JLG 120-SXJ ANSI Service Manual - Manual (Page 35)

SECTION 3 - CHASSIS & TURNTABLE
3121105 – JLG Lift – 3-7
5. If bearing inspection shows no defects, reassemble
bearing 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.
Bearing Replacement
1. Removal.
a. From ground control station, operate the boom
lift control and raise boom adequately to provide
access to frame opening or, if equipped, to the
rotary coupling.
NEVER WORK BENEATH THE BOOM WITHOUT FIRST PROVIDING
ADEQUATE OVERHEAD SLING SUPPORT AND/OR BLOCKING.
b. Attach an adequate support sling to the boom
and draw all slack from sling. Block the boom if
feasible.
NOTE: Steps c and d apply to those machines equipped
with a rotary coupling.
c. From under side of machine frame, remove bolts
and lockwashers which attach rotary coupling
retaining yoke to 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 cou-
pling. Use a suitable container to retain any
residual hydraulic fluid. Immediately cap lines
and ports.
e. Attach suitable overhead lifting equipment to the
base of the turntable weldment.
f. Use a suitable tool to scribe a line on the inner
race of the swing bearing and on the underside
of the turntable. This line 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.
g. Use the lifting equipment to carefully lift the com-
plete turntable assembly from the bearing.
Ensure that no damage occurs to the turntable,
bearing or frame mounted components.
h. Carefully place the turntable on a suitably sup-
ported trestle.
i. 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 bearing upon installa-
tion. 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.
2. Installation.
a. Position the bearing on the machine frame.
b. Use suitable lifting equipment to carefully lower
the swing bearing into position on the frame.
Ensure that the scribed line of the outer race of
the bearing aligns with the scribed mark on the
frame (if a new swing bearing is used, ensure
that the filler plug fitting is at 90 degrees from the
fore and aft centerline of the frame).
JLG INDUSTRIES RECOMMENDS THAT ALL REMOVED BEARING
NUTS AND BOLTS BE DISCARDED AND REPLACED WITH NEW
NUTS AND BOLTS. SINCE THE SWING BEARING IS THE ONLY
STRUCTURAL LINK BETWEEN THE FRAME AND TURNTABLE, IT
IS IMPERATIVE THAT SUCH REPLACEMENT HARDWARE MEETS
JLG SPECIFICATIONS. USE OF GENUINE JLG HARDWARE IS
HIGHLY RECOMMENDED.
c. Apply a light coating of Loctite #277 to the new
bearing bolts, and loosely install the bolts and
washers through the frame and outer race of
bearing.
IF COMPRESSED AIR OR ELECTRICALLY-OPERATED IMPACT
WRENCH IS USED FOR TIGHTENING THE BEARING ATTACH-
MENT BOLTS, THE TORQUE SETTING ACCURACY OF THE TOOL
SHOULD BE CHECKED PRIOR TO USE.
d. Following the Torque Sequence diagram shown
in Figure 3-6., tighten the bolts to an initial
torque of 180 ft. lbs. (244 Nm). Then following
the same sequence tighten the bolts to a final
torque of 240 ft. lbs. (325 Nm).
e. Remove the lifting equipment from the bearing.
f. Use suitable lifting equipment to carefully posi-
tion the turntable assembly above the machine
frame.