1
®
SD-05-1269
Bendix
®
ASA-5
™
Automatic Slack Adjuster
DESCRIPTION
The Bendix
®
ASA-5
™
automatic slack adjuster is designed
for use on cam actuated drum brakes of the type in use on
most highway vehicles. Like a manual slack adjuster, the
ASA-5
™
slack adjuster multiplies and transforms the linear
force of the air actuator into a rotational force or torque which
is used to apply the foundation brake. Additionally, the
ASA-5
™
slack adjuster automatically adjusts the clearance
between the brake lining and drum to compensate for wear.
A variety of ASA-5
™
slack adjuster configurations are offered
including both straight arm and 5/8" yoke offset models.
The ASA-5
™
slack adjuster is offered in arm lengths of 5,
5-1/2 and 6 inches and worm gear splines to accommodate
the standard 1-1/4" and 1-1/2" SAE 10C, 24, 28 and 37
tooth splines.
Either of two yoke designs (easy-on and quick connect) in
combination with an external manual adjuster hex provides
for convenient installation and maintenance of the ASA-5
™
slack adjuster. Note: The manual adjuster hex is
intended for use during installation. CAUTION:
Automatic slack adjusters should not be adjusted
manually to correct excessive pushrod stroke.
OPERATION
GENERAL
The automatic adjustment provided by the Bendix
®
ASA-5
™
slack adjuster results in consistent brake lining to drum
clearance and brake actuator stroke. The key to its operation
is the ability to complete the brake adjustment during the
early part of each brake application and to cease adjusting
as resistance to brake cam rotation begins to build. This
aspect of the adjuster mechanism’s operation prevents over-
adjustment caused by lining compression, actuator bracket
deflection, drum and foundation brake component distor-
tion, or brake component wear.
The ASA-5
™
slack adjuster incorporates a clutch-type
adjuster mechanism that continuously adjusts in very small
increments as lining and drum wear occurs. The adjustments
made by the ASA-5
™
slack adjuster are, therefore, not in
specific increments relative to actuator stroke.
BOOT
LINK
LINK PIN
YOKE PIN
YOKE
WORM
GEAR
LUBE
FITTING
FIGURE 1 - ASA-5
™
AUTOMATIC SLACK ADJUSTER
BRAKE APPLICATION
When the brakes are applied, the linear travel of the brake
actuator’s push rod causes the ASA-5
™
slack adjuster to
rotate the foundation brake camshaft which in turn begins
to force the brake shoes into contact with the drum. When
the ASA-5
™
slack adjuster rotates, the yoke assembly pivots
on the yoke pin causing the link to be pulled upward.
The “teeth” on the link mesh with the adjuster mechanism
pinion. As the link is pulled it travels first through its free
play and then causes the pinion to rotate. Rotation of the
pinion is transmitted through the clutch spring to the worm
and shaft. Worm and shaft rotation results in worm gear
rotation which in turn adjusts (or repositions) the brake
camshaft.
When the foundation brake shoes contact the drum, the
camshaft begins to resist rotation and friction between the
worm gear and worm builds, preventing further rotation of
To Next Page
General
