flow filtering, which passes all the oil through the filter; and bypass filtering where only a part of the oil
is continuously bypassed through the filter. Full-flow filters have relief valves that can open to take the
oil out of the filter's path when the pressure drop across the filter is excessive.
Air, supplied by an air compressor, is used to operate brakes on military diesel-electric
locomotives. The airbrake system is made up of a compressor to supply air, two main reservoirs to cool
and store it, and a governor to control the compressor's pumping. It also consists of the brake cylinders,
mechanical linkage, and valves. Pistons and rods of the brake cylinders are connected through the brake
levers to the brakeshoes. Air pressure forces the pistons outward and transmits the force through the
rods and levers to the brakeshoes and applies them to the wheels.
Several kinds of airbrakes are used on diesel-electric locomotives and a clear distinction must be
made among them. Controlled by levers from the operator's cab, airbrakes are automatic, independent,
or a combination of the two. On locomotives used in foreign service, a vacuum brake system is used.
a. Automatic brakes control both locomotive and train. Pressure is maintained in the brake pipe
the entire time the train is operating. Reducing pressure applies the brakes and returning it to normal
releases them. On each car in the train, an auxiliary reservoir holds air for the brake cylinders. The air
in the cylinders is used to activate the brake linkage.
b. Independent brakes control only the locomotive. They are used generally for yard switching
service and for trains of a few cars because car brakes don't operate, resulting in rough operation and
c. Both independent and automatic brakes are sometimes used so that greater control is
possible. The two systems are completely separate and have separate controls.
d. In vacuum brake operation, the compressed-air brake pipe is cut out and the vacuum brake
valve connected. The locomotive and train automatic brakes are then controlled by the vacuum brake
valve and the independent brake by the independent brake valve handle. Military railway switchers and
other diesel-electric locomotives in the military fleet designed for foreign service have