Page:Popular Science Monthly Volume 56.djvu/340

326 as many positive as negative poles, no more and no less. Railway motors at the present time are made with four poles. The external appearance can be understood from Fig. 15, while Fig. 16 and Fig. 17 will serve to elucidate the internal construction. In Fig. 15 the motor casing is marked M, and, as will be seen, it forms a complete shell. The motion of the armature shaft is transmitted to the car-wheel axle F through a pinion, which engages with a spur gear secured to the latter. In Fig. 16 the pinion and gear are marked N and L respectively. As it is necessary that the armature shaft and the axle be kept in perfect alignment, the motor casing M is provided with suitable bearings for both, those for the armature shaft being marked P P in Fig. 16, and one of those for the axle being marked T in Fig. 15. It will be understood from the foregoing that the motor is mounted so as to swing around the car-wheel axle as a center, but, as it is not desirable to have all this dead weight resting upon the wheels without any elasticity, the motor is carried by the crossbars B B, Fig, 15, which rest upon springs s s at each end. The beam A and a similar one at the farther end of the B B bars extend out to the sides of the car truck and are suitably secured to the latter. The coils w w are the ends of the field coils and the armature connections, and to these



the wires conveying the current from the trolley are connected. The cover C on top of the motor at one end closes an opening through which access to the commutator brushes is obtained. The armature is shown at H in Fig. 16 and the commutator at K in the same figure. Directly under the armature may be seen one of the field magnet coils, it being marked R.

As will be noticed in Fig. 16, the motor casing is made so as to open along the central line, and the lower half is secured to the