Harper's Electricity Book for Boys

by Joseph H. Adams

The Controller

[Fig. 12] is a view of a type of controller that is used on the platform of trolley-cars. The cover is removed to show the contacts, inside, by which the electric power is turned on gradually by the controller handle. The trains of electric cars that run on the elevated structures and in the subways of our large cities are supplied with power from a “third rail” placed by the side of the track, on insulating supports, and the motors on all the cars are controlled from a single “master-controller” on the front platform of the forward car. This system of control, known as the “multiple-unit” system, gives electric trains several advantages over the old kind, drawn by steam-locomotives; such as they used to have on the New York elevated roads, for example. For one thing, the train can be started much more quickly, since all the motors begin to turn the car-wheels at the same instant. Then again, the system enables a long train of cars to be controlled as easily as a single car, and better “traction” between wheels and track is obtained.

Electric Locomotives

Several of the great steam-railroads are now adopting the electric locomotive to draw their trains. [Fig. 13] is a view of one of the great continuous current electric locomotives that are used by the New York Central Railroad to handle many of its passenger-trains in and out of the Grand Central Station, in New York city. The motors of this powerful electric engine, unlike those of trolley-cars, are “gearless”; that is, their armatures are fixed directly on the locomotive axles so that they revolve at the same speed as the driving-wheels.

Fig. 13

All of the railway motors considered thus far have been of the continuous-current type, although the current to operate them is often obtained from alternating current transmission-systems, through rotary converters, as described above. The alternating current is also beginning to be employed to drive cars and trains. One type of alternating current railway motor, designed for “single-phase” operation, is in use on several interurban systems in this country, running on high-voltage alternating current most of the time, but on continuous current when within the city limits.

Other Forms of Electric Traction

Electric traction also includes electric automobiles, supplied by storage-batteries; a slow-speed electric locomotive for drawing canal-boats, and called “the electric mule”; and an ingenious gasolene-electric outfit for driving cars by electric motors without any trolley, third rail, or storage-battery. The last-mentioned arrangement consists of a set of electric car-motors mounted on the trucks in the usual way, but supplied with current by a dynamo mounted on the car itself and driven by a gasolene-engine. Thus the car carries its own power-station about with it, and is independent of any outside source of electricity.

The old alchemists sought to transmute matter from one form to another; and especially lead and other “base metals” into gold, in order that they might grow rich by concentrating the precious metal in their own selfish hands. The modern miracle that electricity works for us, the transmutation of energy, is a higher and broader thing, because it multiplies and distributes the world’s good things.