James Alfred Ewing

“ A small electric motor, which hangs below the line and is geared by spur and chain gearing to a pair of driving-wheels, forms the locomotive. In general, the line is electrically divided into equal sections, which have the same length as a single train, so that the front carriage is always on the section in advance of the rear carriage. The train is furnished with a continuous conductor from end to end, through which it makes electric contact between the section in front and the section behind, and the motor is included in the circuit of this conductor. ”

“ Electric traction by storage batteries.In all the instances which have been referred to above, electricity is employed as a means of transmitting power as it is wanted from a generating station to the cars, through a conductor extending along the track. Another method of effecting electric traction is to carry a store of energy on the car or on a special locomotive, by using secondary batteries which are charged from time to time at the generating station. ”

“ Leakage is thus restricted to the continuous and well-insulated conductor, together with that section of the surface conductor which is in contact with the former at any one time; and the system has the further advantage that it gives the means of providing an automatic block by which successive trains are kept from overtaking one another.
The form and disposition of the motor-dynamo and the mode by which it is connected with the driving-axle of the car are matters in which much variety of practice exists. ”

“ Other trains at other places in the line receive the same current, each by breaking for the time the ordinary contact between the two sections it touches, and substituting a contact through its own conductor and motor. When a train leaves a section it replaces the switch that makes contact with the section behind. If, however, there are more than one train on the line, an automatic block system is added to prevent one from overtaking another by letting the section which a train leaves stand insulated for a time. No control is exercised from the vehicles themselves ”

“ There is no separate locomotive, the motor-dynamo being on the car itself. In 1882 Messrs Siemens constructed an electric tramway in the mines of Zankerode, in Saxony, and built for it a locomotive able to draw 8 tons at a speed of 71/2 miles an hour. Overhead conductors were employed, consisting of a pair of insulated I-shaped rails fixed to the roof of the workings; the current was conveyed to and from the locomotive by means of a pair of contact carriages sliding on these conductors, and connected with the car by short flexible cables. ”

“ Mr Reckenzaun's car is carried by two bogie trucks, one under each end, and each bogie carries a motor whose axle, placed longitudinally, drives a central spur-wheel on one axle of the bogie by means of a worm. An advantage possessed by two motors is that, by coupling them in series or parallel, or by using one only, the driver is able to command different grades of power without the use of resistance coils. In cars driven by storage batteries the same object may be secured by various groupings of the cells. ”

“ A good battery using zinc as the active metal consumes from 1 to 2 lb of zinc per hour per horse-power developed; a good steam-engine consumes from 2 to 3 Ib of coal in doing the same amount of work, and the cost of zinc is about fifty times that of coal. Hence, notwithstanding modern improvements in electro motors, the cost of producing mechanical power by means of electricity, when a zinc-consuming battery is the source, is still prohibitive. ”

“ The question of gearing is complicated by the fact that the frame of the car oscillates vertically with respect to the axles. Spur-wheels, worm-gear, friction gear, belts, multiple-band gear, and chain-gear are or have been used. ”

“ As developed by the inventor, in conjunction with Messrs Ayrton and Perry, the system is especially adapted to the transport of goods at a slow speed, in localities where the traffic would be insufficient to support an ordinary railway. ”

“ Where roads cross the line the rails are cut out of circuit, and the current is carried past the gap by underground cables, but switches are provided by which the current can be sent into the insulated sections if re quired. Each car takes 24 passengers, and runs at a speed of 12 miles an hour. ”