To show the "works" of an automobile it is necessary to remove the body or top of the car. What remains is called the chassis (Fig. 182).

Starting in front of the seat we see the handle, which is a lever for setting the engine in motion. Underneath the hood is the engine. The lever connects to the engine. Front of the engine is a heavy fly-wheel. The shaft of the engine is continued to the gear-box which contains the gears for altering the speed of the driving wheels to that of the engine. In the rear of the gear-box is the propelling shaft, which connects by means of bevel gears, a special device of gears called a differential, to the axle of the driving wheel to which the power of the engine is transmitted. The engines, gear-box, etc., are all mounted on the frame of the car. Between the frame and axle are the springs which absorb the shocks caused by bumping over rough roads.

Fig. 178.   The Action of a Two Cycle Engine. The explosive mixture is taken into the crank case through a non return valve at a on the up stroke of the piston. It is compressed on the downstroke and allowed to flow into the cylinder when the piston passes over and uncovers the port b. The charge is compressed on the upstroke of the engine, is fired and expanded on the downstroke, and exhausted when the piston passes over and uncovers the part c. D is a deflecting plate to deflect the explosive mixture toward the top and preventing it from going out at c.

Fig. 178. - The Action of a Two-Cycle Engine. The explosive mixture is taken into the crank case through a non-return valve at a on the up stroke of the piston. It is compressed on the downstroke and allowed to flow into the cylinder when the piston passes over and uncovers the port b. The charge is compressed on the upstroke of the engine, is fired and expanded on the downstroke, and exhausted when the piston passes over and uncovers the part c. D is a deflecting plate to deflect the explosive mixture toward the top and preventing it from going out at c.

Sometimes the power is transmitted from gear-box to axle by means of chains. In this case there is a sprocket wheel on a shaft behind the gear-box, and a larger sprocket wheel attached to the hubs of the driving wheels. The axles of the driving wheels are fixed to the springs and wheels revolve around them.