s here that air is stored for use in all air operated devices on
the locomotive, except the brake.

37. Q. Explain the operation of the parasite governor.

A. The operation of this governor is much the same as the compressor
governor, and differs only in that the supply valve is open when it is
in its lower position.

38. Q. At what pressure is the regulating spring adjusted?

A. About fifteen pounds.

39. Q. What pressure is required in the main reservoir before air is
admitted to the parasite reservoir?

A. At least fifteen pounds above that in the brake pipe.

40. Q. What pressure is obtained in the parasite reservoir?

A. The same as that in the main reservoir, when the main reservoir
pressure is fifteen pounds greater than that in the brake pipe.

41. Q. What will prevent the charging of the parasite reservoir, and
what should be done?

A. This may be caused by the feed valve being improperly adjusted,
sticking in open position or leakage of main reservoir air past the
valve to the feed valve pipe and governor top.

=WESTINGHOUSE 9-1/2 OR 11-INCH COMPRESSOR=

42. Q. What is the duty of the air compressor?

A. To furnish the compressed air used in the operation of the brakes,
and all other air operated appliances on both locomotive and cars.

43. Q. Explain the operation of the steam end of the compressor.

A. When steam is turned on at the boiler it flows through the steam pipe
and governor, entering the compressor at the steam enlet, then through
the steam passage "a" to the reversing valve chamber "C" also to the
main valve chamber "A" between the differential pistons 77 and 79. The
area of the piston at the right being greater than the one at the left,
the main valve is moved to the right, (See Fig. 2) admitting steam to
port "b" which leads to the lower end of the steam cylinder; steam is
now free to flow under the main piston, forcing it upward. When the
piston has almost completed its upward stroke, the reversing plate 69 on
top of the piston 65 engages a shoulder on the reversing rod 71, moving
the rod and reversing valve 72 upward (See Fig. 3). The upward movement
of the reversing valve closes the ports "f" and "h" and opens port "g";
thus permitting steam to enter the chamber at the right of the large
piston 77, balancing the pressure on this piston, and the pressure
acting on the right side of the small piston 79--the chamber at the left
being open to the exhaust--will force the m