The
crankshaft is carried in main bearings with replaceable
steel shells lined with a thin layer of special
bearing metal. At the front end the shaft carries a gear
which drives the camshaft, injection pump and oil pump.
The rear end carries the flywheel.
The aluminium-alloy pistons have three compression and
two oil rings. The upper compression ring of
every piston is hard chromium plated to cut wear on
cylinder liners and piston rings to a minimum. Like
the main bearings, the big-end bearings are fitted with
replacement shells.
The cylinder head carries the inlet and exhaust valves
and the injectors. Inlet valve sealing surfaces and all
valve stem ends are faced with stellite, a
heat-resisting alloy which greatly lengthens life. Valve
seats are shrunken-in replaceable rings of alloy-steel
Working Principles
The engine is
designed on the four-stroke principle and it's operating
cycle is illustrated in the following
figures.
fig 4
fig5
Fig 4.
Inlet Stroke
Just before the
top dead centre is reached, the inlet valve opens so
that the piston sucks fresh air through the air filter
and into the cylinder on it's way down again. The inlet
passage in the cylinder head is shaped to give the
entering air a rotating motion in the cylinder.
Fig 5.
Compression Stroke
The piston now moves upwards with both valves closed.
This compresses the air, raising it's temperature above
the ignition temperature of the fuel. A specially shaped
combustion cavity in the piston top increases air
rotation during this stroke. Shortly before the piston
reaches the top dead centre again, fuel is injected to
mix with the swirling air with resulting combination as
the pressure increases.
fig 6
fig 7
Fig 6.
Power Stroke
Combustion vastly
increases pressure and forces the piston downwards in
the cylinder to perform the
useful work.
Fig 7.
Exhaust Stroke
The exhaust valve
opens immediately before the bottom dead centre is
reached and the piston starts
moving upwards again to expel the combusted gases. |
