National Crane Published 8-01-2017 Control # 287-11 4-41
NBT40 SERVICE MANUAL BOOM MAINTENANCE
BOOM CALIBRATION
Top/rear Wear Pads
1. With a pair of inside/outside calipers, measure the inside
width of the outer section (W
i
) within 2 in of the top plate
at the front and back of the boom and record the
smallest measurement. If the section has cylinder
anchor bars, take a measurement directly in front of
those bars.
2. The top rear wear pads also act as the top side pads.
These pads are anchored in place by means of offset
retainers which are bolted on to the inner boom top
plates. Two different offset retainers are utilized, one
stamped 0.53 and the other stamped 0.59. These
numbers correspond to the distance the mounting holes
are placed off the centerline of the part. Use a
combination of 0.53 and or 0.50 wear pad retainers on
upper inner section to obtain a 0.00 - 0.06 clearance
between these wear pads (W
o
) and inside width (W
i
) of
outer section. Stamp wear pad retainers with R (right) or
L (left) and with 2, 3, 4 or 5 (boom stage) in position as
shown. Stamp top plate of boom sections with R or L
corresponding to and in same general location as stamp
on wear pad mounting plates as shown.
Inner Side Pads
1. With a pair of inside/outside calipers, measure the inside
width of the outer section (W
i
) at the front and back of
the boom within 3 in of the bottom plate and record the
smallest measurement. If the section has cylinder
anchor bars, take a measurement directly in front of
these bars.
2. With the inside/outside calipers, measure the outside
width of the inner section (W
o
) at the rear, lower side pad
location. Record the largest measurement.
OUTSIDE
CALIPERS
INSIDE
FIGURE 4-13
OUTER SECTION
CYLINDER
ANCHOR
BARS
FIGURE 4-14
OUTER SECTION
CYLINDER
ANCHOR
BARS
CYLINDER
ANCHOR
BARS
FIGURE 4-16
W
o
1 PLC BOTTOM
INNER SECTION
FIGURE 4-17
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