Lesson Note on Components of a Transmission Unit (Clutch): Construction and Operation of a Single Plate Clutch for SS2

Class: Senior Secondary School 2 (SS2 / SSS 2)
Term: 1st Term
Week: 6
Age: 16 years
Duration: 45 minutes
Subject: Auto Mechanic Work
Curriculum Theme: Transmission System
Previous Lesson: Components of a Transmission Unit (Clutch): Identification of Parts and Characteristics of Clutches.
Topic: COMPONENTS OF A TRANSMISSION UNIT (CLUTCH) CONSTRUCTION AND OPERATION OF A SINGLE PLATE CLUTCH.
Subject Matter: Meaning of COMPONENTS OF A TRANSMISSION UNIT (CLUTCH) (definition of clutch unit), various parts in a transmission system (clutch, gearbox, related components), construction and operation of a single plate clutch (how it transmits power, how it disengages).

Specific Objectives

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

Cognitive Domain:

• Define a clutch unit.
• List various components of a vehicle’s transmission system.
• Explain the construction of a single plate clutch.
• Describe the operation of a single plate clutch during engagement and disengagement.

Affective Domain:

• Appreciate the importance of the clutch in vehicle operation.
• Value the need for proper maintenance of transmission components.

Psychomotor Domain:

• Identify actual components of a transmission system on a live vehicle or diagram.
• Sketch a simple diagram of a single plate clutch.

Social Domain:

• Collaborate with peers to identify and discuss transmission components.

Reference Materials

The following resources were used in planning this lesson:

• Senior Secondary Schools Education Curriculum
• State Unified Scheme of Work
• Auto Mechanics for Senior Secondary Schools by A.K. Ojo

Instructional Materials

The teacher will teach this lesson with the aid of:

• A live vehicle (if available)
• Actual clutch and gearbox components
• Posters and charts showing transmission systems
• Diagrams of a single plate clutch

Rationale for the Lesson

Understanding the clutch unit and its operation is important for pupils learning auto mechanics. This knowledge helps them to understand how power is transmitted in a vehicle and how to diagnose and repair issues related to the transmission system.

Prerequisite/Previous Knowledge

Pupils have a basic understanding of motor vehicle components and how an engine produces power.

Lesson Content/Board Summary

COMPONENTS OF A TRANSMISSION UNIT (CLUTCH)

Definition of Clutch Unit

A clutch is a mechanical device that connects and disconnects power transmission between the engine and the gearbox. It allows the driver to smoothly engage or disengage the engine from the transmission, enabling gear changes and stopping the vehicle without stalling the engine.

Various Parts in a Transmission System

The transmission system is responsible for transferring power from the engine to the drive wheels. The following are major components of a transmission system:

• Clutch
• Gearbox (manual or automatic)
• Propeller shaft (for rear-wheel drive vehicles)
• Differential
• Drive shafts (axle shafts)
• Universal joints
• Half shafts

Construction and Operation of a Single Plate Clutch

A single plate clutch is commonly used in manual transmission vehicles. It consists of several key components:

Construction

• Flywheel: Attached to the engine crankshaft, it provides a friction surface for the clutch plate.
• Clutch Plate (Friction Disc): A disc with friction material on both sides, splined to the gearbox input shaft.
• Pressure Plate: A metal plate that presses the clutch plate against the flywheel.
• Diaphragm Spring (or Coil Springs): Provides the force to press the pressure plate against the clutch plate.
• Release Bearing (Throw-out Bearing): Pushed by the clutch fork, it disengages the clutch.
• Clutch Fork: Pivots to move the release bearing.
• Clutch Cover: Encloses the pressure plate and diaphragm spring assembly.

Operation (Engagement)

When the clutch pedal is released, the clutch is engaged, and power is transmitted from the engine to the gearbox:

1. Step 1: The diaphragm spring pushes the pressure plate against the clutch plate.
2. Step 2: The clutch plate is firmly clamped between the flywheel and the pressure plate.
3. Step 3: Friction created between these surfaces causes the clutch plate to rotate with the flywheel.
4. Step 4: Since the clutch plate is splined to the gearbox input shaft, engine power is transferred to the gearbox.

Operation (Disengagement)

When the clutch pedal is pressed, the clutch is disengaged, interrupting power transmission:

1. Step 1: The driver presses the clutch pedal, which moves the clutch fork.
2. Step 2: The clutch fork pushes the release bearing towards the diaphragm spring.
3. Step 3: The release bearing presses against the center of the diaphragm spring, causing its outer edges to pull the pressure plate away from the clutch plate.
4. Step 4: The clutch plate is no longer clamped, allowing it to spin freely from the flywheel.
5. Step 5: Power transmission from the engine to the gearbox is interrupted, allowing for gear changes or stopping the vehicle.

