JLG 4017RS Service Manual - Manual (Page 75)

3-35 3614RS, 4017RS
Boom
Elongation
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.
a. Extend Chains (fourth to third section)
When the original length (3) of 305 mm (12.00 in) per
foot of extend chain between the fourth and third
boom sections has elongated from wear to a length (4)
of 313 mm (12.36 in), the chain should be discarded and
replaced.
Measure across a span of 16 pins 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 is 313 mm(12.36
in). If the measurement is more than 313 mm (12.36 in),
the chain should be replaced.
b. Extend Chains (third to second section)
When the original length (3) of 317 mm (12.5 in) per
foot of extend chain between the third and second
boom sections has elongated from wear to a length (4)
of 325 mm (12.8 in), the chain should be discarded and
replaced.
Measure across a span of 10 pins 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 is 325 mm(12.8
in). If the measurement is more than 325 mm (12.8 in),
the chain should be replaced.
Distorted or Battered Link Plates
Distorted or battered link plates (5) on a leaf chain can cause
tight joints and prevent flexing.
Turning or Protruding Pins
Highly loaded chain, operating with inadequate
lubrication can generate abnormal frictional forces
between pin and link plates. When chain is allowed to
operate in this condition, a pin or series of pins, can
begin to twist out of a chain, resulting in failure.
Examine the pin head rivets to determine if the “VEE”
flats are still in correct alignment (6). Chain with rotated/
displaced heads (7) or abnormal pin protrusion (8)
should be replaced immediately.
DO NOT attempt to repair the chain by welding or
driving the pin(s) back into the chain. Once the press fit
integrity between outside plates and pins has been
altered, it cannot be restored.
Any wear pattern on the pin heads or the sides of the
link plates indicates misalignment in the system. This
condition damages the chain as well as increases
frictional loading and should be corrected.
MY1360
3
4
8
MZ1466
5
MZ1465
6
7
8