TM 5-4940-228-14
CHAPTER 8
REPAIR OF AIR MOTOR
8-1. General.
The air motor is precision built rotary type air
motor. The top clearance between rotor and bore in
housing is 0.0015 to 0.002 in (0.0038 -0.0051 cm).
Total end clearance between sides of rotor and end
plates is 0.002 to 0.004 in (0.0051 to 0.0102 cm).
Vanes are continuously self-adjusting and will last
5,000 to 25,000 hours, depending upon speed oper-
ating pressure and precautions taken in maintain-
ing the motor.
8-2. Prior to Disassembly.
If the air motor is reported to be sluggish or inef-
ficient, try flushing with a pertoleum based solvent
such as kerosene or diesel fuel in a well ventilated
area.
a. Pour two ounces (60 ml) of petroleum based
solvent into air inlet opening.
b. Rotate rotor shaft by hand in both directions
for a few minutes. This will dissolve and loosen for-
eign matter which could have built up inside.
c. Connect an air line to air motor inlet and
apply air pressure slowly until there is no trace of
vapor in exhaust air.
d. Reinstall air motor on pressure (paint) tank
and test it for proper operation (para 8-5g).
e. Check muffler felts for grease, dirt or other
foreign matter. If dirty, replace felts and install
muffler onto air motor. If unsatisfactory results are
obtained proceed to disassembly procedure.
8-3. Disassembly.
Use Figure 8-1 as a guide and disassemble as fol-
lows:
a. Remove six screws (6) from dead end plate (8).
b. Hold housing (13) firmly, preferably in a vise,
and tap exposed end of rotor (11) with a soft ham-
mer until dead end plate (8) is free from dowel pins
(12).
C A U T I O N
Do not pry end plates (7 or 8) with a
screw driver, as it will dent the sur-
face of the plates and housing causing
leaks
NOTE
Count the number of gaskets (9) re-
moved from each end plate (7 and 8).
When reassembling, the same amount
will have to be installed.
c. Unscrew end cap (1), remove gasket (2) and
press out bearing (3).
d. Pull rotor (11) thru housing (13) until clear of
bearing (4). Four vanes (10) can now be lifted out of
rotor (11) slots.
e. Remove six screws (6) which attach drive end
plate (7) to housing (13). Place block of wood
against inside surface of drive end plate (7) and tap
until drive end plate (7) is free from dowel pins (12).
f. Pry out shaft seal (5) and discard, then press
out bearing (4) from drive end plate (7).
8-4. Cleaning and Inspection.
a. Clean all parts, except bearings, with a petro-
leum based solvent. Wipe bearings with a clean rag.
b. Inspect all parts for damage or excessive wear.
Replace parts as necessary.
8-5. Reassembly.
Use Figure 8-1 as a guide and proceed as follows:
a. Press bearing (3) into dead end plate (8).
Place gasket (2) over threads of end cap (1) and
screw end cap (1) into dead end plate (8).
b. Place gasket (9) on face of housing (13). Line
up dead end plate (8) with holes in gasket (9) and
housing (13), screw in six screws (6) and tighten.
8-1