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 greets the pupils, reviews the previous lesson briefly, and asks pupils what happens when a driver changes gears in a manual car. The teacher then introduces the topic of the clutch.
Pupils’ Activity: Pupils respond to questions and listen attentively as the teacher introduces the lesson.
Learning Point: Pupils are prepared for the new lesson and connect it to previous knowledge.

Step 2: Meaning of Clutch Unit

Time: 5 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines a clutch unit as a device that connects and disconnects power from the engine to the gearbox. The teacher explains its purpose in allowing gear changes and stopping without stalling.
Pupils’ Activity: Pupils listen and copy the definition into their notebooks.
Learning Point: Pupils understand the fundamental role and definition of a clutch.

Step 3: Various Parts in a Transmission System

Time: 7 minutes
Teaching Skill: Listing/Demonstration
Teacher’s Activity: The teacher lists and explains various parts of a transmission system using diagrams, charts, and by pointing them out on a live vehicle or actual components if available.
Pupils’ Activity: Pupils observe, identify the components, and note them down.
Learning Point: Pupils can identify and name major components of a transmission system.

Step 4: Construction of a Single Plate Clutch

Time: 8 minutes
Teaching Skill: Explanation/Visualisation
Teacher’s Activity: The teacher explains the construction of a single plate clutch, detailing each component (flywheel, clutch plate, pressure plate, diaphragm spring, release bearing, clutch fork) with the aid of real parts or diagrams.
Pupils’ Activity: Pupils observe the components, ask questions, and make mental notes of their arrangement.
Learning Point: Pupils understand the individual parts and assembly of a single plate clutch.

Step 5: Operation of a Single Plate Clutch (Engagement)

Time: 6 minutes
Teaching Skill: Step-by-step Explanation
Teacher’s Activity: The teacher explains the process of clutch engagement, describing how power is transmitted from the engine to the gearbox when the clutch pedal is released, using diagrams or components.
Pupils’ Activity: Pupils listen carefully and follow the explanation, asking for clarification where needed.
Learning Point: Pupils understand how the clutch transmits engine power to the transmission.

Step 6: Operation of a Single Plate Clutch (Disengagement)

Time: 5 minutes
Teaching Skill: Step-by-step Explanation
Teacher’s Activity: The teacher explains the process of clutch disengagement, describing how power transmission is interrupted when the clutch pedal is pressed, again using visual aids.
Pupils’ Activity: Pupils pay attention and describe the disengagement process.
Learning Point: Pupils understand how the clutch disconnects engine power for gear changes.

Step 7: Evaluation/Review

Time: 5 minutes
Teaching Skill: Questioning/Assessment
Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

1. What is the main function of a clutch unit in a vehicle?
2. Mention three components of a vehicle’s transmission system.
3. List three main components involved in the construction of a single plate clutch.
4. Briefly explain how a single plate clutch engages.

Pupils’ Activity: Pupils answer orally and in writing.
Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 4 minutes
Teaching Skill: Summarization/Assignment
Teacher’s Activity: The teacher summarizes the key points of the lesson, emphasizing the importance of the clutch. The teacher then assigns homework: “Draw a labelled diagram of a single plate clutch.”
Pupils’ Activity: Pupils listen to the summary and copy down the homework.
Learning Point: Pupils consolidate their learning and prepare for further study.

Lesson Keywords

• Clutch – A mechanical device that connects and disconnects power transmission.
• Transmission – The system that transmits power from the engine to the driving wheels.
• Gearbox – A part of the transmission system that changes the speed and torque from the engine.
• Flywheel – A heavy wheel attached to the crankshaft that provides inertia and a friction surface.
• Pressure Plate – A component that clamps the clutch plate against the flywheel.
• Clutch Plate – A disc with friction material that transmits power when engaged.
• Engagement – The state where the clutch connects the engine to the gearbox.
• Disengagement – The state where the clutch disconnects the engine from the gearbox.

Differentiation

The teacher will provide visual aids like diagrams and actual components for visual learners. Practical demonstration on a live vehicle will cater to kinesthetic learners. Explanations and discussions will support auditory learners. Pupils with slower comprehension will be given additional support and simpler questions, while advanced learners can be challenged to research different types of clutches.

Note for teachers using this lesson plan

Ensure that safety precautions are observed when working with a live vehicle or actual components. Emphasize the practical application of the lesson content. Encourage pupils to ask questions and participate actively in demonstrations. If a live vehicle is not available, detailed diagrams and video demonstrations can be used effectively.