SkyTrak 8042 Service Manual - Manual (Page 90)

Boom
3-52 6036, 6042, 8042, 10042, 10054
Cracked Plates
Inspect the chains very carefully, front and back as
well as side to side, for any evidence of cracked
plates. If any one crack is discovered, the chain
should be replaced in its entirety.
It is important, however to determine the cause of
the crack before installing a new chain so the
condition does not repeat itself.
The types of cracks are:
• Fatigue Cracking -
Fatigue cracks (9) are
a result of repeated
cyclic loading beyond
the chain’s endurance
limit.
• Stress Corrosion
Cracking - The
outside link plates
are particularly
susceptible to stress
corrosion cracking (10).
• Corrosion Fatigue Cracking - Corrosion
fatigue cracks are very similar to fatigue
cracks in appearance. Corrosion fatigue is the
combined action of an aggressive
environment and cyclic stress.
Other Modes of Failure
• Ultimate Strength Failure -
These types of failures are
caused by overloads far in
excess of the design load.
Either fractured plates (11)
or enlarged holes (12) can
occur. If either of these
failures occurs, the chain
should be replaced immediately.
• Tight Joints
- All joints in
the chain
should flex
freely. Tight
joints (13)
resist flexing.
If the problem is caused by dirt or foreign substance
packed in the joints, clean and lubricate thoroughly
before re-installing the chain.
If the problem is caused by corrosion and rust or
bent pins, replace the chain.
3.10.3 Expose Chains for Inspection
e. Extend Chains
1. Park the machine on a firm, level surface. Place the
transmission control lever in (N) NEUTRAL, engage
the park brake switch and raise the boom to a
horizontal (level) position.
2. Fully extend the boom until both extend chains are
taut. Shut the engine OFF.
The extend chains will be visible for inspection with the
machine in this state.
While doing the chain inspection, check all chain clevis
ends for distortion or cracking and sheaves for bearing
wear or grooving from the chain.
If during the inspection, any chain is found to be damaged
or stretched, the chain must be replaced. It is
recommended that when any chain is replaced, that all
the chains and clevises be replaced at the same time.
f. Retract Chains
The three retract chains are only partially visible through
the rear of the boom with all the sections retracted. It is
possible to see a section of the retract chain as the boom
is slowly extended. If there is ANY question that one or all
the retract chains are damaged, the boom should be
removed and disassembled with the retract chains being
inspected and replaced if necessary.
Note: DO NOT attempt to repair a chain. Replace a
stretched or damaged chain with a new part. Always
replace both the chain and the clevis. It is recommended
that when any chain is replaced, that all chains and
clevis’ be replaced at the same time.
MZ1467
9
MZ1468
10
MZ1469
MZ1470
11
12
MZ1471 13