Elevation System Servicing; General; Lift Chain Wear Inspection; Lift Chain Length Adjustment - Big Joe PDBB-20-T12 Operation, Maintenance, Repair Parts List

8-1. GENERAL.

The elevation system includes the outer mast, inner
mast, platform, lift chains, lift cylinder, and ram head.

8-2. LIFT CHAIN WEAR INSPECTION

Both lift chains should be replace when either chain is
worn enough to increase it's length by 3% or more. To
make this determination proceed as follows.
Using a section of chain that sees the most frequent
operation over the chain sheaves, isolate a vertical
portion under tension from the weight of platform.
Measure the distance between pin centers on 20 verti-
cal links. If the section measures 12.88" or more, the
chain should be replaced.
New chain anchor pins should be installed when
chains are replaced. Never replace a partial section of
chain and never repair a damaged chain. Refer to
paragraph 8-4. when installing new chain.

8-3. LIFT CHAIN LENGTH ADJUSTMENT.

1. Lower the platform fully, then disconnect battery.
WARNING: Before attempting any adjustment, make
certain power is disconnected.
2. Loosen top jam nuts (17,
bolts (16).
3. Take up slack in both lift chains with hex nut (15)
on the adjusting bolt. Strive for equal tension on
chains.
4. Align adjusting bolts so each clevis pin is parallel
to ram head (9).
CAUTION: At least 3 full threads must be present
below hex nut (15) after completion of
adjustment.
5. Tighten jam nuts securely while maintaining align-
ment of adjusting bolts.
6. Reconnect battery.
7. Test chain by operating carriage. If slack is still
apparent, repeat above procedure.

8-4. LIFT CHAIN REPLACEMENT.

1. With the lift truck wheels securely blocked and
with brake set, raise forks approximately three
901357
SECTION 8

ELEVATION SYSTEM SERVICING

Figure 8-1) on adjusting
feet from floor and position blocks or strong sup-
ports under inner mast (4,
2. Lower platform until it is supported by the block
and the load chains are slack, then disconnect
battery.
WARNING: Before attempting any actual replace-
ment, make certain power is discon-
nected.
3. Remove cotter pin (12,
(11) from end of chain connected to mast cross
brace.
4. Remove cotter pin (12) and clevis pin (11) from
chain adjusting bolt (16).
5. Remove chain from ram head assembly (9) and
lay aside for repair.
6. Position new chain in place on ram head assem-
bly (9).
7. Connect one end of the chain to adjusting bolt
(16) and secure with clevis pin (11) and cotter pin
(12).
8. Connect the other end of the chain to mast cross
brace with clevis pin (16) and cotter pin (16).
9. Adjust chain according to paragraph

8-5. LIFT CYLINDER REMOVAL.

1. With the lift truck wheels securely blocked and
with brake set, raise platform approximately three
feet from floor and position blocks or strong sup-
ports under inner mast (4,
2. Lower inner mast onto support. Check that
arrangement is secure before proceeding.
3. Disconnect battery.
4. Remove two cap screws (7), two lock washers
(8), one cap screw (6) and one lock washer (5)
that join the top of the inner mast (4) to the ram
head (9).
5. Open the emergency lowering valve and, at the
same time, manually push the ram down as far as
possible. The chains will become slack and need
not be removed.
6. Close the emergency lowering valve.
7. Remove overflow tubing retainers alongside of
the lift cylinder assembly (10).
Figure 8-1).
Figure 8-1) and clevis pin
8-3.
Figure 8-1).
8-1