Boom Chain Tension & Adjustment - JLG sky trak mmv Service Manual

General Information, Specifications and Maintenance
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 (1) or
enlarged holes (2) can occur. If either of these
failures occurs, chain should be replaced
immediately. (Refer to Section 4.3.6, c. Chain
Replacement .)
• Tight Joints - All joints in the chain should flex
freely. Tight joints (3) resist flexing and increase
internal friction, thus increasing chain tension
required to lift a given load. Increased tension
accelerates wear and fatigue problems.
If the problem is caused by dirt or foreign sub-
stance 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. (Refer to Section
4.3.6, c. Chain Replacement .)
1
3
2.64
2
2.13.21 Boom Chain Tension & Adjustment
a. Boom Chain Tension Check
1 000
MS21902
1. Park the vehicle on level ground. Place the travel
select lever in [N] NEUTRAL, place the neutral lock
lever in the [N] NEUTRAL LOCK position, engage
the parking brake switch and raise the boom to a
horizontal (level) position.
2. Fully extend the boom, then retract it 2" (51 mm)
(one inch per section). Shut the engine off.
3. Measure the sag (4) in the top extend chains
between the bottom of the chains and the top of the
intermediate boom (5) at their closest point.
Acceptable boom chain sag is between 1.5-2.5"
(38-64 mm). If the measurement is less than 1.5"
MM2090
(38 mm), the boom chains may need to be adjusted.
Before making any adjustment to the extend chains,
check the following measurement at the rear of the
boom, as described in Steps 4-9.
MM2100
MM2110
MT1750
Model MMV Rev. 12/04