Marine Installation Manual
2021-08
6-6
6 Engine Dynamics
6.2 External lateral forces and moments
X72DF
6.2
External lateral forces and moments
The external lateral forces and moments (lateral engine vibrations resulting in
‘rocking’) are generated by the combustion process and to a small extent by the
reciprocating masses of the running gear. The lateral forces depend on the
CMCR and engine speed.
Figure 6
-
4 Forces through the engine
The forces between the piston and the connecting rod reaction cause a lateral
force to act on the crosshead guide rails. The lateral forces at the guide rails are
transmitted to the engine block and to the foundation.
The resulting lateral forces and moments may excite resonances of the combined
engine and foundation system. In addition, hull resonances or local vibrations in
the engine room may be generated.
SM-0514
F
T
F
L
F
R
F
G
F
P
F
C
F
G
= Gas force
F
P
= Piston force
F
C
= Connecting rod force
F
L
= Lateral force
F
R
= Radial force
F
T
= Tangential force
