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 TM 55-1905-217-34
inch .003 inch or .005 inch feeler stock are more practical and suitable than a single feeler gage. Clearances should be
measured from both the inlet and outlet sides of the blower. Use feeler gage set J 1698-02.
(21) A specially designed feeler gage set J 1698-02 for the blower clearance operation is available. Time the rotors
as follows:
(a) Time the rotor to have .002 inch to .006 inch clearance between the TRAILING edge of the UPPER rotor and
LEADING edge of the LOWER rotor ("cc" clearance) measured from both the inlet and outlet sides as shown in figure 3-
29. If possible, keep this clearance to the minimum (.002 inch). The check the clearance between the LEADING edge of
the UPPER and the TRAILING edge of the Lower rotors ("cc" clearance) for the minimum clearance shown. Rotor-to-rotor
measurements should be taken 1 inch from the governor end, at the center, and 1 inch from the drive end.
(b) After determining the amount one rotor must be revolved to obtain the proper clearance, add shims back of the
proper gear as shown in figure 3-32 to produce the desired result. When more or less shims are required, both gears must
be removed from the rotors. Placing a .003 inch shim in back of a rotor gear will revolve the rotor .001 inch.
(c) Install the required thickness of shims back of the proper gear and next to the bearing inner race and reinstall both
gears. Recheck the clearances between the rotor lobes.
(d) Determine the minimum clearances at points "A" and "B" shown in figure 3-33. Insert the feeler gages between
the end plates and the ends of the rotors. This operation must be performed at the ends of each lobe, making twelve
measurements in all.
(e) Check the clearance between each rotor lobe and the blower housing at both the inlet and outlet side-twelve
measurements in all. See figure 3-33 for the minimum clearances.
(22) After the blower rotors are timed, complete the assembly of the blower as outlined below.
(23) Refer to figure 3-31 and attach the blower rotor drive hub (20) and drive hub plates (21) to the blower gear as
follows:
(a) Attach the rotor drive hub plates (21) to the drive hub (20) with three bolts (24), lockwashers and plain washers.
Tighten the bolts to 25-30 lb-ft torque.
(b) Attach the rotor drive hub and drive plates to the right-hand helix rotor timing gear with three bolts (19), lock
washers, plain washers and three spacers (36). Tighten the bolts to 25-30 lb-ft torque.
(c) Check the runout of the splines in the rotor drive hub with an indicator. The spline runout must not exceed .020
inch total indicator reading.
(24) Affix a new gasket (10) to the blower rear end plate cover (18).
(25) Position the end plate cover over the end plate dowel pins, then push the cover against the end plate. Install
the ten bolts and lock washers. Tighten the bolts to 13-17 lb-ft torque.
(26) Refer to figure 3-35 and attach the fuel pump, water pump, blower drive shaft cover and governor weight
housing to the blower.
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