Technical data

14
The crankshaft may be manufactured and installed in the engine of two production sizes
(nominal values). The crankshaft with the connecting rod and main bearing journals manufactured
according to the second nominal size has additional marking on the first web. The size of the main
and connecting rod webs as well as respective marking of the crankshaft is given in Section 4.1.
The piston is made of aluminium alloy. The combustion chamber is made in the piston
head. The piston has four grooves in its upper part; the first three grooves are intended for filling
the compression rings and the fourth for the oil ring. The piston of the D-245 engine is fitted with
an insert of special cast iron under the upper trapezoid-shaped compression ring. The holes for
piston pins are bored in the piston pin boss.
According to the external diameter of the skirt, the pistons are sorted according to three
size groups (Б=L, С=M and М=S). The group is marked on the piston head. The piston sizes are
given in Section 4.1. When being mounted in the engine, the sleeves and pistons must be of the
same size group.
The piston rings are made of cast iron. The upper compression ring is chromium-plated,
having rectangular cross section and no marking. It is mounted in the groove in arbitrary manner.
The second and third compression rings are conic and have marking “up” on the end surface at
the lock. The oil ring is box-shaped and fitted with spiral steel extender.
The upper compression ring of the D-245 engine is made of high-strength cast iron and
has the shape of isosceles trapezium while the other rings are unified with those of the D-243 en-
gine.
The diagram of mounting of the piston rings is given in Fig. 33.
The piston pin is hollow, made of chromium-nickel steel. The axial shift of the pin in the
bosses is restricted by stop rings.
The connecting rod is made of steel and has double-T section. A bush is pressed in its
upper head. There are holes for lubricating the piston pin in the upper head and bush of the con-
necting rod.
The insert bed in the lower head of the connecting rod is bored as an assembly with the
cover; therefore the connecting rods are not interchangeable. The connecting rod and its cover
have the same numbers stamped on their surfaces. Moreover, the connecting rods have the weight
groups according to the weights of the upper and lower heads. The designation of the group ac-
cording to the weight is stamped on the end face of the connecting rod upper head. The engine
shall be fitted with the connecting rods of the same group.
The inserts of the main and connecting rod bearings of the crankshaft are made of
steel and aluminium. The inserts of the main and connecting rod bearings of two sizes in accord-
ance with nominal sizes of the crankshaft are used in the diesel engines. The four repairing sizes of
the inserts are provided also for repairing the diesel engine.
The flywheel is made of cast iron and bolted to the crankshaft flange. The gear ring is
pressed onto the flywheel.
1.2.2.4 Valve Gear Link
The valve gear link includes gears, camshaft, intake and exhaust valves as well as their
fasteners and actuators, such as followers (pushers), push rods, rocker arms, rocker shafts, adjust-
ing screws with nuts, plates, valve keepers, valve springs, brackets and rocker axle.
The camshaft is supported by three journals and is connected with a crankshaft via tim-
ing gears. The three bushes pressed in the cylinder block bores serve as camshaft bearings. The
first bush (from the fan side) made of aluminium alloy has a thrust shoulder keeping the camshaft
from the axial travel; the other bushes are made of cast iron.
The cam followers (pushers) are made of steel and have spherical bottoms. Since the
camshaft cams are made with small inclination, the push rods are in rotary motions during the
work.