JLG 450A_AJ Series II Service Manual - Manual (Page 53)

SECTION 3 - CHASSIS & TURNTABLE
3121180 – JLG Lift – 3-3
3.2 TORQUE HUB (MACHINES BUILT
BEFORE S/N 0300071527)
Roll, Leak, and Brake Testing
Always roll and leak test Torque-Hub units before disas-
sembly and after assembly to make sure gears, bearings,
and seals are working properly. The following information
briefly outlines what to look for when performing these
tests.
NOTE: Brake must be released before performing roll test.
Pressurize brake using Brake Leak Test procedure
below or tighten bolts into piston through end plate
(See Brake Disassembly Procedure).
NOTE: Bolts must be removed while performing brake
release test.
ROLL TEST
The roll test determines if gears are rotating freely and
properly. You should be able to rotate gears by applying
constant force to the roll checker. If you feel more drag in
gears only at certain points, 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 concerned if gears in your unit seem to
roll hard as long as they roll with consistency.
LEAK TEST (MAIN UNIT)
The leak test makes sure the unit is air tight. You can tell if
your unit has a leak if the pressure gauge reading on your
leak checking fitting starts to fall after unit is pressurized
and allowed to equalize. Leaks most likely occur at pipe
plugs, main seal, and wherever O-rings or gaskets are
located. Exact location of a leak can usually be detected
by brushing a soap and water solution around the main
seal and where O-rings or gaskets meet on unit exterior,
then checking for air bubbles. If a leak is detected in a
seal, O-ring, or gasket, the part must be replaced and unit
rechecked. Leak test at 10 psi for 20 minutes.
BRAKE TEST
FAILURE TO PERFORM THIS TEST MAY RESULT IN DAMAGED
OR INEFFECTIVE BRAKE PARTS.
Input Brake - 1,850 in-lb (208 Nm) Static,
225 psi (15.5 bar) Full Release
3000 psi (207 bar) maximum O-ring check.
If brake does not release at these pressure values, inspect
and repair, or replace brake.
Tightening and Torquing Bolts
If an air impact wrench is used to tighten bolts, extreme
care should be taken to ensure bolts are not tightened
beyond their specified torque.
The following steps describe how to tighten and torque
bolts or socket head cap screws 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 bolt circle and tighten remaining
bolts.
4. Use a torque wrench to apply specified torque to
bolt “A”.
5. Using the same sequence, crisscross around bolt
circle and apply equal torque to remaining bolts.