h. The release valve is attached to the AB valve to allow the air pressure to be drained from the auxiliary
reservoir alone or from both the auxiliary and the emergency reservoirs. Rods connected to this valve extend to
both sides of the car, near the middle, so that they can be hand-operated easily. When the rod is pulled part way
through the extent of its travel, air is released from the auxiliary reservoir alone; when it is pulled all the way
out, air is exhausted from both sides of the reservoir. The KC brake system has a release valve that is also
operated by rods.
i. The release control retainer is a valve located at the end of the car in the vicinity of the handbrake. It is
used to retain air in the brake cylinder for varying periods, depending on the position of the handle, while the
reservoirs are being recharged. It is used mainly in mountainous territory. The position of the handle is
regulated manually by a member of the crew.
j. The brake cylinder contains a spring-loaded piston and piston rod.
When air pressure enters the
cylinder, the piston is pushed outward against spring tension forcing the piston rod to move outward. When the
air pressure is exhausted, the spring returns the piston to its original position, pulling the piston rod inward and
thus releasing the brakes.
k. The live cylinder lever is connected to the piston rod, the cylinder lever rod, the floating lever, and the
top rods. When the piston rod moves, the live cylinder lever is actuated and transfers the motion and pressure
through these other rods and levers to the live truck levers, discussed in paragraph 3.6. To one end of the live
cylinder lever, the handbrake rod is attached; however, this rod is part of the manual braking apparatus
discussed in the next section.
6.7. SUMMARY
Each railway car is equipped with its own individual braking system. Earlier cars had a straight airbrake
system with the sole air supply located on the locomotive. Later cars were equipped with reservoirs and valves
operated automatically by variations in air pressure. The first of these was the KC system with triple valve,
auxiliary reservoir, and brake cylinder connected in one unit. In interchange service in the United States, the
AB system has replaced the older KC system. With a modified and more efficient triple valve, it has a dual-
compartment reservoir capable of storing air pressure for emergency application of the brakes. The AB system
has the triple valve, reservoir, and brake cylinder mounted separately. Although main air lines or train lines
must be connected on
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