Figure 1-50.-Expansion tank.

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 increased expansion. 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. 1-37