Under this title should be included the frame, axles, springs, wheels, steering gear and brakes.
From the beginning it was recognized that the different strains and stresses set up by the passing of the wheels over uneven ground and by the motor and driving mechanism, must be taken care of before reaching the body of the automobile, which otherwise would soon go to pieces.
Fig. 1. Views of Plain Frame.
The Frame.—Therefore, not only springs had to be interposed between the body and the wheel axles, but also a substructure for the body, called the frame, which must be rigid enough to prevent any destructive strains from reaching the body.
In Fig. 1, A shows a top view of a frame made up of channel bars and B shows a side view to illustrate how the torsion or twist takes place. It will be understood that the frame thus made is not designed to lend itself to the entire inequalities of the road, as the springs are interposed for that purpose.
Experience in the construction and use of tubular frames, as first employed in bicycles, proved too expensive for assembling, when used in automobiles. The tubular form of construction was very soon displaced by frames consisting of metal parts bolted or riveted together. The main or side members are now usually made of channel steel which gives great rigidity and strength, compared with its weight.
Fig. 2. Quarter Elliptic.
How the Frame is Suspended.—The important feature is to mount this frame on the axle. The frame, carrying a body and all the load of the vehicle, has to permit three distinct movements.