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(last edited July 19, 2005) Front Page | Recent Changes | Title Index | User Preferences | Random Page | HelpThe means by which the train brakes are controlled. On the classic air brake, the driver's brake valve has five positions: Release and Charging, Running, Lap, Application and Emergency. In "Release and Charging" the brake pipe is supplied with air from the main reservoir and the pressure rises to release the brakes and recharge the auxiliary reservoirs. In "Running", the brake remains released but a feed valve, attached to the driver's brake valve, is connected between the main reservoir supply and the brake pipe. This valve holds the brake pipe release pressure against any small leaks in the pipe.
The "Application" position drains air from the brake pipe to apply the brakes. "Lap" is selected when the brake pipe air has fallen to the level required by the driver to give the application he wants. In this position the connection between the brake pipe and the brake valve is closed. In the "Emergency" the brake pipe air is dumped through a large opening in the valve so the air exhausts more quickly than with a normal application. For more details, see Air Brakes.
The electro-pneumatic brake will also have a driver's brake valve if the air brake is provided as well. Electrical connections are added to the operating spindle so that movement of the handle can operate either brake. Later e-p systems with no brake pipe use what is called a "brake controller", which is simply an electrical controller to change the switch connections to the train control wires as required.
