit.
