Today, we’re going to talk about brakes and how they work.
Although many modern cars have brakes on all four wheels operated by a hydraulic system, a vehicle’s braking system’s core concept remains the same. An object is in motion, and it needs to stop being in motion. Let’s use some physics to explain this:
Working Principle of Brake – The Simple Physics
Brakes utilize friction to slow down the car. When the car is in motion, the wheel has energy in the form of movement, also known as kinetic energy. The brakes apply friction that generates heat, known as thermal energy. Once all the kinetic energy transforms into thermal, your car stops.
All vehicles use the same concept to come to a stop. The only difference is how that friction is applied. In simple words, this was all about how brakes work, thank you — just kidding!
Now, let’s talk about the hydraulic brake system. Shall we?
Hydraulic brakes principle
So the hydraulic braking system. Oh, wait! before moving ahead with hydraulics, you should know about Pascal’s Law by the French scientist Blaise Pascal. (It’s important, trust me.)
Pascal’s Law signifies the basis of all hydraulic systems, briefly stating that the pressure exerted anywhere upon an enclosed liquid is transmitted in all directions with the same pressure throughout the container. This principle allows generating considerable forces with relatively small efforts.
Now, as you have a brief idea of the pascal law, let’s continue with the hydraulic system. Hydraulic systems function by using pressurized fluid (In this case, glycol-ether based brake fluids). Another way to put this is that the pressurized fluid makes everything work. Let’s see how.
Hydraulic Brake System
As mentioned before, modern cars have brakes on all wheels, operated by a hydraulic system. Many vehicles have four-wheel disc brakes, i.e. all wheels have disc brakes – but some have discs for the front and drums for the rear wheels. You might ask why?
It is simply because the front wheels take the complete load of the car when brakes are applied. Therefore, many vehicles have disc brakes at the front, which are commonly more efficient than the drum brakes. However, drum brakes are adequate but more cost-effective.
Generally, high-performance or expensive cars use all wheels disc braking systems, while some cars use the all-drum system. Also, If you have no idea about discs or drum brakes, don’t worry. We are going to discuss this further.
Look at the Hydraulic brake mechanism below:
- When you push the brake pedal, it depresses the piston in the primary cylinder.
- The piston forces the brake fluid along the pipe.
- The Hydraulic brake fluid pressure distributes evenly around the system and goes to each wheels’ secondary cylinder.
- Where the fluid transmits a massive force on the brakes.
- The force applied on brakes creates friction between brake pads and disc brake rotors (circular discs connected to each wheel) which eventually stops the vehicle.
Modern cars manufactured these days come with twin hydraulic systems, with two primary cylinders (just in case one fails).
Sometimes in the twin hydraulic system, one system works the front brakes and the other for the rear; or one system works all four brakes and the other works the front ones only. There are multiple ways to work this out.
Other Types of Braking Systems
There are a variety of braking systems other than hydraulics. I will try to enlist a few of them below
Electromagnetic braking system
Apply brakes using magnetic power? Yes, many modern and hybrid vehicles use Electromagnetic braking systems.
This system works on the basic principle of electromagnetism to provide frictionless braking. This mechanism leads to the increased life span of brakes as there is no friction, hence less wearing out of brakes.
Also, this braking system is relatively smaller in size compared to the traditional braking systems. That’s why The trams and trains mostly use this.
Servo braking system
In this type of braking system, the pressure applied on the pedal is increased.
It is also known as vacuum or vacuum-assisted braking because it uses the vacuum generated in the engines and the power assistance to reduce effort.
The air intake system in the engine’s intake pipe is used for a petrol engine and a vacuum pump in diesel engines.
Mechanical braking system
A mechanical braking system was an initiator in the braking system journey but was announced to be less effective later.
The handbrake and emergency brakes work on the mechanical braking system. In this type of braking system, various mechanical linkages carry the force to the brakes like cylindrical rods, fulcrums, springs, etc., which stops the vehicle.
