TM 5-3810-300-24&P-3
BLOWER 3.4
(.002"). Then check the clearance between the
Figs. 26 and 27 for the minimum clearances.
LEADING edge of the LOWER and the
TRAILING edge of the UPPER rotors ("c"
After the blower rotors are timed, complete the assembly
clearance) for the minimum clearance shown in
of the blower as outlined below.
Fig. 27. Rotor-to-rotor measurements should be
taken one inch from the governor end, at the
1. On the former reduction blowers, install the rotor
center, and one inch from the drive end.
drive and driven gears on the rotor shafts as
follows:
2. After determining the amount one rotor must be
revolved to obtain the proper clearance, add
a. Place the blower housing and rotor
shims back of the proper gear as shown in Fig.
assembly, air inlet side of housing facing
28 to produce the desired result. When more or
up, on the bench with the timing gear end
less shims are required, both gears must be
of the blower facing the outside of the
removed from the rotors. Placing a .003" shim in
bench.
back of a rotor gear will revolve the rotor .001".
b. Start the left-hand helix driven gear on the
3. Install the required thickness of shims back of
shaft of the left-hand helix rotor with the
the proper gear and next to the bearing inner
omitted serrations in the gear and the
race and reinstall both gears. Recheck the
shaft in alignment. Then, tap the gear on
clearances between the rotor lobes.
the shaft and against the timing gear with
a plastic hammer, or install the gear with
4. Determine the minimum clearances at points "A"
the gear installers J 6270-6, 7 and 8.
and "B" shown in Figs. 26 and 27. Insert the
feeler gages, as shown in Fig. 29, between the
c. If removed, install the drive gear bearing in
end plates and the ends of the rotors. This
the right-hand helix drive gear with the
operation must be performed at the ends of each
number on the race of the bearing facing
lobe, making twelve measurements in all. See
the outside face of the gear.
Figs. 26 and 27 for the minimum clearances.
d. Lubricate the bearing in the drive gear with
5. Check the clearance between each rotor lobe
engine oil, then place the drive gear on the
and the blower housing at both the inlet and
rotor shaft with the numbered side of the
outlet side - twelve measurements in all. See
bearing facing out.
Fig. 28. Diagram Showing Proper Location of Shims for Correct Rotor Lobe Clearances
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