Blower Assembly - TM-10-3930-634-340051

TM 10-3930-634-34

gears, using a suitable dial indicator. Backlash shall be

(7) Replace all gaskets and seals.

0.0005 inch to 0.0025 inch with new gears, or a maxi-

(8) Inspect threaded openings and hardware for

mum of 0.0035 inch with used gears. Replace the gears

damaged threads. Chase damaged threads with the

if backlash exceeds 0.0035 inch.

correct size tap or die. Replace all damaged hardware.

(10) After the blower rotors and gears have been

f. Reassembly. Refer to figure 3-19 and reassemble

installed, the blower rotors must be timed. When prop-

the blower assembly as follows:

erly positioned, the blower rotors run with a slight

(1) Press two teflon oil seals (30) in counterbores

clearance between the rotor lobes and walls of the

of each end plate (29) as follows:

housing.

(a) Place the plate on the bed of an arbor press.

(11) The clearance between the rotors may be es-

(b) Lubricate the outside diameter of the new

tablished by moving one of the helical gears out or in

seal and using a suitable installer tool, press the seal

on the shaft relative to the other gear by adding or re-

(lip facing down) into the counterbored hole until the

moving shims (22) between the gear hub and the rotor

shoulder on the installer tool contacts the plate.

spacers.

NOTE

(12) It is preferable to measure the clearance with

The seal must be positioned below the fin-

a feeler gage comprised of two or more feelers, since a

ished face of the place within 0.002 to 0.008

combination is more flexible than a single feeler gage.

inch.

Take measurements from both the inlet and outlet

(2) Place front end plate on two wood blocks and

sides of the blower.

install the rotors (31) in the end plate, gear end up. In-

(13) Measure the clearance between the rotor

stall the housing (32) over the rotors and, making sure

lobes and the housing as shown in figure 3-21. Take

that the oil seals are properly positioned on the rotors,

measurements across the entire length of each rotor

install the rear end plate over the blower housing.

lobe to be certain that a minimum clearance of 0.004

(3) Attach two thrust washers (27) to the front

inch exists at the air outlet side (B, fig. 3-20) and a

end plate with bolts (26).

clearance of 0.0075 inch exists at the inlet side (A, fig.

(4) Attach three spacers (25) and thrust plate (24)

3-20).

to front end plate with bolts (23). Tighten bolts to 7-9

(14) Measure the clearance between the rotor

lbft of torque and check clearance between thrust

lobes, across the length of the lobes. Rotate the gears

plate and thrust washers. The clearance shall be

until the lobes are at their closest relative position (C,

0.001-0.003 inch.

fig. 3-20). The clearance between the lobes should be a

(5) Position the rotors so that the missing serra-

minimum of 0.010 inch.

tions on the gear ends of the rotor shafts are 90

(15) Measure the clearance between the end of the

apart. This is accomplished by positioning the rotors in

rotors and the front end plate as shown in figure 3-22.

a "T" shape with the missing serrations in the upper

The clearance should be a minimum of 0.006 inch.

rotor facing to the left, and the missing serrations in

NOTE

the lower rotor facing the bottom (fig. 3-20). Install

Push and hold the rotor toward the end plate

the shim (22, fig. 3-19) and spacers (21) in the counter-

at which the clearance is being measured.

bore in rear face of rotor gears (19 and 20). Place gears

(16) Measure the clearance between the end of the

on end of shafts with missing serration in alignment

rotors and the rear end plate in the same manner. The

with missing serrations on shaft.

clearance should be a minimum of 0.009 inch.

(6) Tap the gears lightly with a soft hammer to

(17) Remove the screws (1, fig. 3-19) and washers

seat the gears on the shaft. Then, rotate the gears until

used to temporarily secure the front end plate to the

punch marks on the face of gears match. If the punch

housing. Install gasket (14), cover (13), reinforcing

marks on the face of gears do not match, reposition the

plates (11 and 12) and secure with screws (l). Tighten

gears.

screws to 23 lb-ft. of torque.

(7) Wedge a clean cloth between the blower

(18) Assemble the coupling assembly as follows:

rotors. Use the blower rotor gear retaining bolts and

(a) Place the spring support (10) on two blocks

plain washers to press the gears on rotor shafts.

of wood.

Tighten bolts uniformly until gears are tight against

(b) Position the spring seats in the support,

shoulder on the shafts. Remove gear bolts, plain

apply grease to the springs to hold the leaves together,

washers, and cloth.

then slide the two spring packs (fifteen leaves per

(8) Place pilots (16 and 18) in the counterbore of

pack) in place.

gears (19 and 20) respectively, and start the twelve

(c) Place the drive cam (7) over the end of an in-

point bolt (15) in rotor shaft and start the hex head

stalling tool, insert tool between the spring packs and

bolt (17) in the rotor shaft. Tighten the bolts to 25-30

press the cam in place (fig. 3-23).

lb.-ft of torque.

(19) Position coupling assembly on gear (20).

(9) Measure the backlash between the blower

3-23