the war the Griffon was rather displaced by the
Vulture until the latter Griffon was resurrected engine than the Merlin
was discarded, then the as the need for a larger was again realised as a marks of Merlin Spitfires
ENGINE COOLANT OUTLETS TO HEADER TANK
mum performance low down we were pressed. A quick decision was reached
somewhat to put the
MAGNETO INCLINED DRIVE
Griffon II came the numbers,
into some Spitfire VIII's, which then be- mark XII; these were built in limited but effectively squashed the opposition.
F.A.A. and R.A.F. Requirements
'] hese models of the Griffon wer,e all fitted with single-stage, two-speed blowers, and this basic type has progressed for Fleet Air Arm use (vide the Fairey Firefly), whilst the special needs ofthe
AIRSCREW REDUCTION WHEEL
been met by the two-speed, two-
expected, the Grifton owes a fair amount to Merlin
development, that various Griffon have Merlins.
but what is peculiarly interesting is practices initially proved on the
Basically the engine is, of course, on the same lines as the Merlin, although the detail design is new pretty well throughout. Oneofthe most important innovations is in taking the cam- and mag-drives
Detail of front end showinghow •cam drive and magneto drive are taken from re- duction gear.
upon in order to relieve operation from as much
the valve variation
as possible: semi-floating
by interpolating a coupling between the
and the driving
the reduction gearing and, in tion, by taking the camdrives
I COOLANT CONNECTION1 I FROM SKIRT TO HtAO
greatly sion to
reduced in their transmis- the camshafts. Further, air-
screw inertia constant rate
results in a reasonably of r.p.m., and,to top-
off the allows 'overall
advantages, the front drive
mits the larger and more engine to go into existing
.._ CYLINDER BLOCK SECURING STUD
Whilst onthe subject ofthe cank- shaft, we might as well deal with
that interesting component. ol course, machined all over
It is, from a
0 1 BRAIN TO CRANKCASE
and is fully
of No. 1,
cection through cylinder and head illustrating simple valve gear and large coolant areas.
Three-quarter front view of crankshaft with semi-floating toothed annulus in front coupling. Note the detachable counterweights on crank throws.
PORT CAMSHAFT DRIVE
both throws of No. 4 and the reai throw of No. 6 bearings each hav- ing a separate balance weight bolted to them. Vibratory troubles inthe crankshaft have been very few, but a pointer to the Derby standard is that the firing order geography was selected to give optimum crankshaft harmonics.
Perhaps the most novel feature of the crank assembly is that the main bearings and big ends are all
lubricated from the hollow interior
of the novel, having
This scheme, though
is by no first tried
means new, Rolls it years ago ; how-
ever, the Griffon engine in which it
is the first has become
tice. Feed is into each shaft and,in addition to pressure, shaft rotation
end ofthe the system provides a
A great is that the
of the system
of oil supplied
ing is not influenced by shaft / bearing movement.
relative Jn ad jr"""
tion, each main journal has internal standpipes which act as sludge traps as well as permitting, by a variation in their diameter, a means
amount of oil supplied ticular bearing.
Another interesting feature ofthe crankshaft is that it is rigidly connected neither to the front nor
the rear driven members. front end an internally annulus is bolted on, this
At the toothed meshing
semi-floating is internally
splined to a coupling latter is splined at its
shaft. The front endto