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Repair instructions
Checking preload
39. After calculating the shims required according to
points “A” and “B”, place the calculated shim on top
of the bearing race and install special tool 884830 on
the vertical shaft. Use torque gauge 9999177 and
turn the shaft one revolution per second. The mini-
mum preload value should be 1.2 Nm (10.6 lb.ft.)
and maximum preload value should be 2.3 Nm
(20.3 lb.ft.).
If the preload is too high, the shim thickness on top
of the bearing race should be reduced.
If the preload is too low, the shim thickness on top of
the bearing race should be increased.
Checking backlash
Propeller Nut
41. Lock the vertical shaft to prevent it from being
turned. Install Duoprop propeller nuts and or cone on
the propeller shafts. Rig a dial indicator gauge against
the wings of the rear nut as far out on the wing as
possible. Check the flank clearance of the front gear
by turning the propeller shaft (both ways) by hand to
check the backlash. The clearance at the wing should
be 0.08–0.17mm (0.003–0.007"), which results in a
clearance of 0.15–0.30mm (0.006–0.013") at the gear.
Propeller Cone
42. If the rear propeller is locked with a propeller cone,
measuring the gear backlash must be done the same
way as when measuring using the propeller nut.
The only difference is that the measuring must be
done 8 mm (0.315") in from any of the tips of the
cone’s wings, and towards the propeller shaft center.
The measuring is done at the same radius from the
propeller shaft center as when measuring is done on
the propeller nut.
Slack in the propeller shaft
40. Install tool 884941 on the tubular shaft (until it bot-
toms on the shaft). Tighten screw (1) on the tool and
then slide a dial gauge into the tool. Turn the shaft
one turn and read the run-out on the dial gauge. The
run-out must not exceed 0.07 mm (0.0027"). To meas-
ure slack in the propeller shaft, press the shaft to-
wards and away from the dial gauge while you read off
the bearing slack. Turn the shaft to different positions
and read off each time. Bearing slack must not ex-
ceed 0.03 mm (0.0012").
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