Objectives • Explain the basic principles of braking, including friction, pressure, and heat dissipation • Describe hydraulic system operation, including master cylinder, control valves, and safety switches • Understand the operation of power brakes
Introduction • Kinetic energy: energy that wants to stay in motion • Apply brakes to stop a car: dry friction changes motion energy to heat energy • Temperature in brake linings can be 600°F • Friction resists movement between surfaces • Coefficient of friction varies • Temperature, rubbing speed, surface condition • During a stop • Vehicle weight shifts to front brakes • Front breaks wear out faster
Brake Linings • Linings are bonded or riveted to disc backing • Newer pads integrally molded • Lining types • Asbestos linings: health hazard • Semimetallic linings: sponge iron and steel fibers • Metallic linings: used in heavy-duty and racing conditions • Ceramic linings: use ceramic and copper fibers to control heat
Drum and Disc Brakes • Drum brake systems • Metal brake drums bolted to wheels • Disc brake systems • Rotor and caliper, similar to bicycle
Hydraulic Brake System Operation • Brake pedal depression • Moves piston in master cylinder • Fluid under pressure is pushed to slave cylinder • Slave cylinders are located at each wheel • Pascal’s Law: • Pressure in an enclosed system is equal and undiminished in all directions • Force = Pressure x Area • Force applied to brake linings increases with larger diameter wheel cylinder
Hydraulic Brake Fluid • Glycol-based fluids are hygroscopic • Absorb water • Brake fluid • Higher boiling point than water • DOT specifications • List both dry and wet boiling points
Brake Hose and Tubing •
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- Spring '16
- Siva Krishins