Furthermore, an understanding of brake system functionality will help you better understand when something goes wrong. The majority of modern day vehicleshave brakes on each of the four wheels. These wheels function with a hydraulic system. The comparable efficiency of disc brakes makes them ideal for the front of the vehicle while the rear wheels often have drum brakes. Certain low-cost and high-performance vehicles have all-disc braking systems.
The manner in which auto brakes function is interesting both in terms of physics and design. The force applied by the foot is multiplied quite rapidly to bring the vehicle to a halt. Therefore, the vehicle must multiply the force of the foot either through the multiplication of the hydraulic force or leverage created with a mechanical advantage.
The brake sends the force directly to the tires with the use of friction. The tires also rely on friction to send the force to the road. Most modern day vehicles are designed with two hydraulic circuits along with two master cylinders. The use of two cylinders and circuits ensures one will function in the event that the other fails. In certain situations, the circuit will work the brakes along the front while the other works the rear brakes.
Alternatively, each circuit can work both the brakes in the front and back. In fact, some brake systems are designed for a single circuit to work all four brakes. This is precisely why the brakes in the rear of the vehicle are intentionally made to be less powerful than those in the front of the vehicle. The majority of vehicles are equipped with a pressure-limiting valve that is load-sensitive. Rubber sealing rings round the pistons are designed to let the pistons slip forward gradually as the pads wear down, so that the tiny gap remains constant and the brakes do not need adjustment.
Many later cars have wear sensors leads embedded in the pads. When the pads are nearly worn out, the leads are exposed and short-circuited by the metal disc, illuminating a warning light on the instrument panel. A drum brake has a hollow drum that turns with the wheel. Its open back is covered by a stationary backplate on which there are two curved shoes carrying friction linings. The shoes are forced outwards by hydraulic pressure moving pistons in the brake's wheel cylinders , so pressing the linings against the inside of the drum to slow or stop it.
Each brake shoe has a pivot at one end and a piston at the other. A leading shoe has the piston at the leading edge relative to the direction in which the drum turns. The rotation of the drum tends to pull the leading shoe firmly against it when it makes contact, improving the braking effect.
Some drums have twin leading shoes, each with its own hydraulic cylinder; others have one leading and one trailing shoe - with the pivot at the front. This design allows the two shoes to be forced apart from each other by a single cylinder with a piston in each end.
It is simpler but less powerful than the two-leading-shoe system, and is usually restricted to rear brakes. Shoe travel is kept as short as possible by an adjuster.
Older systems have manual adjusters that need to be turned from time to time as the friction linings wear. Later brakes have automatic adjustment by means of a ratchet. Drum brakes may fade if they are applied repeatedly within a short time - they heat up and lose their efficiency until they cool down again.
Discs, with their more open construction, are much less prone to fading. Apart from the hydraulic braking system, all cars have a mechanical handbrake acting on two wheels - usually the rear ones. The handbrake gives limited braking if the hydraulic system fails completely, but its main purpose is as a parking brake. For a car tire , the coefficient of dynamic friction is much less than the coefficient of static friction.
The car tire provides the greatest traction when the contact patch is not sliding relative to the road. When it is sliding like during a skid or a burnout , traction is greatly reduced. Let's say for example that the distance from the pedal to the pivot is four times the distance from the cylinder to the pivot, so the force at the pedal will be increased by a factor of four before it is transmitted to the cylinder.
Also if the diameter of the brake cylinder is three times the diameter of the pedal cylinder. This further multiplies the force by nine. All together, this system increases the force of your foot by a factor of If you put 10 pounds of force on the pedal, pounds kg will be generated at the wheel squeezing the brake pads. There are a couple of problems with this simple system. What if we have a leak? If it is a slow leak, eventually there will not be enough fluid left to fill the brake cylinder, and the brakes will not function.
If it is a major leak, then the first time you apply the brakes all of the fluid will squirt out the leak and you will have complete brake failure. The master cylinder on modern cars is designed to deal with these potential failures. Be sure to check out the article on How Master Cylinders and Combination Valves Work , and the rest of the articles in the brake series see the links on the next page , to learn more.
Sign up for our Newsletter! Mobile Newsletter banner close. Mobile Newsletter chat close. Mobile Newsletter chat dots. Mobile Newsletter chat avatar. Mobile Newsletter chat subscribe. Bleed your brake lines to get any air out of your system. This means that your brakes will be pumped while someone watches the bleeder valve and closes the valve when brake fluid begins to flow through. Have your brake pads and rotors inspected to ensure that they are in excellent working condition.
Thank you! We need your help. Would you share your experience on one of these sites? If we fell short, please tell us more so we can address your concerns. Notice: JavaScript is required for this content.
0コメント