ELECTRO-DYNAMIC MACHINE.

Globe, Volume XXI, Issue 1800, 27 November 1879, Page 3

ELECTRO-DYNAMIC MACHINE.

Many attempts have been made to apply the motive power obtained from electricity to the working of locomotives, but no satisfactory result was obtained. However, a step forward has been made in this direction in Berlin with apparent success. There are two lines of rails laid down, which, as ina narrow-gauge line, return into themselves in a ring-shaped curve. The length is about 300 metres. In the middle is an isolated third line, consisting of an upright continuous iron plate. The locomotive carries two rollers, with which it stands in connection with the isolated middle line. The essential portion of the locomotive is formed by an electro-dynamic machine, one pole of which is connected with the middle line, and the other with the pair of outer rails through the outer wheels. Similarly, the machine which produces the current stands in the machine-room in connection through one pole with the middle line, and through the other pole with the outer pair of rails. When, therefore, the dynamical machine in the locomotive is on the railway the electric current produced in the machine soon runs through it and causes it to rotate and to impart its rotatory motion to the wheels of the locomotive, and the latter continues to move until the current is interrupted. Even an imperfect state of isolation on the part of the railß does not materially affect the action of the machine. When the locomotive is moving, its conducting wires form much better conductors than the damp earth. If the current is interrupted, the damp ground is not a sufficient conductor to keep the dynamo-electrical action going. The magnetism of the machines producing the current consequently disappears, and the result is that the subordinate stream through the earth is also interrupted. A great advantage is possessed by the transmission of electric force from the {act that the locomotive, whether moving slowly or quickly, always works up to its full power—an effect which has hitherto been an unsolved problem in mechanics, When the machine that gives the power has to do much work, and so goes slowly, the counter-currents it produces are also correspondingly weak, and the current through the conductors thereby undergoes an increase in strength to a similar extent. By this means the electro-magnetism and, corresponding to this, the attractive power of the machine, are increased? The dynamoelectric locomotive has the further advantage that it carries in itself the power which can be employed as a brake, inasmuch as it becomes itself the primary or current-producing machine when it rotates more rapidly than the actual machine. In judging of the per formances of the electric locomotive in the Berlin Exhibition, it must be remembered that it was not constructed for the purr ose on which it has been applied—that is, to propel the three elegant little passenger carriages which are attached to it. Each carriage holds from eighteen to twenty persons, and all three are drawn in from one to two minutes round the circular railway of 300 metres in length. The looomotive was originally made for the purpose of drawing up coals out of the pit. Nevertheless its performances are very remarkable, and render it certain that there are many cases in which electric locomotives may be employed with advantage. The question of the extent to which electro-dynamic locomotives may possibly be employed is as yet difficult to decide. Apart from the question of the possibility of a sufficient isolation, it depends on the conductive resistance of the rails. According to Dt Siemen's view this requisite on long railways may be partly satisfied by setting up from time to time new primary dynamo-electric machines, which would maintain the necessary electric tension between the middle and the outer rails.