Sunday, May 13, 2012

How car brakes work

In theory...
Imagine how much force you need to stop a fast-moving car. Simply pressing with your foot would not generate enough forceto apply all four brakes hard enough to bring you quickly to a stop. That's why brakes use hydraulics : a system of fluid-filled pipes that can multiply force and transmit it easily from one place to another.
When you press on the brake pedal, y...our foot moves a lever that forces a piston intoa long, narrow cylinder filled with hydraulicfluid. As the piston plunges into the cylinder, it squirts hydraulic fluid out through a long and narrow pipe at the end (much like squirting a syringe). The narrow pipe feeds into much wider cylinders positioned next to the car's four brakes. Because the cylinders near the brakes are much wider than the one near the brake pedal, the force you originally applied is multiplied greatly, clamping the brakes hard to the wheels.
Caption: When your foot presses the brake lever, brake fluid squeezes out of a narrow cylinder, through a tube, into a much widercylinder. This system, known as hydraulics, greatly increases the force you supply.
In practice...
1. Your foot pushes on the brake pedal.
2. As the pedal moves down, it pushes a class 2 lever (a kind of simple machine ), increasing your pushing force.
3. The lever pushes a piston (blue) into a narrow cylinder filled with hydraulic brake fluid (red). As the piston moves intothe cylinder, it squeezes hydraulic fluid out of the end (like a bicycle pump squeezes out air).
4. The brake fluid squirts down a long, thin pipe until it reaches another cylinder at the wheel, which is much wider.
5. When the fluid enters the cylinder, it pushes the piston in the wider cylinder (blue) with greatly increased force.
6. The piston pushes the brake pad (green) toward the brake disc (gray).
7. When the brake pad touches the brake disc, friction between the two generates heat (red cloud).
8. The friction slows down the outer wheel and tire, stopping the car.

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