Brakes. Midland Belly/Bottom Dump Trailer 4.6MB, Belly/Bottom Dump Trailer

5.2.8 BRAKES

All components in the brake system must be maintained in good condition for the system to perform at top efficiency. It is recommended that brakes and associated components be checked, serviced and maintained per the Preventative

Maintenance Schedule (PMP) for the trailer. In this section, the basic brake disassembly and assembly procedure will be covered. Refer to the axle manufacturers service manual for a more detailed repair and rebuilding procedure.

Check brakes frequently to keep them in top condition. Poorly maintained brakes will not stop the trailer as effectively as wellmaintained brakes and in the extreme could fail completely leaving no brakes or no ability to stop the unit.

Fig. 67 BRAKE SYSTEM

It is recommended that the driver checks the brakes at least once during each working day when checking tire pressure and performing a quick visual of the unit. Place your hand on each brake drum to check the temperature of the drum. All drums should be approximately the same temperature if the system is functioning properly. If any drum is significantly warmer or colder than the rest, it indicates a problem.

Determine the cause of the problem and correct it before resuming work. By discovering and correcting it while it is a minor issue; major repair, expense and down time can be prevented.

At 25,000 miles (40,000 km) or every 3 months when the axle is raised off the ground for the complete wheel end inspection, check the brakes at the same time. When the wheels are turned by hand, the wheel end should decrease speed slowly. If it does not, the brakes could be dragging or there could be a problem with the bearings. Dragging brakes will also be detected by hot drums during the daily drum temperature checks. Adjust the brakes to correct the problem.

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Remove the brake dust covers

(if so equipped) to access the shoes. Check the thickness of the linings. Reline or replace shoes when the lining thickness is less than 1/8 inch (3 mm).

Uneven wear among the brake shoes on a trailer indicate that the braking system has not been set or maintained properly causing uneven application and wear.

If uneven lining wear appears, reset the system to provide even application of all the shoes. Do not operate when the linings are less than 1/8 inch (3 mm) to prevent the lining anchor rivet or bolts from contacting the drum.

Head contact with the drum will cut grooves in the surface and require extra machining to remove them when rebuilding the brakes.

Fig. 68 EXPLODED VIEW

Several types of friction material are available for use on the brake shoes. Each has its own friction coefficient and braking characteristics. Select the one that best fits your application but do not mix materials on the same trailer. Differing materials require different application forces to obtain the same braking force and a braking system can only apply one force when it is properly set.

Recent changes in environmental laws have banned the use of asbestos including brake linings. Always use the appropriate safety gear when removing brake shoes containing asbestos from your trailer.

Replace the shoes that are equipped with approved material.

Fig. 69 AXLE

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A.

Removing Brakes:

1. Position the trailer on a level hard surface.

2. Exhaust all the air from the air system.

3. Jack the axle up and place on safety stands.

4. Remove the wheel assembly from the axle.

5. Release the slack adjuster (Refer to Section

5.2.6).

6. Disable or cage spring brakes if so equipped.

7. Drain oil from hub and remove spindle end components.

8. Remove the hub and drum assembly.

Support with a hoist as the assembly slides off the spindle. Use a puller if required.

9. Remove roller retaining clip from the bottom and top brake shoe cam rollers.

10. Disconnect and remove bottom shoe return spring.

11. Rotate bottom shoe to remove retaining springs.

12. Lift top shoe to remove.

13. Disconnect push rod from slack adjuster.

14. Back off and remove slack adjuster.

15. Remove cam shaft.

B. Installing Brakes:

1. Inspect all the components. Replace any that are cracked, bent or worn.

2. Lubricate the camshaft spline, slack adjuster gear and slack adjuster pins with anti-seize compound.

3. Install cam shaft and slack adjuster. Secure with snap rings.

4. Adjust slack adjuster to its required angle and attach to the push rod. Release slack adjuster pawl if so equipped.

5. Use a good quality brake grease to lubricate the anchor pins and rollers where they contact the brake shoes.

6. Place the upper shoe in position.

7. Place the lower shoe in position and attach 2 new retaining springs.

8. Rotate lower shoe forward and attach new brake shoe return spring.

9. Install both cam rollers and secure with retainers.

10. Install and secure the remaining wheel and components.

11. Repeat with other wheel ends as required.

12. Tighten all fasteners to their specified torque.

Description

1. Hub-cap bolts

2. Hub fill plug

3. Adjustment nut - manual bearing adjustment (double nut)

4. Jam nut - manual bearing adjustment

5. Brake mounting bolt

6. Two-piece dust shield bolts (shown)

• Forged spider

7. Bolt-on bushing bolts

8. Cam bushing bolts

9. Air chamber nuts

Fig. 70 BRAKE/WHEEL END COMPONENTS

Torque Range

N.m

(lb-ft)

10-15

15-20

Tighten to 100, loosen, tighten to 50, loosen

1/4 turn

250-300

130-165

13-20

20-27

136

68

340-408

177-224

15-20

25-35

25-35

80-125

20-27

34-48

34-48

109-170

Fastener

Size

5/16"

3/8"

Size depends on axle model and ajustment method.

5/8"

3/8"

3/8"

3/8"

5/8"

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5.2.9 SLACK ADJUSTERS

5.2.9.1 HALDEX AUTOMATIC SLACK ADJUSTER

The Haldex S-ABA automatic brake adjuster is a clearance sensing brake adjuster that maintains a nominal distance or clearance between lining and drum.

When the Adjuster is Installed:

With the brake in the released position, the control arm is fixed to the anchor bracket.

The adjustment hex is rotated until the shoes contact the brake drum and then backed off 1/2 turn. When the brake is applied on the first application, the endless rack rotates to the correct position and sets itself.

When the Brake Applies:

When the brake is applied, the adjustment regulator rotates through the normal clearance angle and the shoes contact the drum. The torque increases and the wormshaft is moved axially, causing the coil spring to be compressed and the clutch wheel to disengage. The adjustment components are free to rotate as the brake continues to apply.

When the Brake Releases:

When the brake is released, the torque decreases returning the wormshaft to the clutch wheel and re-engaging the teeth.

The adjustment regulator rotates through the normal clearance angle and the brake is released. If lining wear has taken place the adjustment regulator advances the clutch wheel reducing the excess clearance during the release stroke.

Fig. 71 HALDEX SLACK ADJUSTER (TYPICAL)

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