so far has been on a single cylinder engine. A single cylinder provides one power impulse
every two crankshaft revolutions in a four-stroke-cycle engine and is delivering power
only one fourth of the time. To provide for a more continuous flow of power, modem engines
use four, six, eight, or more cylinders.
series of cycles discussed previously take place in each cylinder.
four-stroke cycle, six-cylinder engine, for example, the throws on the crankshaft are set
120 degrees apart, the throws for cylinders 1 and 6, 2 and 5, 3 and 4 being in line with
each other (fig. 2-9).
The cylinders fire or deliver power strokes in the following order: l-5-3-6-2-4. The power
strokes follow each other so closely that there is a fairly continuous and even delivery
of power to the crankshaft.
additional leveling off of the power impulses is desirable, so the engine runs more
smoothly. A flywheel (fig. 2-9) is used to achieve this result.
how the flywheel functions, lets consider a single cylinder engine. It is delivering
power only one fourth of the time during the power stroke.
other three strokes, it is absorbing power to push out the exhaust gas, to pull in a fresh
charge, and to compress the charge. The flywheel makes the engine run without varying much
of the speed during each revolution. It is a heavy steel wheel, attached to the end of the
crankshaft. When it is rotating, considerable effort is required to slow it down or stop
it. Although the wheel does slow down somewhat as it delivers power to the engine during
the exhaust, intake, and compression strokes, the wheel speed increases during the power
stroke. In effect, the flywheel absorbs some of the engine power during the power stroke
and then provides it back to the engine during the other three strokes.
multi-cylinder engine, the flywheel functions in a similar manner. It absorbs power when
the engine tends to speed up during the power stroke, and it provides power to the engine
when the engine tends to slow down during intervals when little power is being delivered
by the engine.
In addition to
the engine itself, which is the power producer, there must be accessory systems to provide
the engine with other requirements necessary to operate it. These systems are the fuel
system, the lubrication system, the electrical system, the cooling system, and the exhaust