the accelerated emergency release function.
automatically releases the brake by reducing auxiliary
b. AB-1-B Control Valve (used with AB-1-B brakes)
(3) Rapid recharge. A rapid increase of brake
(1) The AB-1-B control valve is the same as the
standard AB control valve except for the addition of a
pipe pressure is obtained when release is started by
filling with selector valve portion and longer emergency
using the emergency reservoir (which remains fully
portion bolting studs. The filling piece is bolted on
charged during a service application).
between the pipe bracket and the emergency portion.
(2) A safety valve is provided on the selector
emergency during service application is eliminated by
valve portion which limits brake cylinder pressure for
separation of the parts controlling the service and
severe brake applications, but is closed off from the
brake cylinder in emergency. The proper setting for the
safety valve is 60 pounds.
Emergency brake cylinder pressure approximately 20
(3) A connection is made from the signal line to
percent higher than that obtainable from a full service
the filling piece which automatically adjusts the selector
valve for either passenger or freight service. When
operated in passenger service, signal pressure
(6) Speed of emergency. Speed of emergency
automatically adjusts the selector valve to provide a
through the train is approximately 40 percent faster than
direct build-up of emergency brake cylinder pressure.
the former standard freight brake.
(4) When operated in freight service, the
(7) Development of emergency pressure.
absence of signal line pressure automatically adjusts the
Development of emergency brake cylinder pressure in
selector valve to provide the standard three-stage
steps at a controlled rate prevents damaging shocks.
development of emergency brake cylinder pressure.
Emergency pressure is available at all times.
(5) In service braking the operation of this equipment is
b. AB-1-B Freight Brake. The AB-1-B brake is the
the same as the AB equipment.
same as the standard AB brake equipment with the
addition of a filling piece with a selector valve portion,
c. A-2-A Quick-Service Valve (When Equipped).
which is applied between the pipe bracket and
The A-2-A quick-service valve (fig 8-10) insures prompt
emergency portion of the AB control valve. The service
brake pipe reduction and positive brake application.
and emergency portions are standard in all respects to
the AB control valve, but the studs holding the filling
piece and emergency portion to the pipe bracket are
longer than standard.
(1) The brake cylinders are equipped with a
piston and rod connected through the brake levers,
AB and AB-1-B Brake System Components
brake rods, and brakeshoes. When the piston is forced
outward by the air pressure, force is transmitted through
The components for both the AB and AB-1-B brake
the rods and levers applying the brakeshoes to the
systems are the same unless otherwise noted:
wheels. A release spring forces the piston to the release
position when air pressure is exhausted from the
a. AB Control Valve (used with AB brakes). The
opposite end of the cylinder. A packing cup presses
AB valve (fig. 8-9) consists of the following components:
against the cylinder walls and prevents the escape of air
past the piston.
pipe bracket, which is permanently
mounted on the car and carries the pipe connections so
(2) Periodic cleaning, oiling, and testing of the
that no pipes need to be disconnected to remove a
brake cylinder is performed without removing the
valve portion. It also contains a removable hair strainer
cylinder from the car.
to keep foreign matter out of the valve portions.
e. Combined Auxiliary and Emergency Reservoir.
(2) The service portion, which controls the
The auxiliary and emergency reservoirs are combined
charging of the reservoirs and the service application
and release of brakes.
compartments. One serves as storage for auxiliary air
pressure and the other for
(3) The emergency portion, which controls the
quick-action feature, high brake cylinder pressure, and