Air Brake Manual

A brake chamber (11) (14) (32) is a circular container
divided in the middle by a flexible diaphragm. Air
pressure pushing against the diaphragm causes it to
move away from the pressure, forcing the push rod
outward against the slack adjuster. The force
exerted by this motion depends on air pressure and
diaphragm size. If a leak occurs in the diaphragm,
air is allowed to escape, reducing the effectiveness
of the brake chamber. If the diaphragm is completely
ruptured, brakes become ineffective.
Brake Chamber and Slack Adjuster (Brakes on)
Air inlet
Brake chamber
Mounting
bolts
Push rod
Clevis and pin
Slack
adjuster
Front brake chambers (32) are usually smaller than
those in the rear because front axles carry less
weight.
A brake chamber is usually mounted on the axle,
near the wheel that is to be equipped for braking. Air
pressure is fed through an inlet port. The air pushes
against the diaphragm and the push rod. The push
rod is connected by a clevis and pin to a crank armtype
lever called a “slack adjuster.” This converts
the pushing motion of the push rod from the brake
chamber to a twisting motion of the brake camshaft
and S-cams. When the air is exhausted, the return
spring in the brake chamber returns the diaphragm
and push rod to the released position.
As indicated by its name, the slack adjuster adjusts
the “slack” or free play in the linkage between the
push rod and the brake shoes. This slack occurs as
the brake linings wear. If the slack adjusters are not
adjusted within the limitations, effective braking is
reduced and brake lag time is increased. If too much
slack develops, the diaphragm will eventually
“bottom” in the brake chamber, and the brakes will
not be effective.
Diaphragm
Diaphragm return
spring
Ball Indent Slack Adjuster
Manual Slack Adjusters
Positive Lock Slack Adjuster
Lock screw
Locking collar
Adjusting bolt
Worm shaft
Adjusting bolt
Worm gear
Grease fitting
Spline
Spline
17