Lesson Note on Suspension System—Leaf Spring and Coil Spring: Fault Tracing and Identification for SS2

Class: Senior Secondary School 2 (SS2 / SSS 2)
Term: 1st Term
Week: 8
Age: 16 years
Duration: 45 minutes
Subject: Auto Mechanic Work
Curriculum Theme: Automotive Systems
Previous Lesson: Components of a Transmission Unit (Gear Box): Sliding Mesh Gearbox and Reverse Mechanism.
Topic: SUSPENSION SYSTEM—LEAF SPRING AND COIL SPRING
Subject Matter: Meaning of SUSPENSION SYSTEM—LEAF SPRING AND COIL SPRING (definition of suspension system types), leaf spring (construction, function), coil spring (construction, function), tracing faulty system (fault identification)

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

• Define a suspension system.
• Describe the construction and function of leaf springs.
• Explain the construction and function of coil springs.
• Identify common symptoms of a faulty suspension system.

Affective Domain:

• Appreciate the importance of a functional suspension system for vehicle safety and comfort.
• Develop interest in diagnosing suspension issues.

Psychomotor Domain:

• Distinguish between leaf spring and coil spring components.
• Trace potential faults in a suspension system based on symptoms.

Social Domain:

• Collaborate with peers to discuss different types of suspension springs.

Reference Materials

The following resources were used in planning this lesson:

• Senior Secondary Schools Education Curriculum
• State Unified Scheme of Work
• Auto Mechanic Work for Senior Secondary Schools, Book 2
• https://www.dummies.com/homes/automotive/how-your-cars-suspension-system-works/
• https://www.caranddriver.com/features/a36214828/leaf-spring-vs-coil-spring/

Instructional Materials

The teacher will teach this lesson with the aid of:

• Actual leaf spring
• Actual coil spring
• Chart showing different suspension systems
• A hydraulic suspension model (if available)

Rationale for the Lesson

This lesson helps pupils understand how a vehicle’s suspension system works to provide a smooth ride and maintain tire contact with the road. It enables them to identify different types of springs and recognize signs of a faulty suspension, which is important for vehicle safety and performance.

Prerequisite/Previous Knowledge

Pupils should have basic knowledge of vehicle chassis and the main components of a car.

Lesson Content/Board Summary

SUSPENSION SYSTEM—LEAF SPRING AND COIL SPRING

Definition of Suspension System

The suspension system of a vehicle is a group of components that connects the vehicle to its wheels, allowing relative motion between the two. It helps to absorb shocks from road irregularities, ensures a smooth ride, and maintains tire contact with the road for stability and control.

Types of Suspension Springs

The main types of springs used in vehicle suspension systems include:

• Leaf springs
• Coil springs
• Torsion bars
• Air springs

Leaf Spring

A leaf spring is a simple form of spring commonly used in the suspension of wheeled vehicles. It consists of several layers of metal (leaves) of varying lengths, stacked one upon the other.

Construction:

• Main Leaf: The longest leaf, usually with eyes formed at both ends for attachment.
• Graduated Leaves: Shorter leaves stacked below the main leaf.
• Centre Bolt: Holds the leaves together at the center.
• U-Bolts: Clamp the spring to the axle.
• Bushings: Fitted into the eyes for mounting to the chassis.

Function:

• Supports the weight of the vehicle.
• Absorbs road shocks and vibrations.
• Helps maintain wheel alignment.
• Transfers braking and driving forces to the chassis.

Coil Spring

A coil spring is a mechanical device, which is typically used to store energy and subsequently release it, to absorb shock, or to maintain a force between contacting surfaces. It is made from a metal rod wound into a helix.

Construction:

• Spring Wire: High-strength steel wire formed into a coil.
• Pigtail/Tangential Ends: Specific shapes at the ends for proper seating.
• Variable Rate Coils: Some springs have varying coil spacing or wire thickness to provide progressive stiffness.

