Thomas Codrington

“ 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. ”

“ Steam traction.The application of steam as a motive power on street tramways is attended with special difficulties, arising from the conditions under which the engines have to work. A tramway engine must be able to draw its load up steep gradients, demanding perhaps seven or eight times the power required on a level, and it must have the necessary adhesion without being too heavy for the permanent way. It must be capable of traversing sharp curves, of going backwards or forwards with safety, and of stopping and starting quickly. ”

“ The system has advantages on double lines with few and easy curves when the gradients are long and steep, and it can be employed on gradients too steep for steam traction. On level lines it is doubtful if it could compete in economy with steam, or even with horse traction, unless with a very frequent service of cars, though then it presents the advantages of being comparatively quiet, and free from smoke and steam, and of admitting a frequent service of cars with little extra cost. ”

“ 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. ”

“ 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.
Points and crossings.For horse traction fixed points of chilled cast-iron or steel are sufficient, as the driver can turn his horses and direct the car on to either line of rails. When mechanical power is used, drop points or movable points are required. In the former the groove leading 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. ”

“ 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 1^ or 2 inches. Such a tramway will stand steam traction and the heaviest street traffic, but the rail, which is of an expensive section, requires entire renewal when the head is worn out. ”

“ Passing places.A single line of tramway must have passing places for the cars, consisting of pieces of double line of length sufficient to hold two 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. ”

“ Large boiler-power is required to reheat the engine reservoirs quickly, and this cannot be afforded for only a few engines, but, when worked on a sufficient scale, the fireless engines are claimed to be economical, the economy resulting from the generation of the steam in large stationary boilers. ”

“ The speed of the cable, which is gene rally 6 to 8 miles an hour, is thus imparted to the car gradually and without jerk. The arrangements for passing the pulleys, for changing the dummy and cars from one line to the other at the end of the road, for keeping the cable uniformly taut, and for crossings and junctions with other lines are of considerable ingenuity. When the cars are cast off from the cable they must be stopped by hand brakes, which on steep gradients especially must be of great power. ”

“ 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. ”

“ 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. ”

“ There is a considerable loss of heat during the expansion of the air which is attended with a serious loss of pressure, and in Mékarski's system, which has been in use for the propulsion of tramcars at Nantes for seven years, the loss of pressure is considerably lessened by heating the air during expansion. The air, at a pressure of 426 lb per square inch, is stored in cylindrical reservoirs beneath the car, and before use is passed through a vessel three quarters full of water heated to 300° F., by which it is heated and mixed with steam. ”

“ 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. ”

“ Compressed air.Compressed air as a motive power offers the advantage of having neither steam nor the products of combustion to be got rid of. In Scott Moncrieffs engine, which was tried on the Vale of Clyde tramways in 1876, air was compressed to 310 ft on the square inch, and expanded in the cylinders from a uniform working pressure to that of the atmosphere. ”

“ Over the rope is a slot 3/4 inch wide, in which travels a flat arm of steel connecting the dummy car with the gripper which grasps the cable. The flat arm is in three pieces, the two outer ones constituting a frame which carries the lower jaw of the gripper, with grooved rollers at each end of it, over which the cable runs when the gripper is not in action. ”

“ The motive power is trans mitted from a stationary engine by a rope of steel wire running always in one direction up one track and down the other, in a tube midway between the rails, on pulleys which are arranged so as to suit curves and changes of gradient as well as straight and level lines. ”

“ Several methods of superheating by passing the exhaust steam through the fire have been adopted, but they are all attended with an increased consumption of fuel, which in cold damp weather is considerable. ”

“ 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. ”

“ In San Francisco a main charged with air at a pressure of about 120 lb per square inch has been laid along the tram route, from which reservoirs on the cars are charged by means of standpipes and flexible connexions at convenient points, the operation taking a very short time. ”