Mechanical brakes were used in several old automobile vehicles, but they are archaic nowadays due to their less effectiveness.
Types of brakes
Okay, I know you have no idea about the types of brakes. So let me help you with, what are the different types of brakes?
What are drum brakes?
After hand levers, early automotive brake systems used a drum design on all four wheels. A drum brake contains a round hollow drum inside that turns with the wheel. (Literally, it’s open)
The open back gets covered with a stationary backplate, which includes a set of curved brake shoes (Brake shoes and Brake pads have similar functionality). The brake shoes are pushed outwards against the drum by hydraulic pressure, moving the pistons in the brake’s wheel cylinders, pressing the linings against the drum’s inside to slow the wheel when the brake pedal is pressed. The return springs pull the brake shoes a little back when the brakes are released.
The shoe travels as short a distance as possible with the help of an adjuster. Earlier, systems had a manual mechanism that needed to be adjusted as the friction linings wore off. Later ratchets helped in automatic adjustments of brakes.
This brake system looked promising but had one major flaw. Under high braking conditions, like repeated high-speed slowdowns, drum brakes may fade and lose their efficiency due to the heat build-up inside the drum. On the other hand, disc brakes, with their more open construction, are much less prone to fading.
Do you remember the basic principle of the brake system? (Don’t scroll, I will explain it here only)
It suggests a vehicle stops when the movement (Kinetic Energy) turns into heat (Thermal Energy). Due to this reason, drum brakes can only work as long as they absorb the thermal energy generated by slowing the wheels down.
What are disc brakes?
A disc brake has a disc that rotates with the wheel. That’s it! Okay, sorry, I promise this was the last joke.
Disc brakes design is far better than that of drum brakes. Instead of housing the major components within a metal drum, disc brakes use a slim rotor and a small calliper with a bracket to mount the rotor.
The calliper contains two brake pads, one on each side of the rotor. Once again, fluid is used to transfer the brake pedal’s movement into the brake pads through small hydraulic pistons present in the calliper. Then the brake pads clamp together to stop the car.
As the piston moves, the rubber rings (also known as a seal) around them twists by dragging and stretching on the piston. When the brakes are released, the piston is allowed to move out freely while the slight amount of drag caused by the seal stops the complete retraction of the piston to its previous position and so takes up the slack caused by the brake pads wear, eliminating the need for adjustments.
The pistons in the calliper move only a little distance to apply the brakes, and the pads barely move from the disc when the brakes are released as they have no return springs.
But when we compare the heavy braking scenario. the drum brakes allow heat to build up inside the drum, whereas the rotor used in disc brakes is completely exposed to the external air. The rotors tendency to fade or overheat is reduced with this exposure.
The primary differences between the drum and discs brakes were tested on the race tracks. The disc brake systems helped the racers take their speed “deeper” and apply more prominent braking force even at the last possible second without overheating the components. With all the automotive industry advancements, the discs braking system was made available on everyday rides.
Aside from the hydraulic braking system, all cars also have a mechanical handbrake designed for parking but can also be used for limited braking if the hydraulic system completely fails.
It has a direct mechanical link to the wheel brakes. Unlike the hydraulic system, the Handbrakes operate by a cable from the lever next to the driving seat.
The handbrake lever pulls a cable connected to the brakes with the help of smaller levers. A ratchet on the handbrake lever keeps the brake on, and the push-button disengages the ratchet and frees the lever.
Anti-lock braking system
There might be a situation in which, under repetitive heavy braking, so much weight may unload from the rear wheels that they lock, possibly causing a dangerous skid.
Now you might wonder, what does it mean when wheels lock up? ‘Locking up’ is when the brakes stop the wheel while the car is still in motion, causing the tyre to rub over the ground without rotating, i.e. the skid.
To overcome this issue, anti-lock braking systems, also known as ABS, was introduced. Such a system applies and releases the brakes rapidly to prevent the wheels from locking and improving steering control while braking.
I know this might not be enough, but I will try keeping articles updated. Please do check out other articles on Torq Curve.