Lesson Notes By Weeks and Term - Junior Secondary 2

Gears 2

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TERM – 3RD TERM

WEEK FIVE

Class: Junior Secondary School 2

Age: 13 years

Duration: 40 minutes of 5 periods each

Date:

Subject: BASIC TECHNOLOGY

Topic: GEARS 2

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

  1. Define gear ratio
  2. Define gear Speed
  3. Identify functions of lubricants in gear.

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,

demonstration, videos from source

INSTRUCTIONAL MATERIALS:   Videos, loud speaker, textbook, pictures,

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

PRESENTATION

TEACHER’S ACTIVITY

STUDENT’S

ACTIVITY

STEP 1

INTRODUCTION

The teacher describe and carry out simple calculations of gear ratio.

Students pay

attention

STEP 2

EXPLANATION

Teacher discusses gear Speed.

Students pay

attention and

participate

STEP 3

DEMONSTRATION

Teacher discusses functions of lubricants in gear.

Students pay

attention and

participate

STEP 4

NOTE TAKING

The teacher writes a summarized

note on the board

The students

copy the note in

their books

 

NOTE

GEARS 2

 Gear Ratio

Gear ratio is a measure of the relationship between the number of teeth on two gears that are meshed or connected. It is expressed as a ratio, indicating how many times one gear will rotate in comparison to the other. The gear ratio is essential for understanding the relationship between input and output speeds or torques in a gear system.

The gear ratio R can be calculated using the formula:

R = Number of Teeth on Driven Gear

        Number of Teeth on Driving Gear

For example, if you have two gears, one with 20 teeth (driving gear) and another with 40 teeth (driven gear), the gear ratio would be

R = 40/20 = 2

 This means that for every rotation of the driving gear, the driven gear will rotate twice.

Example 1: A pair of bevel gears consists of a pinion rotating at 300 rpm. The pressure angle is . The PCD of the pinion and gear at their large ends are 150 mm and 200 mm respectively. Determine the gear ratio.

Solution

 Given data,

D1 = 150 mm

D2 = 200 mm

Gear ratio = D2/D1

       = 200/150

Gear ratio =  4/3

Gear ratios are crucial in various applications, such as vehicles, machinery, and robotics, where they determine the speed and torque relationships within a system.

Gear Speed

Gear speed typically refers to the speed at which a gear or a set of gears in a mechanical system rotates. It's determined by the ratio of the number of teeth on the driving gear to the number of teeth on the driven gear. Different gear ratios can affect the speed and torque of a system, commonly seen in vehicles where gears are used in transmissions to achieve optimal performance at varying speeds.

Functions of lubricants in gear

Lubricants in gears serve several crucial functions:

  1. Lubricants minimize friction between gear teeth, preventing wear and tear, and enhancing the overall efficiency of the gear system.
  2. By forming a protective film, lubricants reduce metal-to-metal contact between gear teeth, thereby minimizing wear and extending the lifespan of the gears.
  3. Gears generate heat during operation due to friction. Lubricants help dissipate this heat, preventing overheating and potential damage to the gears.
  4. Lubricants act as a barrier against moisture and contaminants, protecting gear surfaces from corrosion.
  5. Proper lubrication helps dampen vibrations, reducing noise generated by gear movement.

EVALUATION: 1. What is gear speed?

  1. Identify 5 functions of lubricants in gear
  2. Calculate the gear ratio for a gear train where number of gear on the driven is = 10, number of gear on the driver is = 20?

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively