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 TM 55-1905-217-34
on the left-hand helix rotor, and the omitted serrations in the gears in line with the omitted serrations on the rotor shafts.
(g) Thread an installer screw J 6270-8 in the end of each rotor shaft until it bottoms. Place gear installer J 6270-6
over the installer screw and against the right-hand helix gear, and gear installer J 6270-7 over the installer screw and
against the left-hand helix gear; then, thread a nut on each installer screw (fig. 3-34).
Figure 3-34. Installing rotor gears on shaft for preliminary check of clearance.
(h) Place a clean shop towel between the rotors, and another one between the rotor and the housing to prevent the
rotors from turning. Then turn the nuts on the installer screws clockwise and force the gears into position tight against the
shims and bearing inner races.
NOTE
Both gears must be pressed on the rotor shafts at the same time.
(i) Remove the rotor timing gear installers from the rotor shafts.
(j) Place a lockwasher (26, fig. 3-31) and the gear retaining washer (27) on one of the gear retaining bolts. Thread
the bolt into the right-hand helix rotor shaft, and guide the lugs on the retaining washer in the slots in the gear hub, then
bend one of the tangs on the lock washer over into the slot of the retaining washer. Tighten the gear retaining bolt to 55-65
lb-ft torque.
(k) Place a lockwasher (26) and the fuel pump drive coupling disc (35) on the remaining gear retaining bolt. Thread
the bolt into the left- hand helix rotor shaft and guide the lugs on the disc in the slots in the gear hub, then bend one of the
tangs on the lock washer over into the slot in the disc. Tighten the gear retaining bolt to 55-65 lb-ft torque.
(1) Bend one of the tangs of each lock washer over against the head of the gear retaining bolt.
(16) After the blower rotors and timing gears are installed, the blower rotors must be timed.
(17) The blower rotors, when properly positioned in the housing, run with a slight clearance between the lobes.
This clearance may be varied by moving one of the helical gears in or out on the shaft relative to the other gear.
(18) If the right-hand helix gear (28) is moved out, the right-hand helix rotor (29) will turn counterclockwise when
viewed from the gear end. If the left-hand helix gear is moved out, the left-hand helix rotor (30) will turn clockwise when
viewed from the gear end. This positioning of the gear, to obtain the proper clearance between the rotor lobes, is known as
blower timing.
(19) Moving the gears OUT or IN on the rotor shafts is accomplished by adding or removing shims between the
gears and the bearings.
(20) The clearance between the rotor lobes should be checked with 1/2 feeler gages. When measuring clearances
of more than .005 inch, laminated feeler gages that are made up of .002.
3-48
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