326 



POPULAR SCIEXCE MONTHLY. 



as many positive as negative poles, no more and no less. Rail- 

 way motors at tlie 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 en- 

 gages 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 under- 

 stood 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 Avithout any elas- 

 ticity, 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 



Fig. 16. — Eailw.vv ^loroii with Casing Open, .'showing Akmati're in Lower Half. 



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 

 arnuitiii-o is shown at // in Fig. 10 ;iii<1 llic commutator at K in 

 the same figure. Directly under the aniiatui'c may be seen one 

 of the field magnet coils, it being marked B. 



As will be noticed in Fig. 1 0, the motor casing is made so as to 

 open along the central lino, and tlic lowci- lialf is secured to the 



