A SEMINOR   ON  “BRAKE DRUM ”

Guided By Prof. S.N.DATEY

Submitted By Sk Samsuddin.

INTRODUCTION

A drum brake is a brake in which the friction is caused by a set of shoes or pads that press against a rotating drum-shaped part called a brake drum.

The term "drum brake" usually means a brake in which shoes press on the inner surface of the drum. When shoes press on the outside of the drum, it is usually called a clasp brake.

 

HISTORY

The modern automobile drum brake was invented in 1902 by  “Louis Renault” though a less-sophisticated drum brake had been used by Maybach  a year earlier.In the first drum brakes, the shoes were mechanically operated with levers and rods or cables. From the mid-1930s the shoes were operated with oil pressure in a small wheel cylinder and pistons.

FUNCTIONS

To stop the vehicle in shortest possible distance in case of emergency.

To control the vehicle when it is travel along the hills.

To keep the vehicle in desired position after bringing it in complete rest when there is no driver.

CONSTRUCTION

The Break Drum consist of

following components..

Back Plate Brake drum Wheel cylinder Brake shoe Brake lining Return spring Piston

BACK PLATE

The Back Plate serves as the base on which all the components are assembled. It attaches to the axle and forms a solid surface for the wheel cylinder, brake shoes and assorted hardware. Since all the braking operations exert pressure on the back plate, it needs to be very strong and resistant to any wear and tear or corrosion.

BRAKE DRUM The Brake Drum is generally

made of a special type of cast iron. It is positioned very close to the brake shoe without actually touching it, and rotates with the wheel and axle. As the lining is pushed against the inner surface of the drum, friction heat can reach as high as 600 degrees F.

The Brake Drum must be: Accurately balanced. Sufficiently rigid. Resistant against wear. Highly heat-conductive. Lightweight.

WHEEL CYLINDER

One wheel cylinder is used for each wheel. Two pistons operate the shoes, one at each end of the wheel cylinder.

When hydraulic pressure from the master cylinder acts upon the piston cup, the pistons are pushed toward the shoes, forcing them against the drum.

When the brakes are not being applied, the piston is returned to its original position by the force of the brake shoe return springs.

BRAKE SHOE

Brake shoes are made of two pieces of sheet steel welded together. The friction material is attached to the lining table either by adhesive bonding or riveting.

WORKING

The drum brake stops the tire from rotating by using the hydraulic pressure transmitted from the master cylinder to the wheel cylinder to press the brake shoe against that brake drum, which is rotating together with the tire.

When the hydraulic pressure to the wheel cylinder disappears, the force of the return spring pushes the shoe away from the inner surface of the drum and returns it to is original position.

ADVATAGES

Drum brakes are smaller for the same brake force.

Drum brakes don't need a hydraulic system for activation.

Due to simple in construction it can be easiliy repair.

Due to the fact that a drum brake's friction contact area is at the circumference of the brake, a drum brake can provide more braking force than an equal diameter disc brake.

DISADVANTAGES

The use of many clips and springs makes overhaul of the brake drum assembly very time-consuming.

Another problem with drum brakes is that if a vehicle is driven through water, it takes longer to get the brakes working effectively.

When the drums are heated by hard braking, the diameter of the drum increases slightly due to thermal expansion, this means the brakes shoes have to move farther and the brake pedal has to be depressed further.

APPLICATIONS

It is mainly used to stop the vehicle in shortest possible distance in trucks, cars and in other automobiles.

REFRENCES

Automobile Engineering- S.D.Ambatkar

www.autozone.com  www.brakesdrumsindia.com

THANK YOU