190105a Air Brake System Fundamentals

Define friction

the resistance between two moving bodies

Braking systems convert moving vehicle energy into what?

Heat energy

If GVWR is doubled, the stopping power is ______.

Doubled

If the speed of a moving vehicle is doubled, the stopping power is ______.

Increased 4x

If both speed and GVWR of a vehicle is doubled, the stopping power is ________.

Increased 8x

Advantages to air brake systems (over hydraulic brakes)

• system does not have to be bled when connecting/disconnecting trailers

• inexpensive compared to hydraulic brake system parts

• can accept small degree of system leakage and maintain braking effort

Disadvantages to air brake systems (over hydraulic brakes)

• lag time

• susceptible to contamination

When a volume of air is compressed ½ its original volume, its pressure will ______.

double

When a volume of air is compressed ½ its original volume, its temperature will ________.

Double

Define lag time

The time required for the air system to apply the brakes

Component of basic air brake system that connects the air system to the foundation brakes

Brake chambers

Component of basic air system that allows the operator to regulate brake application pressure

Dual circuit brake valve (foot pedal, treadle valve)

Governor function

Limit maximum air system pressure

• shuts off compressor at maximum pressure

• lets compressor start pumping again when it falls 25psi below

Slack adjusters function

• convert linear motion to rotary motion

• multiply the braking force from the brake chamber

• provide a place for brake adjustment

Why are connecting lines & fittings important to air brake systems?

The size/degree of fitting angle can affect the speed of air flow through the system.

How to calculate coefficient of friction

Amount of pull required (lbs) divided by the weight of the object/vehicle (lbs)

Define brake fade

Excessive heat causes lining material to vaporize, creating a gas layer between the shoes and the drums. The coefficient of friction is then reduced.