Function:

• Supports the vehicle’s weight.
• Compresses and expands to absorb vertical shocks from the road.
• Works in conjunction with shock absorbers to dampen oscillations.
• Allows for independent wheel movement in many modern suspension designs.

Tracing Faulty Suspension System

Identifying a faulty suspension system involves observing specific symptoms and inspecting components.

Common Symptoms of a Faulty Suspension System:

• Sagging: One corner or side of the vehicle sits lower than the others.
• Unusual Noise: Clunking, squeaking, or rattling sounds, especially over bumps.
• Uneven Tyre Wear: Tires show excessive wear on one side or in patches.
• Excessive Bouncing: The vehicle continues to bounce after hitting a bump.
• Poor Steering Control: Difficulty steering, wandering, or pulling to one side.
• Fluid Leaks: Oil or fluid leaking from shock absorbers or struts.
• Visible Damage: Cracked, broken, or rusted springs; bent control arms.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher asks pupils about their experience with driving on bumpy roads and how cars manage to provide a comfortable ride.
Pupils’ Activity: Pupils share their experiences and thoughts on how cars handle bumps.
Learning Point: Pupils are introduced to the concept of vehicle comfort and stability.

Step 2: Meaning of Suspension System

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines the suspension system, explaining its main purpose and components, using the chart.
Pupils’ Activity: Pupils listen attentively, ask questions for clarification, and take notes.
Learning Point: Pupils understand the definition and basic function of a suspension system.

Step 3: Leaf Spring

Time: 10 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher demonstrates an actual leaf spring, explaining its construction (main leaf, graduated leaves, center bolt, U-bolts) and its functions in a vehicle.
Pupils’ Activity: Pupils observe the leaf spring, identify its parts, and write down its construction and functions.
Learning Point: Pupils understand the construction and functions of a leaf spring.

Step 4: Coil Spring

Time: 10 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher demonstrates an actual coil spring, explaining its construction (spring wire, ends) and its functions, comparing it with the leaf spring.
Pupils’ Activity: Pupils observe the coil spring, identify its features, and note its construction and functions.
Learning Point: Pupils understand the construction and functions of a coil spring.

Step 5: Tracing Faulty Suspension System

Time: 8 minutes
Teaching Skill: Guided Discovery/Problem Solving
Teacher’s Activity: The teacher guides pupils to identify symptoms of a faulty suspension system, providing examples like sagging, unusual noise, and uneven tyre wear.
Pupils’ Activity: Pupils identify and discuss various symptoms that indicate a faulty suspension system.
Learning Point: Pupils learn to recognize signs of a malfunctioning suspension system.

Step 6: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. Define a vehicle’s suspension system.
2. List three components of a leaf spring.
3. State two functions of a coil spring.
4. Mention three symptoms of a faulty suspension system.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher summarizes the key points of the lesson, emphasizing the importance of a well-maintained suspension system for safety and comfort. The teacher also assigns homework.
Pupils’ Activity: Pupils listen to the summary and copy the assigned homework.
Learning Point: Pupils reinforce their understanding of the topic.

Lesson Keywords

• Suspension System – The system that connects a vehicle to its wheels, allowing relative motion.
• Leaf Spring – A type of spring made of stacked metal leaves.
• Coil Spring – A helical spring made from a wound metal rod.
• Sagging – When a part of the vehicle sits lower than normal due to a weak spring.
• Uneven Tyre Wear – When a tire wears out faster or more on one side due to suspension issues.

Differentiation

For pupils who grasp concepts quickly, the teacher can challenge them to research other types of suspension systems like torsion bars or air suspension. For those needing more support, the teacher will provide additional visual aids and simplified explanations, ensuring hands-on interaction with the actual springs.

Note for teachers using this lesson plan

Ensure that actual leaf and coil springs are available for demonstration to enhance practical understanding. Encourage pupils to ask questions and relate the lesson to real-life vehicle experiences. Emphasize safety precautions when handling vehicle components.