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A brake shoe is an mechanical piece of equipment that is responsible for direct stoppage of a vehicle.

As a person is sleeping, their brain still continually emits brain waves. These brain waves can be measured in terms of alpha and beta waves to determine the quality of sleep a person is having.

Brake Shoe

Definition

The brake shoe is a piece of mechanical equipment in a drum brake system that is involved with the direct stoppage of the car by using itself as the contact component.

Description

The brake shoe is a uniform crescent shaped piece of metal. It is about a foot long in diameter, and has a plate of metal perpendicular to its plane that is about two inches wide. On top of this plane is a layer of brake lining. The brake shoes along with other braking components are housed inside a cylinder called the drum. The drum is connected to the axle of the wheel and spins along with the wheel. ^[1] There are two shoes in every drum. The front shoe is called the primary and the rear shoe is the secondary shoe. ^[2] They are placed along the interior surface of the drum with the opening of the crescents facing each other. The top of the crescent is pointing toward the top of the cylinder, and the metal plate that is perpendicular to the brake shoe outlines the circumference of the drum. The shoes are usually made out of pressed steel, cast iron, or cast aluminum. Steel shoes are the most effective material for brake shoes because they can match the heat expansion of the steel drum from friction.

Background

The drum brake system was invented in 1902 by Louis Renalt. The beginnings of the drum brake system involved the use of a wooden block. Drivers on horse drawn carriages would pull on a lever that would press a block of wood against steel rimmed wheels. Today, there is no longer a wooden block, but a metal brake shoe. The first drum brake system had the same concept as the modern day drum brake, but instead of the use of hydraulic pressure, there were only rods, levers, and cables. ^[3] For half a century, the disc brake had been the alternative for braking systems in automobiles.

Purpose & Features

The sole purpose of the brake shoe is to use itself as a contact force to bring a car to a stop. The brake shoe is part of an elaborate drum brake system. There are many components of inside the drum: wheel cylinder, actuators, springs, backing plate, and more. However, all these components are meant to serve the brake shoe. ^[4] The drum brake system’s sole purpose is to manipulate the exertion of a driver stepping on a brake pedal, and magnify this force to cause the brake shoes to press against the drum. When a driver steps on the brake, brake fluid is delivered from the master cylinder to the piston inside the drum. The expansion and contraction of the piston causes the brake shoe to wedge on and off the spinning surface of the drum. The force created by the brake shoe on the drum, brings the drum and the axle to a halt. ^[5] The brake shoe itself is covered by a brake lining to prevent metal to metal contact of the shoe to the drum. However due to constant friction with the walls of the drum, the lining will eventually wear out. As the brake lining continually wears out, the braking of the vehicle will be less and less effective. If the metal of the brake shoe is exposed and comes in contact with the actual drum, damage to the drum brake will occur. ^[6]

Brake Lining

The brake lining needs to be a soft, but yet contactable material that is also heat resistant. It is a strip of woven copper and asbestos fiber that is riveted onto the brake shoe. The brake lining is like the rubber sole on a pair of shoes. The brake lining is meant to be consumed by the action of braking and therefore is commonly replaced.

Emergency brake

Another important aspect about the drum brake system is that it provides a very simple alternative to emergency parking. The brake shoes can be incorporated with a lever system that is controlled by the hand brake. When a driver pulls on the hand brake, the lever yanks on the brake shoes and causes them to wedge against the surface of the drum. All this can be done without any hydraulic pressure.

Comparisons & Drawbacks

Compared to the disc brake system, the drum brake is not as effective. The disc brake is more powerful and efficient in bringing a vehicle to a halt. The drum brake is more cost effective. However, there does exist a compromise between economical and efficiency. Most automobiles have a set of front disc brakes and a set of rear drum brakes. Automobiles are usually front wheel drive, so therefore the more powerful disc brake is installed on the front wheels to save manufactures capital. The drum brakes are usually installed on the rear wheels because it creates a simpler emergency brake system. ^[7]

References