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TM 10-3930-671-24
13.1. Upright Maintenance
Upright Down Drift (Fork Drift) Test ............................................... F-497
Upright Maintenance ...................................................................... F-498
Lift Chain Maintenance................................................................... F-498
Fork Removal ................................................................................ F-500
Carriage Removal .......................................................................... F-501
Upright Removal............................................................................. F-502
Upright Mounting Parts................................................................... F-504
Upright Mounting ............................................................................ F-504
Installation ...................................................................................... F-504
Upright Installation.......................................................................... F-505
Upright Down Drift (Fork Drift) Test
To check upright (fork) drift, a rated capacity load is
placed on the forks, lifted up and held to determine how
much the position of the lift cylinder(s) change (drift) in a
specified length of time.
Refer to Section 2. 1, Service Specifications, for
maximum fork drift specifications.
It is recommended that a test load, made up of a full
capacity load equally distributed on a 48" x 48" pallet, be
used. The material used to make up the test load must
be arranged (stacked) to provide load stability and must
not extend beyond the pallet. It must be secured on the
pallet. Refer to the truck nameplate for capacity rating.
An upright or carriage can move unexpectedly.
•
Do not walk or stand under raised forks.
•
Keep clear of load and carriage when
making any checks and adjustments.
•
Keep your arms and fingers away from
moving parts of the upright. Do not reach
through upright open areas.
•
Failure to follow these warnings can result
in serious injury.
1. Adjust fork width to maximum which will
accommodate the test load. Space forks as wide
as possible to provide even distribution of
weight.
2. Position the load on forks. Keep forks level
during pick up. Enter pallet with test load as far
as possible; test load and/or pallet should be in
contact with load back rest.
3. Raise carriage and test load 12-15 inches (305-
381 mm) off the floor. Tilt upright slightly
backward (approximately 1-2 degrees from
vertical) at the same time.
4. Shut off the truck. Turn key switch OFF.
5. Stand at one side of the upright, not under the
load, and measure and mark the initial position
of the upright rails with a pencil or marker (see
Figure 1).
6. Let upright with test load stand in the raised
position for the specified test time.
7. Check the movement of the reference mark.
Mark the new position of the upright by making a
new mark on the movable rail in line with original
mark on fixed rail.
8. Determine the change in position by measuring
the distance between marks on rails. Make a
record of this dimension.
9. Compare the change in dimensions with the
specifications.
Figure 1. Mark initial position on rail.
F-497
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