rail inches tramways rails cars feet laid steam wheels power
TRAMWAY. Originally a tramway signified a wheel track laid with timbers, and afterwards with iron plates, having a flange on the inner edge by which wheels of the ordinary sort were kept in the track (see RAILWAY). The introduction of the flanged wheel and edge rail caused tramways to be superseded by railways, but not until many miles of tramroads had been laid and successfully worked in various parts of the United Kingdom. Although the name is sometimes given to a light railway, by a tramway is now generally understood a street railway, constructed so as to interfere but little with the ordinary traffic, on which vehicles having flanged wheels are propelled by animal or mechanical power. Tramways in this sense originated in the United States.
A street railway for passengers was laid in New York in 1832, but it was soon removed on account of the accidents caused by it. In 1852 a French engineer, Loubat, revived tramways in New York, and they were soon afterwards laid in other American cities. A short line was also laid in Paris in 1853. The rails used were of wrought-iron, 5 inches wide, having a groove for the flanged wheels of the cars 11 to 21 inches wide and 1 to 1 inches deep (fig. 1). To lessen the inconvenience to was introduced, consisting of a flat surface 3 to 5 inches wide, p \ the outer side 1 inch higher and ---72-7z/' //1 flanged wheels of the cars run. Fig. 1. Fig. •. This form of rail is still very general in America, and is a good one for the tramways, though not for the general public. In 1858-9 Train, an American, endeavoured to obtain an Act of Parliament authorizing tramways in London ; failing in that, he laid tramways, by consent of the road authority, first in 1860 at Birkenhead, and soon afterwards in London. The rail laid at Birkenhead had a step of 1 inch between flat surfaces 3 inches and 11 inches wide. That laid in London was narrower, with a step of half an inch, but the slippery flat surface and the step of the rail .caused serious inconvenience and numerous accidents to carriages, and the tramways were removed in a few months, after one of them had been successfully indicted as a nuisance. In Birkenhead, in spite of complaints of the inconvenience caused to the general traffic, the original rails remained until 1864, when, after a short length had been laid as an experiment with a rail of the grooved section now in general use (fig. 3), the whole of the tramway, several miles in length, was relaid with it. The tramway was subsequently indicted as a nuisance, but the trial resulted in a verdict in favour of the grooved rail. In 1868 an Act of Parliament authorizing the construction of about 61 miles of tramways in Liverpool was obtained ; and in 1869-71 Acts for 61 miles of tramways in London were passed, and were soon followed by other Acts for tramways in Glasgow, Dublin, Edinburgh, and other provincial towns.
In 1870 the Tramways Act was passed, enabling the Tram. Board of Trade to make provisional orders authorizing the ways construction of tramways in Great Britain, with the con- Act. sent of the local authorities, and giving considerable powers for regulating their construction and working. By the Act the gauge, unless otherwise prescribed by special Act, is to be such as will admit of the use of carriages constructed for use on railways of a gauge of 4 feet 81 inches. Tramways for which Acts had been previously obtained were of 4 feet 81 inches gauge, to comply with a standing order intended for railways, and not to make them available for railway rolling stock, which the narrow groove of an ordinary tramway rail will not admit. There is reason to think that a narrower gauge, such as 3 feet 6 inches, is often sufficient and preferable to the 4 feet 81 inches gauge.
Tramways in towns, authorized by provisional order, are to be constructed in the middle of the road, and are not to be so laid that for 30 feet and upwards a less space than 9 feet 6 inches shall be left between the outside of the footpath and the rail, if. one-third of the owners or occupiers of premises abutting upon that part of the road object. Vehicles are thus enabled to stop at the road side without hindrance from the tramcars. To leave 9 feet 6 inches on each side of a single line of tramway of 4 feet 81 inches gauge a street must be upwards of 24 feet wide. No carriage used on a tramway must extend more than 11 inches beyond the outer edge of the wheels, and there must be a space of at least 15 inches between the sides of the widest carriages or engines to be used, when passing one another. A width of not less than 3 feet 2 inches between double lines and at passing places is thus necessary, and a double line of tramway, leaving 9 feet 6 inches space on each side, requires a street at least 32 feet 6 inches wide between the footways. In narrow roads there is a convenience in having the tramway at the side, and it is sometimes provided for in special Acts. The space between the rails, and for 18 inches beyond them, is repairable as part of the tramway. Power is given to local authorities to purchase tramways at the expiration of twenty-one years, and they may be removed under certain circumstances.
