JLG sky trak mmv Service Manual page 78

General Information, Specifications and Maintenance
Elongation
When the original length (1) of 12.00" (305 mm) per
foot of new chain has elongated from wear to a
length (2) of 12.36" (313 mm), the chain should be
discarded and replaced. (Refer to Section 4.3.6, c.
Chain Replacement .)
It is important to measure the chain in the section that
moves over the sheaves because it receives the most
frequent articulation. Measuring the chain near its
clevis terminals could give an inaccurate reading.
The ends of the chains, near the clevis terminal, will
not have flexed as frequently, if at all, as nearer the
middle of the chains.
Measure across a span of 17 pins (16 links) at the
center of the extend chain. Measure from pin center
to pin center. Because the retract chain is inside the
boom you will not be able to measure the chain.
The maximum measurement allowed is12.36"
(313 mm). If the measurement is more than 12.36"
(313 mm), the chain should be replaced. (Refer to
Section 4.3.6, c. Chain Replacement .)
2.62
1
2
Edge Wear
Check the chain for wear on the link plate edges
caused by running back and forth over the sheave.
The maximum reduction of material should not ex-
ceed 5%. This can be compared to a normal link plate
height by measuring a portion of chain that does not
run over the sheave.
The new chain link measures .713" (18 mm) (3). If the
measurement of the worn chain is less than .677"
(17 mm) (4), the chain should be replaced. (Refer to
Section 4.3.6, c. Chain Replacement .)
MM2120
3
4
MM2050
Model MMV Rev. 12/04