inner rail (22) and outer rail (23). Position the outer rail
on the inner rail so that the inner rail rollers slide in the
outer rail track. Move the outer rail along until it contacts
Dry cleaning solvent, P-D-680, used to clean
the stop pads. It must move freely, without binding or
parts is potentially dangerous to personnel and
drag. If binding or dragging is present, check welds or
property. Avoid repeated and prolonged skin
bends made during repair; correct the cause of drag or
Do not use near open flame or
excessive heat. Flash point of solvent is 100° F.
b. Turn the inner and outer rail assembly over
- 138° F. (39° C. - 59° C.).
and block the outer rail so that it is level and the trunnion
brackets are clear of the ground. Slide the outer rail
3-4. Cleaning and Inspection
down until the rollers stop it; support the outer rail so that
it is level. Use a pry bar to move the inner rail fully to one
a. Clean all metal parts of the mast assembly,
side. Maximum clearance between rails and rollers on
except the rollers, with cleaning solvent P-D-680. Wipe
the side forced apart is 1/32 inch. Check for this
off dirt, dust, and grease and oil deposits.
clearance on the full length of the inner rail for the outer
b. Clean the rollers by wiping with a cloth
rail roller, and down to 20 inches below the outer rail
dampened in cleaning solvent P-D-680.
rollers for the inner rail rollers. Add or remove shims
c. Inspect all metal parts for wear, distortion, or
behind the rollers to maintain this maximum clearance.
other damage; replace defective parts.
Check again for clearance; readjust if necessary.
d. Inspect the trunnion bushings for wear,
scoring, distortion, or other damage; replace bushings if
The inner rail is made with a slight taper so that the
e. Inspect stop pads for wear, cracks, distortion,
bottom is wider than the top. Make the outer rail
or other damage; replace damaged stop pads.
roller adjustments with the inner rail in the fully
f. Inspect inner and outer rail assemblies for
extended position or the rail will bind when
cracks, breaks or distortion; repair inner and outer rails
by welding or straightening. Replace rails if they cannot
Install the mast assembly (para 2-6b ).
Refer to figure 3-1 and reassemble the mast
assembly. Note the following:
a. Place the shims (8) and two rollers (7) on the