Abstract
ONE of the most interesting sights in connection with the Exhibition at Paris, is the electrical tramway; it is a practical evidence of the great future in store for conductors: How then, in these conditions, is the motor of the carriage connected with the fixed generator placed in the Exhibition at the Palais del Industrie? This is the problem which M.M. Boistel and Sappey, the engineers of Messrs. Siemens, have completely solved, after electricity as a motive power. From an article in La Nature we give some of the leading features of this recent application of electricity. In the case of a tramway the question is a complicated one, for the rails cannot be isolated, and they therefore cannot be used as several fruitless attempts, which almost always precede successes of this kind. In the preliminary experiments made at the workshop in the Rue Picot; they made use, as conductors, of a brass tube electrically connected with the carriage by a traverser, the function of which we shall explain; the wheels and rails will serve as the return wire. This system worked well at the workshop. In practice a special difficulty was encountered. The dirt sticking to the rails and felloes of the wheels formed a sort of crust so insulating as to prevent adequate communication with the earth. The increase of resistance produced by this interposition of finely conducting bodies was often sufficient to arrest the vehicle. The remedy was happily beside the evil, and a second conductor was established parallel with the first, in communication with the second pole of the generator, on which runs a second traverser, identical with the former. These two cars follow on their respective tubes the movements of the vehicle, and ensure a good and constant communication between the electrical generator and the motor. Fig. 1 represents the carriage and the station at the Place de la Concorde. At the height of the knife-board are seen the two conducting tubes supported at certain distances by posts, and in the intervals by iron wires, like the floor of a suspension bridge. The carriage is exactly the same as the ordinary tramway car. The motor is placed underneath the feet of the inside passengers; it is a Siemens dynamo-electric machine, with horizontal inductors similar to that which produces the current in the Palais de l'Industrie. The distance traversed is about 500 metres, and is accomplished in one minute. The work expended reaches 8 horse-power in the curved part; on a level straight run it does not exceed 31/2 horsepower. The transmission of motion to the wheels is effected by means of a fall-chain. By a happy coincidence, which belongs to the very nature of the electric motor, the static effort is maximum when the motor is in repose. This renders the starting very easy, and no difficulty is met with from this point of view. To regulate the speed, resistances are introduced into the general circuit, which reduces the intensity of the current, and consequently the work of the motor; this operation is very simply effected by means of a lever placed at each end of the carriage. For stopping, the current is broken, and at the same time an ordinary brake is applied.
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The Electric Tramway . Nature 25, 13–14 (1881). https://doi.org/10.1038/025013a0
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DOI: https://doi.org/10.1038/025013a0