Lesson Notes By Weeks and Term v3 - Senior Secondary 3
Braking system and its parts
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Braking system and its parts
Download the Lessonotes Mobile Nigeria 2025 app for faster lesson access on Android and iPhone.
Subject: Automobile Parts Merchandising
Class: Senior Secondary 3
Term: 3rd Term
Week: 3
Theme: Automobile Parts
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Watch on YouTubeThis topic provides an in-depth understanding of the braking system in automobiles, a critical component for vehicle safety and performance. For Nigerian learners in Automobile Parts Merchandising, grasping this topic is essential for accurate identification, sourcing, stocking, and sales of brake components. It directly impacts their ability to serve customers effectively, advise on proper maintenance, and contribute to road safety in Nigeria, where vehicle roadworthiness is a major concern. Upon completion of this topic, students will be able to: Define a braking system and explain its fundamental purpose in an automobile.
This section delves into the core concepts of the braking system, outlining its purpose, types, components, and operational principles. 2.
1. Definition and Purpose of a Braking System A braking system is a mechanical, hydraulic, or pneumatic system in a vehicle designed to decelerate or stop its motion by converting kinetic energy into heat energy, which is then dissipated into the atmosphere. Its primary purpose is to ensure the safe operation of the vehicle by allowing the driver to control its speed, bring it to a complete stop, and keep it stationary when parked. 2.
2. Principles of Braking Braking relies on the principle of friction. When the brake pedal is pressed, a force is applied to the braking components, creating friction between stationary and rotating parts. This friction opposes the motion of the wheels, slowing them down. 2.
3. Types of Braking Systems Service Brake (Foot Brake): The primary braking system used to slow down or stop the vehicle during normal operation. It can be hydraulic (most common), pneumatic (in heavy-duty vehicles), or electromagnetic. Parking Brake (Hand Brake/Emergency Brake): A secondary, mechanical braking system primarily used to hold the vehicle stationary when parked. It can also serve as an emergency brake if the service brake fails.
Engine Brake (Exhaust Brake): Commonly found in heavy-duty vehicles (e.g., trailers, trucks) to assist in slowing down, especially on long descents, by restricting exhaust flow or altering valve timing to create back pressure. 2.
4. Main Components of a Hydraulic Braking System (Most Common in Nigerian Passenger Vehicles) A hydraulic braking system uses incompressible brake fluid to transmit force from the brake pedal to the wheel brakes.
Brake Pedal: The input device pressed by the driver to initiate braking.
Master Cylinder: This converts the mechanical force from the brake pedal into hydraulic pressure. It consists of a reservoir for brake fluid and one or two pistons.
Explanation: When the pedal is pressed, the pushrod pushes the piston(s) in the master cylinder, forcing brake fluid through the brake lines. Dual master cylinders provide a safety feature, separating the braking system into two independent circuits (e.g., front/rear or diagonal) so that if one fails, the other can still provide some braking.
Brake Booster (Vacuum Booster): A device that amplifies the force applied to the brake pedal, making it easier for the driver to apply the brakes. It uses vacuum from the engine's intake manifold.
Explanation: A vacuum booster uses the pressure difference between atmospheric pressure and engine vacuum to assist the driver. When the brake pedal is pressed, a valve opens, allowing atmospheric pressure to act on one side of a diaphragm, pushing it to assist the master cylinder piston.
Brake Lines/Hoses: Steel tubes (lines) and flexible rubber hoses that carry brake fluid from the master cylinder to the wheel brakes. Flexible hoses are used where there is relative movement (e.g., connection to calipers or wheel cylinders).
Brake Fluid: A specially formulated hydraulic fluid designed to withstand high temperatures and transmit pressure efficiently. Must be incompressible.
Types: DOT 3, DOT 4, DOT 5.1 (glycol-based, hygroscopic), DOT 5 (silicone-based, non-hygroscopic). Most Nigerian vehicles use DOT 3 or DOT
4. Wheel Brakes: The actual braking mechanisms at each wheel. These are typically Disc Brakes or Drum Brakes. 2.4.
1. Disc Braking System Components Predominantly used on front wheels, and increasingly on rear wheels of modern vehicles.
Brake Disc (Rotor): A metal disc (cast iron) attached to the wheel hub that rotates with the wheel.
Brake Caliper: A component that houses the brake pads and piston(s). It mounts over the brake disc.
Types: Fixed caliper (has pistons on both sides) or Floating/Sliding caliper (has pistons on one side, slides to apply force to both pads).
Brake Pads: Friction material (composite of metallic fibres, ceramic, or organic compounds) bonded to a steel backing plate. They are pressed against the brake disc to create friction.
Caliper Piston(s): Hydraulic pistons inside the caliper that push the brake pads against the disc when brake fluid pressure is applied.
Caliper Bracket/Mounting: Secures the caliper to the steering knuckle or axle housing. *2.4.2. the brake disc.
