Page 57 - Introduction to Marine Engineering

44 Diesel engines

Ahead Astern

Top dead Top dead
centre (T.D.C.), centre (T.D.C.)

1 Pumping
2 Injection before T.D.C.
3 Injection after T.D.C.
Fuel pump cam 4 Dwell
Oil drain Rotating vane

Camshaft
Oil pressure Geared camshaft drive
from crankshaft
through intermediate
wheels
Oil pressure

Lost motion Oil drain

Lost motion clutch
Figure 2.27 Reversing arrangements

longer stroke than the earlier RL series, it has a cylinder-head exhaust
valve providing uniflow scavenging.
The bedplate is single-walled and arranged with an integral thrust
bearing housing at the aft end (Figure 2.28). Cross members are steel
fabrications although the centre section, incorporating the main bearing
saddle tie-bolt housings, may be a steel forging. To resist crankshaft
loading and transverse bending, the main bearing keeps are held down
by jackbolts.
The crankcase chamber is arranged by using individual A-frames for
columns which are also the mountings for the double-slippered
crosshead guides. The A-frames are joined together by heavy steel plates
and short angle girders to form a sturdy box frame. The A-frames in
way of the thrust block are manufactured as a one-piece double column