Identifier: americanaunivers14newy (find matches)
Title: The Americana; a universal reference library, comprising the arts and sciences, literature, history, biography, geography, commerce, etc., of the world
Year: 1908 (1900s)
Authors:
Subjects: Encyclopedias and dictionaries
Publisher: New York : Scientific American Compiling Dept.
Contributing Library: University of California Libraries
Digitizing Sponsor: Internet Archive

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current isconverted into direct current of 500 to 600 voltspressure and distributed to the trolley wire inthe manner already described. (A diagram ofsuch a transmission is shown in Fig. 7.) Thehigher the pressure of the alternating current,the smaller may be made the cross-section ofthe transmission w-ire. The usual voltage isfrom 10,000 to 20,000 volts, although pressuresmuch higher than this have been used. A three-phase alternating current requiring three trans-mission wires is the common practice. Thealternating current method of transmission hasbeen used to some e.xtent on city street rail-ways, but it only shows economy over directcurrent transmission where the traffic is veryheavy and the distance ver> great, and conse-quently its use is limited to the very largestcities. Rolling Stock.— The type and size of the carvaries largely with the locality and the kindof service given by the line. The electric carmay be divided into three parts, the truck, the STREET RAILWAY CARS.
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8. noublf truck car, stmi-tcii- ;:. : t\l .■ .: lo. Typical car for inlcrurban service. I I STREET RAILWAY CONSTRUCTION body, and the electrical equipment. The truckconsists of the wheels, axles and the steel fram-ing which ties them together. It is built entirelyindependent of the body which rests on it.A car which has one truck under it is knownas a single truck car, and one which has twoindependent swiveling trucks is called a doubletruck car. Car bodies up to a length of 20 feetusually have single trucks and when of a greaterlength, double trucks. The ordinary wheel inuse on city roads is 33 inches in diameter, andon suburban roads, 36 inches. The car body may be open or closed, and insome instances the bodies are changed on thesame trucks, according to the season of the year.A recent type of car, called the convertible orsemi-convertible, which may be converted quicklyfrom open to closed and lice versa, has provenvery popular. The seats may be cross or lon-gitudinal, or a combi

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