Quantcast Engine Flywheel

Figure 12-21.-Sectional view of a typical vibration damper. Engine Flywheel The  flywheel  mounts  at  the  rear  of  the  crankshaft near the rear main bearing. This is usually the longest and  heaviest  main  bearing  in  the  engine,  as  it  must support the weight of the flywheel. The  flywheel  (fig.  12-22)  stores  up  rotation  energy during  the  power  impulses  of  the  engine.  It  releases this  energy  between  power  impulses,  thus  assuring less  fluctuation  in  engine  speed  and  smoother  engine operation.  The  size  of  the  flywheel  will  vary  with  the number  of  cylinders  and  the  general  construction  of the engine. With the large number of cylinders and the consequent overlapping of power impulses, there is less need for a flywheel; consequently, the flywheel can be relatively small. The flywheel rim carries a ring gear, either  integral  with  or  shrunk  on  the  flywheel,  that meshes with the starter driving gear for cranking the engine.   The   rear   face   of   the   flywheel   is   usually machined and ground and acts as one of the pressure surfaces  for  the  clutch,  becoming  a  part  of  the  clutch assembly. Figure 12-23.-Camshaft and bushings. Valves and Valve Mechanisms Most engines have two valves for each cylinder, one intake  and  one  exhaust  valve.  Since  each  of  these valves  operates  at  different  times,  separate  operating mechanisms  must  be  provided  for  each  valve.  Valves are  normally  held  closed  by  heavy  springs  and  by compression  in  the  combustion  chamber.  The  purpose of  the  valve-actuating  mechanism  is  to  overcome  the spring pressure and open the valves at the proper time. The  valve-actuating  mechanism  includes  the  engine camshaft,  camshaft  followers  (tappets),  pushrods,  and rocker arms. CAMSHAFT.—The camshaft (fig. 12-23) is enclosed in the engine block. It has eccentric lobes  (cams)  ground on it for each valve in the engine. As the 12-19


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