It appears from a parliamentary return that in 1886 there were 779 miles of street tramways open for traffic in Great Britain, on which a capital of £11,503,438 had been expended, the net receipts for the year being £563,735, and the working expenses 79 per cent. of the gross receipts.
The grooved rail first laid in England was 4i inches wide and Con.
an inch thick, having a tread strucor rolling surface for the wheel tion.
bottom, and 1 inches wide at 1 I )1_ 11) the top (fig. 3). The rail was g 11li spiked through to a longitudinal /NI timber laid. on cross sleepers, and secured to them by angle brackets and spikes. This rail and method of laying were generally adopted, but it was found that the heads of the spikes wore Fig. 3.
off, and the rails required respikin„,.. and split and worked loose at the joints. A rail known her. This constitutes a good fastening, and the flanges give stiffness to the rail, but the clips cause gaps between the rail and the paving stones, which lead to the formation of ruts alongside the rails. The longitudinal timbers, instead of being laid on cross sleepers, on which the paving does not bed well, are often fixed in cast-iron chairs connected by transverse tie-bars. A bed of concrete is always laid under the longitudinal timbers, and should extend to the whole width of the paving. The rails first laid weighed 40 lb per yard, but it was soon found desirable to increase the weight to 60 lb per yard. It is, however, impossible to fish the joints of rails like the above, and it was found that the working of the joints under the passage of the cars loosened the ends of the rails, dislocated the paving, and damaged both the tramway cars and ordinary vehicles. Tramways proved hardly able to withstand heavy street traffic ; and to provide for steam traction a stronger form of rail and a better system of permanent way became necessary. Many forms of iron bearings have been devised, the rail being either supported continuously or on chairs at intervals. In the best of these the tram rail can be replaced when worn without disturbing the foundation. In the system used in Liverpool cast-iron longitudinal sleepers weighing 80 and 90 lb a yard carry steel rails of a T section (fig. 4) weighing 40 lb a yard, both sleepers and rails being held down by bolts to jaws anchored in the concrete foundation. The rails can be renewed and the sleepers can be taken up with very little disturbance of the paving.
Steel rails of a flatfooted or a bridge section, and of such a depth as to constitute both rail and sleeper, are also used. In some of the latest and best examples the rail is of a flatfooted section (fig. 5), 6 or 7 inches deep, and 6 or 7 inches wide at the base, weighing 65 to 93 lb per yard. The head has a groove either planed out or rolled in it, giving the usual profile to the upper surface. The joints are fished in the ordinary way, and are as strong as the rail itself. Cross ties are sometimes used, but when the rail is slightly bedded in the concrete foundation they are dispensed with. The paving is set in cement close against the rail, and is bedded directly or in sand on the base of the rail, upon which there is a bearing of 11 or 2 inches. Such a tramway will stand steam traction and the heaviest street traffic, but the rail, which is of all expensive section, requires entire renewal when the head is worn out. Iron or steel continuous bearings are less elastic, and therefore more jarring and noisy than timber sleepers.
