A.J.S. 16 Instruction Book - Engine O I L Pump
ENGINE O I L PUMP
(see Illustration 4)
The pump has only one moving part. This is the plunger which revolves and reciprocates.
Rotation is caused by the worm gear on the timing side flywheel axle. Reciprocation
is caused by the guide pin which engages in the profiled groove cut on the plunger.
Oil is fed to the pump through the lower of the two oil pipes between tank and crank-
case and is returned through the upper pipe,
If, for any reason, the crankcase is dismantled the oil pump plunger must be
removed
from its housing before attempting to separate the crankcase halves.
It is
not necessary to remove the small timing pinion which will pass through in situ.
Important
Under no circumstances must either the pump plunger or guide screw be disturbed
in ordinary routine maintenance.
ENGINE OIL CIRCULATION—SINGLES
The oil pump forces oil through:—
(a)
Passages drilled through the timing side flywheel axle, timing side flywheel and crank
pin to lubricate the timing side bearing and the big-end bearing. The splash passes
to interior of cylinder, to lubricate the cylinder and piston, and then falls into the
crankcase sump.
(b)
A passage in timing gear case where it "builds up" to a predetermined level to
lubricate the timing gears and then overflows into the crankcase sump.
(c)
Through a pipe from the front of oil pump housing to the rocker box by which
all rocker gear and valve stems are lubricated and then falls through the push rod
cover tubes and tappet guides to the timing gear case and, from there, drains into
the crankcase sump, as detailed in
(b)
.
The oil pump extracts oil in the crankcase sump and returns it to oil tank. On its way
it passes the magnetic filter located in the crankcase sump.
ENGINE L UBR I CAT I O N SYSTEM—TWINS
This is of the d r y sump type. Two separate gear type oil pumps are used, one for
delivery and the other for returning oil to the tank. Oil feeds by gravity to the delivery
pump, by which it is forced, under pressure, to various parts of the engine, from whence
it drains back to the crankcase sump to be collected by the return pump and returned
to the tank. The return pump has a much larger capacity than the delivery pump to
ensure that the crankcase is kept clear of excess oil.
ENGINE OIL PUMPS
Each pump is independently driven, at half engine speed, from the ends of the two
camshafts. They each consist of a pair of close fitting gear wheels in a cast Iron body.
The gears of the delivery pump are considerably narrower than those of the return pump,
giving the latter the necessary extra capacity to ensure efficient scavenging.
ENGINE OIL C I R C U L A T I O N — T W I N S
Oil, from the oil tank, is fed by gravity, through a coarse mesh metal filter, via an external
pipe, to the suction side of the delivery pump, from whence it is discharged, under
pressure, to a large and easily detachable filter that is housed in the crankcase.
After passing through the filter the main supply is directed to the crankshaft centre
bearing and thence, through passages in the crankshaft, to each big-end, the splash from
which provides adequate cylinder lubrication.
The oil supply to rockers and push rods is a by-pass from the main feed, controlled by a
cylindrical block which is rotated by the exhaust camshaft. This is housed in the
driving side crankcase to the right and above the non-return valve. (See illustration 9).
Oil fed to the rocker gear drains into the camshaft tunnels, which have a spill level.
Surplus oil overflows into the timing gear compartment. The four drilled oilways
m the cylinder heads are intentionally restricted by metering plugs. In the event of
an oil shortage to the rocker gear, these oil ways should be checked for obstruction,
Oil is built up in the timing gear compartment to a pre-determined level to lubricate
the train of gears, the surplus flows into the crankcase and is returned to the tank.
A special copper washer is used under the cap covering the rotating block, which
must
not
be substituted by a different type.
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