Mechanical Brakes: Types, What Are They & How Do They Work
Mechanical brakes are a type of brake system that uses friction to slow or stop a moving vehicle. They convert the kinetic energy of the moving vehicle into heat energy through friction. Mechanical brakes press brake pads against a rotating disc or drum to create friction and slow the vehicle (Mechanical Brakes Selection Guide).
Mechanical braking systems are composed of pads, calipers, drums or rotors attached to the wheels of the vehicle. When the brake pedal is pressed, it activates the system to push the pads against the drum or disc, slowing the wheels. The friction between the pads and rotors/drums converts the vehicle’s momentum into heat, slowing it down.
Compared to hydraulic brakes which use brake fluid, mechanical brakes use cables, levers, springs, and linkages to activate the braking mechanism. Mechanical brakes are a simper and more affordable option, but hydraulic brakes generally offer better performance.
Types of Mechanical Brakes
There are several main types of mechanical brakes commonly used in vehicles and machinery:
Disc Brakes
Disc brakes have a rotating disc attached to the wheel hub that rotates with the wheel. Calipers with brake pads squeeze the disc to slow or stop the wheel’s rotation. Disc brakes provide excellent stopping power and are commonly used on the front wheels of cars and motorcycles.
Drum Brakes
Drum brakes have curved brake shoes that press against the inner surface of a rotating drum attached to the wheel hub. As the shoes press against the drum, friction slows the wheel. Drum brakes are a traditional design still used on many rear wheels and some transmissions.
Caliper Brakes
Caliper brakes use two brake pads which squeeze the rim of a bicycle wheel between two arms of the caliper. They provide excellent braking power and modulation. Caliper brakes are nearly universal on road and mountain bikes.
Bicycle Brakes
Along with caliper brakes, other common types of bicycle brakes include V-brakes, cantilever brakes, disc brakes, and coaster brakes. Bicycle brakes provide stopping power with minimal weight.
How Disc Brakes Work
Disc brakes use a pair of brake pads to squeeze a rotor attached to the wheel in order to stop the rotation of the wheel. The main components of disc brakes include:
Rotors
The rotor, also called a disc, is a metal disc that attaches to the wheel hub. It rotates along with the wheel. The rotor provides the friction surface that the brake pads clamp onto when the brakes are applied. Rotors are typically made of cast iron for durability and heat dissipation.
Calipers
The caliper houses the brake pads and pistons. When the brake pedal is depressed, the caliper uses hydraulic pressure to force the brake pads against the rotor. This clamping force slows and stops the rotation of the rotor and wheel.
Brake Pads
The brake pads provide the friction material that clamps onto the rotor. Pads are composed of a metal backing plate with friction material bonded to it. As the pads wear down over time, they will need to be replaced.
When the brakes are applied, the pads move inward and squeeze against the sides of the rotor. This friction between the pads and rotor surface slows the rotation of the wheel. Disc brakes provide excellent stopping power as the pads clamp down directly on the rotor, rather than pushing outward on a drum.
Source: https://auto.howstuffworks.com/auto-parts/brakes/brake-types/disc-brake1.htm
How Drum Brakes Work
Drum brakes use rotating drums attached to the wheel hubs that act as the friction surface for brake shoes. When the brakes are applied, the brake shoes are forced outward against the inner surface of the drum.
Inside each brake drum are two brake shoes lined with friction material. The brake shoes pivot at one end and are connected to a wheel cylinder at the other end. When the brakes are applied, hydraulic pressure pushes the wheel cylinders out, which in turn pushes the brake shoes outward against the drum.
The friction between the brake shoes and drum slows down the rotation of the drum and wheel, stopping the vehicle. As the wheel turns, it also drags the drum around. This provides automatic self-energizing, as the friction creates more braking force and stops the vehicle faster.
The key components of drum brakes are:
- Drums – the rotating friction surface attached to the wheel hub.
- Brake shoes – curved pads that press against the drum when braking.
- Wheel cylinders – hydraulically operated pistons that push shoes outward.
Drum brakes are a simple and inexpensive design that has been used for decades. However, they lack the stopping power, heat resistance, and performance of disc brakes in more demanding applications.
How Caliper Brakes Work
Caliper brakes are a common type of disc brake found on most modern vehicles. The brake caliper is the mechanism that squeezes the brake pads against the surface of the brake rotor to stop the wheel from spinning.
Caliper brakes consist of the following main components:
- Caliper housing – This is the outer part of the caliper that holds all the internal components in place.
- Caliper arms – Most calipers have one or two arms that extend from the housing across the surface of the brake rotor. The brake pads are mounted to the ends of these arms.
- Brake pads – The brake pads provide the friction that stops the rotor from spinning when compressed against it. Modern pads are usually made of semi-metallic or ceramic compounds.
- Pistons – Inside the caliper housing are one or more pistons. These are pushed outwards by brake fluid pressure, forcing the caliper arms and pads to clamp down onto the rotor.
When you apply the brakes, hydraulic pressure from the brake master cylinder is transferred to the caliper via the brake lines. This pressure pushes the caliper pistons outwards. The outbound pistons in turn push the brake pads on the ends of the caliper arms into contact with the rotor surface.[1]
The friction between the spinning rotor and stationary pads converts the vehicle’s kinetic energy into heat, slowing the vehicle down. The caliper design ensures the pads clamp evenly across the rotor surface, providing efficient and balanced braking power.
