JLG 40H Service Manual - Manual (Page 80)

SECTION 2 - PROCEDURES
2-60
– JLG Lift – 3120240
Wear Tolerance.
1. From the underside of the machine, at rear center,
with the boom fully elevated and fully retracted (See
Figure 2-32a.), using a magnetic base dial indicator,
measure and record the distance between the swing
bearing and frame. (See figure 2-34.)
2. At the same point, with the boom at horizontal and
fully extended (See Figure 2-32b.), using a magnetic
base dial indicator, measure and record the distance
between the swing bearing and frame. (See Figure
2-34.)
3. If a difference greater than.057" (1.45 mm) is deter-
mined, the swing bearing should be replaced.
4. If a difference less than.057" (1.45 mm) is deter-
mined, and any of the following conditions exist, the
bearing should be removed, disassembled, and
inspected for the following:
a. Metal particles in the grease.
b. Increased drive power required.
c. Noise.
d. Rough rotation.
5. If bearing inspection shows no defects, reassemble
and return to service.
THE SWING BEARING IS ONE OF THE MOST CRITICAL POINTS
ON AN AERIAL LIFT. IT IS HERE THAT THE STRESSES OF LIFT-
ING ARE CONCENTRATED, AT THE CENTER OF ROTATION.
BECAUSE OF THIS, PROPER MAINTENANCE OF THE SWING
BEARING BOLTS IS A MUST FOR SAFE OPERATION.
Replacement and Devcon Application
Procedures on Machines Built Prior to Mid
of 1991.
1. Removal.
a. From Ground Control station, operate the
boom adequately to provide access to
frame opening or, if equipped, to rotary cou-
pling.
NEVER WORK BENEATH THE BOOM WITHOUT FIRST ENGAGING
BOOM SAFETY PROP OR PROVIDING ADEQUATE OVERHEAD
SLING SUPPORT AND/OR BLOCKING.
b. Attach an adequate support sling to the
boom and draw all slack from sling. Prop or
block the boom if feasible.
c. From underside of the machine frame,
remove bolts and lockwashers which attach
the retaining yoke of the rotary coupling to
the coupling housing.
HYDRAULIC LINES AND PORTS SHOULD BE CAPPED IMMEDI-
ATELY AFTER DISCONNECTING LINES TO AVOID THE ENTRY OF
CONTAMINANTS INTO THE SYSTEM.
d. Tag and disconnect the hydraulic lines
from the fittings on the top and sides of
the rotary coupling. Use a suitable container
to retain any residual hydraulic fluid. Imme-
diately cap lines and ports.
e. If machine is not equipped with a rotary
coupling, tag and disconnect hydraulic lines
running through center of turntable and
frame. Use a suitable container to retain any
residual hydraulic fluid. Immediately cap
lines and ports.
f. Attach suitable overhead lifting equipment
to the base of the turntable weldment.
g. Use a suitable tool to scribe a line on the
inner race of the swing bearing and on the
underside of the turntable. This will aid in
aligning the bearing upon installation.
Remove the bolts, nuts and washers which
attach the turntable to the bearing inner
race. Discard the nuts and bolts.
h. Use the lifting equipment to carefully lift the
complete turntable assembly from the bear-
ing. Ensure that no damage occurs to the
turntable, bearing or frame-mounted com-
ponents.
i. Carefully place the turntable on a suitably
supported trestle.
j. Use a suitable tool to scribe a line on the
outer race of the swing bearing and the
frame. This line will aid in aligning the bear-
ing upon installation. Remove the bolts and
washers which attach the outer race of the
bearing to the frame. Discard the bolts. Use
suitable lifting equipment to remove the
bearing from the frame, move the bearing to
a clean, suitably supported work area.