Air Brake Mock
#1. How can you tell how much air pressure is in the service reservoirs?
The reservoir pressure gauge is connected to the service reservoir. It shows how much air pressure is in the reservoir. In a dual-circuit system, there will be either two gauges, one for each circuit’s service reservoir, or a single gauge with two needles. The gauges are mounted on the instrument panel so you can monitor reservoir air pressures while you drive.
#2. In a tractor-trailer, the connections between the tractor and the trailer include which of the following components?
of the steps in coupling a tractor to a trailer is to connect the service line and supply line through their gladhand couplers.
#3. What function does the alcohol evaporator perform?
When the air compressor runs, an alcohol evaporator puts alcohol vapor into the air brake system to help prevent water in the lines or valves from freezing. Ice in the lines or valves can cause them to stop working.
#4. The "Trucks Stop Here – Check Brakes" sign before a steep downgrade is
Wherever a “Trucks Stop Here – Check Brakes” sign is posted, truck drivers are required to stop in the pullout area and inspect the vehicle’s braking system before proceeding
#5. When inspecting the brake chambers, you should check for which of the following?
During your pre-trip inspection, check each brake chamber for cracks, holes, or corrosion. Make sure they are mounted securely. Make sure there are no loose or missing clamps. Make sure that pushrod travel is unobstructed and not excessive.
#6. You're driving a vehicle equipped with a dual air brake system. The low air pressure warning signal comes on, but one system still has normal pressure. What should you do?
Virtually all large commercial vehicles today are equipped with a dual-circuit air brake system for greater safety. A dual air brake system has two separate air brake systems, both controlled by the same set of brake controls. Each system has its own air tanks, hoses, lines, etc. The primary system typically operates the regular brakes on the rear axle or axles. The secondary system operates the regular brakes on the front axle (and possibly one rear axle). If one system loses air pressure, you’ll still be able to stop your vehicle by using the brakes controlled by the other system, but your vehicle’s braking distance will increase, which isn’t good. Better to bring your vehicle to a safe stop and get the brakes repaired.
#7. When are water-cooled brakes used?
Many vehicles that operate on industrial roads are extremely heavy. Stopping these heavy vehicles puts a lot of pressure on their brakes, which can cause the brakes to overheat. When brakes overheat, the drums expand away from the brake linings, leading to brake fade (loss of braking effectiveness). Some of these vehicles use water directed at the brake drums to help prevent brake drum overheating
#8. In determining how well your air brake system works, which is NOT a significant factor?
The faster you drive or the greater your vehicle’s weight, the longer your braking distance will be. A fully loaded tractor-trailer can weigh over 36 metric tons. The weight of a 180-pound man is only a fraction of one percent of that, so the effect should be insignificant.
#9. Which type of trailer can be towed before the service tanks are full?
Instead of providing air pressure to both the service brakes and the spring brakes at the same time, trailer brake subsystems give priority to one or the other. Trailers with spring brake priority supply compressed air to the spring brakes (to release them) before the service tanks have filled. Trailers with service tank priority fill the service tanks before supplying the spring brakes. Trailers more than 25 years old were more likely to implement service brake priority. Today’s modern trailers are more likely to implement spring brake priority. Ask your employer or a qualified person whether your trailer uses spring brake priority or service tank priority.
#10. The low air warning device must activate by the time that tank air pressure falls to
The low air pressure warning device will activate a red warning light on the dashboard if air pressure in the primary or secondary service tank has fallen to 414 kPa (60 psi) (although some manufacturers’ systems activate at higher pressures).
#11. If the low air pressure warning activates, you should
The low air pressure warning device will activate when air pressure falls to around 60 psi. This is a sign of something seriously wrong with your brake system. Stop your vehicle immediately and don’t drive it again until the problem has been corrected. At 60 psi, your service brakes still have enough braking power to stop your vehicle safely – but not if air pressure falls much lower.
#12. An S-cam is found in
An S-cam is part of a drum brake in large commercial vehicles. As the S-cam rotates, it forces the brake shoes away from one another and presses them against the inside of the brake drum.
#13. Air pressure monitoring gauges are located on the _________ of the vehicle.
The air supply pressure gauge is connected to the service tank. It shows how much air pressure is in the tank. In a dual-circuit system, there will be either two gauges, one for each circuit’s service tank, or a single gauge with two needles. The gauges are mounted on the instrument panel so you can monitor tank air pressures while you drive.
