This is the disagreeable characteristic of a differential, that makes one wheel spin when it touches a slippery spot on the road, and stalls the car, because the other wheels cannot get any driving power.
CHAPTER VI
THE DRIVE
The term used to designate the transmission of power from the engine to the wheels, is called the drive.
In nearly all cars the engine shaft runs fore and aft, and consequently is at right angles to the axles. This, of course, necessitates some sort of gearing between the engine shaft and axle. This change is made in the bevel gear drive hereafter explained.
As the engine is mounted on the frame of the car, which rests on springs, and the axle is below the springs, it is obvious that the drive must be transmitted between two parts which have a relative up and down movement.
This necessitates several things, structurally, which should be considered.
First. A flexible joint must be interposed in the system, where a shaft is used to transmit the power.
Second. Torsion rods are necessary to prevent the housing or casing of the rear axle from turning, due to reaction of the driving bevel gear.
Third. A rod, or rods, are required to prevent a fore and aft movement of the rear axle. The rods run from the ends of the rear axle housing to some convenient point on the frame.
Illustrating Power Transmission.—For convenience, these mechanical elements are illustrated on a frame.