Air Brake System Parts PDF

# Air Brake System Parts ## Air Compressor - The air compressor pumps air into the air storage tanks. - Can be gear or belt driven. - Can be either air or liquid cooled. - Can be lubricated by engine oil or self lubricating. - Runs the entire time the engine is on, thus it has a governor. ## Go...

# Air Brake System Parts ## Air Compressor - The air compressor pumps air into the air storage tanks. - Can be gear or belt driven. - Can be either air or liquid cooled. - Can be lubricated by engine oil or self lubricating. - Runs the entire time the engine is on, thus it has a governor. ## Governor - Controls when the air compressor pumps air into the tanks. - When air pressure in tanks reaches "cut-out" level, stops compressor from pumping air into tanks. - Once that pressure drops below the "cut-in" level, it allows the compressor to pump air into tanks. ## Air Tanks - Used to store compressed air. - Has drains to drain off water that collects due to the effects of compressing air. - Can be either manually operated or automatic. - Manual drains will either have a pull chord or a twist valve. ### Air Tanks Continued - **Alcohol Evaporator:** Helps to reduce the risk of ice in air brake valves and other parts. Alcohol container must be checked daily to ensure that it will function properly. - **Safety Valve:** Installed into the first tank. It protects the system from being over pressurized should the governor fail. Usually set to open at 150psi. If valve ever pops open, get serviced immediately. ## Brake Pedal - Used to stop the truck. - Supplies pressure to brakes to apply them. - The harder you push, the more pressure is applied. - **NEVER** push your brake pedal with spring brakes set. - Pressing and releasing the brakes a lot reduces the amount of air pressure in the tanks and could cause you to lose too much air to continue driving safely. ## Foundation Brakes - **Drum Brake:** Diagram of a drum brake labeled with: - Brake drum - Brake chamber - Slack adjuster - Adjusting nut - Axle - Return spring - Brake cam - Cam roller - Brake - Brake shoe lining ## Brake Drum, Shoes, and Linings - Located on each end of all axles. - Wheels are bolted to the drums. - Braking components are located in the drum. - Brake shoes or linings are pushed against drum. - Friction is what causes braking to occur. - Friction creates heat which could make your brakes not function properly, preventing you from being able to stop. Use foot brake with caution when going down hill. ## S-Cam Brakes - Pushing in brake pedal supplies air to each brake chamber - Diagram of a s-cam brake labeled with: - Air Chamber - Diaphragm - Return spring - Brake liner - S-Cam - Pushrod - Slack adjuster - Brake drum - Roller - Adjuster - Air pressure pushes the rod out, moving the slack adjuster turning the cam shaft. - This turns the s-cam which then pushes against the brake linings putting them in contact with the break drum. - Releasing the break pedal evacuates the air, thus allowing the s-cam to rotate back and releases the brake linings from the drum. - The harder you push, the more pressure is applied. ## Other Brake Types - **Wedge Brakes:** - Uses a wedge instead of an s-cam. - Wedge is pushed in between the two brake shoes, forcing them into contact with the drum. - Can have a either one or two brake chambers depending on the amount of wedges (either one or two). - May be manual or self adjusting. - Not very common. - **Disc Brakes:** - Air acts upon brake chamber and push rod, just like s-cam, but instead of an s-cam, there is a power screw used. - Air pressure turns the power screw. - Power screw clamps disc between brake lining pads of a caliper. - Not very common. ## Supply Pressure Gauges - All vehicles with air brakes have them. - If the vehicle has a dual system, there will be two gauges or a single one with two needles. (Primary and Secondary) - Tells you how much air is in the tanks. - Application gauge shows how much pressure you're applying to the brake pedal. - Low air warning must come on before tank falls below 55 psi. Usually red light with buzzer. ## Front Brake Limiting Valve - On some pre-1975 trucks - Thought to reduce skidding on slick surfaces. - Turns out it only reduces stopping power. - Front wheel braking is good under all conditions. - Some vehicles have automatic front wheel limiting valves. Not controlled by driver. ## Stop Light Switch - Controlled by air pressure. - Activates brake lights. ## Parking Brake Controls - As pictured. Some older units have levers instead to a button. **Caution:** Never push in brake pedal while the parking brakes are set. This can cause a lot of damage. There is 3500 psi on the brakes when they are set. If you press the brake pedal, then you are supplying air to the brake chambers as an opposing force against the spring brakes. You can cause catastrophic damage to brake system if you do this. ## Dual Parking Control Valves - Some Vehicles such as busses have a separate air tank used to release spring brakes. - Made so you can move the vehicle in an emergency. - Push in valve to use air from separate tank to release spring brakes. - Once you release the button, the spring brakes reapply. - There is only enough air in the tank to do this a few times. So, plan this move carefully. ## Anti-Lock Brakes (ABS) - **When it became required:** - Tractors with air brakes made on or after 3/1/1997 - Other vehicles with AB required after 3/1/1998 - **Malfunction Lights:** - When you turn key, should come on and go right off. - If light stays illuminated, ABS isnt working properly. - **Trailer ABS:** If no ABS light, check for wires near brakes on trailer. Have amber malfunction lights on left rear or front. - **About ABS:** Doesn't shorten following or stopping distance. Designed to prevent wheels from locking up while braking. ## Dual Air Brakes - Two separate brake systems. - One set of controls. - Let pressure build to a minimum of 100 psi before moving. - Low air buzzer and light should go off at a minimum of 55 psi. - Warning should come on if pressure drops at or below 55 psi. ## Inspecting Your Brakes - Please read out of CDL Manual, Section 5, pages 6 & 7 - This section is VERY important so pay very close attention! ## Using Air Brakes - **Normal Stopping:** Push pedal down, control pressure with which you push. Come to a smooth, safe stop. - **Braking with ABS:** BRAKE NORMALLY! Only helps you to avoid a skid by keeping your tires from locking up. - **Emergency Stops:** When someone pulls out in front of you, know what to do. You can use controlled or stab braking. - **Stopping distance:** Takes much longer to stop and unloaded tractor trailer. Continue to next slide for more.