same, then h will remain parallel with the axle. If, however, the steering wheels are set to turn a corner, the wheel b being on the inner or smaller curve, then the wheel a will have to move faster than b, and the arm f will be pulled through a greater angle than the arm g, and the cross-piece h will cease to be parallel with the axle. The parts will take the positions shown by the dotted lines. Such an apparatus could only act through part of one revolution of the wheels, but so far as it acts, it permits the pull on either wheel to remain of equal value, though one wheel moves more quickly than the other.
The principle illustrated by this diagram may now be followed in fig. 4, which illustrates a common form of live axle
_0248.jpg)
Fig. 3. Diagram to illustrate Differential Action
driven by a horizontal jointed rod from the motor and a bevel pinion. The functions performed by the parts are the same as those having the same letters in fig. 3.
The differential gear consists of two bevel wheels f and g, each tooth of which acts in the same way as the arms f and g of fig. 3, and two or more bevel pinions h each of which acts in the same way as the cross-piece h in fig. 3, but by means of its teeth bearing upon the teeth f and g of the bevel wheels instead of the one tooth or arm f or g in fig. 3. These bevel pinions are loose upon the pins on the end of the piece k, just as the piece h is loose on the pin k in fig. 3, but instead of the pin k being pulled by a rod it is carried round by the bevel wheel j, acting in the same way but
