MECHENG236 Brakes Flashcards
What is a brake?
Device for arresting or preventing the motion of a mechanism usually by means of friction
Brake system components
Master cylinder
Brake fluid
Disc brake assembly
Brake lines and hoses
Drum brake assembly
Disc brake components
Caliper assembly
Disc pads
Disc/rotor
Wheel struds
Wheel bearing
Drum brake components
Backing plate
Wheel cylinder
Hardware and springs
Brake shoes
Self-adjuster
Parking brake cable
What are fail-safe brakes
Brakes that by default are engaged in the stop position and require power to disengage and let the mechanism work
If a power failure or fault occurs, the brake is automatically engaged
Commonly electromagnet circuit to disengage the brake
Disc brake required braking torque depends on
Force applied normal to braking surface
coefficient of friction between braking surfaces
radial distance of braking surfaces
number of contact areas
Band brake required braking torque depends on
force applied to generate tension in the band
geometry of leverage
coefficient of friction between braking surfaces
contact angle and radius
Brake pad materials
Semi-metallic: The most common brake pads are semi-metallic and consist of 30~65% metallic powder (copper, steel, etc.) bound together by organic resin and molded into the pads.
* Ceramic: The best and most expensive. Great for supercars, but not so good for normal cars because they take too long to get up to operating temperature.
* Non-Asbestos Organic pads are made of rubber, and sometimes some metal powder, and fibers such as fibre glass, or Kevlar, bound together with resins such as cellulose. They tend to wear fast and are only suitable for day-to-day road driving.
Brake design considerations
Heat resistance and wear to prolong the life of brakes.
* Size and weight constraints
* Integration in vehicle/machine (e.g wheel, shaft, hub)
* Cost of materials and components
* Simplicity of design and access for maintenance
Different types of automotive braking system components
Mechanical components
-brake pedal
-disc/drum brake
Hydraulic components
-Master cylinder (pump)
-Slave/wheel cylinder (actuator)
Pneumatic components
-Power brake booster
Electronic components
-Warning lights/switches
-Anti-lock braking system (ABS)
ABS components
Wheel sensors
Control module
Modulator unit
Wheel sensors
Gear pulser
Brake disc
Common brake failure and problems for disc brakes, drum brakes, and band brakes
Disc brakes:
-Loss of pressure in hydraulic system
-Pads wearing too thin
-Disc warping
Dum brakes:
-Contamination causing loss of friction
-Overheating of drum - brake fade
Band brakes:
-Brake grab or chatter
