JLG 20VP (3120849) Service Manual - Manual (Page 50)

SECTION 2 - SERVICE PROCEDURES
2-32 – JLG Lift – 3120849
g. When mast slide pads are shimmed properly,
there should be no side to side movement of
slide pad in rail channel. Mast sections should
be very snug in channels but still be able to slide
in channel by hand.
49. Slide mast section-4/-5 to top of section-3/-4.
50. Insert threaded ends of chain assembly (attached to
top of mast section—2/3) through the chain anchor
plate located on bottom of extended mast section-4/
-5. Loosely thread two (2) 3/8"-16UNC nuts onto
stud threads on each chain. Chains will be adjusted
later in assembly.
51. Slide mast section-4/-5 back into mast section-3/-4
until bottom ends of masts are even. Check to make
sure chain set attached to top of section-2/-3 is seat-
ing properly in chain sheave wheels attached to top
of mast section-3/-4. (Mast sections-2, -3 and -4 may
need to be restrained to keep their slide pads from
pushing out the bottom of mast sections-1, -2 and -
3).
52. At bottom of mast assembly, thread all chain adjust-
ing nuts on threaded ends until they are snug
against the anchor plates and all slack is removed
from chains. Check that chains are seated in their
sheave wheels at top of mast assembly. Also, ends
of mast sections should be even with each other.
Mast assembly should now be complete.
2.9 MAST TO BASE FRAME INSTALLATION
IF BATTERIES ARE STILL MOUNTED, REMOVE BATTERIES FROM
THEIR TRAYS BEFORE LAYING THE BASE FRAME IN A HORIZON-
TAL POSITION.
1. Using an overhead crane or suitable lifting device
capable of supporting the weight of the base frame,
attach a sling strap or chain to the front crossmem-
ber of the base frame. Carefully tilt the base frame
back until the front is pointing up and the back is
resting on the counterweight/battery trays. Be sure
base is very stable and at a 90° angle to work sur-
face before proceeding.
2. Using a sling and suitable lifting equipment (i.e.
overhead crane) lift the mast assembly (balanced in
middle) into position in front of the base frame.
3. Extend hydraulic cylinder out from bottom of mast
assembly approximately one (1) foot. (Caps on
extend and return ports will need to be removed to
extend cylinder. Catch any hydraulic fluid expelled
from return port in a container to prevent spillage
onto work area).
4. Carefully position the mast into base frame assem-
bly, (base frame and mast assembly must be held at
90° angle to each other).
5. Slide port end of hydraulic cylinder through hole in
base frame cylinder mounting channel. (Return port
(tube side) of cylinder must be on right side facing
bottom of base and mast).
6. Align threaded hole in side of hydraulic cylinder
head with hole in tab on bottom side of cylinder
mounting channel. Secure hydraulic cylinder to cyl-
inder mounting channel tab using a 5/16"-18UNC x
5/8" long hex head bolt and flat washer.
7. Carefully push mast assembly and base assembly
together until the four (4) holes on bottom rear of
mast align with holes in the base frame mast support
crossmember.
8. Attach mast to base using four (4) 3/8"-16UNC x 1"
long hex head bolts, locknuts and flatwashers,
(place a flatwasher under bolt head and nut and
mount with nuts on inside of frame).
9. Locate the two (2) mast support braces, attach to
sides of base frame using a 3/8"-16UNC x 1" long
hex head bolt, nut and flatwashers each brace,
(place a flatwasher under bolt head and nut and
mount with nuts on inside of frame. Use access hole
in bottom of frame to attach nut inside frame).
10. Before setting machine upright on base, install a
short 90° elbow fitting, flow control valve and
another short 90° elbow fitting on the end of the flow
control valve in the extend (left) port on bottom of
hydraulic cylinder. Install a long 90° elbow fitting on
return (right) port. Use sealant tape on fitting
threads. Cap ports until hydraulic lines are installed.
11. Carefully set machine in an upright position on its
base frame wheels.
12. Locate the mast support bracket. Attach mast sup-
port bracket to mounting holes halfway up back of
mast using four (4) 3/8"-16UNC x 2-3/4" long hex
head bolts, locknuts and flatwashers. (Place a flat-
washer under bolt head and nut and mount with
nuts on inside of frame).
13. Using a 4 ft. level, ensure mast is set to vertical
(plumb) on the base frame.
14. When mast is vertical (plumb), attach support
braces, (bolted to base), to the mast support
bracket, (bolted to mast), using 3/8"-16UNC x 2-3/4"
long hex head bolts, nuts and flatwashers. (Place a
flatwasher under bolt head and nut and mount with
nuts on inside of bracket).
15. After securing mast to base frame, using 4 ft. level
again check that mast is vertical (plumb) on base
frame.