National Crane Published 5-27-2018 Control # 039-06 9-21
800D INSTALLATION
AFTER FRAME MODIFICATION
If additional suspension reinforcing is required, as may
be the case with a truck frame that tapers down to
approximately 6 in (15.24 cm) deep through the suspension,
a channel may be fabricated through the suspension for
additional strength. To do this, install the angle as described
in the previous step, making sure that the long leg of the
angle extends to the top of the truck frame. A bar of the same
material strength, thickness, length and flange width as the
reinforcing angle is then added to the top of the truck frame.
The bar is butt welded to the top of the forward reinforcing,
then skip-welded with 6 in (15.24 cm) of weld, 6 in (15.24
cm) no weld, etc., along both edges of the bar, front to back.
Length of after frame (AF) may have to be modified for
crane installation. If AF is too long, cut off excess and
remove any cross members from back of truck frame. If AF is
too short, the frame will have to be lengthened. Use
channels fabricated from 100,000 psi (758 MPa) yield
material that are the same size as the truck frame. Weld
these channels to the ends of the existing truck frame
channels. Bevel the ends of the channels to get 100% weld
joints with Grade 90 weld material. Fabricate an inner
channel of the same thickness as the truck frame channels
to span the weld joint for at least 12 in (30 cm) on each side
of joint. Plug weld this channel to the inside of the truck
frame, then skip weld the inside edge of the top and bottom
flanges to the truck frame flanges.
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