Section III. MAST ASSEMBLY

TM 10-3930-621-34

g. Install adapter (26) and packing set (27) in

stuffing box (30) bore and install packing (29) and ring

10-7. Assembly

(28) in outside groove of stuffing box.

a. Refer to figure 10-2 and assemble as follows:

h. Install stuffing box assembly, nut (24), and wiper

b. Dip all packings (13, 15, 21, 27 and 29), wiper

(23) on rod (31). Tighten nut (24) securely, then back of

ring (23), guide ring (12), plunger rod (31), and nut (24)

approximately 1/8 turn.

in hydraulic system oil before each is installed.

i. Insert plunger rod (311 with assembled parts in

c. Install ring (16) and packing (15) in follower (18)

tube assembly (10).

and install cup (17), follower, spacers (19 and 20), and

packing (21) on rod (31).

Note. Be certain all ;part, are clean and those

d. Install packing (15) in guide ring (12) bore and

which require soaking in hydraulic system oil have been

packing (13) and backup ring (14) in groove on outside

so serviced. Be sure no dirt o, r water is in tube

diameter of guide ring. Do not overexpand backup ring.

assembly.

Caution: Never use sharp tools or instruments when

j. Install packing retainer (25) with screw (22).

installing rings or packings.

k. Screw on yoke (6) on rod (31).

e. Install guide ring (12) on plunger rod (31).

f. Install nut (11) on rod (31) and torque nut to 300

10-8. Installation and Adjustment

foot-pounds.

Install

cotter

(32).

Refer to TM 10-3930-621-12 for installation and

adjustment procedures.

Section III. MAST ASSEMBLY

10-9. Description

Chain guards, mounted on the crossheads and cylinders,

a. The mast assembly is a three section mast

keep the chains from sticking the cylinder plungers and

assembly designed to provide lifts up to 180 inches.

packing. Rams from the, outer cylinders lift and lower

Three units, nested together, comprise the unit; an outer

the carriage along the length of the inner mast by means

mast, intermediate mast, and an inner mast. Each mast

of the chains. The center cylinder of the cluster has the

consists of a structural steel frame, with mounting

ram anchored at the bottom of the intermediate mast and

brackets and blocks welded to it to support the cylinders,

the top of the cylinder attached to the inner mast.

chains, and bearings.

f. The bottom of the outer mast has pivot blocks,

b. The intermediate and inner masts ride on roller

with bearings, for mounting to the truck. Pivot blocks are

bearings, enabling them to telescope up and down.

also provided on the outer mast to connect the tilt

Alinement of the mast channels is accomplished by

cylinders to the mast.

adjusting the roller bearings.

g. An interlock assembly, spring actuated, is

c. A carriage, designed to mount lifting forks, is

mounted on the right beam of the inner mast. The

supported by chains leading from the outer cylinders of

interlock assembly locks all three mast sections in the

the cylinder cluster. Action of the chains, cylinders, and

lowered position until full free lift is accomplished. When

mast raise and lower the carriage.

full free lift is reached, the carriage stop screw strikes the

d. Power to raise and lower the carriage and masts

interlock assembly to release it, allowing all mast

is provided by hydraulic oil pressure to a cylinder

sections to function completely.

assembly and cylinder cluster. The cylinder assembly is

a single cylinder attached to the inner portion of the

10-10. Operation

intermediate mast with the cylinder ram extending

a. When the lift handle on the control valve is

through an opening in the intermediate mast and

pulled to the rear, hydraulic oil pressure is delivered to

anchored at the lower part of the outer mast.

the two outer cylinders of the cylinder cluster. Pressure

The cylinder cluster, consisting of three

forces the cylinder rams to extend upward raising the

cylinders, is mounted forward of the cylinder assembly in

chains and lifting the carriage up the mast. Speed of lift

the intermediate mast. The rams of the two outer

is controlled by engine speed and by valve opening.

cylinders mount the two crosshead and chain bearing

b As the carriage reaches the top of the inner

assemblies, with the chains attached to adjusting bolts in

mast the two outer cylinder rams will be extended to their

mounting brackets on the cylinders. The chains extend

farthest point of travel. With the handle pulled to the

over the bearings and attach at the other end to anchors

rear,

the

hydraulic

oil

pressure

will

the

carriage.

10-5