How Bicycle Brakes Work
There are several common types of bicycle brakes:
Rim brakes are the most traditional type of bike brake. They work by squeezing brake pads against the sides of the wheel rim to slow the bike down. The pads are actuated by caliper arms that connect to a brake cable. Rim brakes provide good stopping power in dry conditions but can lose effectiveness when wet (Wikipedia).
Disc brakes use brake pads that squeeze against a metal disc attached to the wheel hub. They provide consistent braking performance in all conditions. Hydraulic disc brakes are the most common type for bikes today. They use fluid compression to engage the pads rather than cables (Bikeradar).
Coaster brakes apply stopping force through the pedal drivetrain when pedaling is reversed. They are simple and low maintenance but do not provide high braking power (Wikipedia).
Advantages and Disadvantages of Mechanical Brakes
Mechanical brakes have certain advantages and disadvantages compared to other brake types like hydraulic brakes. Some of the key factors to consider are stopping power, cost, and maintenance.
In terms of stopping power, mechanical disc brakes can provide strong and consistent braking, even in wet or muddy conditions. They offer better modulation and heat dissipation compared to rim brakes. However, hydraulic disc brakes tend to have superior stopping power overall due to the self-adjusting nature and hydraulic leverage.[1]
Regarding cost, mechanical brakes are typically less expensive than hydraulic brakes. The simpler mechanical design reduces manufacturing costs. Mechanical brakes only require a brake cable and lever, keeping parts costs down.[2]
For maintenance, mechanical brakes are easier for the average user to service and adjust themselves. Hydraulic brakes require more specialized tools and expertise to bleed the system. However, hydraulic brakes are self-adjusting as the pads wear down, reducing routine maintenance.[1]
Overall, mechanical brakes provide sufficient stopping power for most riders at a lower upfront and ongoing cost. But riders prioritizing maximum braking performance may still prefer hydraulic brakes.
Hydraulic vs Mechanical Brakes
Hydraulic and mechanical braking systems operate using different mechanisms and offer various advantages and disadvantages in comparison.
Mechanical brakes use brake cables connected to brake levers and calipers to apply stopping force. They are mechanically actuated through cable tension. Hydraulic brakes use brake fluid running through hoses and tubes connected to the brake lever, master cylinder, and caliper pistons to apply braking force. They are hydraulically actuated through fluid pressure.
Some key differences between hydraulic and mechanical braking systems include:
- Hydraulic systems typically provide stronger braking power and better modulation than mechanical systems. The hydraulic pressure allows more braking force to be applied smoothly.
- Hydraulic brakes are more responsive with less lag time than mechanical brakes. There is very little cable or hose compression.
- Hydraulic systems are self-adjusting as the brake pads wear, while mechanical systems need to be manually adjusted.
- Mechanical brakes are often cheaper and easier to service and repair than hydraulic brakes.
- Hydraulic brakes require bleeding to remove air bubbles, while mechanical brakes do not.
- Hydraulic brakes tend to be more weather-resistant and consistent in different conditions than mechanical brakes.
Overall, hydraulic disc brakes offer superior braking power and control for most riders. But mechanical disc brakes can provide reliable stopping power at a lower cost and easier maintenance.
Brake Troubleshooting and Maintenance
Proper brake maintenance is crucial for safety and performance. Here are some common mechanical brake issues and how to address them:
Squealing or squeaking can indicate that the brake pads are contaminated or worn out. Try cleaning the rotors and pads with isopropyl alcohol or replacing the pads. Make sure to bed in new pads properly.
Spongy or weak braking force is often due to air in the lines or worn pads. Bleed the brakes and replace the pads if needed. Check that the mounting hardware is tight.
Uneven brake pad wear can be caused by a stuck or dirty caliper piston. Clean and lubricate the caliper pistons. Replace pads in complete sets to avoid braking imbalance.
Rotors can become warped over time from heat or improper bedding. Resurface or replace warped rotors. Allow time for rotors to cool between rides.
Replacing pads and rotors should be done in complete sets. Follow manufacturer instructions for proper hardware and bed-in procedures. Clean rotors with isopropyl alcohol before installing new pads.
Most mechanical disc brakes have adjustment dials or barrel adjusters to set pad clearance. Refer to manufacturer instructions for proper adjustment methods. Leave 1-2mm of clearance between pad and rotor.
Conclusion
In summary, mechanical brakes utilize friction to slow down or stop a moving vehicle. The main types discussed are disc brakes, drum brakes, caliper brakes and bicycle brakes. Disc brakes use brake pads to clamp onto a rotor, drum brakes use shoes to press against a drum, caliper brakes use pads against a wheel rim, and bicycle brakes use pads against the wheel rim or disc. Mechanical brakes have advantages like being inexpensive, simple to maintain, and good dry braking. Disadvantages are being less efficient than hydraulics, prone to fading when overheated, and requiring more physical effort. Looking ahead, mechanical brakes will continue improving but likely not replace hydraulics soon. Engineers constantly refine friction materials and leverage ratios to enhance performance. Meanwhile new designs emerge, like electronic brakes that automatically adjust pad clearance. But hydraulic brakes offer unparalleled power, modulation and weather resistance. Mechanical systems remain ideal for cost-sensitive applications. Overall, understanding mechanical brake types and operation empowers drivers, riders and technicians to use them effectively.