Bendix Commercial Vehicle Systems DOUBLE ANCHOR PIN CAM BRAKE 5/04 User Manual

Bendix® Double Anchor Pin Cam Brake

SD-22-3260

FIGURE 1

GENERAL DESCRIPTION

The Bendix 16-1/2” x 7” double anchor pin cam brake is designed for use on heavy duty highway vehicles. It is a mechanically actuated, leading /trailing shoe brake with a fixed position cam and anchors.

The brake consists of two fabricated steel shoe assemblies individually anchored to a cast iron torque spider and actuated by a single forged cam shaft. T wo retaining springs secure the shoe assemblies to their respective anchor pins. The twin webs of each shoe assembly engages the anchor pin on one end and the cam roller on the other. A single shoe to shoe return spring is used to maintain constant contact between the shoe, cam roller and cam.

OPERATION

The Bendix cam brake operates in the following manner during a braking application. The force of the push rod of the actuator is converted from a linear force to a rotary torque. This is accomplished by use of the slack adjuster . This torque is transferred to the cam shaft of the foundation brake due to the spline of the cam shaft being connected to the gear of the slack adjuster. On the opposite end of the cam shaft is the S-Cam which when rotated lifts the cam rollers. This spreads the brake shoe ends apart and pivots the shoes about the anchor pin so the brake lining comes in contact with the rotating brake drum. The friction created by the lining pressure against the drum generates the torque necessary to provide a retarding force to slow down the vehicle. The energy of the vehicle in motion is converted to heat at the surface of the drum and lining. The heat raises the temperature of the drum. The heat is stored in the drum and finally dissipated to the air.

FIGURE 2 - 16-1/2” DOUBLE ANCHOR PIN S-CAM BRAKE

Key No. Description Qty.

1 Snap ring 1 2 Spacer washers #reqd. 3 Yoke pin 1 4 Slack adjuster 1 5 Yoke 1 6 Cotter pin 1 7 Washer 1 8 Grease seal 2

9 Bushing 2 10 Cap screw 4 11 Lock washer 4 12 Actuator bracket and cam tube 1 13 Brake shoe assembly 2 14 Cam roller 2 15 Cam roller bushing 2

Key No. Description Qty.

16 Anchor pin 2 17 Anchor pin bushing 2 18 S-Cam shaft 1 19 Cam head washer 1 20 Shoe return spring 1 21 Spring retainer pin 2 22 Anchor spring 2 23 Dust shield 2 24 Rubber inspection plug 2 25 Cap screw 6 26 Star washer 6 27 Actuator 1 28 Nut 2 29 Washer 2 30 Sealing Ring 1

PREVENTIVE MAINTENANCE

1. BRAKE ADJUSTMENT Weekly , or whenever push rod stroke exceeds maximum

distance listed on the following chart. For complete adjustment information, see Bendix Service Data Sheet SD-05-1.

Full Pressure

Ser- Service Max. Max. Stroke

vice Diaphragm Stroke at which Act- Effective With Brakes

uator Area Outside Max. Brakes Should Be

Type (Sq. In.) Diameter Stroke Adjusted Readjusted

short as

possible

without 24 24 7-7/32 2-1/4 brakes 1-3/4 30 30 8-3/32 2-1/2 dragging 2

2. BRAKE LUBRICA TION Grease camshaft bracket with vehicle manufacturer’s

recommended chassis lube. Lube once every six months or at each chassis lubrication.

3. BRAKE RELINE The life of the brake lining is dependent on many factors

such as the material of the lining, type of operation the vehicle is used for, and the driver of the vehicle. If driving conditions require frequent braking, lining replacement will be required more often. Reline when lining thickness at center of shoe is 1/4”. Refer to section “Reline Procedure”.

4. BRAKE OVERHAUL As often as necessary to maintain adequate brake

performance. NOTE: When overhauling brake system, provide equal service to all drive axle brakes on the vehicle.

WARNING! PLEASE READ AND FOLLOW THESE INSTRUCTIONS TO AVOID PERSONAL INJURY OR DEATH:

When working on or around brake systems and components, the following precautions should be observed at all times:

1. Park the vehicle on a level surface, apply the

parking brakes, and always block the wheels. When working around or under the vehicle, stop the engine and remove the key from the ignition. Always keep hands away from chambers as they may apply as system pressure drops. Always wear safety glasses.

2. When working in the engine compartment, the

engine should be shut off and the ignition key should be removed. Where circumstances require that the engine be in operation, EXTREME CAUTION should be used to prevent personal injury resulting from contact with moving, rotating, leaking, heated or electrically charged components.

3. Do not attempt to install, remove, disassemble or assemble a component until you have read and thoroughly understand the recommended procedures. Use only the proper tools and observe all precautions pertaining to the use of those tools.

4. Following the vehicle manufacturer’s recommended procedures, deactivate the electrical system in a manner that safely removes all electrical power from the vehicle.

5. If the vehicle is equipped with an air over hydraulic brake system or any auxiliary pressurized air system, make certain to drain the air pressure from all reservoirs before beginning

ANY work on the vehicle. If the vehicle is equipped with an AD-IS air dryer system or a dryer reservoir module, be sure to drain the purge reservoir.

6. Never connect or disconnect a hose or line containing pressure; it may whip. Never remove a component or pipe plug unless you are certain all system pressure has been depleted.

7. Never exceed manufacturer’s recommended pressure.

8. Never attempt to disassemble a component until you have read and understand all recommended procedures. Some components contain powerful springs and injury can result if not properly disassembled. Use only proper tools and observe all precautions pertaining to use of those tools.

9. Use only genuine Bendix® replacement parts, components and kits.

A. Use only components, devices and mounting

and attaching hardware specifically designed for use in hydraulic brake systems.

B. All replacement hardware, tubing, hose,

fittings, etc. must be of equivalent size, type and strength as the original equipment.

10. Components with stripped threads or damaged parts should be replaced rather than repaired. Do not attempt repairs requiring machining or welding unless specifically stated and approved by the vehicle and component manufacturer.

11. Prior to returning the vehicle to service, make certain all components and systems are restored to their proper operating condition.

™

FIGURE 3 - REMOVING CAM ROLLERS

FIGURE 4 - REMOVING SHOE RETURN SPRING

FIGURE 6 - REMOVING SLACK ADJUSTER

FIGURE5 - REMOVING SHOES

FIGURE 7 - REMOVING ACTUA TOR BRACKET

PREP ARATION

1. Park vehicle on a level surface and prevent movement by means other than the brakes.

2. If equipped with spring brakes, cage the spring on all axles to be worked on.

3. Drain air from all reservoirs.

4. Raise the axle, to be worked on until the tires clear the ground.

5. Turn the slack adjuster adjusting screw in the opposite direction used to adjust the brakes until the cam rollers return to the start position on the S-cam.

6. Remove wheels and drums using the procedures specified in the vehicle maintenance manual.

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