JLG 9MP Service Manual - Manual (Page 46)

SECTION 5 - MAST COMPONENTS
5-2 – JLG Lift – 3121163
5.2 MAST CHAINS AND SEQUENCING
CABLES ADJUSTMENT
Mast Chain Adjustment (See Figure 5-2.)
The intention of this procedure is to assure equal load dis-
tribution between the individual chains of a mast section
chain sets. Also to set the platform height above the base
frame when the platform is completely lowered.
Adjust using the following procedure;
1. With mast retracted, step into the platform and
bounce your weight up and down a few times to be
certain platform is at the bottom of travel. Be certain
the chain set is seated in the sheaves properly at the
top of the mast.
2. Then with no load in the platform check the clear-
ance from the frame under the platform, to the top of
the machine base frame, it should be approximately
1 inch (2.54cm). (See Figure 5-2.)
NOTE: Mast section-1 is fixed to the base and mast section-
2 is attached to the lift cylinder, these sections
require no adjustment.
3. To adjust, elevate the platform until the chain anchor
adjust nuts are accessible at the front and bottom of
the mast section 3 (platform mounting section).
NEVER WORK UNDER AN ELEVATED PLATFORM UNTIL PLATFORM
HAS BEEN SAFELY RESTRAINED FROM ANY MOVEMENT BY BLOCK-
ING OR OVERHEAD SLING.
4. Unthread the (jam) nuts from the adjusting nuts
below the chain anchor plate.
5. Tighten (to raise mast section), or loosen (to lower
mast section) the adjusting nut against the anchor
plate on each chain. Adjust the nuts the amount
required to raise or lower the mast section to obtain
the proper platform height when the mast is
retracted.
NOTE: It is more important that the (threaded ends) studs
protruding on the adjustments are equal side to side
than it is that the tension in the chains is equal. The
chain equalizer plate will always assure equal ten-
sion, but if the adjustment isn’t equal as described,
the chains may tend to pull to one side or the other.
The threaded end of the chain may need to be
restrained while tightening the adjust nut to keep the
chain from twisting.
6. After making an adjustment retract the mast all the
way and check if the platform height is adjusted
properly as shown in Figure 5-2.
7. Repeat steps (5) and (6) until the proper platform
height is obtained.
8. Once mast section adjustment is completed, apply
loctite #242 to the threads under the (jam) nuts that
were loosened. Then re-tighten the loosened (jam)
nuts until tight against the top (adjust) nut.
9. Run mast through several cycles to verify chain
adjustments and ensure no interference exists
between chain anchor brackets and mast.
Sequencing Cable Adjustment (See Figure 5-2.)
1. Retract mast completely, and check the sequencing
cable on outside of masts for excessive slack. Adjust
only to remove slack from cable.
2. Tighten nylock-nut just enough to remove excessive
slack from sequencing cable. The springs should
not be compressed more than 25% after adjusting.
NOTE: Adjustment and spring compression will vary due to
cable stretch as mast lift and lower cycles accumu-
late. If cable cannot be adjusted to remove slack,
either the mast chain is adjusted improperly (plat-
form to low) or the cable has stretched and needs
replaced.
3. Run mast through several cycles to verify cable
adjustments and ensure cable is seated in the
sheave properly.