Types: Fixed caliper (has pistons on both sides) or Floating/Sliding caliper (has pistons on one side, slides to apply force to both pads).
Brake Pads: Friction material (composite of metallic fibres, ceramic, or organic compounds) bonded to a steel backing plate. They are pressed against the brake disc to create friction.
Caliper Piston(s): Hydraulic pistons inside the caliper that push the brake pads against the disc when brake fluid pressure is applied.
Caliper Bracket/Mounting: Secures the caliper to the steering knuckle or axle housing. 2.4.
2. Drum Braking System Components Often used on rear wheels, especially in older or smaller vehicles, and as the parking brake mechanism in some disc-equipped vehicles.
Brake Drum: A cylindrical cast iron housing that rotates with the wheel.
Brake Shoes: Curved metal structures with friction material (linings) on their outer surface. They press against the inside surface of the brake drum.
Wheel Cylinder: A hydraulic cylinder mounted inside the brake drum, containing pistons that push the brake shoes outwards against the drum.
Return Springs: Springs that pull the brake shoes back to their original position when the brake pedal is released.
Adjusters (Self-adjusters): Mechanisms (e.g., star wheel) that automatically adjust the brake shoes' position to compensate for lining wear, maintaining a consistent shoe-to-drum clearance.
Parking Brake Cable: A mechanical cable connecting the parking brake lever to the brake shoes, bypassing the hydraulic system to apply the rear brakes. 2.
5. Common Braking System Faults and Associated Parts for Replacement Understanding common faults helps in identifying necessary parts for replacement, crucial for a parts merchandiser.
Symptom: Spongy Brake Pedal / Low Brake Pedal Cause: Air in the hydraulic system, low brake fluid, worn master cylinder, leaking brake lines/hoses.
Parts for Replacement: Master cylinder, brake fluid, brake lines/hoses.
Symptom: Hard Brake Pedal Cause: Faulty brake booster, vacuum leak to booster, seized caliper/wheel cylinder, contaminated brake fluid.
Parts for Replacement: Brake booster, vacuum hose, caliper, wheel cylinder, brake fluid.
Symptom: Squealing/Grinding Noise during Braking Cause: Worn brake pads (metal-on-metal), worn brake shoes, worn brake discs/drums, foreign material embedded in pads.
Parts for Replacement: Brake pads, brake shoes, brake discs/rotors, brake drums.
Symptom: Vehicle Pulls to One Side during Braking Cause: Seized caliper piston, faulty wheel cylinder, contaminated brake fluid, unevenly worn brake pads/shoes, collapsed brake hose, air in one brake line.
Parts for Replacement: Brake caliper, wheel cylinder, brake hose, brake pads/shoes, brake fluid (bleeding required).
Symptom: Pulsating Brake Pedal / Steering Wheel Vibration during Braking Cause: Warped brake discs/rotors (most common), out-of-round brake drums.
Parts for Replacement: Brake discs/rotors (can sometimes be machined/resurfaced, but replacement is often safer/more efficient), brake drums.
Symptom: Leaking Brake Fluid Cause: Damaged brake lines/hoses, leaking master cylinder, leaking caliper, leaking wheel cylinder.
Parts for Replacement: Brake lines, brake hoses, master cylinder, brake caliper, wheel cylinder.
Symptom: Parking Brake Not Holding Cause: Stretched parking brake cable, worn brake shoes, misadjusted parking brake.
Parts for Replacement: Parking brake cable, brake shoes. Worked
Example: Identifying Brake Parts for a Customer in Nigeria A customer walks into your auto parts store in Lagos, Nigeria, stating that their 2010 Toyota Camry's brakes are making a loud grinding noise whenever they apply the pedal, and the car feels like it's taking longer to stop. They also mention that the steering wheel vibrates when they brake hard.
Step 1: Diagnose Symptoms.
Grinding noise: Strong indication of severely worn brake pads, potentially metal-on-metal contact, damaging the brake discs.
Longer stopping distance: Consistent with worn brake pads/discs, reduced friction. Steering wheel vibration during hard braking: Classic symptom of warped brake discs (rotors).
Step 2: Identify Affected System and Components. The symptoms point directly to the service brake system, specifically the wheel brake components (pads and discs) for the front wheels (where vibration is typically felt most acutely).
Step 3: Recommend Parts for Replacement. Given the grinding and vibration, it is highly likely that the front brake pads are completely worn and the front brake discs.
Longer stopping distance: Consistent with worn brake pads/discs, reduced friction. Steering wheel vibration during hard braking: Classic symptom of warped brake discs (rotors).
Step 2: Identify Affected System and Components. The symptoms point directly to the service brake system, specifically the wheel brake components (pads and discs) for the front wheels (where vibration is typically felt most acutely).