The profile of the upper surface of tram rails has been little altered since the first grooved rail was devised for Birkenhead in 1863, though slight modifications have been made in the form of the groove with the object of lessening tractive resistance. For the sake of the ordinary traffic the groove should not exceed 1 inch in width, and a rounded section with sides splaying outwards facilitates the forcing out of the mud and dirt. A nearly upright side next the tread or rolling surface with a splay on the inner side throws the mud away from the wheel. The upper corners of the rail should be angular, to make as thin a joint as possible between the rail and the paving. There has been a tendency to diminish the width, and a rail as narrow as 3 inches has been laid. A deviation from the usual profile has been adopted in Liverpool, where the groove is in the middle of a rail 31 inches wide.
Paving. A tramway must not only afford a good rolling surface capable of bearing the weights running ou it, but it must also be able to resist the shocks of heavy vehicles crossing the rails in all directions. The space between the rails, and for 18 inches beyond them, which is repairable with the tramway, is always paved, sometimes in provincial towns and in the suburbs of London with wood, but generally with stone sets in the best manner on a concrete foundation. The sets alongside the rail should be carefully dressed and fitted to make a thin joint. There is much extra wear, and a tendency to form a rut alongside the rail, arising from ordinary wheels using the tram rail, and unless the surface of the paving is kept to the level of the rail the wheels of carriages are caught by the rail, and damage and accidents are caused. To resist the wear near the rails, chilled cast-iron blocks have been used where the traffic is great. On a macadamized road there is the same tendency to form a rut along the outer edge of the tramway paving, which is to some extent prevented by giving a serrated edge to the paving. There is always great difficulty in keeping the road surface to the level of the paving, and it is better to pave the entire width of a street in which a tramway is laid.
Although cars can be drawn round very sharp curves, the latter Curves. should be as easy as passible. A radius of 150 to 200 feet is the least that should be used when there is any choice, but necessity may compel the use of curves of 50 or even 30 feet radius. On such curves, however, the cars are liable to be strained, and the resistance to traction is greatly increased.
A single line of tramway must have passing places for the ears, Passing consisting of pieces of double line of length sufficient to hold two places. cars at least, with connecting curves and the necessary points and crossings. Where steam or other mechanical power is to be used the passing loops should be at least 200 feet in length. There is inevitable delay and interference with the street traffic at passing places, and where cars are to be run at frequent intervals it is better to lay down a double line if the street is wide enough. It is a great advantage to the ordinary traffic to have the cars moving always in the same direction on the same line of rails.
For horse traction fixed points of chilled cast-iron or steel are Points sufficient, as the driver can turn his horses and direct the car on to and either line of rails. When mechanical power is used, drop points cross-or movable points are required. In the former the groove leading logs. into the road to be taken is of the full depth, and the other groove shallow, so that the engine and cars naturally take the former.
On coming out of the shallower groove to the deeper there is, however, a drop encountered which is damaging to the rolling stock, and especially to the engines. Movable points require setting by hand, or they are actuated by a spring or balance weight. In one form of spring point one groove is filled up by a tongue which is pressed down by wheels passing out of a loop, but which forms the side of the groove for wheels running the opposite direction. A spring point of steel, which is forced aside by the flange of the wheel passing out, and shuts close again by its own elasticity, is also successfully used. A movable point on one side of the way is sufficient. Crossings are either built up front rails cut to the required angle, or they are cast solid in steel or chilled iron. Filling pieces of the same material, roughened on the surface for foothold, are inserted between the rails at the angles of points and crossings. Both points and crossings wear rapidly, and are troublesome to maintain in good condition, and when not so maintained are dangerous to ordinary traffic.
The tramcars generally in use in the United Kingdom are con- Cars. strutted to carry 22 persons inside and 24 outside. They are 16 feet long in the body, or 24 feet including the platforms at each end, and weigh 21 to 2t tons when empty and about 51 tons when fully loaded. Smaller cars to carry 20 or 14 persons inside, drawn by one horse, are useful to run at short intervals when the traffic is not great, a frequent service of cars being a great element of success. The car wheels are usually of steel or chilled iron, with a flange half an inch deep, and are fitted with powerful brakes. The axles are about 6 feet apart, giving a short wheel-base to enable the cars to pass sharp curves, but with the disadvantage of overhanging ends. Cars to be drawn by mechanical power, especially if outside passengers are to be carried, should have a flexible wheel-base, either by means of bogie frames or radiating axles. In Hamburg and Copenhagen tramcars have wheels without flanges, and a small guiding wheel running in the groove, which can be raised to allow the car to leave the track.
