SECTION 4 – BOOM
4-16
USTC
January 15, 2001
TELESCOPE CYLINDER
The telescope cylinder is located in the boom.
Through several sets of cables the cylinder extends
and retracts each of the boom sections proportionally.
When extending the barrel end of the cylinder moves
with the rod end pinned to the pedestal end of the
boom base section.
The cylinder is double-acting with cartridge-style
holding valve located in the port block. Because the
barrel end extends the port block is located on the rod
end of the cylinder rather than the butt end.
Removal
Removal of the cylinder requires the hoist to be laid
back. The boom can remain mounted on the truck or
removed.
If boom remains mounted, use all applicable precau-
tions to prevent dropping the cylinder or slipping of
maintenance personnel.
1. Park truck in a location with adequate room for
extending cylinder out back of boom (approxi-
mately 25 ft.). Set Park Brake.
2. Lay back hoist. Refer to hoist layback proce-
dure.
3. Evenly remove four nylon insert lock nuts from
extend cables.
Note: If a single nut is removed completely with
tension on any remaining cables, the “free” cable
will retract into boom and completely boom
disassembly will be required.
4. Remove six socket head bolts which secure the
cable retainer block to the base section.
5. Using truck hydraulics, extend cylinder approxi-
mately 2 ft. This will extend the rod end of the
cylinder with the cable retainer block to provide
access to hoses connections. It may be necessary
to lift cylinder to extend trunnion ears through
retainer blocks inside base section.
6. Disconnect hydraulic hoses and cap hoses and
cylinder ports.
7. Remove retaining ring and pin securing cable
retainer block to rod end of cylinder.
8. Remove cotter pins on four lower retract cable
sheaves and push sheave pins back flush with
Telescope
Cylinder
Retainer
Plates
Retract Cable
Retainer Plate
Base Section
Cylinder
Mounting Pin
Figure 4-11. Telescope Cylinder
