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Brake System Fundamentals. Walla Walla Community College Automotive Technology. Typical System (No ABS). Typical Layout of System (with ABS). Brake Pedal Design Advantage by Leverage. First Mechanical Advantage is Driver’s foot Length of Lever determines force applied Uses Fulcrum
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Brake System Fundamentals Walla Walla Community College Automotive Technology
Brake Pedal DesignAdvantage by Leverage • First Mechanical Advantage is Driver’s foot • Length of Lever determines force applied • Uses Fulcrum • Pedal Ratio 10 5:1 2.5 inches 0.5 inch 2 5
Sliding Caliper • Applies pressure to two pads on opposite sides of rotor • Caliper • Sliding • Fixed • Friction Material exposed to air
Fixed Caliper • Applies two pistons to opposite sides of rotor • Caliper stays stationary • Disc Brakes require higher hydraulic pressure
Brake Plumbing • Rigid steel brake lines are double wall • Flexible hoses connect rigid lines on vehicle to each wheel • Transmits hydraulic fluid to each wheel
Pressure Control Valves All systems use one or more valves
Wheel Cylinder • Wheel cylinder or caliper pistons are “slave cylinders” • Change hydraulic pressure back into mechanical force • Can use one or two cylinders at each wheel
Cable Parking Brake Parking or “Emergency” Brake
Parking Brake Systems • Foot or Hand Brake • Are cable controlled • Several Styles • As shown • Drum in hat • Driveline
Brake System Principles • Kinetic Energy • Mass • Weight • Speed • Inertia and Momentum
Friction Principles • Kinetic and Static Friction • Friction and Pressure • Friction and Surface Area • Coefficient of Friction • Brake Fade Friction changes kinetic energy into heat (thermal) energy.
Brake Friction Materials • Five Characteristics • Resist Fading with increased temp • Resist fading when wet • Recover quickly • Wear gradually • Quiet Bonded or Riveted
Braking Dynamics • Weight Transfer • Weight Distribution • Braking Power • Friction Efficiency • Brake to Wheel • Wheel to Road Surface • Traction Efficiency • Skidding
Hydraulic Principles • Fluids cannot be compressed • Fluids can transmit Movement • Acts “Like a steel rod” in a closed container • Master cylinder transmits fluid to wheel cylinder or caliper piston bore. • Fluids can transmit and increase force • Force Pressure Area
The area of the piston is determined by using the formula: 3.14 X R2
The amount force is calculated by multiplying the pressure times the area P X A = Force
Hydraulics - it’s how the pressure is multiplied and transferred
The pressure that is applied at piston A is the same as what is applied to piston B
The hydraulic pressure is the same, but the applied force can be changed by changing the piston size.
The caliper piston needs more applied force for multiple reasons