Great Dane Champion CP Manual de manutenção - Página 6
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Imprimir páginabrake care and adjustment
The trailer brake system will perform safely and
efficiently only as long as it is properly maintained
and not abused. Trailer brakes should be inspected
frequently in connection with a Trailer Preventive
Maintenance (TPM) Program. Out-of-adjustment brakes
can cause increased stopping distance, shorter brake
component life, and a greater tendency for the trailer
to jackknife.
warning
Prior to performing maintenance on any air
brake system component, chock the wheels.
The system air pressure should be exhausted
by opening the reservoir drain cocks.
AIR SYSTEM AND BRAKE OPERATION
Proper operation of the brake systems requires a
firm seal between the air brake couplers. Inspect the
couplers for seal damage and cracked housings. Some
couplers are equipped with filters. These filters must be
cleaned at regular intervals to prevent malfunction of
the brake systems. Inspect the air hoses for cracking
and for frayed connections. Be sure air hoses are not
rubbing on any metal surface or each other. Replace or
repair damaged components.
Keep the air system clean. All air tanks should be drained
daily to remove moisture and other contaminants. See
Freezing Weather Maintenance.
Some air valve manufacturers discourage the use of air
line antifreeze. Use may result in deterioration of seals
in these valves.
If you use Teflon tape or other thread sealers to seal
threaded connections in your air lines, be careful not
to allow pieces of the sealer to enter the air system.
It can clog passages into the valves and cause them
to malfunction.
Keep the air system tight. The air system cannot be
charged properly if there are leaks in reservoirs, lines,
hoses, or valves. Always check the tractor pressure
gauge for unusual drops or extended buildup times.
Run the tractor engine until the air brake system
pressure gauge shows at least 105 psi. Listen for air
leaks. With the engine off, check the gauge reading
with no brakes applied. The gauge reading loss should
not exceed three psi in one minute.
With the engine still off, apply the brakes fully for two
minutes. The gauge reading drop should not exceed
four psi in one minute.
With engine still off, slowly open drain cocks in the
trailer's air tanks and allow the pressure to drop gradually.
In a system employing spring brake control valves, the
spring brakes should function and apply the brakes.
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In a system that does not employ spring brake control
valves, the relay emergency valve should function and
apply the brakes.
warning
Serious air leaks in the trailer's braking system
are hazardous conditions that require the trailer
to be placed out of service until they are
properly corrected.
A schedule for periodic cleaning, inspection, adjustment
and lubrication of brake equipment should be estab-
lished by the operator, based on past experience and
severity of operation.
BRAKE SHOES
Brake shoe designs vary, depending on the type of
brake and brake manufacturer. Some brakes require
special tools. If you have problems removing brake
shoes, refer to the brake manufacturer's manual.
BRAKE SHOE SPRINGS
Replace weak or unmated brake shoe springs whenever
they cause pulling or dragging brakes. The springs are
constantly expanding and contracting in the confined
hot area of the brake drums. Excessive heat during
expansion will cause them to weaken.
BRAKE LINERS
The certified Gross Axle Weight Rating (GAWR) in many
cases is determined by the friction level of the brake
liners. The friction level is determined by the axle and
vehicle manufacturer to provide the required brake
torque as prescribed by governmental regulations.
NOTICE:
When replacing liners, be sure to use
liners with the same friction level as those removed
from the trailer so that the GAWR is not reduced.
REFACING DRUM
It is not a good practice to reface brake drums. Refacing
can weaken the drums, making them unable to dissipate
all the heat generated by brake applications, and making
them susceptible to distortion and heat cracks.
If brake drums must be refaced on cam-type brakes,
when oversized linings are used, precautions regarding
cam travel should be checked to prevent sticking cams
or cam rollover. This problem often exists when the
linings become worn. It may be necessary to install
oversized rollers to prevent this problem.
OVERSIZE LINERS
To compensate for material removed when refacing
brake drums, X (1/16" oversize) and XX (1/8" oversize)
liners are furnished by the lining manufacturers. When
oversize liners are used the drums should be machined
in increments of 1/16" (radius increased 1/16").
warning
Enlarging the drum diameter may permit the
cam to rotate beyond its maximum lift when the
lining becomes worn. This can result in sticking
cams or cam rollover.
To avoid this condition and to obtain maximum
lining wear, oversize roller cam followers or
wear plate shims (depending on the brake
design) should be installed when the liners
become approximately 50% worn.
BRAKE SHOE ROLLER CAM FOLLOWERS
Roller cam followers are available in four sizes, each
having been designed for a specific purpose.
STANDARD SIZE (1.250")
Standard rollers are used when installing standard
lining with standard drums, X lining with 1/16" oversize
drums, or XX lining with 1/8" oversize drums.
If the drums have been refaced and oversize rollers later
installed, the oversize rollers must be removed and
standard rollers installed when the new liners are
installed.
1/8" OVERSIZE (1.375")
Use 1/8" oversize cam followers when you install
standard liners with worn or trued drums that are 1/32"
oversize. Circle grind the liners a few thousandths less
than the drum diameter.
brake adjusters
AUTOMATIC ADJUSTERS
Several different brands of automatic adjusters are
common. Because adjustment differs, refer to the
maintenance and adjustment information from the
manufacturer.
Some automatic slacks are equipped with an adjust-
ment pawl which eliminates loss of adjustment. This
pawl must be removed prior to backing off on the
adjustment to prevent damage to the splined pawl
and adjusting screw.
1/4" OVERSIZE (1.500")
Use 1/4" oversize cam followers when X liners have
been installed with 1/16" oversize drums and standard
rollers. The standard rollers should be removed and
1/4" oversize installed before the lining becomes worn
to the point when the brake cam is no longer effective.
1/2" OVERSIZE (1.750")
Use 1/2" oversize cam followers when XX liners and
1/8" oversize drums have been used. The standard
rollers should be removed when the liners become
approximately 50% worn, and 1/2" oversize rollers
should be installed.
CAM PLATE SHIMS
When standard liners are installed with worn or trued
drums, or when X or XX liners have been installed and
are approximately 50% worn, shims or a combination of
shims should be installed under each of the cam wear
plates to permit the cam to be returned to the full
release position. Shims are available in 1/64", 1/32" and
1/16" thicknesses.
BRAKE DUST SHIELDS
The brake spiders used for mounting the brake shoe
assembly parts also become the mounting for optional
dust shields.
The use of dust shields should be determined by
conditions encountered by the trailer. Operations in
mud, sand, dirt, water, and other forms of foreign
materials should be the governing factors. When these
conditions exist during winter months and maximum
cooling is desirable during summer months, dust
shields are easily installed or removed.
NOTICE:
Failure to use dust shields during months
where gravel chips, etc., are used on roads may
allow drums to be scored by these materials. Dust
shields may provide the desired protection.
NOTICE:
Automatic adjusters may seem to be
over-adjusting and may seem to be more sensitive
until brakes are properly burnished.
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