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34
fig. 3.
59
Piston
CD
Piston head
®
Lands
@
Piston skirt
©
Slipper
fig. 3.
60
Piston ring sectional
view
CD
Top
ring
®
Oil
ring
@
Second ring
3
ENGINE
point
toward
the point
of weaker
pressure, which,
is before top-dead-center.
By
so
doing, the piston
can escape the high pressure and makes it possible
to eliminate the piston slap.
Piston is
made
with a do me head to give it
extremely
high
strength.
Further, this
will
enable
higher compression ratio and
limit
overheat ing of the
piston.
The
skirt
of
the piston is
designed slippered
on
the side
where no
side
load is app lied.
This
is
to reduce weight
and also to minimize the fri-
ctional area.
Piston pin is of
a
floating type and is set in
place
by
ring
clips.
The
bottom
side of
the piston
head
is
provided with reinforcement fins for
added
strength
as well as for a better
cooling
affect.
Oil drain holes are mode
just
below the oil
ring
groove
to
allow
the oil
to
flow
bock into the
crankcase.
(Fig. 3. 59)
V.
Piston Ring Construction
The piston
rings
performs a vital function of
form-
ing a seal between
the
piston and cylinder;
controlling
the lubrication of the cylinder wall and dissipating
the
heat of
the
piston produced by the combustion.
The cond
itio
n of the piston will hove considerable
effect on
the
power developed by the engine.
Rings are
mode
of special cast
iron
for greater
strength,
wear and heat resistance, and possesses
good
heat
conducting
qualities.
Further, the cylinder
wall contacting surface of the top and oil rings ore
given a hard chrome plated surface
and
11nished by
wet honing
for
greater wear resistance and good
sealing.
To
prevent
ring
flutter, the rings ore
made
thinner
and
greater in
depth
to increase
the
pressure against
the
cylinder wall.
Further,
the
top and the second
rings
are mode at a slight toper
were it
contacts
the
cylinder
wa
ll so that
the
wear-in time
is hastened.
Oil ring grooves
and
the bottom of the second
rings are scalloped to
improve
oil
control
and pre-
venting oi
l
entry
into
the combustion chamber which
woul
d cause carboning up of the
spark
plugs, piston,
rings and etc.
Whe
n
assembling the
rings,
make
certain that
the
ring
manufacturer's mark adjacent to the
ring
gap
is on the top and the
gaps
for the three
rings
should
be spaced
equally apart.
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