1. Air loss in a straight truck or bus should not be more than ____ with the engine off and the brakes released. 2. To make an emergency stop with air brakes, using the stab braking method, you should:
Pump the brake pedal rapidly and lightly. Brake hard until the wheels lock, and then get off the brakes for as much time as the wheels were locked Brake as hard as you can, get off the brakes when the wheels lock, get back on the brakes when the wheels start rolling again. Press hard on the brake pedal and apply full hand valve until you stop. 3. You should know that your brakes are fading when: Pressure on the brake pedal is released and speed increases. You have to push harder on the brake pedal to control your speed on a downgrade. 4. To check the free play of manual slack adjusters on s-cam brakes you should: Park on level ground, chock the wheels, and release the parking brakes. Stop on level ground and apply the parking brakes.
Park on level ground and drain off air pressure before adjusting. Park on a slight grade, release the parking brake, apply the service brakes, and check for vehicle movement. 5. If the air compressor should develop a leak, what keeps the air in the tanks? 6. When driving down a long steep hill you should: Use stab braking. Begin braking when you are 10 M. P. H. above your safe speed. Release the brake when you are 5 M. P. H. below your safe speed. Use the trailer brakes. 7. The brake system that applies and releases the brakes when the driver uses the brake pedal is the: Service brake system. Emergency brake system. Parking brake system. None of the above. 8. The most common type of foundation brakes found on heavy vehicles is the: 9. Vehicles with air brakes must have: At least two air tanks. An air pressure gauge to show the pressure available for braking. An air pressure gauge, to show air used by the brake chambers for braking.
None of the above. 10. The driver must be able to see a warning that is given before air pressure in the service air tanks falls below: With today s modern air brake systems, brake fade is the only reason that a modern air brake system will fail. We know that air brakes systems are reliable because these are widely placed on vehicles that transport our most precious cargo school buses. When brakes are applied the brake shoes are forced out against the brake drum. The friction between the brake shoe and the drum creates heat. Heat is the byproduct of any braking system. The friction creates drag and slows the wheel. If the wheel has traction (good contact with the road surface) than the vehicle will slow and come to a stop, under most conditions. Many commercial vehicles experience brake fade during downhill braking situations. Still, with advances in engine brake technology a driver has to work pretty hard to get an air brake system to experience brake fade and ultimately fail.
If an air brake system fails, the driver has applied the brakes continuously in a hard, downhill braking situation for a long period of time. Owing to the fact that the brake cannot dissipate the heat, the metal of the brake drum heats up and expands. If the drum expands enough, the brake shoes will not be able to contact the drum. When this event happens, your braking system has experienced brake fade and your brakes have failed. General Rules: Go down the hill in the same gear that you used to climb the hill. That rule often doesn t work however owing to the fact that there are a lot of hills in the Rocky Mountains that you don t have to go up to go down. The Monte Creek hill from Vernon to Kamloops, BC is one example. So what do novice drivers do? Most trucks are now 13 or 18 speed transmissions.
If you are operating a tandem-tandem truck (18-wheeler) and the grade is single digits, than 5th gear with the engine brake on full. If you are heavier than a tandem-tandem, or the grade is in the double digits, you will want to start down the hill in 4th gear. If you need to use the brakes while descending the hill, use the brakes intermittently. Allow the engine to run up to 1800rpm and than using the brakes, brake firmly and bring the tachometer down to 1400rpm. Release the brakes fully between brake applications to allow the air to cool the brake drums. Every weekend in British Columbia, air brake instructors instil fear into students: Using your brakes is bad and you will die. Consequently, students are reluctant to use the brakes when going downhill. Yet, brakes must be used, but used correctly. If the brakes are used intermittently and have time to cool in between brake application, than these will operate splendidly.