JLG X20JP - X600AJ Service Manual - Manual (Page 26)

SECTION 3 - CHASSIS & TURNTABLE
3-2 – JLG Lift – 3121623
Checking The Rubber Tracks
Figure 3-3. Rubber Track Structure
The structure of the rubber track is illustrated in Figure 3-3.
The steel ropes and the metal core are imbedded into the
rubber. The carved profiles are used to give traction when
moving over loose land. They are situated in the lower part
resting on the ground, while the wheel guides situated inside
the track, prevent the track from escaping from the guide
rollers.
CAUSES OF DAMAGE
1. Breakage of the steel ropes
Excessive tension causes the steel ropes to break in
the following conditions:
a. when stones or foreign bodies accumulate
between the track and the under-carriage
frame;
b. when the track escapes from its guide;
c. in the case of strong friction such as rapid
direction changes.
2. Wear and breakage of the metal cores
As for breakage of the steel ropes, stated above,
excessive tension may cause the metal cores to
bend or break, as may the following causes:
a. incorrect contact between toothed wheel and
track;
b. breakage of internal rollers;
c. functioning on sandy land.
3. Separation of the metal cores
Figure 3-4.
a. The metal core acts as a type of adhesive of
the rubber between the core itself and the
steel ropes. Separation may be caused by
excessive tension as breakage of the ropes
for the following reasons:
b. The metal cores have been wound by the
worn toothed wheel as indicated in the figure.
When this wear and abrasion is detected, the
toothed wheel must be replaced as soon as
possible.
c. If it breaks, as stated in item 2, "Wear and
breakage of the metal cores", the track must
be replaced because this damage leads to a
complete loss of functions.
4. Abrasion and fatigue cracks
a. The cracks at the base of the carved profile
occur due to bending fatigue of the rubber
caused by the toothed wheel and the track-
tensioning wheel.
b. The cracks and bends on the edge of the rub-
ber are due to manoeuvres with the track in
presence of cement kerbs and edges.
Figure 3-5.
c. The cracks and abrasions in the rubber on the
tracks of the roller guide originate from fatigue
from the compression of the rubber by the
weight of the wheel, together with functioning
on sandy land, or repeated and abrupt
changes of direction.
d. Abrasion of the carved profiles may occur
especially if slewing on concrete surfaces or
on gravel or hard surfaces are carried out.
e. The damage indicated in paragraphs a, b,
and c above, must not be considered fatal for
the track and, even if in presence of gradual
PATTERN
WHEEL SIDE
SPROCKET
HOLE
METAL CORE
STEEL WIRE
g
WORN PARTS
CRACK