Podcast
Questions and Answers
Air brakes use ____ to make the brakes work.
Air brakes use ____ to make the brakes work.
compressed air
The ____ brake system applies and releases the brakes when you use the brake pedal during normal driving.
The ____ brake system applies and releases the brakes when you use the brake pedal during normal driving.
service
The _____ brake system applies and releases the parking brakes when you use the parking brake control.
The _____ brake system applies and releases the parking brakes when you use the parking brake control.
parking
The ______ brake system uses parts of the service and parking brake systems to stop the vehicle in a brake system failure.
The ______ brake system uses parts of the service and parking brake systems to stop the vehicle in a brake system failure.
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What does the air compressor do?
What does the air compressor do?
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The air compressor is connected to the engine through ________.
The air compressor is connected to the engine through ________.
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How may the air compressor be cooled?
How may the air compressor be cooled?
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If the compressor has its own oil supply, what must you be sure to do?
If the compressor has its own oil supply, what must you be sure to do?
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What does the air compressor governor do?
What does the air compressor governor do?
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What do the air storage tanks do?
What do the air storage tanks do?
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What level is the 'cut-out' level?
What level is the 'cut-out' level?
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What is the 'cut-in' level?
What is the 'cut-in' level?
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The number and size of air tanks varies among vehicles. The tanks will hold enough air to allow the brakes to be used several times even if the compressor stops working.
The number and size of air tanks varies among vehicles. The tanks will hold enough air to allow the brakes to be used several times even if the compressor stops working.
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Why is water and compressor oil in compressed air bad for the air brake system?
Why is water and compressor oil in compressed air bad for the air brake system?
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What does the alcohol evaporator do?
What does the alcohol evaporator do?
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If the safety valve releases air, what should you do?
If the safety valve releases air, what should you do?
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To stop, the brake shoes and linings are pushed against the inside of the drum.
To stop, the brake shoes and linings are pushed against the inside of the drum.
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What is the most common kind of foundation brake?
What is the most common kind of foundation brake?
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What do supply pressure gauges do?
What do supply pressure gauges do?
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What does the application pressure gauge do?
What does the application pressure gauge do?
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If you are driving an older vehicle with a front brake limiting valve, which position should the control be in?
If you are driving an older vehicle with a front brake limiting valve, which position should the control be in?
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Tractor and straight truck spring brakes will come on when the air pressure drops to what range?
Tractor and straight truck spring brakes will come on when the air pressure drops to what range?
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When the spring brakes are on, what should you not do?
When the spring brakes are on, what should you not do?
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All vehicles with air brakes must have a low air pressure warning signal.
All vehicles with air brakes must have a low air pressure warning signal.
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Front wheel brakes are good under all conditions.
Front wheel brakes are good under all conditions.
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Before driving a vehicle with a dual air system, what should you be sure to do?
Before driving a vehicle with a dual air system, what should you be sure to do?
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When should the warning light and buzzer come on?
When should the warning light and buzzer come on?
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A dual air brake system has two separate air brake systems which use a single set of brake controls.
A dual air brake system has two separate air brake systems which use a single set of brake controls.
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If a vehicle has air brakes, you still only need to follow the seven-step inspection procedure.
If a vehicle has air brakes, you still only need to follow the seven-step inspection procedure.
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What is the most common problem found in roadside inspections?
What is the most common problem found in roadside inspections?
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Study Notes
Air Brake System Overview
- Air brakes utilize compressed air for operation.
- There are three main brake systems in air brake setups:
- Service brake system: Engages brakes via the brake pedal during normal driving.
- Parking brake system: Activates parking brakes with a dedicated control.
- Emergency brake system: Utilizes components from both service and parking systems to stop the vehicle in case of a failure.
Air Compressor Functionality
- The air compressor is responsible for pumping air into storage tanks (reservoirs).
- It connects to the engine via gears or a v-belt.
- Types of air compressors include:
- Air cooled
- Engine cooling system
- Ensure oil levels are checked before driving if the compressor has a separate oil supply.
Air System Controls
- The air compressor governor regulates the operation of the air compressor, allowing pumping when pressure falls to the "cut-in" level (approximately 100 psi) and stopping at the "cut-out" level (around 125 psi).
- Air storage tanks are crucial for holding compressed air, and their size varies among vehicles, providing enough air for several brake applications if the compressor fails.
Importance of Air Quality
- Compressed air can contain harmful water and compressor oil, which could freeze and lead to brake failure in cold conditions.
- The alcohol evaporator injects alcohol into the air system to mitigate ice formation in brake components.
Brake Operation and Components
- When braking, shoes and linings press against the drum for effective stopping.
- The S-cam type is the most common foundation brake.
- Supply pressure gauges indicate the amount of pressure in air tanks, while application pressure gauges show the air pressure being applied to the brakes.
Vehicle Safety Features
- Vehicles must have a low air pressure warning signal to alert the driver when pressure is insufficient.
- In older vehicles equipped with a front brake limiting valve, the control should typically be set to normal when driving.
Spring Brakes Activation
- Tractor and straight truck spring brakes engage when air pressure drops to 20 to 45 psi.
- Do not press the brake pedal when the spring brakes are activated to prevent damage.
Dual Air Brake Systems
- A dual air brake system contains two distinct systems operated by one set of controls, requiring that the air compressor builds a minimum of 100 psi pressure in both systems before driving.
- Warning signals activate when air pressure falls below 60 psi in either primary or secondary systems.
Inspection and Maintenance
- The most prevalent issue in roadside inspections is out-of-adjustment brakes.
- Vehicles with air brakes require adherence to regulations beyond the standard seven-step inspection process.
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Description
This quiz covers the essential components and functionality of air brake systems, including service, parking, and emergency systems. Learn about the role of air compressors and their controls in maintaining optimal braking performance. Test your knowledge on the principles of compressed air in vehicle operation.
