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the
case
of
major repairs, it is recommended that the
crankpin
bearing bushings be
replaced.
This will
pro-
tect .the crankpins from pr.ematur.e wear.
Connecting R.ods Assembled
with
Bushings
The connecting rods are
steel,
forged,
having an
I -shaped cross-section. Pressed into the connecting rod
small end
is a bronze bushing whose opening is made
with
a great accuracy to
ensure
the correct fitting
of
the
piston
pin.
The big end of the connecting rod is
de-
tachable,
not
symmetrical,
with
~hin-wall'ed
interchan-
geable bushings. For
correct installing
of the connect-
ing rods
on
the
crankshaft, the connecting
rod
blades
are provi.ded
with
lugs
which
must be
directed
out-
wards with
respect
to the crankshaft web
(for the ·right-
hand connecting rod,
the
lug should
be
directed
to-
wards the flywheel; for the !·eft-hand
·
c onnecting
rod,
towards
the
centrifuge)
.
The
connecting rod
caps
are not
interchangeable.
The nuts of ·the connecting
rod
bolts <lire tightened up
and
locked by
cotter pins.
The use
·of
old cotter
pins
is
inadmissible.
Piston, Piston R.ings
and
Piston Pins
Engine piston 15
(Fig. 5)
consists
of a spherical
head, skirt, and bosses.
The
piston
is
provided with
four groo ves
in
which the piston rings are fitted.
Two upper compression
rings
14 provide the required
air-tightness of
the
cylinder,
thus preventing
the gas
ieakage from the combustion-chamber into
t
he
crank-
case. Two lower oil scraper rings
13
are used to remo-
ve excessive oii from
the
cylinder walls.
The
axis of
the
piston
pin
hole is displaced
by
1.5 mm from
the piston
centr
eplane.
For
1his reason,
the
pis·
t on
moves
smoothly, without shocks, within
the
clearance between
the
piston skirt and
the
cyl'inder
walls \Vihen the direction of movement
is
ohanged
at
the
upper dead centre.
Fitted
on
the piston head
is a poin-
ter to indicate the correct
position
of the
piston
in
the
cylinder.
When mounting,
s~e
that the pointer,
on the
both
pistons, is
dir.
e cted
forward,
i.
e. towards
the
centrifug.e.
The piston
rings are
manufactured
f·rom a special
grade of cast
iron and
are
provided
with
straight
locks. When
installing
the piston with rings
into
the
cylinder,
ensure that
piston ring
gaps are within
0.25
and
0.5
mm.
23
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