TM 55-203
removed and replaced with a new one. Where a small
must also be inspected, tested, and lubricated. Brakes
chain shaft secured in a bracket fastened to the
found inoperative because of a lack of lubrication will be
underframe is used, a gear on the small shaft meshes
cleaned to permit oil or grease to reach the movable
with a gear on the vertical brake shaft. These gears
parts.
should be inspected for proper mesh, cracked or broken
teeth, and cracked or broken gears. The gears must be
b. Mechanical Causes. When the brakes are
properly fastened to the respective shafts, and the
found to be inoperative because of mechanical causes,
shafts themselves should be secure and not bent,
the defective parts must be removed and replaced.
cracked, or broken. A cracked or broken shaft will
Brakes that cannot be repaired at shop or repair tracks
eventually damage the gears and gear teeth, thus
or those removed from demolished cars should be sent
making the handbrake inoperative. Any damage to
to reclamation points. Parts of one type of brake should
shaft or gears should be immediately remedied by repair
not be used to replace parts of another type.
or by replacement with a new part.
c. Welding or Brazing.
Welding or brazing
f. Connection to Foundation Brake Rigging. At the
mechanical parts of geared handbrakes is prohibited.
point where the handbrake equipment connects to the
However, worn holes or pads on front and rear housing
foundation brake rigging, a little play must be present to
plates may be built up by electric welding to provide a
allow for leverage; free movement while the car is
proper seating for bushings or collars. Bushings may be
moving; and free, easy movement when the handbrake
tack welded to front or rear housing plates to prevent
is applied.
loss or turning and wearing of larger holes in either
plate.
g. Gears and Gear Housing. The gear housing
must be held securely in position on the car. Any
d. Chain.
Vertical and horizontal handbrakes
missing or loose holding parts must be tightened or
chains should be inspected to insure that they are
replaced. The handbrake should be operated to see
securely pinned or anchored at each end to their
whether there is any stiffness or extreme slack in its
respective operating parts Any loose connections should
operation. If there is evidence of either, it must first be
be remedied immediately. Careful inspection should be
determined that the cause is not in some other part of
made to see if handbrake chains or connections are
the equipment. If no ,other defect can be located, the
dragging on car axles, and corrective action taken. The
gearbox should be opened and its parts inspected. Any
constant contact and movement of handbrake chains
badly worn or damaged parts should be replaced. Any
resting on car axles result in chains being worn through,
loose parts should be tightened. Frequently, when
as well as the abrading of axle surfaces. This situation
defects are located in the gear housing, the best
can be dangerous, particularly on tank cars loaded with
procedure is to remove the entire housing from the car,
flammable materials.
install a new housing, and send the defective one to the
shop for repairs.
e. Bellcrank. If the particular handbrake system
employs a bellcrank, the bellcrank must be secure and
h. Safety Appliances. All appliances such as brake
should pivot freely. The bracket holding the bellcrank
steps, hand holds, brake wheels, ratchet pawls, etc.,
must also be secure. If the bellcrank is bent, it might
required for the safe and proper operation of handbrake
possibly be straightened without impairing its operating
equipment must be inspected frequently. Any defects
efficiency. However, if the bend is pronounced or if the
must be remedied immediately.
bellcrank is cracked or broken, the crank must be
Section III. AIRBRAKES
resisted by the friction of the wheel on the rail, caused
8-7.
Principles of the Airbrake System
by the load or weight on the wheel. The AB freight
brake equipment is used on freight cars operating in
a. General. The term airbrake refers to the type of
interchange in the United States. On oversea railroads,
brake in which compressed air is used to cause the
single-capacity, (K type) freight car brake equipment
brakeshoe pressure. Airbrakes are used (in rail service)
(some cars have no airbrakes) and vacuum brake
to prevent the movement of cars or locomotives, and
equipment are the most common types of equipment.
when in motion, to control the speed or stop them as
Personnel who have anything to do with train handling
desired. These results are obtained through the friction
and the maintenance of equipment,
or holding force resulting from pressing the brakeshoes
against the wheel tread or disc faces, which in turn is
8-9
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