INTRODUCTION TO THE HMMWV - OD1615 - LESSON 3/TASK 1
other fashions. In this case, the system is divided front and rear. If a
brake fluid leak develops in one circuit, the other circuit still provides
emergency stopping capability. As the brake pedal is depressed under normal
operating conditions, it forces the primary piston forward to cover the
primary compensating port. At this time, the primary chamber is sealed and
direct hydraulic pressure is transmitted to the secondary piston.
As the
brake pedal continues to travel, the secondary piston covers the
compensating port.
Further application of the brake pedal develops the
pressure required to apply the brake components.
Should a leak develop in the primary circuit, the brake system would not be
rendered useless. During the application of the brakes, the primary piston
would continue to move forward, unable to build up pressure due to the
malfunction. Approximately halfway through its maximum stroke, the primary
piston contacts the secondary piston.
Further application of the brake
would force the secondary piston forward to develop pressure in the
secondary system, which would allow for braking action to take place in two
wheels.
Should the secondary circuit fail, braking for the other two wheels would
still be available.
The primary piston would move forward and cover the
primary compensating port as before.
Because of the rupture in the
secondary circuit, the secondary or floating piston would be moved to its
extreme stop by the force of the return spring. Further application of the
brake would develop enough pressure in the primary circuit to apply the
brakes connected to this circuit, thereby allowing the vehicle to maintain
some stopping ability.
(2) Brake Lines. The brake lines used on the HMMWV are of 3/16 of an
inch seamless steel tubing with flared fittings. Flexible hoses connect the
brake lines to the wheel calipers.
(3) Brake Fluid.
In paragraph 3c(l), on the previous page, it was
stated that the master cylinder contains .69 pints of BFS.
The entire
system, master cylinder, lines, calipers, etc. contains 1.2 pints of BFS.
Hydraulic brake fluid is the liquid medium in the brake system used to
transmit fluid motion and pressure to the wheel brake components. The
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