3-144. BLOWER - MAINTENANCE INSTRUCTIONS.
(1) The blower supplies the fresh air needed for combustion and scavenging. Its operation is similar to
that of a gear-type oil pump. Two hollow, three-lobe rotors revolve with very close clearances in a housing
bolted to the cylinder block. To provide continuous and uniform displacement of air, the rotor lobes are made
with a helical (spiral) form.
(2) Two timing gears, located in the rear end-plate of the rotor shafts, space the rotor lobes with a close
tolerance; therefore, as the lobes of the upper and lower rotors do not touch at any time, no lubrication is
(3) Oil seals located in the front and rear blower end plates prevent air leakage and also keep the oil
used for lubricating the timing gears and rotor shaft bearings from entering the rotor compartment.
(4) The blower upper rotor is driven by the blower drive shaft which is coupled to the upper rotor timing
gear by means of a flexible drive hub located in the flywheel housing.
(5) A flexible coupling, formed by an elliptical cam, driven by two bundles of leaf springs which ride on
four semi-cylindrical supports and spring seats is attached to the blower drive gear and prevents the transfer of
torque fluctuations to the blower.
(6) The blower drive gear is mounted in the blower drive gear support and in addition to driving the
blower, drives the governor, water pump and fuel pump.
(1) Oil drains from the valve operating mechanism on the cylinder head into the camshaft pocket in the
cylinder block; then, when it reaches a certain level, the oil flows from the pocket into cavities at the upper
corners of the blower and through passages in the blower and end plates to lubricate the bearings, governor
and water pump drives at the front end, and bearings and gears at the rear end of the blower. A slinger
attached to the front end of the lower rotor shaft throws oil onto the front roller bearings and governor weights.
A dam in the blower end plates maintains oil at a level adequate to submerge the lower portion of the slinger
and the driven gear.
(2) Surplus oil overflows the dams in the end plates and return through two drilled holes in the cylinder
block to the engine crank. case.