Every one of us knows that The Brake system of the vehicle is the most important safety system as it ensures the safety of million of lives. Can we imagine a wagon without a brake system!!? ….. RIDICULOUS.
From D-Brake liquid-cooled led drive line brake (LCDB) to Anti-lock Braking System (ABS), we advanced a lot. Let’s know more what these cool sounding terms are…
Dual-circuit braking system:
A typical dual-circuit braking system is the one in which each circuit acts on both front wheels and one rear wheel. Pressing the brake pedal forces fluid out of the master cylinder along the brake pipes to the slave cylinders at the wheels, the master cylinder has a reservoir that keeps it full.
Modern cars have brakes on all four wheels, operated by a hydraulic system. The brakes may be disc type or drum type. The front brakes play a greater part in stopping the car than the rear ones because braking throws the car weight forward on to the front wheels. Many cars, therefore, have disc brakes, which are generally more efficient, at the front and drum brakes at the rear. An all-disc braking system is used in some expensive or high-performance cars whereas the all-drum system is used in some older or smaller cars. Let’s talk further in detail about disk and drum brakes.
Disk brakes also contain piston in the caliper frame shown below which pushes brake pads and squeezes disk. The basic type of disc brake is with a single pair of pistons. There may be more than one pair like in dual-circuit brakes, or a single piston operating both pads, like a scissor mechanism, through different types of calipers – a swinging or a sliding caliper.
The pistons press on friction pads that clamp against the disc from each side to slow or stop it. The pads are shaped to cover a broad sector of the disc.When the brake is applied, fluid pressure forces the pads against the disc. The pistons move only a tiny distance to apply the brakes, and the pads barely clear the disc when the brakes are released. They have no return springs.
Rubber sealing rings around the pistons are also there 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.
Cars now 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. A drum brake with a leading and a trailing shoe, which has only one hydraulic cylinder; brakes with two leading shoes have a cylinder for each shoe and are fitted to the front wheels on an all-drum system.
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. With the brakes on, the shoes are forced against the drums by their piston. 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. In either type, return springs pull the shoes back a short way when the brakes are released. 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.