What is the advantage of hydraulic brake over air brake?

Hydraulic Brake

A hydraulic brake is a braking system that uses brake fluid to transfer the force from the brake pedal to the brake components. Here’s a basic overview of how it works:

Brake Pedal: When you press the brake pedal, it activates a piston in the master cylinder.

Master Cylinder: The master cylinder contains brake fluid and converts the mechanical force from the pedal into hydraulic pressure.

Brake Fluid: The brake fluid is a special fluid designed to withstand high temperatures and provide consistent pressure. It travels through hydraulic lines to the brake components.

Brake Lines: These are tubes that carry the brake fluid from the master cylinder to the brake calipers or wheel cylinders.

Calipers/Wheel Cylinders: In disc brake systems, the calipers contain pistons that squeeze the brake pads against the brake disc (rotor). In drum brake systems, the wheel cylinders push the brake shoes against the inside of the drum. Both systems use the hydraulic pressure from the fluid to create the braking force.

Brake Pads/Shoes: These are the friction components that press against the brake disc or drum to slow down the vehicle.

Air Brake

An air brake is a braking system that uses compressed air to apply the brakes. It's commonly used in heavy-duty vehicles like trucks, buses, and trailers due to its ability to handle high loads and provide consistent braking performance. Here’s an overview of how air brakes work:

Compressor: The system includes an air compressor, which is usually driven by the vehicle’s engine. This compressor generates compressed air and stores it in air tanks.

Air Tanks: These tanks store the compressed air until it's needed for braking.

Brake Pedal: When the driver presses the brake pedal, it releases compressed air from the tanks into the braking system.

Control Valves: Air brakes use various control valves to regulate the flow of compressed air. The primary valve is the foot valve or treadle valve, which controls the amount of air sent to the brake chambers based on how hard the driver presses the brake pedal.

Brake Chambers: These chambers contain diaphragms that move when compressed air is applied. In service brakes, this movement pushes a pushrod that activates the braking mechanism. In parking brakes, the brake chambers hold the brakes in place when the vehicle is stopped.

Braking Mechanism: In disc brake systems, air brakes apply force to the brake calipers, which squeeze the brake pads against the rotor. In drum brake systems, air pressure expands the brake shoes against the inside of the drum.

Emergency and Parking Brakes: Air brake systems often include separate mechanisms for emergency and parking brakes, which are applied by spring actuators and released by compressed air.

Working Principle

Hydraulic Brakes: Operate using brake fluid to transfer force from the brake pedal to the braking mechanism. When you press the brake pedal, the brake fluid is pushed through lines, which applies pressure to brake pads or shoes, causing them to clamp onto the rotors or drums and slow the vehicle.

Air Brakes: Use compressed air to apply force. When the brake pedal is pressed, air pressure is sent through hoses to the brake chambers, which push a piston that engages the brake pads or shoes.

Performance

Some of the advantages of the hydraulic brake over pneumatic brakes are as follows:

●Hydraulic brakes can generate higher forces as compared to air/pneumatic brakes. In short, they can provide higher braking torques but the actuation speed is slower as compared to pneumatic brakes.

●No need of compressed air cylinder, or a source of pressurized air for actuation. Master cylinders and tandem cylinders help in maintaining appropriate pressures inside the hydraulic brake line.

●Take lesser space as compared to complete air brake system.

●Hydraulic brakes give a controlled and smoother braking experience when compared to air brakes. Seriously speaking, they should not be compared for comfort because air brakes are used as emergency brakes in many vehicles.

●Hydraulic brakes are simpler and generally easier to maintain than air brakes. They use brake fluid to transfer force from the pedal to the braking mechanism, which typically results in fewer parts and less frequent maintenance.

●Hydraulic systems can provide quicker response times because the brake fluid transmits force more directly compared to the air pressure in air brake systems.

●Hydraulic brakes often offer more consistent performance under varying conditions. The brake fluid is less affected by temperature changes than air pressure, which can help maintain braking efficiency.

●Hydraulic brakes are typically easier to install and adjust, especially in smaller vehicles. They don't require complex air compressor systems or reservoirs, making them more straightforward to set up.

●Hydraulic braking systems are generally lighter than air braking systems, which can be advantageous in applications where weight is a concern.

●Hydraulic brakes provide a smoother and more controlled braking experience. The braking force is applied uniformly, which can lead to smoother stops and better vehicle control.

Summary:

That said, air brakes are often preferred for larger vehicles like trucks and buses due to their ability to handle higher loads and their built-in fail-safe mechanisms. The choice between hydraulic and air brakes depends largely on the application and specific requirements of the vehicle.

On the other hand, pneumatic brakes have some really good advantages over hydraulic brakes, if the brake line length and the actuation speed of the brakes are of prior importance.