MIL-DTL-14055G
4.7.6.2 Preparation of test apparatus.
4.7.6.2.1 Wheel cylinder assemblies.
a. Use new wheel cylinder assemblies PIN SAE RM-14a or equivalent having diameters as specified
in 4.7.6.1.b.
b. Pistons (PIN SAE RM-12 or equivalent) shall be made from unanodized ASTM B209, aluminum
alloy 2024-0.
c. Disassemble cylinders and discard rubber cups.
d. Clean all metal parts with isopropyl alcohol and dry with clean compressed air.
e. Inspect the working surfaces of all metal parts for scoring, galling or pitting and cylinder bore
roughness and discard all defective parts.
f. Remove any stains on cylinder walls with crocus cloth and isopropyl alcohol.
g. If stains cannot be removed, discard the cylinder.
h. Measure the internal diameter of each cylinder at locations approximately 0.75 in (19 mm) from
each of the cylinder bores, taking measurements in line with the hydraulic inlet opening and at
right angles to the center line.
i. Discard the cylinder if any of these four readings exceeds maximum or minimum limits of 1.1285 -
1.126 in (28.66 - 28.60 mm).
j. Measure the outside diameter of each piston at two points approximately 90 degrees apart.
k. Discard any piston if either reading exceeds maximum or minimum limits of 1.124 - 1.123 in
(28.55 - 28.52mm).
l. Select parts to insure that the clearance between each piston and mating cylinder is within
0.003 - 0.005 in (0.08 - 0.13 mm).
m. Use new test cups that are free of lint and dirt.
n. Discard any cups showing imperfections such as cuts, tooling marks, molding flaws or blisters.
o. Measure the lip and base diameters of all test cups with an optical comparator or a micrometer to
the nearest 0.001 in (0.025 mm) along the center line of cups and at right angles to this center line.
p. Determine base diameter measurements within 0.032 in (0.8 mm) of the bottom edge and parallel
to the base of the cup.
q. Discard any cups if the two measured lip or base diameters differ by more than 0.003 in
(0.08 mm).
r. Average the lip and base diameters of each cup.
s. Determine the hardness of all cups by the procedure specified in 4.7.2.
t. Clean rubber parts with isopropyl alcohol and a lint-free cloth.
u. Dry with clean compressed air.
v. Dip the rubber and metal parts of the wheel cylinders, except housings, in the fluid specified in
MIL-PRF-46176 and install them in accordance with manufacturer's instructions. Rubber boots
shall not be used.
w. Manually stroke the cylinders to insure that they operate easily.
x. Install cylinders in the simulated brake system.
4.7.6.2.2 Master cylinder assembly.
a. Use a new PIN SAE RM-15a master cylinder or equivalent having a PIN SAE RM-13 piston or
equivalent made from ASTM B36/B36M copper alloy UNS No. C26800, temper H02 and new
standard PIN SAE RM-4a primary master cylinder test cup or equivalent and a PIN SAE RM-5a
SBR secondary master wheel cylinder test cup or equivalent, and PIN SAE RM-3 wheel cylinder
b. Inspect and clean all parts as specified in 4.7.6.2.1.
c. Measure each land of the master cylinder piston at two points approximately 90 degrees apart.
d. Discard the piston if any of these readings exceed maximum or minimum limits of 1.124 - 1.123 in
(28.55 - 28.52 mm).
e. Dip the secondary cup in the test brake fluid, assemble on the piston, and maintain the assembly
in a vertical position at 73.4°F ± 9°F (23°C ± 5°C) for at least two hours.
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