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Understanding Hydraulic Braking System

With the understanding of the braking system in automobiles, discussing the hydraulic type is very necessary as it’s widely used. The braking system uses hydraulic fluid to transmit the brake pedal or level force to the final drum shoes or disc caliper for the braking to prevail.

In a hydraulic braking system, the mechanical force from the brake pedal is transmitted and converted into the hydraulic pressure by the help of the master cylinder. This will be further explained.

The hydraulic brake system works with the principle of pascal’s law. The laws state whenever pressure is applied on fluid it travels uniformly in all the directions. Today we’ll be looking at the definition, functions, construction, applications, components, diagram, types, working, as well as advantages and disadvantages of the hydraulic braking system.

components of hydraulic braking

What is hydraulic braking system?

A hydraulic brake system is a braking mechanism that uses brake fluid to transmit force to the system. The fluid transfer pressure from the controlling mechanism to the braking mechanism.

The hydraulic braking system is widely used in low-speed four-wheelers such as Tata Ace. It works with the drum type, while the disc type is used in almost all cars. It’s also used on some bikes. The single-acting hydraulic bakes are used in front-wheel brakes of some pulsar while dual-acting hydraulic brakes are used in almost all conditions mentioned above.

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Functions of hydraulic braking system

Below are the functions to hydraulic braking system in the automotive system:

  • Hydraulic brake generates very high force compare the mechanical braking.
  • The final braking is quick and effective, that’s why it’s used on high-performance vehicles.
  • Frictional wear and tear that occurs in the mechanical braking system are much reduced to an optimum level in the hydraulic braking system.
  • Chances of brake failure are reduced in the hydraulic braking system compared to the mechanical types, because of the direct connection between the actuator (brake pedal or lever) and the brake disc or drum.
  • The hydraulic braking system is very easy to fix due to its less complexity compared to mechanical brakes.

Construction

The construction of a hydraulic braking system involves the arrangement of the following part:

Brake pedal or level, a pushrod, which is also known as actuating rod, a master cylinder assembly carrying piston assembly. It’s made up of either one or two pistons, a return spring, a series of gaskets or o rings, and a fluid reservoir. The construction of a hydraulic braking system is containing reinforced hydraulic lines and the brake caliper assembly consists of one or two hollow aluminum or chrome-plated steel pistons. It’s known as caliper pistons. There is a set of thermally conductive brake pads and a rotor, which is also known as brake disc or drum attached to an axle.

A glycol-ether based brake fluid filled the system to transmit to force to four wheels. Though other fluids can also be employed. Suddenly, manufacturers begin to design passenger vehicles with drum brakes on the four wheels. Conventionally, disc brake is used in the front wheel while drum brakes are employed for the rear wheel.

The disc brakes have better heat dissipation and greater resistance to fading, and as well safer than drum brakes. This is why four-wheel disc brakes have vastly increased over the year. Also, hydraulic brakes offer faster and more consistent pad withdrawal upon the pedal release.

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Applications

The common application of hydraulic brakes that make it popular is because it’s used in vehicles. The system is widely used due to its great advantages. Various types of transportation and rolling stock industries like aerospace, heavy transport, marine, and off-highway system also make great use of the hydraulic braking system. The system is also designed in industrial equipment such as machine tools, pumps, conveyors, motors, robotics, and automation. The vast usage is because the mechanical braking system can’t offer better as it does and it’s significantly easier to modulate.

Components of hydraulic brake system

Below are the components of the hydraulic brake system and their functions:

Drum brake:

Drum brakes are a small round drum designed with a set of brake shoes in it. The brake shoes are supported on a back-plate that is attached to the axle-casing with bolts. It rotates along with wheels and it resists the rotation of the wheel when the brake pedal is pressed. The shoes move toward the drum for the braking to take place.

Disk brake:

Disk brakes are designed with a disc-shaped metal rotor bolted to the wheel hub. The metal rotor spin within the wheel. As the brake pedal is pressed, the brake pads are pressed against the disk, causing the vehicle or device to slow down.

Brake pedal:

Just as it’s common on automobiles to have brake pedal to apply brakes, the hydraulic braking system also uses such. The pedal is connected to the master of the cylinder using a mechanical cord or linking rod.

Master cylinder:

The master cylinder is part that converts the applied force from the pedal to hydraulic pressure. The function of the part is to develop pressure, equalize the required pressure for braking, and also prevent contaminants such as water and air. Components of the master cylinder include housing, reservoir, piston, rubber cup, pressure, check valve, etc.

Wheel cylinder:

A wheel cylinder in the hydraulic brake system help in converting hydraulic pressure to mechanical pressure. in its working, it pushes the brake shoes towards the drum. The wheel cylinder is categorized into two which include a stepped wheel cylinder and a single-piston wheel cylinder.

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Brake lines or hoses:

Brake lines or hoses help in transferring high-pressure fluid between different components. the difference between the two is that brake lines are rigid in construction, made with double-wall steel tubes. This brake hoses are flexible and can be moved. Hydraulic fluids pass the component as the brake pedal is pressed.

