Great Dane Champion CP Panduan Pemeliharaan - Halaman 7

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parking brakes

All axles (except some converter dolly axles) are

equipped with air/spring actuators. Each actuator is

separated into two units. The base unit applies the

service brakes. The top unit contains a coil spring that

must be compressed by air within the chamber to

release the parking brakes. Loss of air pressure in the

supply line to the brake chamber will automatically

apply parking and/or emergency braking.

In case of a service brake system air failure, when the

spring brakes are applied in an emergency stop, a

spring brake air reservoir retains enough stored air to

release the spring brakes at least once by means of the

tractor parking brake control.

In the absence of air pressure, a manual release is pro-

vided to allow release of the spring brake (see following

instructions).

To manually release parking brake actuators:

1. Always position wheel chocks at both front and rear

of tires before manually releasing parking brakes.

2. A parking brake release tool may be stored in a

pocket on the side of the brake chamber. (See

photo.)

brake balance

Differences in crack pressures on hold-off valves on

tractors and trailers can lead to air pressure imbalances

that cause the trailer brakes to do a majority of the

braking. Another contributing factor to premature trailer

brake wear is torque imbalances created by differences

in brake linings.

These imbalances can lead to greatly reduced trailer

brake lining life, trailer brake drum heat checking, heat

cracking and breakage.

The air pressure imbalance typically ranges from 4 to 6

psi between the tractor and trailer. The trailer industry

has been using 4 to 5 psi crack-pressure air valve

systems and tractor manufacturers in some cases

are using 8 to 10 psi hold-off valves.

This imbalance will cause the trailer to do nearly all the

braking in low-air pressure applications. And because

3. Insert the detachable release bolt through hole in

head. Turn the release bolt clockwise until it stops

and locks, then pull the release bolt out as far as

possible, and run the nut down, holding the bolt in

place.

Using a hand wrench, turn the release bolt nut

clockwise until the bolt extends about three inches.

Make sure the release bolt is locked properly in the

piston.

The parking brake coil spring is now caged.

danger

DO NOT operate your trailer with parking

brakes caged or in any other way disabled.

Never attempt to open a brake actuator. The

internal spring is very dangerous. Do not repair

spring brakes. Discard only by using proper,

approved procedures. If this procedure is not

known, contact the actuator manufacturer or

Great Dane Trailers before removing the actua-

tor from the trailer. Never operate the trailer

with the end-cover cap removed.

warning

FMVSS-121 revisions made mandatory 10-8-92

require air system supply lines to be protected

to at least 70 psi. The 70 psi (multifunction)

emergency air valves require that tractor air

compressor governors be set at 105 psi

(minimum) to assure full release of the trailer

parking brakes.

most normal braking is done at air pressure applications

of 10 to 15 psi, this means that routinely, the trailer

brakes are the ones that are stopping the vehicle in

all but the hardest braking.

One simple way to see if an imbalance situation exists

is to use a duplex gauge that measures air pressures at

the coupler and the actuator air chamber. This will show

if there is an imbalance situation between the tractor

and the trailer.

Another method is to use a special balance kit such as

the ones available from the major brake manufacturers.

The balance kits include gauges to check air pressures

in the trailer chambers, the tractor chambers and at the

coupler, and electronically compares them. Industry

standards recommend the tractor and trailer should be

within 1 and 2 psi.

This detailed check takes about two and one-half hours.

It's important to check a representative tractor and trailer

each time you order equipment.

oil seals and hub caps

OIL SEALS

Oil seals vary in design and installation. Refer to the

seal manufacturer's manual for proper installation with

proper tool.

To insure leak-free operation replace oil seals each time

you remove a hub. Never reuse seals, even if they show

no signs of leakage.

HUB CAP INSTALLATION

1. Clean the hub cap and the face of the hub.

2. Position the gasket.

wheel bearings

ADJUSTMENT

For maximum bearing life, adjust and lubricate bearings

properly at regular intervals depending upon trailer

speeds, loads, and general operating conditions.

1. Clean bearings, hub, and seals.

2. Replace any worn or damaged parts.

3. Pack hub and bearings with specified lubricant.

4. Assemble bearings and hub on axle sleeve.

5. Install thrust washer if used.

6. Install wheel bearing adjusting nut. Thread nut

against bearing or thrust washer as you rotate

wheel. Be sure there is sufficient clearance between

brake shoe and drum so brake shoe drag will not

interfere with bearing adjustment.

7. Tighten adjusting nut to 50 lb-ft torque while you

rotate hub in both directions to be sure all bearing

surfaces are in contact.

8a. For axles that have single-nut construction, back off

adjusting nut 1/8 to 1/6 turn. Cotter pin (or lock) nut

in place.

8b. For axles that have double-nut lock construction,

back off adjusting nut 1/6 to 1/4 turn. Assemble

wheel bearing nut lockwasher.

A) For assemblies using a bending type lockwasher,

tighten jam nut with torque wrench

as follows:

Torque Lb-Ft

Nut Size

Minimum

Maximum

1-1/8" to 2-5/8"

100

150

2-5/8" and over

100

200

Bend lockwasher over both adjusting and jam nuts

to complete the assembly.

Keeping an eye on your brake service records will also

flag imbalance problems. If you are seeing 300,000

miles on tractor linings and 70,000 miles on trailer

linings, there's obviously an imbalance problem.

NOTICE:

Never reuse a gasket.

3. Install the hub cap. If you are installing a transpar-

ent hub cap, install the reinforcing ring on the out-

side. Install the capscrews and lockwashers. When

installing a transparent hub cap, do not tighten to

exceed 15 lb-ft torque.

4. Remove the fill plug and pour oil to the level

specified on the cap. Allow sufficient time for the

oil to seep into the hub cavity and recheck.

B) For assemblies using a dowelled adjusting nut

and pierced lockwasher, tighten jam nut with a

torque wrench as follows:

Torque Lb-Ft

Nut Size

Minimum

Maximum

1-5/8" to 2-5/8"

200

300

2-5/8" and over

250

400

9. For single nuts with lock features built into the nut

(ie. Pro Torque, Axilok), refer to the vendor

maintenance manual.

10. Keep the resulting end play within limits of .001"

to .003".

NOTICE:

Remove the set screw lock device in the

serrated nut prior to attempting jam nut removal.

Make sure to replace allen screw to prevent torque

loss. Never use hammer and chisel to remove

axle nuts.

warning

Failure to back off the inner adjusting nut could

cause bearing and axle spindle overheating or

damage, which could result in the wheel locking

up or coming off during vehicle operation.

warning

Failure to torque the outer lock nut properly

could cause the wheel to come off during

vehicle operation.