Lesson Note on Steering Boxes Types and Functions for SS1 (SSS 1)

Class: Senior Secondary School 1 (SS1, SS 1, SSS1, SSS 1)
Term: 2nd Term
Week: 7
Age: 15 years
Duration: 45 minutes
Subject: Auto Mechanic Work
Curriculum Theme: Auto Mechanic Work
Previous Lesson: Steering System Functions and Components.
Topic: STEERING SYSTEM – Steering Boxes Types and Functions
Subject Matter: rack and pinion steering box, cam and worm steering box, recirculating ball steering box, comparison of steering box types

Specific Objectives

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

Cognitive Domain:

• Define a steering box.
• List the different types of steering boxes.
• Explain the function of each type of steering box.
• Compare the different types of steering boxes based on their characteristics.

Affective Domain:

• Appreciate the importance of different steering box designs in vehicles.
• Value the role of steering boxes in vehicle control and safety.

Psychomotor Domain:

• Identify examples of rack and pinion, cam and worm, and recirculating ball steering boxes.
• Differentiate between various steering box types when presented with illustrations or actual components.

Social Domain:

• Work cooperatively with peers to discuss the functions of different steering boxes.

Reference Materials

The following resources were used in planning this lesson:

• 9 Years Basic Education Curriculum for Basic Technology (JSS) and Auto Mechanic Work (SSS).
• State Unified Scheme of Work for Senior Secondary Schools.
• Auto Mechanic Work for Senior Secondary Schools by A. O. Oyenuga.

Instructional Materials

The teacher will teach this lesson with the aid of:

• Actual steering boxes (rack and pinion, cam and worm, recirculating ball) if available.
• Charts and posters illustrating different types of steering boxes and their internal components.
• Diagrams showing the working principle of each steering box type.

Rationale for the Lesson

This lesson helps pupils understand the mechanisms that allow a vehicle to be steered accurately and safely. Understanding different steering box types enables pupils to identify and appreciate the engineering behind vehicle control, which is important for future mechanics and responsible drivers.

Prerequisite/Previous Knowledge

Pupils are expected to have a basic understanding of the vehicle steering system and its general purpose.

Lesson Content/Board Summary

STEERING SYSTEM – Steering Boxes Types and Functions

Steering Box Definition

A steering box is a mechanical device in a vehicle’s steering system that converts the rotational motion of the steering wheel into the linear motion required to turn the road wheels.

Types of Steering Boxes and Their Functions

1. Rack and Pinion Steering Box

This type of steering box consists of a circular gear (pinion) attached to the steering shaft, which meshes with a linear gear (rack) that moves horizontally. The movement of the rack is transferred to the steering arms, turning the wheels.

The function of the rack and pinion steering box is to provide a direct and responsive steering feel, commonly used in smaller and modern vehicles.

Advantages include:

• Simple design.
• Lightweight.
• Direct steering response.
• Fewer linkages.

2. Cam and Worm Steering Box

In this system, a worm gear on the steering shaft engages with a cam or roller mounted on a sector shaft. As the steering wheel turns the worm, the cam or roller moves the sector shaft, which then transmits motion to the steering linkage.

The function of the cam and worm steering box is to provide a robust and durable steering mechanism, often found in older or heavy-duty vehicles.

Advantages include:

• Strong and durable.
• Can handle heavy loads.
• Good for larger vehicles.

3. Recirculating Ball Steering Box

This steering box uses a worm gear on the steering shaft that engages with a nut, inside which steel balls recirculate to reduce friction. The nut has teeth on its outer surface that mesh with a sector gear, which rotates the pitman arm and moves the steering linkage.

The function of the recirculating ball steering box is to offer a smooth and low-friction steering action, commonly used in trucks and larger cars.

Advantages include:

• Reduced friction due to recirculating balls.
• Smooth operation.
• Durable and robust.

Comparison of Steering Box Types

The following points compare the different steering box types:

• Mechanism: Rack and pinion uses a direct gear mesh; Cam and worm uses a worm and cam/roller; Recirculating ball uses a worm, nut, and recirculating balls.
• Friction: Rack and pinion has moderate friction; Cam and worm has higher friction; Recirculating ball has lower friction due to balls.
• Steering Feel: Rack and pinion offers a more direct and responsive feel; Cam and worm and Recirculating ball can feel less direct.
• Application: Rack and pinion is common in modern passenger cars; Cam and worm and Recirculating ball are found in older cars, trucks, and heavy vehicles.
• Complexity: Rack and pinion is simpler; Recirculating ball is more complex due to ball mechanism.

