Heavy Duty Braking Fundamentals exam questions and answers

AL Factor The size or surface area of a brake chamber multiplied by the length of the slack adjuster in inches Anti-fade An opposite condition of heat fade where the coefficient of friction increases as the brakes get hotter. Automatic Slack Adjusters (ASAs) Automatically adjust brake stroke to maintain the correct shoe-to-drum clearance. Brake Block Brake friction material that is 0.75 inch (19mm) thick. Brake Fade The inability of the brakes to maintain its effectiveness Brake Foundations The braking components found at the wheel ends Brake Lining Brake friction material that is 0.05 inch (13mm) thick. Brake Torque The force applied to the foundation brakes during braking. Cam Brakes Brakes that use an "s" shaped cam that twists between two rollers to expand a set of brake shoes. Cam-opposite A situation when the cam rotates opposite the drum's rotation to energize the brakes. Cam-same A situation when the cam rotates the same direction as the drum's rotation to energize the brakes. Cast Drums Brake drums made from cast iron. Centrifuge Drums Brake drums made with a cast iron core surrounded by a steel band. Chemical Fade A type of brake fade that takes place when steam or gases from vaporized lining materials form between hot lining and the drum reducing the coefficient of friction. Clearance sensing ASA A type of automatic slack adjuster that reduces pushrod travel based on torque input to the ASA. Coefficient of Friction The amount of friction between two particular objects in contact; calculated by dividing the force required to move the object by the weight of the object. Edge Code A code representing the CoF of a brake and it's composition. Federal Motor Vehicle Safety Standard 121 (FMVSS 121) Performance and safety standards legislation for air brakes. Floating caliper A disc brake caliper that floats on two pins. Glazing A cause of brake fade characterized by a hard glassy burnt appearance to the lining surface diminishing it CoF. Heat Fade The loss of reduction in the coefficient of friction as the brake temperature increases. Inertia Shift Weight that moves from the rear of the vehicle to the front during braking. Left and Right hand camshafts S-cams used on either side of a vehicle that rotate in opposite directions. Long Stroke Chambers Brake chambers manufactured with a 3 inch, (76mm), stroke. Manual Slack Adjusters A manually adjusted lever between the brake chamber and the S-cam all but obsolete today. Mechanical Fade Loss of brake effectiveness that occurs when drums expand due to heat. Non-asbestos Organic (NAO) Lining Brake friction material commonly used in line haul tractors where far less braking takes place. Power Springs Springs in brake actuators used to apply park brakes or internal pushrod lock mechanisms. Release Bolt A bolt that compressed the power spring of spring brakes and releases the park brake. Roto-chambers Actuators with a unique diaphragm construction which delivers consistent output force regardless of pushrod position. S-cam A cam shaft used to force brake shoes onto the brake drum. Self-energization A braking effect that causes the shoe drum friction to rotate the brake shoe int