MIL-DTL-14055G
4.7.6.2.3 Tubing. Use double wall steel tubing 1/4 inch (6.3 mm) outside diameter or 5/16 inch (7.94
mm) outside diameter meeting SAE J527. Tubing from one outlet of master cylinder to the pair of wheel
cylinders or to the single wheel cylinder shall alternately be replaced with new tubing for each test
(minimum length 3 feet (915 mm)). Uniformity in tubing size is desirable between master cylinder and
wheel cylinder; 1/4 in (6.3 mm) tubing is more adaptable with available tube connectors. The standard
PIN SAE RM-15a master cylinder has two outlets for tubing, both of which should be used.
4.7.6.2.4 Assembly and adjustment of test apparatus.
a. Install wheel and master cylinders.
b. Fill the system with brake fluid conforming to MIL-PRF-46176, bleeding all wheel cylinders and the
pressure equipment and gauges to remove entrapped air from the system.
c. Operate the actuator manually to apply a pressure of more than the required operating pressure
and inspect the system for leaks.
d. Adjust the actuator and pressure relief valve to obtain a pressure of 1000 ± 50 psi
(68.95 ±3.45 bar) at the end of the stroke of approximately 1 in (25 mm).
e. The pressure buildup rate versus cylinder stroke and time shall correspond to the rate portrayed
on figure 3.
f. The wheel cylinder piston travel is approximately 0.19 ± 0.01 in (4.8 ± 0.25 mm) when a pressure
of 1000 ± 50 psi (68.95 ±3.45 bar) is reached.
g. Adjust the stroking rate to 1000 ± 100 strokes/h.
h. Record the fluid level in the master cylinder standpipe at 73.4°F ± 9°F (23°C ± 5°C) with the
master cylinder piston in the fully returned position.
4.7.6.3 Stroking test procedure.
a. Run a pressure versus stroke curve utilizing the pressure recorder to determine conformance
to 3.4.5.2:
1. At room temperature before stroking.
2. After the fluid is at the test temperature.
3. Before shutdown at the test temperature.
4. And at room temperature after stroking.
b. Operate the system at 16,000 ± 1,000 cycles at 73.4°F ± 9°F (23°C ± 5°C).
c. Repair any leaks and add fluid to the master cylinder standpipe to bring the fluid level to the level
originally recorded at room temperature with the piston fully returned.
d. Start test again and raise the temperature of the fluid in the master cylinder within 6 ± 2 hours to
248°F ± 9°F (120°C ± 5°C).
e. During test, observe operation of the master cylinder for complete piston return and wheel
cylinders for proper operation.
f. Observe fluid level in relation to the room temperature level at random intervals.
g. Continue the test to 94,000 total recorded strokes which shall include the number of strokes during
operation at 73.4°F ± 9°F (23°C ± 5°C), the number of strokes required to bring the system to the
operating temperature of 248°F ± 9°F (120°C ± 5°C), plus the number of strokes at this operating
temperature.
h. Stop the test, and with the master cylinder piston in the fully returned position to relieve retained
pressure in the system, allow the equipment to cool to room temperature. Inspect to determine
conformance to 3.4.5.3.
i. Record the amount of fluid required to replenish any loss of fluid to the 73.4°F ± 9°F (23°C ± 5°C)
and 1000 ± 50 psi (68.95 ±3.45 bar), examine wheel cylinders for leakage and add and record
volume of fluid required to bring the fluid level to the 73.4°F ± 9°F (23°C ± 5°C) original level to
determine conformance to 3.4.5.1.
j. Within 16 hours remove the master and wheel cylinders from the system, retaining the fluid in the
cylinders by immediately capping or plugging the ports.
k. Disassemble the cylinders, collecting the fluid from the master cylinder and wheel cylinders in a
glass jar.
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