482 



POPULAR SCIENCE MONTHLY. 



struction each wheel is driven independently and the axle C, in Fig. 3, 

 remains stationary, as in any ordinary vehicle; but in a single motor 

 equipment, arranged as in Fig. 2, the wheels are fastened to the axle 

 and the latter rotates. When a carriage runs round a short curve the 

 outer wheels will revolve faster than the inner ones, if free to move in- 

 dependently, as in Fig. 3. If they are rigidly attached to the axle, as in 

 Fig. 2, one or the other will have to slide over the ground, and this is 

 decidedly objectionable with rubber tires. To prevent this* slipping 

 of the wheels in rounding curves, the axles, in designs following the 

 construction of Fig. 2, are made in two parts, and the gear P is ar- 

 ranged so as to drive the two halves, imparting to each one the proper 

 velocity. Gear wheels of this kind are called compensating gears; they 

 are made in many designs, but the most common form ; s that illus- 

 trated in Fig. 1. In this drawing J j s the gear l> of Fig. 2, and BB 



Fig. 4. Compensating Gears. 



Simii.i: VtoToi: Equipments. 



are bevel gears which arc mounted upon studs C, which are virtually 

 the spokes of wheel J.I. Large bevel gears E and F are placed on 

 either side of A E, being secured to G, which is one-half of the axle, 

 and F and It, which is the other half. If the carriage is running in a 

 straight lino, the two parts of the axle G and // will revolve at the same 

 velocity and the gears BB will not revolve around the studs C, hut in 

 rounding a curve one of the halves of the axle will revolve faster than 

 the other and then the gears B will rotate round the studs C. The 

 compensating gear is not a feature peculiar to electric vehicles; it is 

 used on all kinds of automobiles when the construction is such as to 

 require it. 



If a compensating gear is placed upon the axle the Latter, instead of. 

 supporting its end of the vehicle, will itself have to he supported, for as 

 it is cut in two at the center, it has no supporting strength. By placing 

 the compensating gear on another shaft this difficulty can be overcome. 

 Fig. 5 shows the construction used by the Columbia Company in its 

 single motor equipment. In this arrangement the motor casing is 

 made of sufficient length to reach from one side of the vehicle to the 

 other. The armature and field magnets of the motor, which are the 

 parts that develop the power, are located at A and the compensating 



