Emile Garcke

“ Commercial Results.—Interest in the commercial results of tramway enterprise is practically limited to electric traction, since other forms of traction have been almost entirely superseded owing to their economical inferiority. The main advantages of electric traction over horse traction lie in the higher speed, greater carrying capacity of cars, and the saving in power over a system in which only a small proportion of the power source is available at one time. ”

“ An important point is the proper selection of the size of car. A small four-wheeled car is suitable to continual traffic of comparatively small volume, but when the traffic is heavy cars of larger capacity are advisable. A serious burden on tramways is the cost of insurance against accidents, although the number of serious accidents on electric tramways is exceedingly small in proportion to the number of passengers carried, the ratio of tramway accidents of all kinds being about one accident to every 15,000 passengers. ”

“ 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 left-hand 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. ”

“ Steam, compressed air and gas traction possess the disadvantages that each car has to carry the dead weight of power-producing machinery capable of maintaining speed up to the maximum grade. Cable traction has the disadvantages that the speed of the cars is limited by the speed of the cable, that the range and complexity of the system are restricted, and that construction is expensive. ”

“ Those forms of electric traction in which the power is supplied to the cars from an outside source have many advantages. Only the weight of the. motors has to be carried. These are efficient over a wide range of speed, accelerate quickly, have a large reserve of power and are clean and silent. The electric conduit and surface contact tramways do not require any disfiguring overhead wires. They have, however, troubles of their own. The construction of the electric conduit is so expensive that its choice must necessarily be limited to large cities. ”

“ Economy in electrical, energy is, in its broader aspects, secured by purchasing current from an outside source, in. preference to generating it at a special station. The average cost per unit of electricity for all tramway undertakings in the United Kingdom is 1·06., but one tramway company which purchases its energy from a large power company pays, only 0·85d. per unit. In its narrower aspects economy in current may be secured by reducing waste car mileage—that is to say, eliminating the running of cars at times and places where they are not required for an adequate service. ”

“ The weight of the car body is supported eccentrically on the truck, so that about 70% to 80% is available for adhesion under the driving-wheels. While this form of truck has many merits, it also has many disadvantages. The small wheels easily leave the rails, while the adhesion of the driving-wheels compared with a four-wheeled car is considerably reduced. Quick acceleration is difficult, and on a greasy rail much energy is lost in slipping. The use of equal-wheeled bogies with a motor on every axle gets over the difficulty of the loss of adhesion but at a greatly increased cost. ”

“ A failure of insulation or the sticking of a switch may allow a live stud to be unprotected in the roadway. The weight of the car and consequently the power required to move it is considerably increased by the skate, magnet and battery which have to be carried.
For simplicity of working the overhead system easily comes first. The conductors are out of reach, they can easily be doubly or trebly insulated, and with their insulators are open to inspection. The poles and wiring can be erected without closing or obstructing the street. ”

“ The limitation of stops is another source of economy, the average cost per stop on a system having been found to be 0·17 d. A slight increase in the maximum speed of tramcars would also improve the net results by reducing the proportion of standing charges (wages, &c.) to the traffic capacity of the system without making the cost of maintenance or current more than slightly greater. A 15% increase in average speed means a saving of 1/4d. per car mile. ”

“ The current consumption is increased, the first cost is greater, and there are four instead of two motors to be maintained. Steel-tired wheels have largely replaced the castiron chilled wheel for many years used on tramcars. While the various forms of trucks are common both to British and American practice, car body construction differs in many points. The single-deck car is universal outside the United Kingdom, where, although many single-deck cars are worked, the greater number are of the double-deck type. ”

“ 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 formed of concrete, with cast-iron yokes spaced at intervals of 4 ft. to support the slot beams. ”

“ 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. ”

“ Fencing is erected, but level-crossing gates are often omitted, and cattle guards only are used to prevent animals straying on the track. These sleeper tracks on private ground are cheap to maintain if well constructed in the first instance. Speeds of 20 to 25 m. an hour have been sanctioned on electric lines of this character, worked by ordinary tramway rolling stock. There is no purchase clause in the Light Railways Act, but arrangements for purchase of the undertaking were usually made with the local authorities and the terms embodied in the order. ”

“ The adjustment of fares and stages to their proper value is a question now carefully studied by tramway managers along with many problems of economy in working. The close adjustment of the service to the fluctuations in traffic is one source of economy which is being more seriously considered. Many systems have adopted top covers to cars in order to carry more passengers during wet weather. ”

“ From the above figures it will be noticed that the capital cost per mile has increased as a result of the adoption of electric traction, while at the same time the percentage of the return on the capital has been reduced notwithstanding that the rate of working expenditure has fallen and the number of passengers carried per mile has increased, the fares charged having been disproportionately reduced. ”

“ 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. ”

“ Horse traction, however, limited the weight of the car and the speed of travelling. The substitution Advantages of Different Systems.of steam traction for horse traction was a great advance. Higher speeds and quicker acceleration were obtained, and larger and more comfortable cars could be worked. The power, however, was limited, and the locomotives, built as light as possible, were expensive in first cost and maintenance. Cable traction, owing to the heavy first cost of the track, requires a great density of traffic to make it pay. ”

“ Modern car bodies are mounted either on a single four-wheeled truck, with a fixed or rigid wheel-base, or on two four-wheeled bogies or swivelling trucks. Four-wheeled radial trucks have been tried on several tramways, but they have not proved satisfactory. The wheel-base of the fixed or rigid truck usually varies from 6 to 7 ft. The length of the wheel-base should be determined by the radius of the sharpest curve. To obtain steady running it should be made as long as possible. Two motors are generally fitted on a car. ”

“ Some systems carry passengers over 21/2 m. for one penny, workmen being carried twice the distance for the same sum. Halfpenny fares are represented as a boon to the working man, but they have been abandoned as a failure after several years’ trial on several systems, and in Glasgow it is found that halfpenny fares contribute only 20·4% of the early morning traffic, while the penny fare contributes 72·3% of that traffic. ”

“ There is no doubt that the extended yoke greatly increases the strength of the track. The slot beams weigh 60 ℔ per yard. The conductor bars are of mild steel, T-shaped. They weigh 22 ℔ per yard and are supported on insulators at intervals of 15 ft. Each insulator is covered over in the roadway with a cast-iron frame and movable lid. There are two conductor rails—positive and negative—so that the whole circuit is insulated from earth. The conduit or tube is formed of cement concrete. ”

“ The slot was 3/4 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. ”

“ At the lower end of this moving piece a carbon contact piece is attached. When the magnet carried by the car passes over a stud, the moving piece is magnetically attracted to the cable against the pull of the spring. In the Lorain and the Dolter systems the studs are raised slightly above the road surface—which is an objectionable feature—and the current is collected by a skate, suspended under the car, touching the project in surface. ”

“ 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 100 ℔. 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. ”