Page:Popular Science Monthly Volume 57.djvu/492

482 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 independently, 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 D is arranged 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 illustrated in Fig. 1. In this drawing A is the gear D of Fig. 2, and BB

are bevel gears which are mounted upon studs C, which are virtually the spokes of wheel AA. 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 H, which is the other half. If the carriage is running in a straight lino, the two parts of the axle G and H will revolve at the same velocity and the gears BB will not revolve around the studs C, but 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