An Intro to Hydraulic Brakes for Those Interested in Auto Mechanic Training
If you’ve ever looked at the brake lines trailing from the handles of a bicycle to the pads lining its wheels, you’ve seen the basic technology behind hydraulic brakes. Systems that use fluid pressure to transmit force between a point of contact and the brake pads are also what are used in cars, and what allow a light push on a pedal to bring an incredibly heavy vehicle to a halt.
As an auto mechanic, your day-to-day tasks will involve diagnosing and repairing braking systems. Here’s an introduction to how they work.
Fluid Mechanics and Pascal’s Law
Hydraulic brakes, and all modern hydraulic technologies, owe something to 17th-century French thinker Blaise Pascal. He made many lasting contributions to mathematics, religion, and physics, including Pascal’s Law in 1647-48.
The law is a foundational principle in fluid mechanics, and states that a change of pressure at any point of an incompressible fluid is distributed equally throughout the fluid. The discovery of this law is what enabled the creation of the modern hydraulic brake system, the technology mechanics encounter during their auto careers.
All brakes on personal vehicles use fluids to operate, meaning they follow Pascal’s Law. Because a human foot wouldn’t be able to generate the pressure necessary to bring a heavy vehicle to a stop, we use our knowledge of hydraulic pressure to construct braking systems that will. The area of contact between the foot and the pedal is much more spread out than the tiny piston it compresses, so the force is multiplied many times over through the system.
Different Braking Systems & Their Components
Though all personal vehicles use hydraulic braking technology, there are some slight differences. There are two popular kinds of hydraulic braking systems: disc brakes and drum brakes. Disc brakes can be found on the front wheels of all modern vehicles, but lower-end models will sometimes use drum brakes on the back wheels. The systems are both very similar, but disc brakes are better overall because they dissipate heat faster. The front brakes do most of the work, so it’s sensible to use disc brakes on them.
Both types of braking systems contain a hydraulic fluid reservoir called the master cylinder, with a piston that pushes the fluid and springs that bring the piston back to its place. They also include brake lines that transmit the hydraulic pressure from the fluid, and a caliper assembly that contains the brake pads and piston.
Both disc and drum brakes work on the principle of using hydraulic pressure to press a friction material against a spinning component and stop it. Within disc brakes, the brake pads are pressed against a spinning rotor. Within drum brakes, brake shoes are pressed outward against a spinning metal drum. During your auto mechanic training, you’ll learn how to diagnose and maintain both kinds of systems.
Common Issues That Those in Auto Careers Should Know
Because of how important braking systems are to the safe and effective functioning of autos, they need to be regularly maintained. The friction material that coats the brake pads become worn over time and need to be replaced. Rotors or drums also wear out as they get older.
The hydraulic system can become ineffective if it isn’t perfectly tuned, and low brake fluid, air within the brake lines, a blown brake line, or a fluid leak can all present issues. Brake fluid that is old and has absorbed too much water can boil with repeated use. These issues can all be avoided with proper preventive maintenance.
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