Brakes provide the means of slowing or stopping the driven equipment (like bike etc.) effectively and safely in a very short time period.
Types of Brakes
- Disc brake
- Drum brake
A disk brake works on the principle of Pascal’s Law/Principle of transmission of fluid pressure. The disc brake is a mechanism for slowing or stopping the rotation of a wheel from its motion. It is normally made of cast iron, but in some cases, it is also made of composites such as carbon-carbon or ceramic -matrix composites. This is linked to the wheel and/or the axle. To stop the wheel, friction material in the form of brake pads is forced against both sides of the disc. Friction caused, on the disc wheel will slow or stop.
- Parts of disc brake
- Brake Pads – These provide the friction surface that is pressed against the brake rotors.
- Disc Rotors – These discs are attached to the wheel, and slow the car using friction from the pads.
- Brake Caliper – These press the pads against the rotors to generate friction between the two.
- Master Cylinder – Master cylinder is a hydraulic component which houses one or more pistons, a brake fluid reservoir, brake lines, seals, and springs. These are arranged in such a manner that the mechanical force applied by a rider onto the brake pedal/brake lever is converted into hydraulic pressure that eventually brakes the rotors via the brake calipers. The master cylinder multiplies the mechanical brake force by transferring high pressure on the brake calipers.
Following are the types of Master Cylinder :
- Single Circuit Master Cylinder
- Tandem Master Cylinder OR Dual Circuit Master Cylinder
- Brake Lines – It is multilayer hoses that transmit pressure from the master cylinder to the calipers, which typically utilize a Teflon inner lining surrounded by a braided nylon, Kevlar, or stainless-steel reinforcing layer.
- Brake Fluid – The brake fluid transfers the lever force into pressure, and eventually amplifies the braking power. To do this effectively, the fluid must have properties like non-compressibility, low viscosity, high boiling-point, non-corrosive, and excellent lubricity for master-cylinder and caliper pistons seals. A total of 4 grades of brake fluids are available, namely, DOT 3, 4, 5 and 5.1 in which DOT 3 and 4 are commonly used in motorcycles.
When the brake lever is pulled, the high pressure fluid from the master cylinder pushes the piston outward. The piston pushes the brake pad against the rotating disc. As the inner brake pad touches rotor, the fluid pressure exerts further force and the caliper moves inward and pulls the outward brake pad towards the rotating disc and it touches the disc.
Now both the brake pads are pushes the rotating disc, a large amount of friction is generated in between the pads and rotating disc and slows down the vehicle and finally let it stop. When the brake pad is released, the piston moves inward, the brake pad moves away from the rotating disc. And the vehicle again starts to move
- Disk brake requires less effort (brake torque) to stop the vehicle compared to drum brakes.
- It generates less heat compared to drum brakes for the same brake torque.
- Ease of maintenance as disk brake is outside the wheel rim.
- It cools down faster.
- In drum brakes, if worn out brake shoes are not changed at proper time they can damage the drums however, disk brakes do not have such problems.
- It is less likely to skid compare to drum brakes in wet condition (when applied with caution).
- It is safer than drum brakes under hard braking conditions.
- It has brake pad wear indicator which is not present in drum brakes.
- The disc brake system is effective to reduce the vehicle’s speed, but it is not as effective as drum brakes capable to self-energized to remain stationary while parked.This happens because the brake pads have difficulty in retaining a smooth rotor surface.
- It is expensive.
- More skills required to operate disk brakes. That is the reason why some people are still not comfortable with disk brakes.
- If any air remains in disk brake system, it can be problematic as brakes may not work effectively.
- It requires lot of efforts in maintenance like brake fluid (bleeding), change of brake pads etc.
Carbon Disc Brakes
In this system the friction between the carbon discs and carbon pads produces vast amounts of braking force. The braking force is even far greater than the conventional steel discs. These brakes generally operate typically at a high temperature between 400-1000 °C. Continuous late braking can overheat carbon carbon brakes as they oxidize and wear out faster. The high temperatures needed for carbon carbon brakes to be effective so they cannot be used in the wet. Carbon brakes are basically used in Moto GP.
A drum brake is a traditional break in which the friction is caused by a set of shoes or that press against a rotating drum-shaped part called a brake drum.
The term “drum brake” usually means a brake in which shoes press on the inner surface of the drum.
- Parts of drum brake
- Brake Shoe – The brake shoes are the equivalent of brake pads. Brake shoe is pushes against the spinning surface of the brake drum to create the necessary friction.
- Break Pedal or lever – It is that component of brake assembly through which input to brake is given. The front brake is operated through a lever whereas the rear brake is operated through a pedal.
- Brake Drum – It is made of special type of cast iron. It is positioned very close to the brake shoe without actually touching it, and rotates with the wheel and axle. When the brake lining touches the drum it generates friction heat which sometimes goes up to 600F.
- Brake Cable – As seen in clutch, the brake cable is also the medium to pass the input given by brake lever or pedal. The rear brake sometime uses shaft system as the medium of passing the input.
- Springs – The coil type springs used as return springs when the brake is actuated by pressing lever or handle this spring expands and when you release the lever/pedal the springs contract and bring the brake shoe to their original position.
- Brake panel – It is located outside the brake drum. It acts like cover of brake drum.
In a normal condition the brake drum rotates with the wheel but as the rider presses lever or pedal. The return springs mounted with brake shoes expand. The expansion in springs closes the gap between brake shoes and the drum. It creates friction which stops the drum from moving.
As the drum is fitted into the wheel rim the wheel also stops. When the rider releases lever or pedal, brake cam returns to the original position which contracts the springs. The contractions in springs lead the brake shoes to their original position. Now the wheel can move freely. This is the how the drum brake works.
- Drum brakes can provide more braking force than an equal diameter disc brake.
- Drum brakes last longer because drum brakes have increased friction contact area than a disc.
- Drum brakes are cheaper to manufacture than disc brakes.
- Rear drum brakes generate lower heat.
- Drum brakes have a built-in self energizing effect that requires less input force (such as hydraulic pressure
- Wheel cylinders are simpler to recondition than with disc brake calipers.
- Brake shoes can be remanufactured for future use.
- Excessive heating can happen due to heavy braking, which then can cause the drum to distort, and thus cause vibration under braking.
- It needs to be adjusted frequently
- It is less effective in excessive heat compared to disk brake
- Maintenance of drum brakes is more time-consuming, compared to disc brakes.
Electric motorcycles can use regenerative braking to both slow down the motorcycle and recharge the batteries at the same time.
This system transfers the kinetic energy of an object in motion into potential energy which is converted back into electrical energy during braking and as a result increases efficiency. The converted electrical energy is stored in energy storage devices such as batteries, capacitors,etc which can extend the driving range by up to 10%. These systems are also called kinetic energy recovery systems.