mostly in low-power engines, and the horizontal arrangement where a very flat, underfloor mounting is
Moving up and down inside the cylinders are pistons, connected by connecting rods to the
crankshaft. The crankshaft, shown in figure 1.4, transmits mechanical action from the pistons to drive
the generator. The generator changes the mechanical action into electricity and transmits it through
cables to the traction motors, which change it through a gear arrangement back into mechanical force to
turn the wheels.
Figure 1.4. Crankshaft.
To produce power through an interval of time, a diesel engine must perform a definite series of
operations over and over again. This series is known as a cycle in which suction, compression, ignition,
and exhaust take place in the order listed. If the engine requires four strokes of the piston and two
revolutions of the crankshaft to complete a cycle, it is known as a four-stroke-cycle engine; one
completing the cycle in two strokes of the piston and one revolution of the crankshaft is a two-stroke-
cycle engine. Figure 1.5 illustrates the operating cycles of the two types of engines.
In the four-stroke-cycle engine, air is drawn into the cylinder through the intake valve as the
piston descends on the intake