The tractive force required on a straight and level tramway is Traction. found to vary from 1-17, to 0-6 of the load, according to the condition of the rails. On a tramway in average condition it is about Ad-. The resistance is thus at the best nearly double that on a railway, and sometimes as much as on a good pavement. This is due to the friction of the flange of the wheel in the grooved rail, and to the circumstance that the latter is always more or less clogged with dirt. The clearance between the flange and the groove is necessarily small, as the former must have sufficient strength, and the latter must be narrow. The least inaccuracy of gauge, therefore, causes extra friction, which is greatly increased on curves. By removing the flanges from two of the four wheels of a tramway car Tresca found that the resistance was reduced from Tirir to TicEr of the load. The resistance due to gravity is of course not lessened on a tramway ; and, if TIT of the load be the tractive force required on the level, twice as much, or -2-0- of the load, will be required on a gradient of 1 in 100 and three times as much on a gradient of 1 in 50. To start a tramcar, four or five times as great a pull is required as will keep it in motion afterwards, and the constant starting after stoppages, especially on inclines, is very destructive to horses. Horses employed on tramways are worked only a few hours a day, a day's work being a journey of 10 or 12 miles, or much less on steep gradients. In London a tramcar horse bought at the age of five years has to be sold at a low price after about four years' work. On the Edinburgh tramways, in consequence of the steep gradients, the horses last a less time, and they have to be constantly shifted from steep to easier gradients. The cost:of traction by horses is generally 6d. or 7d, per mile for two horses, and more when the gradients are steep.
Fireless Fireless engines were first tried in New Orleans, and have been cable they must be stopped by hand brakes, 0 :, engines, in successful use on tramways in France for some years. The which on steep gradients especially must .4/11-- _ motive power is obtained from water heated under pressure to a be of great power.
very high temperature in stationary boilers and carried in a The system has advantages on doubleITN ty - ' reservoir, where it gives off steam as the pressure and temperature lines with few and easy curves when the arc reduced. Two tons of water heated to give a steam-pressure of gradients are long and steep, and it can be _.1-:- .\11111 250 lb to the square inch serves for a run of 8 or 10 miles, leaving employed on gradients too steep for steam - ------ -- more than A- of the water and a pressure of 20 to 25 lb above the traction. On level lines it is doubtful if it atmosphere on returning to the boiler. Large boiler-power is could compete in economy with steam, or Flo. 7. - Carrying Pulley. required to reheat the engine reservoirs quickly, and this cannot even with horse traction, unless with a very frequent service of cars, be afforded for only a few engines, but, when worked on a sufficient though then it presents the advantages of being comparatively scale, the fireless engines are claimed to be economical, the economy quiet, and free from smoke and steam, and of admitting a frequent resulting from the generation of the steam in large stationary service of cars with little extra cost. On the cable roads of San boilers. Francisco it has been found that, of the average daily power emtramways in 1876, air was compressed to 310 lb on the square inch, much as 50 per cent. of the power, provided the cars are fully and expanded in the cylinders from a uniform working pressure to loaded and run at short intervals.
that of the atmosphere. There is a considerable loss of heat during Electricity has been applied as a motive power on a tramway Electric the expansion of the air which is attended with a serious loss of about 2 miles long at Blackpool. The current is conveyed by two motors.
