A. As the air used in the locomotive brake cylinders comes from the main reservoir, for the brakes to be operated on this engine it is necessary that its main reservoir be charged.

119.  Q. With a 70-pound brake pipe pressure, what pressure should be had in the main reservoir when using this device?

A. About fifty pounds.

120.  Q. When the dead engine feature is being used, in what position should the automatic and independent brake valves be carried?

A. Running position.

121.  Q. What should be the position of the brake pipe cut-out cock below the brake valve?

A. It should be closed.

DISTRIBUTING VALVE

122.  Q. What is the duty of the distributing valve?

A. To admit air from the main reservoir to the locomotive brake cylinders when applying the brake, to automatically maintain the brake cylinder pressure against leakage, to develop the proper brake cylinder pressure regardless of piston travel and to exhaust the air from the brake cylinders when releasing the brake.

123.  Q. To what is the distributing valve attached?

A. To the distributing valve reservoir.

124.  Q. How many chambers has the distributing valve reservoir?

A. Two; pressure chamber and application chamber.

[Illustration:  Fig. 8.  Release, Automatic or Independent. 
Connections:  Mr, Main Reservoir Pipe; IV, Distributing
Valve Release Pipe; II, Application Cylinder Pipe; CYLS,
Brake Cylinder Pipe; BP, Brake Pipe.]

125.  Q. Name the different pipe connections to the distributing valve reservoir.

A. Referring to Fig. 8, the connection marked “Mr” is the main reservoir supply pipe; “II”, application cylinder pipe; “IV”, distributing valve release pipe; “BP”, brake pipe; “CYLS”, brake cylinder pipe.

126.  Q. To what do these different pipes connect?

A. The main reservoir supply pipe connects the distributing valve with the main reservoir pipe.  The application cylinder pipe connects the application cylinder of the distributing valve with the independent and automatic brake valves.  The distributing valve release pipe connects the application cylinder exhaust port in the distributing valve with the independent brake valve, and through it, when in running position, to the automatic brake valve.  The brake cylinder pipe connects the distributing valve with the different brake cylinders on the locomotive.  The brake pipe branch pipe connects the distributing valve with the brake pipe.

127.  Q. Explain the operation of the distributing valve when making an automatic service application of the brake.