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 and asks them to recall the previous lesson on the general layout of a steering system. The teacher then introduces the topic by asking pupils how the steering wheel’s rotation is converted to wheel movement, leading to the concept of steering boxes.
Pupils’ Activity: Pupils respond to the questions and listen attentively to the introduction of the new topic.
Learning Point: Pupils recall prior knowledge and are prepared for the new lesson.

Step 2: Explanation of Steering Box Definition

Time: 5 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines what a steering box is, using simple terms and referring to its role in the steering system. The teacher may draw a simple diagram on the board or point to an illustration.
Pupils’ Activity: Pupils listen, take notes, and ask questions for clarification.
Learning Point: Pupils understand the basic concept and purpose of a steering box.

Step 3: Introduction to Rack and Pinion Steering Box

Time: 10 minutes
Teaching Skill: Demonstration/Explanation
Teacher’s Activity: The teacher explains the working principle of the rack and pinion steering box, showing an actual component or a detailed chart. The teacher highlights its advantages and common applications.
Pupils’ Activity: Pupils observe the demonstration, ask questions, and take notes on the mechanism and features.
Learning Point: Pupils learn about the structure, function, and application of the rack and pinion steering box.

Step 4: Introduction to Cam and Worm Steering Box

Time: 7 minutes
Teaching Skill: Explanation/Visualisation
Teacher’s Activity: The teacher explains the cam and worm steering box, detailing how the worm gear interacts with the cam/roller. Charts or diagrams are used to illustrate its components and operation. The teacher mentions its typical use.
Pupils’ Activity: Pupils pay attention to the explanation, relate it to the visual aids, and note down key points.
Learning Point: Pupils understand the mechanism and use of the cam and worm steering box.

Step 5: Introduction to Recirculating Ball Steering Box

Time: 7 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher describes the recirculating ball steering box, emphasizing the role of the steel balls in reducing friction. The teacher uses diagrams to show the internal workings and discusses its benefits.
Pupils’ Activity: Pupils listen to the explanation, observe the illustrations, and record important details.
Learning Point: Pupils grasp the design and advantages of the recirculating ball steering box.

Step 6: Comparison of Steering Box Types

Time: 5 minutes
Teaching Skill: Comparative Analysis
Teacher’s Activity: The teacher leads a discussion comparing the three types of steering boxes based on their mechanism, friction, steering feel, and common applications. The teacher may create a simple comparison table on the board.
Pupils’ Activity: Pupils participate in the discussion, contributing their understanding, and noting down the comparative points.
Learning Point: Pupils can differentiate between the various steering box types.

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 a steering box?
2. Mention two types of steering boxes.
3. Explain the function of a rack and pinion steering box.
4. State one advantage of the recirculating ball steering box over the cam and worm type.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 1 minute
Teaching Skill: Summarization
Teacher’s Activity: The teacher briefly summarizes the main points of the lesson, reiterating the types and functions of steering boxes. The teacher assigns homework, asking pupils to draw and label one type of steering box.
Pupils’ Activity: Pupils listen to the summary and copy the homework.
Learning Point: Pupils consolidate their learning and have a task to reinforce understanding.

Lesson Keywords

• Steering Box – A device that converts rotational motion from the steering wheel into linear motion for turning wheels.
• Rack and Pinion – A steering box type with a circular gear (pinion) meshing with a linear gear (rack).
• Cam and Worm – A steering box type where a worm gear engages with a cam or roller on a sector shaft.
• Recirculating Ball – A steering box type using a worm, nut, and recirculating steel balls to reduce friction.
• Pitman Arm – A component of the steering linkage connected to the steering box.

Differentiation

For pupils who grasp concepts quickly, they can be tasked with identifying specific vehicle models that use each type of steering box. For pupils needing more support, the teacher will provide additional visual aids and simplified explanations, focusing on one steering box type at a time before moving to comparisons.

Note for teachers using this lesson plan

Ensure that actual steering box components are handled with care, especially if demonstrating their internal workings. Safety precautions should be observed. Encourage active participation and questions from all pupils to ensure comprehensive understanding.