MIL-DTL-14055G
4.7.6 Heat-pressure stroking.
4.7.6.1 Test apparatus.
a. The test apparatus shall use the stroking fixture apparatus shown on figure 1 with the components
arranged as shown on figure 2.
b. The master cylinder assembly shall be one cast iron housing hydraulic brake master cylinder
having a diameter of approximately 1-1/8 in (28 mm) and fitted with an uncoated steel standpipe.
Master cylinder used is PIN SAE RM-15a 1-1/8 in (28 mm) diameter or equivalent.
c. Brake assemblies:
1. Three cast iron housing straight bore hydraulic brake wheel cylinder assemblies having a
diameter approximately 1-1/8 in (28 mm).
2. Wheel cylinder used is PIN SAE RM-14a or equivalent with stroking fixture apparatus.
3. Three fixture units are required, including appropriate adapter mounting plates to hold the
brake wheel cylinder assemblies as shown on figure 2.
4. The amount of force applied by the actuating mechanism shall be adjustable and capable of
supplying sufficient stroke and thrust to the master cylinder to create a pressure of at least
1000 psi (68.95 bar) in the simulated brake system.
5. A hydraulic gauge and pressure recorder capable of establishing the pressure curve of the
system and monitoring the pressure developed shall be installed on a hydraulic line extending
from the master cylinder to the outside of the oven.
6. This line shall be provided with a shutoff valve and a bleeding valve for removing air from the
connecting tubing.
7. The actuating mechanism shall be designed to provide a stroking rate of approximately 1000
strokes/h.
8. The pressure build up rate versus cylinder stroke and time shall correspond to the rate
portrayed on figure 3.
d. The heated air bath cabinet shall be an insulated cabinet or oven having sufficient capacity to
house the three wheel cylinder fixture assemblies, master cylinder and necessary connections.
The following conditions shall apply.
1. A suitable thermostatically-controlled heating system is required to maintain a motor vehicle
brake fluid temperature of 248°F + 9°F (120°C + 5°C).
2. Heaters shall be shielded to prevent direct radiation of wheel or master cylinders.
3. Fluid temperature shall be monitored at random intervals during the test at the master cylinder
reservoir, using a temperature recording device.
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