Perkins 1106A-70T Operation Manual page 19

UENR0617
Pistons, Rings, and Connecting
rods
Illustration 14
Typical example
The pistons (9) have a combustion chamber in the
top of the piston in order to provide an efficient mix of
fuel and air. The piston pin (8) is off-center in order to
reduce the noise level. The position pin (8) is retained
in the correct position by two circlips (3).
The pistons have two compression rings (1) and an
oil control ring (2). The groove for the top ring has a
hard metal insert in order to reduce wear of the
groove. The piston skirt has a coating of graphite in
order to reduce the risk of seizure when the engine is
new.
The correct piston height is important in order to
ensure that the piston does not contact the cylinder
head. The correct piston height also ensures the
efficient combustion of fuel which is necessary in
order to conform to requirements for emissions.
The connecting rods (4) are machined from forged
molybdenum steel. The connecting rods have bearing
caps (6) that are fracture split . Two connecting rod
bearings (5) are installed between the connecting rod
(4) and the bearing cap (6). The bearing caps on
fracture split connecting rods are retained with Torx
bolts (7). Connecting rods with bearing caps that are
fracture split have the following characteristics:
This document has been printed from SPI2. NOT FOR RESALE.
• The splitting produces an accurately matched
surface on each side of the fracture for improved
strength.
• The correct connecting rod must be installed with
the correct bearing cap. Each connecting rod and
bearing cap have an unique serial number. When
a connecting rod is assembled the serial numbers
for the connecting rod and bearing cap must
match.
Crankshaft
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Illustration 15
Typical example
(1) Crankshaft gear
(2) Crankshaft
(3) Thrust washer
The crankshaft is a chromium molybdenum steel
forging. The crankshaft has seven main journals.
Thrust washers are installed on both sides of number
6 main bearing in order to control the end play of the
crankshaft.
The crankshaft changes the linear energy of the
pistons and connecting rods into rotary torque in
order to power external equipment.
A gear at the front of the crankshaft drives the timing
gears. The crankshaft gear turns the idler gear which
then turns the following gears:
• Camshaft gear
• Fuel injection pump
• The idler gear is driven by the crankshaft gear
which turns the gear of the lubricating oil.
Lip type seals are used on both the front of the
crankshaft and the rear of the crankshaft.
19
Systems Operation Section
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