#14. Brake chambers of size 36 are marked with
Typically, the size of a brake chamber is marked as two numbers on the outside of the brake chamber. The first number is the size of the service brake chamber, and the second number is the size of the spring brake chamber. For example, a Type 36/36 brake chamber has a size 36 service brake chamber and a size 36 spring brake chamber.
#15. Which of these vehicles is most likely to be equipped with air brakes?
Air brakes are favored for large commercial vehicles because (a) they can produce large braking forces (typically thousands of pounds of braking force at each wheel); and (b) unlike hydraulic fluid, compressed air can be rapidly and automatically replenished in the event of a slow leak.
#16. If the brake chambers on opposite sides of an axle are of different sizes, the result may be
The larger the size of the brake chamber, the greater the force applied to the brake. Thus mismatched brake chambers would apply different braking forces to the wheels on opposite sides of the axle. You should check for mismatched brake chamber sizes during your pre-trip inspection.
#17. If there is a loss of pressure in the trailer supply line, you would expect the trailer brakes to be applied and
The tractor protection valve is typically located behind the cab. Both the supply (emergency) and service (control) air lines pass through the tractor protection valve on their way to the trailer. (The valve has intake and output ports for each line.) In the event of a severe loss of air pressure in the supply line (perhaps because the trailer separated from the tractor), the tractor protection valve will close to prevent compressed air from leaving the tractor, so the tractor service brakes will still be able to work. It will also let the air out of the trailer supply line, which will activate the trailer emergency brakes to stop the trailer.
#18. Before beginning the air-loss tests of the air braking system, make sure that the air pressure approximately equals
As described in the British Columbia Air Brake Manual, the first air brake test is a test of the governor’s operation. After the test is performed successfully, rebuild air pressure back to the maximum (at which point the governor should cut out). Then proceed with the air-loss tests. This question is based on the Pre-Trip Procedures sections in the BC Air Brake Manual.
#19. Minimum governor cut-in pressure is
Pump down to approximately 80 per cent of maximum pressure (for example, if maximum is 125 p.s.i., pump down to 100 p.s.i.). Pause and check that air pressure begins to build (to confirm governor cut-in pressure). In all cases, the governor must cause the compressor to cut in before pressure falls below 80 p.s.i. (552 kPa).
#20. ln vehicles with three dash-mounted push-pull valve knobs, how are the valve knobs usually coloured?
These days, most tractors have two dash-mounted valve knobs. The diamond-shaped yellow knob controls the parking brakes for the entire vehicle. The eight-sided red knob controls the trailer air supply valve. Some older tractors also have a blue knob to control the tractor parking brakes independently of the trailer parking brakes.
#21. If there is a loss of air to the service brakes in a trailer with a spring brake priority system, how can you brake the trailer to a stop?
Trailers with spring brake priority supply compressed air to the spring brakes (to release them) before the service tank has filled. If there is a loss of air to the trailer service brakes, the spring brakes may remain released while the service brakes fail to work. If this happens, the only way to brake the trailer is to close the trailer supply valve (by pulling out the red dashboard knob) to cause the trailer’s spring brakes to apply automatically.
#22. Assuming good traction and constant vehicle speed, if you double your vehicle's weight, your vehicle's braking distance will be
The kinetic energy of a moving object is directly proportional to the object’s weight. A vehicle that is twice as heavy has twice the kinetic energy. Brakes use friction to convert the kinetic energy of a moving vehicle into heat. Thus, if you double your vehicle’s weight, it will take twice as long for your brakes to stop your vehicle.
#23. How many air lines must be connected to a DD3 safety actuator brake chamber?
A DD3 safety actuator brake chamber has three air ports: a service port, an emergency port, and a lock port. The lock port controls when the pushrod is locked in the extended (applied) position.
#24. DD3 safety actuators are mostly found in
For parking and emergency brakes, some buses and motor coaches use DD3 safety actuators in place of spring brakes. DD3 brake chambers have a way to mechanically lock a brake in the applied position.
#25. Which of these can strain your vehicle's braking system?
The amount of braking force it takes to stop your vehicle is directly proportional to its weight. The manufacturer has designed the braking system to handle the maximum weight specified by the vehicle’s gross vehicle weight rating (GVWR).