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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