1998 



ELECTRIC WELDING 



divide at greater speed and less cost than is 

 possible with any other type of locomotive. 

 The force of the train on a descending grade 

 is utilized to generate thirty per cent of the 

 power taken from the trolleys in climbing. See 

 LOCOMOTIVE, subhead Electric Locomotive. 



Trolley Lines. In the overhead trolley lines 

 so familiar in city streets, the current is gen- 

 erated in a central power house, and passes 

 along heavy copper wires above the tracks. In 

 the usual type of car it is carried through a 



THE ELECTRIC CAR 



The illustration shows how the electric cur- 

 rent reaches a trolley car and returns to the 

 power house (P. H.) through the rails and the 

 earth. 



small trolley wheel down the trolley pole 

 conductor to the motors under the car, and 

 returns to the power house along the tracks. 

 The trolley wires may be suspended between 

 poles set on either side of the street, or may 

 be attached to an arm of a single pole placed 

 between the tracks. 



Conduit System. In New York and Wash- 

 ington and some European cities, where over- 

 head wires are not permitted, the current is 

 supplied to cars through conductor rails, sunk 

 in slots similar to the cable-slots once used 

 for grip-cars. An arm extends from the motors 

 through the slot and takes up the current by 

 means of rubbing blocks, which press against 

 the charged rail. 



Third-Rail System. Wherever it is practi- 

 cable, the third-rail system has found favor. 

 It is employed almost universally on elevated 

 systems and in subways, and is widely used 

 on interurban lines. The current is conveyed 

 through a third rail, placed beside the track; 

 the motors are fed by shoes of metal which 

 slide along this rail. Such a system is dan- 

 gerous because of the exposed position of the 

 rail that conveys the current, and it can be 

 used with safety only where the right of way 

 is closed to the public. 



Electric Cars. From street ears to locomo- 



tives, the construction of electrically-driven 

 vehicles is simple. The essential parts of a 

 street car are one or more electric motors, at- 

 tached to the driving axles of the car by gears, 

 and a switch on the platform for controlling the 

 current. The motors and the running gear 

 are attached to the trucks on which the car 

 rests, and all parts which would be affected 

 by dust are enclosed in metal casings. (For 

 an explanation of the workings of the motor, 

 see ELECTRIC MOTOR.) The revolving armature 

 shaft, driven by the current received from the 

 power house, is now generally connected 

 directly with the driving axles by cogwheels. 

 For ordinary city service the cars are equipped 

 with four motors one for each axle. Such 

 motors vary greatly in power; those for light 

 service may develop only twenty-five horse 

 power each, while the motors used for inter- 

 urban traffic will often develop 225 horse power. 

 The engines used by the Pennsylvania Railroad 

 in its New York terminals are driven by motors 

 of 2,000 horse power. 



Advantages of Electric Power. The superior- 

 ity of electricity as a motive power has been 

 thoroughly demonstrated in the case of street 

 railways and for interurban service. So far 

 as steam railways are concerned, the case is 

 not yet so clear, but the day is approaching 

 when all trains will be economically run by 

 electricity. The electric locomotive needs 

 neither coal nor water and is less affected by 

 cold weather than is the steam locomotive. It 

 consumes no power while standing still, whereas 

 a steam locomotive burns about one-half as 

 much coal then as when running. But the cost 

 of installing and maintaining electric equip- 

 ment is enormous. 



Mileage and Valuation. The Electric Rail- 

 way Journal gave the electric mileage of the 

 United States as over 43,000 in 1916. The 

 capitalization reached about two and a half 

 billion dollars. Canada, in the same year, had 

 about 1,250 miles of electric lines, capitalized 

 at more than $111,500,000. See, also, ELECTRIC- 

 ITY; ELECTROMAGNETISM. G.B.D. 



ELECTRIC WELDING. The rails of street 

 car tracks are frequently welded so as to form 

 one continuous rail and therefore one con- 

 ductor for the electric current, the trolley wire 

 and the windings of the motors forming the 

 other parts. This welding is done by means 

 of the electric arc, the arc being placed near 

 the junction of the metals to be welded. A 

 flame from the arc falls upon the metals and 

 melts the parts that are in contact. The above 