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Brake fluid:

Brake fluids are the means through which pressure is transfer to the wheel cylinders. Hydraulic brake fluids must have a low freezing point, water tolerance, lubrication, non-corrosiveness, proper viscosity, and high boiling point.

hydraulic braking system diagram: 

hydraulic braking system diagram

Specifications

Below is the performance specification to be considered while choosing a hydraulic brake system:

  • Torque rating – is the maximum torque rating for the brake should equal or exceed the application requirement.
  • Power – is the maximum capacity or power rating for the brake.
  • Speed – This specification applies only to rotary brakes, which is the maximum rotary speed rating.
  • Maximum pressure – the maximum pressure limit for hydraulic brakes.
  • Shaft configuration – how the brake will be mounted (in-line, parallel, or right angle.

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Types of hydraulic braking system

Below are the various types of hydraulic braking system:

Hydraulic brake systems are classified into two bases; The basis of frictional contact mechanism and Basis of brake force distribution.

The basis of frictional contact is of two types, which includes;

  • Drum brake or internal expanding hydraulic brakes
  • Disc brakes or external contracting hydraulic brakes.

The basis of force distribution also has two types of hydraulic brake such as;

  • Single-acting hydraulic brakes
  • Dual-acting hydraulic brakes.

These will be explained in detail in the working principle section.

Working principle

Because there are various types of hydraulic braking systems, we’ll be explaining the working since they vary. Staring from the drum and disc brake to the single and dual-acting hydraulic brakes.

Working of drum hydraulic brake system

In the hydraulic brake type, the actuation of the brake pedal is attached to the piston of a master cylinder by a connecting rod. This in turn pushes the master cylinder’s piston inside the master cylinder, working just like an injection system or medical syringe.

The piston inside the master cylinder compresses the brake fluid, which then offers the conversion of mechanical energy into hydraulic pressure. This highly compressed brake fluid moves inside the brake which then transfers the hydraulic pressure from the master cylinder to the brake drum. As soon as the high-pressure brake fluid enters the drum cylinder or wheel cylinder, the movement of the cylinder piston occurs due to the high pressure. This in turn expands the stationary brake shoes attached to it.

The expansion of the brake shoes causes the frictional contact between the shoes and drum lining (the rotating drum part) to converts the kinetic energy of the vehicle into heat energy, which makes the braking happen.

Working of disc hydraulic brake:

The working of disc hydraulic brake is much similar to the drum hydraulic types but with a slight difference. The difference begins from where the high-pressure brake fluid enters the brake lines.

High-pressure brake fluids enter the disc caliper from the brake lines which then cause the movement in the caliper cylinder’s piston. The caliper cylinder piston causes the movement of the brake pad which is attached to the piston inside the caliper.

The movement of brake pads causes it to clamp with the rotating disc rotor. These components come to frictional contact with each other. This causes the conversion of the vehicle’s kinetic energy into heat energy to occur which causes the vehicle to stop or decelerate.

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Working of single and double-acting drum and disc braking:

Components of the single acting and double acting hydraulic brakes are the same. Whether it’s the drum type single acting brake or disc type single acting brake, there’s no difference. Well, differences may occur in the master cylinder used to decide the brake force distribution. For instance, in bikes single wheel braking or double wheel braking, in vehicles, two-wheel braking, or all-wheel braking.

The working single-acting drum type of braking system is exactly as the above-mentioned principle. that’s for the drum hydraulic braking system. in its working, single wheel or single pf wheels get the braking force.

In the double-acting hydraulic brake, the high-pressure brake fluid from the master cylinder supplies in two directions. i.e. in bike both wheels and cars all-wheel due to the tandem master cylinder.

A single-acting disc hydraulic braking also works just as the disc type of braking which is explained above. The wheel or single pair of wheels gets the braking force. Whereas, the double-acting disc hydraulic brake distribute the high-pressure fluid from the master cylinder in two directions. for instance, in bike both wheels and cars all-wheel due to the tandem master cylinder.

This explanation is for the single and double-acting hydraulic brakes.

Watch the video below to learn more about how the hydraulic braking system works:

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Advantages and disadvantages of hydraulic braking system

Advantages:

Below are the benefits of hydraulic brake in automobiles:

  • It offers equal braking effort to all the four wheels.
  • The applied force can be increased or decreased by changing the size of the piston and cylinder.
  • There is less rate of wear because there are no joints.

Disadvantages:

Limitations of the hydraulic braking system include:

  • Leakage of brake fluid which could spoil the brake shoes.
  • The presence of air pockets can destroy the whole system.

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In conclusion, the hydraulic braking system is better for the choice of braking for automobiles and other mechanical applications. In this article, we’ve learned in detail about the system, which includes, definition, functions, and construction. We also saw the applications, components, types, and working principles of the hydraulic braking system.

I hope you enjoyed the reading, if so, kindly comment, share and recommend this site to other technical students. Thanks!

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