rotor lobes and the trailing edge of the lower rotor lobes
The blower, designed especially for efficient diesel
of the blower.
operation, supplies the fresh air needed for combustion
While the rotor lobe clearance may be adjusted by the
and scavenging. Its operation is similar to that of a
use of shims behind the gears, gear backlash cannot be
gear-type oil pump.
Two hollow three-lobe rotors
corrected. When gears have worn to the point where
revolve with very close clearances in the housing bolted
the backlash exceeds .004", replace the gears.
to the cylinder block. To provide continuous and
uniform displacement of air, the rotor lobes are made
Two timing gears, located on the drive end of the rotor
Oil drains from the valve operating mechanism on the
shafts, space the rotor lobes with a close tolerance;
cylinder head into the camshaft pocket in the
therefore, as the lobes of the upper and lower rotors do
cylinder block. Then, when it reaches a certain level,
not touch at any time, no lubrication is required.
the oil flows from the pocket into cavities at the upper
corners of the blower and through passages in the
Oil seals located in the blower end plates prevent air
blower and end plates to lubricate the bearings,
leakage and also keep the oil used for lubricating the
governor and water pump drives at the front end, and
timing gears and rotor shaft bearings from entering the
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
Lip type oil seals are installed in the blower end plates.
weights. A dam in the blower end plates maintains oil at
a level adequate to submerge the lower portion of the
Each rotor is supported in the doweled end plates of the
slinger and the driven gear.
blower housing by a roller bearing at the front end and a
double row pre-loaded radial and thrust ball bearing at
Surplus oil overflows the dams in the end plates and
the gear end.
returns through two drilled holes in the cylinder block to
The blower upper rotor is driven by the blower drive
shaft which is coupled to the upper rotor timing gear by
Inspection of Blower
means of a flexible drive hub (20 Fig. 1).
The blower may be inspected for any of the following
A flexible coupling, formed by an elliptical cam driven
conditions without being removed from the engine.
by two bundles of leaf springs which ride on four semi-
However, the air shutdown housing must be removed.
cylindrical supports and spring seats is attached to the
blower drive gear (42 Fig. 1), and prevents the transfer
of torque fluctuations to the blower.
When inspecting a blower on an
engine with the engine running, keep
The small diameter rotor blower with a 2.00:1 blower-to-
fingers and clothing away from the
engine speed ratio is employed. This type blower does
moving parts of the blower and run
not use reduction gears. The blower drive gear has 39
the engine at low speeds only.
Dirt or chips drawn through the blower will make deep
Since the lower rotor (timing) gear (14) is also splined to
scratches in the rotors and housing and throw up burrs
the lower rotor shaft, it drives the upper rotor (timing)
between the rotors or between the rotors and the
housing, remove the blower from the engine and dress
The blower rotors are timed by the two rotor (timing)
gears (13) and (14) at the rear end of the rotor shafts.
the rotors if they are too badly scored.
This timing must be correct, otherwise the required
Leaky oil seals are usually manifested by the presence
clearance between the rotor lobes will not be
of oil on the blower end plates and rotors or the inside
surfaces of the housing. This condition may be checked
by running the engine at low speed and directing a light
Normal gear wear causes a decrease in the rotor-to-
into the rotor compartment at the end plates and the oil
rotor clearance between the leading edge of the upper
seals. A thin film of oil radiating away from the seals is
indicative of an oil leak.