JLG 80HX_HX+6_HXER ANSI Service Manual - Manual (Page 73)

SECTION 3 - CHASSIS & TURNTABLE
3120271 – JLG Lift – 3-35
Wear Tolerance
1. From the underside of the machine, at rear center,
with the boom fully elevated and fully retracted (See
Figure 3-14.), using a magnetic base dial indicator,
measure and record the distance between the swing
bearing and frame. (See Figure 3-14.)
2. At the same point, with the boom at horizontal and
fully extended (See Figure 3-14.), using a magnetic
base dial indicator, measure and record the distance
between the swing bearing and frame. (See Figure
3-13.)
3. If a difference greater than 0.057" (1.45 mm) is
found, the swing bearing should be replaced.
4. If a difference less than 0.057" (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
1991
Removal.
1. From the Ground Control station, operate the boom
adequately to provide access to the frame opening
or to rotary coupling
NEVER WORK BENEATH THE BOOM WITHOUT FIRST ENGAGING
BOOM SAFETY PROP OR PROVIDING ADEQUATE OVERHEAD
SLING SUPPORT AND/OR BLOCKING.
2. Attach an adequate support sling to the boom and
draw all slack from the sling. Prop or block the boom
if feasible.
3. From the underside of the machine frame, remove
the bolts and lockwashers which attach the retaining
yoke of the rotary coupling to the coupling housing.
IMPORTANT
HYDRAULIC LINES AND PORTS SHOULD BE CAPPED IMMEDI-
ATELY AFTER DISCONNECTING LINES TO AVOID THE ENTRY OF
CONTAMINANTS INTO THE SYSTEM.
4. Tag and disconnect the hydraulic lines from the fit-
tings on the top and sides of the rotary coupling.
Use a suitable container to retain any residual
hydraulic fluid. Immediately cap lines and ports.
Figure 3-13. Swing Bearing Tolerance Measuring Point