rings to the crank pins. The propeller thrust
is taken by a simple ball thrust bearing at the propeller end of the
crankshaft, this thrust bearing being seated in a steel retainer which
is clamped between the two halves of the crank case. At the forward end
of the crankshaft there is mounted a master bevel gear on six splines;
this bevel floats on the splines against a ball thrust bearing, and,
in turn, the thrust is taken by the crank case cover. A stuffing
box prevents the loss of lubricant out of the front end of the crank
chamber, and an oil thrower ring serves a similar purpose at the
propeller end of the crank chamber.

With a motor speed of 1,450 r.p.m., the vertical shaft at the forward
end of the motor turns at 2,175 r.p.m., this being the speed of the two
magnetos and the water pump. The lower vertical shaft bevel gear and the
magneto driving gear are made integral with the vertical driving shaft,
which is carried in plain bearings in an aluminium housing. This housing
is clamped to the upper half of the crank case by means of three studs.
The cam-shaft carries eighteen cams, these being the inlet and exhaust
cams, and a set of half compression cams which are formed with the
exhaust cams and are put into action when required by means of a lever
at the forward end of the cam-shaft. The cam-shaft is hollow, and
serves as a channel for the conveyance of lubricating oil to each of
the camshaft bearings. At the forward end of this shaft there is also
mounted an air pump for maintaining pressure on the fuel supply tank,
and a bevel gear tachometer drive.

Lubrication of the engine is carried out by a full pressure system.
The oil is pumped through a single manifold, with seven branches to the
crankshaft main bearings, and then in turn through the hollow crankshaft
to the connecting-rod big ends and thence through small tubes, already
noted, to the small end bearings. The oil pump has four pistons and two
double valves driven from a single eccentric shaft on which are mounted
four eccentrics. The pump is continuously submerged in oil; in order to
avoid great variations in pressure in the oil lines there is a piston
operated pressure regulator, cut in between the pump and the oil lines.
The two small pistons of the pump take fresh oil from a tank located in
the fuselage of the machine; one of these delivers oil to the cam shaft,
and one delivers to the crankshaft; this fresh oil mixes with the used
oil, returns to th