Fan and ShroudBaffles and FinsAll stationary air-cooled engines must have fans orblowers of some type to circulate a large volume ofcooling air over and around the cylinder. The fan for theair-cooled engine shown in figure 1-51 is built into theflywheel. When the engine is assembled, the shrouding,or cowling, forms a compartment around the engine sothat the cooling air is properly directed for effectivecooling. Air-cooled engines, such as those used onmotorcycles and outboard engines, do not require theuse of fans or shrouds, because their movement throughthe air creates a sufficient air flow over the engine foradequate cooling.In addition to the fan and shroud, some engines usebaffles or deflectors to direct the cooling air from thefan to those parts of the engine not in the direct path ofair flow. Most baffles are made of light metal and aresemicircular with one edge in the stream of air. Mostair-cooled engines use fins. These are thin, raisedprojections on the cylinder barrel and head. The finsprovide more cooling area or surface and aid in directingair flow. Heat, resulting from combustion, passes byconduction from the cylinder walls and cylinder head tothe fins and is carried away by the passing air.llldllllalrl vlKllzl I Canorotin” +-- :.1-38..
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