JLG 680S, Service And Maintenance Manual

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SECTION 3 - CHASSIS & TURNTABLE
3121234 3-107
3.18 SWING HUB (SN 0300134352 THROUGH
0300189341)
Roll, Leak And Brake Testing
Drive Hub units should always be roll and leak tested before
disassembly and after assembly to make sure that the unit's
gears, bearings and seals are working properly. The following
information briefly outlines what to look for when performing
these tests.
NOTE: The brake must be released before performing the roll test.
This can be accomplished by either pressure testing using
the Brake Leak Test procedure below or by tightening the
12 bolts into the piston through the end plate (See Brake
Disassembly Procedure).
NOTE: Bolts must be removed while performing brake release test.
ROLL TEST
The purpose of the roll test is to determine if the unit's gears
are rotating freely and properly. You should be able to rotate
the gears in your unit by applying constant force to the roll
checker. If you feel more drag in the gears only at certain
points, then the gears are not rolling freely and should be
examined for improper installation or defects. Some gear
packages roll with more difficulty than others. Do not be con-
cerned if the gears in your unit seem to roll hard as long as
they roll with consistency. Release the pressure at the Brake
Housing (6) and remove the test fixtures.
LEAK TEST (MAIN UNIT)
The purpose of a leak test is to make sure the unit is air tight.
You can tell if your unit has a leak if the pressure gauge read-
ing on your air checker starts to fall after the unit has been
pressurized and allowed to equalize. Leaks will most likely
occur at the pipe plugs, the main seal or wherever o-rings or
gaskets are located. The exact location of a leak can usually be
detected by brushing a soap and water solution around the
main seal and where the o-rings or gaskets meet on the exte-
rior of the unit, then checking for air bubbles. If a leak is
detected in a seal, o-ring or gasket, the part must be replaced,
and the unit rechecked. Leak test at 10 psi (0.7 bar) for 20 min-
utes.
BRAKE TEST
The brake test must be performed with the Motor removed
and the Brake Test Plate (T-214404) installed. Install the Hex
Bolts through Brake Test Plate and torque to 80-100 ft. lbs.
(108-135 Nm). Install Roll Checking Tool (T-212731) and apply
210 psi (14 bar) to the o-ring port in the side of the Brake
Housing. The roll checking fixture should roll freely. Increase
the pressure to 3000 psi (207 bar) and perform the Roll Test.
NOTE: Failure to perform this lest may result in damaged or inef-
fective brake parts.
Tightening and Torquing Bolts
If an air impact wrench is used to tighten bolts, extreme care
should be taken to ensure that the bolts are not tightened
beyond their specified torque.
The following steps describe how to tighten and torque bolts
or socket head capscrews in a bolt circle.
1. Tighten (but do not torque) bolt “A" until snug.
2. Go to the opposite side of the bolt circle and tighten
bolt “B” until equally snug.
3. Crisscross around the bolt circle and tighten remaining
bolts.
4. Now use a torque wrench to apply the specified torque
to bolt “A”.
5. Using the same sequence, crisscross around the bolt cir-
cle and apply an equal torque to the remaining bolts.