Air Brakes and Train Handling Rules - Alaska Railroad

67 Car Equipment and Components67.9.1 Auxiliary ReservoirThe auxiliary reservoir provides compressed air for all service braking.67.9.2 Emergency ReservoirThe emergency reservoir provides an additional supply of compressedair during an emergency brake application. This additionalair to the brake cylinder increases brake cylinder pressure above fullservice by approximately 20 percent.67.10 Brake CylinderThe brake cylinder is a cast metal cylinder with a piston connected torods and levers. When brake cylinder pressure is present, the pistonmoves out and applies the brakes by forcing the brake shoes againstthe wheel.When brake cylinder pressure is released, a return spring in the brakecylinder moves the piston back into the brake cylinder, releasing thebrakes.67.11 Retaining ValvesThe retaining valve on each car controls brake cylinder pressureexhaust. All freight cars have retaining valves located at the “B” endof the car or at the side near the control valve.The retaining valve can be positioned to function as follows during abrake release:• Allow the exhaust of brake cylinder pressure to atmosphere• Retain brake cylinder pressure while the system is recharged67.11.1 Three-Position Retaining ValveThe three-position retaining valve includes these positions (seeFigure 67-F):67-10 ARRC Air Brakes and Train Handling Manual June 1, 1996