pressure, and in Meicarski's system, which has been in use for the copper conductors in a central channel beneath the roadway, and propulsion of tramcars at Nantes for seven years, the loss of pres- is communicated to the motors in the car by a collector running under which the engines have to work. A tramway engine must sure is considerably lessened by heating the air during expansion. be able to draw its load up steep gradients, demanding perhaps seven The air, at a pressure of 426 lb per square inch, is stored in cylindrical or eight times the power required on a level, and it must have reservoirs beneath the car, and before use is passed through a vessel the necessary adhesion without being too heavy for the permanent three quarters full of water heated to 300° F., by which it is heated way. It must be capable of traversing sharp curves, of going and mixed with steam. The heat of the latter is absorbed by the backwards or forwards with safety, and of stopping and starting air during its expansion, first to a working pressure which can be quickly. For the safety and convenience of the public the Board regulated by the driver, and then to atmospheric pressure in the of Trade require that tramway engines shall have brakes to each cylinders. At Nantes the average cost for three years for propel-wheel, to he applied by hand and by steam, a governor so arranged ling a car holding 34 persons was about 6d. per mile.
and the machinery and fire must be concealed from view ; no Street tramways worked by means of' a wire rope have been in Cable diameter. It carried 20 passengers inside and 24 outside, weighing several years, and is about to be adopted in 6i tons empty and 12 tons when fully loaded. In a later car the other localities. The motive power is transstock, and the advantage of being able to use cars intended for steel connecting the dummy horses, are in favour of independent engines. They are usually in car with the gripper which general construction similar to locomotives, but are enclosed so as grasps the cable. The flat arm to resemble in outward appearance a short tramcar. The cylinders is in three pieces, the two is actuated either by the engine wheels or by an independent the cable runs when the gripper wheel to prevent the possibility of the brakes being put on when is not in action. The upper the driving-wheels slip. An effectual way of rendering the exhaust jaw is carried by the steam invisible is to condense it by passing it through water in a middle piece, which tank, or through a shower of water let off at each blast, but when slides within the outer the water gets hot it must be changed, and in streets it is difficult frame, and can be de-to get rid of the hot water. Several methods of superheating by pressed by a lever or passing the exhaust steam through the fire have been adopted, but screw, pressing the they are all attended with an increased consumption of fuel, which cable firston the rollers, in cold damp weather is considerable. It is now preferred to pass and then on the lower the steam into tubes exposed to the air on the top of the engine jaw until it is firmly car, from which the condensed water is returned to the feed-tank, held. The speed of the to be again pumped into the boiler at a high temperature. Any cable, which is gene-steam remaining uncondensed passes into tie smoke-box. Corn- rally 6 to 8 miles an pound cylinders have been applied to tramway engines, giving a hour, is thus imparted greater range of power, economizing fuel, and rendering the exhaust to the car gradually steam easier to deal with. The extra complication of a compound and without jerk. The engine is, however, a drawback. arrangements for passhe cost of steam traction with engines of ordinary size is gene- ing the pulleys, for rally 3d. to 4d. per mile run by the engine, and more on lines with changing the dummy 6. - Gripper.
steep gradients. To this must be added for depreciation 10 per and cars from one line to the other at the end of the road, for cent., or, according to some authorities, 15 per cent. on the original keeping the cable uniformly taut, and for crossings and junctions cost of the engines, making altogether 4d. to 6d. per mile run on a with other lines are of considerable ingentramway with average gradients. laity. When the cars are cast off from the - upon the conductors and passing through a narrow slit in the and runs eastward up the Uda, with an imperceptible channel. The return current passes through the rails. The cars gradient, like a gigantic railway cutting enclosed between carry as many as 56 passengers ou a level line. Tramways have two steep slopes, sending another branch south towards also been worked by accumulators at Antwerp and Brussels, but the Kiakhta. After having served, through a succession of weight of them appears to be at present prohibitory to this method of applying electricity, except for short trips. See TRACTION. geological periods, as an outlet for the water and ice which For fuller information, see D. K. Clark, Tramways, their Construction and accumulated on the plateau, it is now utilized for the two Maintenance; F. Sdrafon, L.s Tramways et Ira Chemins de Fer sur Routes;
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