Figure 1-50.-Expansion tank.
Figure 1-51.Air-cooled engine.
surfaces and the cooling air. Some heat must be retained
In air-cooled engines, the cylinders are mounted
for efficient operation. This is accomplished by the use
of thermostatic controls and mechanical linkage that
open and close shutters to control the volume of cooling
air. You will find that air-cooled engines generally
operate at a higher temperature than liquid-cooled
engines, whose operating temperature is largely limited
by the boiling point of the coolant used. Consequently,
greater clearances must be provided between the
moving parts of air-cooled engines to allow for the
independently to the crankcase so that an adequate
volume of air can circulate directly around each
cylinder. The circulating air absorbs excessive amounts
of heat from the cylinders and maintains enough
cylinder head temperatures for satisfactory operation.
The cooling action is based on the simple principle that
the surrounding air is cooler than the engine heat. The
primary components of an air-cooled system are the fan
and shroud and the baffles and fins. A typical air-cooled
engine is shown in figure 1-51.