Step 3: Recommend Parts for Replacement. Given the grinding and vibration, it is highly likely that the front brake pads are completely worn and the front brake discs (rotors) are warped. It's good practice to replace brake pads in axles (both front or both rear) and to inspect/replace discs simultaneously for optimal performance.
Therefore, recommend:
1. Pair of Front Brake Pads (specify for 2010 Toyota Camry).
2. Pair of Front Brake Discs/Rotors (specify for 2010 Toyota Camry).
Additional consideration: While not explicitly requested, also suggest inspecting the rear brakes (pads/shoes, discs/drums) and checking the brake fluid level and condition, as a complete braking system check is always recommended. This provides added value and promotes comprehensive maintenance.
Step 4: Merchandising Best Practice. Inquire about the customer's budget and preference for quality (e.g., OEM equivalent, aftermarket standard, or performance-grade pads). Explain the difference in quality and price points for various brands available in the Nigerian market (e.g., specifying if a part is genuine Toyota, or a reputable aftermarket brand like Bosch, ATE, or specific local imports). * Emphasize the safety aspect of using quality brake parts. This example illustrates how a parts merchandiser connects customer symptoms to specific parts and advises appropriately, drawing on their knowledge of brake systems. 3.
1. Teacher Activities Introduction (10 minutes): Begin by asking students to briefly state the purpose of brakes in a car, linking it to everyday road safety in Nigeria. Project or display images/diagrams of a complete braking system and individual components. Introduce the topic "Braking System and its Parts," stating the learning objectives.
Lecture and Explanation (25 minutes): Deliver a detailed lecture on the types of braking systems (service, parking, engine brake). Explain the principles of hydraulic braking using a diagram of a master cylinder, emphasizing the role of brake fluid. Detail the components of a disc brake system (rotor, caliper, pads, piston) and a drum brake system (drum, shoes, wheel cylinder, springs, adjuster). Use visual aids (diagrams, actual parts if available). Discuss the function of each component clearly and methodically. Component Identification and Discussion (20 minutes): If possible, bring in actual brake components (e.g., worn brake pad, new brake pad, small disc rotor, a caliper, wheel cylinder, master cylinder) for students to observe and handle. Guide students to identify each part and explain its function based on the lecture. Discuss common faults associated with each part and the implications for safety and performance. Fault Diagnosis and Part Recommendation (15 minutes): Present various scenarios of brake problems commonly encountered in Nigerian workshops (e.g., "noisy brakes," "spongy pedal," "car pulls to one side"). Facilitate a class discussion on likely causes and the specific parts that would need replacement for each scenario.
Summary and Q&A (5 minutes): Briefly recap the main points of the lesson. Address any questions or misconceptions students may have. 3.
2. Student Activities Brainstorming (5 minutes): Participate in a brief brainstorming session on the importance of brakes in vehicles and common brake-related issues they might have observed or heard about in Nigeria.
Note-Taking (Throughout Lecture): Actively listen and take comprehensive notes during the teacher's lecture and explanations of concepts and components.
Component Identification (15 minutes): Examine and identify the physical brake components displayed by the teacher. In groups, discuss the function of each component and its role in the braking system. Scenario Analysis and Group Discussion (15 minutes): Work in small groups to analyze provided brake fault scenarios. Discuss and determine the probable cause(s) and identify the specific brake parts that would require replacement. Present their findings to the class.
Questioning: Ask clarifying questions about complex components, operational principles, or troubleshooting scenarios.
Road Safety Advocacy and Public Health: In Nigeria, vehicle roadworthiness, particularly brake functionality, is a critical aspect of road safety. Automobile parts merchandisers, understanding brake systems, can educate customers on the dangers of worn brake pads, discs, or fluid contamination. This knowledge allows them to actively promote scheduled brake maintenance and the use of genuine/quality parts, contributing to reduced road accidents and fatalities across Nigerian roads, particularly on busy highways like the Lagos-Ibadan expressway. This aligns with FRSC (Federal Road Safety Corps) initiatives. Small Business Development and Entrepreneurship: Knowledge of braking systems empowers aspiring Nigerian entrepreneurs to establish and manage auto parts businesses specializing in brake components. They can identify the specific needs of commercial vehicles (e.g., danfos, okadas, keke napeps) versus private cars in their locality, stock appropriate parts, and offer informed advice. For instance, a merchandiser in a commercial hub like Onitsha or Ladipo market can leverage this expertise to source and supply high-demand brake parts, contributing to the local economy and creating jobs. Environmental Impact and Resource Management: The proper maintenance and timely replacement of brake parts, as informed by this topic, can have environmental benefits. Worn brakes lead to inefficient stopping, higher fuel consumption, and increased particulate emissions from excessive friction. By advising on quality parts and proper maintenance, merchandisers indirectly contribute to lower emissions and the responsible disposal/recycling of worn-out brake components, aligning with environmental consciousness in urban Nigerian settings where vehicular pollution is a concern.