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 MIL-HDBK-1038
4.3.6.41 Painting and Corrosion Protection. Purchased mechanical assemblies and
components are usually painted by their manufacturers. Whenever a standard option
for higher quality or grade of paint is available, it should be obtained. There
is rarely any justification for repainting such items, but if required, the
original paint need not be removed, but its surface must be cleaned to obtain a
good bonding with the top coat that is to be applied. Any parts of joints/seams
on these items that might be damaged, penetrated, or degraded by cleaning must be
properly shielded. There is no particular requirement for the applied top coat,
but it must be compatible for bonding with the original paint.
The following surfaces and materials are not to be painted:
a)
Working surfaces of wire rope drums, sheaves, rails and patented
track, wheel and roller treads, etc.
b)
Wire ropes, hooks, and hook nuts.
(These items are periodically
lubricated or have a preservative applied.)
c)
Threaded portions of components intended for making adjustments or
changing settings.
d)
Contact surfaces underneath assembly and mounting fasteners (except
for a primer coating).
e)
Lubrication fittings and equipment data and name plates.
f)
Corrosion resistant metals and plating; such as stainless steel,
copper alloys (bronze), aluminum, and chrome or nickel plating.
4.4
Mechanical-Electrical. All mechanical-electrical components are standard
commercial items, designed and built to industry standards. They are fully
described in catalogs and advertising literature. Typically they are among the
most critical components of any drive, such as brakes and clutches.
4.4.1
Shoe Brakes. Crane shoe brakes have two external shoes, with riveted or
bonded friction linings, that act on the outside diameter of the brake wheel. The
brakes are of a "fail safe" design, being spring-set and electrically released.
The activating spring force is multiplied and applied equally to the two shoes
through intermediate linkage. The brakes are released either by a DC magnet or an
AC solenoid which acts against and overpowers the spring. In the released
position, the linkage is held open by a secondary spring to keep the brake shoes
from dragging on the brake wheel. The shoe brakes are available in standard sizes
and torque ratings. The compression of the activating spring is adjustable to 50
percent of its maximum rating. Brakes are available with self adjusting features
to compensate for friction lining wear. The adjustment automatically maintains
the air gap (the applied torque) within the desired range; however, the brake
condition should be checked periodically. The self adjusting brake feature should
not be included on brakes exposed to environments where freezing or contamination
may cause it to malfunction.
The brakes are base mounted, and are normally installed with the base in
a horizontal position to act on a horizontal brake wheel axis. With minor
modifications, the base can be turned to a vertical position with the brake wheel
axis remaining horizontal. More extensive modifications are required to turn the
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