JLG 660SJ ANSI Service Manual - Manual (Page 99)

SECTION 3 - CHASSIS & TURNTABLE
3120718 – JLG Lift – 3-45
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.
Swing Bearing Replacement
1. Removal.
a. From Ground Control station, operate the boom
adequately to provide access to frame opening
or, if equipped, to rotary coupling.
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 inside turntable, remove mounting hard-
ware which attach rotary coupling retaining yoke
brackets to turntable.
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 of the rotary coupling. Use a
suitable container to retain any residual hydrau-
lic 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 will aid in aligning the bear-
ing upon installation. Remove the bolts and
washers which attach the turntable to the bear-
ing inner race. Discard the 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, then
move the bearing to a clean, suitably supported
work area.
2. Installation.
a. Using suitable lifting equipment, carefully lower
the swing bearing into position on the frame.
Ensure the scribed line of the outer race of the
bearing aligns with the scribed line 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 center line of the frame.
JLG INDUSTRIES RECOMMENDS THAT ALL REMOVED BEARING
BOLTS BE DISCARDED AND REPLACED WITH NEW BOLTS.
SINCE THE SWING BEARING IS THE ONLY STRUCTURAL LINK
BETWEEN THE FRAME AND TURNTABLE, IT IS IMPERATIVE
THAT SUCH REPLACEMENT HARDWARE MEETS JLG SPECIFICA-
TIONS. USE OF GENUINE JLG HARDWARE IS HIGHLY RECOM-
MENDED.
b. Apply a light coating of Loctite #271 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.
SWING
BEARING
FRAME REF.
TURNTABLE REF.
MEASURING
POINT
Figure 3-30. Swing Bearing Tolerance Measuring
Point