Lesson Notes By Weeks and Term - Junior Secondary 3

TERM – 3^RD TERM

WEEK SIX

Class: Junior Secondary School 3

Age: 14 years

Duration: 40 minutes of 5 periods each

Date:

Subject: BASIC TECHNOLOGY

Topic: MACHINE MOTION II

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

1. Define rotary motion
2. Identify and discuss the two types of rotary motion
3. Describe the applications of One way and reversible rotary motion
4. Discuss the importance of converting rotary motion to linear Linear motion

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,

demonstration, videos from source

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

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

NOTE

MACHINE MOTION II

Rotary motion refers to the circular movement of an object around an axis or a point. It involves rotation, where an object turns or revolves around a fixed center, typically in a circular or angular manner.

1. One Way rotary motion: A one-way rotary motion in engineering refers to rotational movement that occurs in only one direction, allowing rotation in a single, predetermined way. This type of motion is often achieved through mechanisms like clutches or ratchets, ensuring movement in a specific rotational direction. An example is a shaft of running car

Applications

Applications of one-way rotary motion are diverse and can be found in various engineering and mechanical systems. Some notable examples include:

I. Socket Wrenches and Tools: As mentioned earlier, ratchet mechanisms in tools like socket wrenches use one-way rotary motion to efficiently tighten or loosen bolts and nuts without the need to reposition the tool.

II. Bicycle Freewheel: The freewheel mechanism on a bicycle's rear wheel allows one-way rotary motion. It enables the wheel to rotate freely in one direction (forwards) while preventing backward movement when the pedals are not actively being turned.

III. Door Closers: Certain door closers use one-way rotary motion mechanisms to control the closing of doors. The mechanism allows the door to close smoothly in one direction, preventing it from swinging back open.

IV. Retractable Seat Belts: In automotive engineering, retractable seat belts often use one-way rotary motion mechanisms to enable smooth and controlled extension when pulled out, while retracting securely when not in use.

2. Reversible Rotary Motion

Reversible rotary motion, on the other hand, allows rotation in both directions. This type of motion is commonly found in various mechanical systems where the ability to change the direction of rotation is essential. It can be achieved through mechanisms such as gears or reversible motors, providing versatility in the operation of machinery or devices. Examples of reversible rotary motion inludes, load down of Cranes, Brakes, Clutches and Ratchets.

Reversible rotary motion, which allows rotation in both directions, finds applications in a wide range of engineering and mechanical systems. Some examples include:

I. Electric Motors: Most electric motors are designed to provide reversible rotary motion. This versatility is crucial in various applications, such as in appliances, industrial machinery, and automotive systems, where the direction of rotation may need to be changed.

II. Gears and Gearboxes: Gears are fundamental in many mechanical systems, and gearboxes often provide a means for reversible rotary motion. This is vital in applications like automobiles, where the ability to move both forward and backward is essential.

III. Conveyor Systems: Reversible rotary motion is employed in conveyor systems to control the movement of materials in both directions along the conveyor belt. This is common in manufacturing and logistics.

IV. Winches and Hoists: Devices like winches and hoists use reversible rotary motion to lift and lower loads. This capability is crucial for tasks such as material handling in construction and industrial settings.

V. Wind Turbines: Some types of wind turbines use reversible rotary motion to harness wind energy and convert it into electricity. This allows the turbine to adapt to changing wind directions for optimal energy generation.

Importance of converting rotary motion to linear Linear motion

Converting rotary motion to linear motion is often necessary in engineering and various applications due to specific needs and advantages. Some of the key reasons include:

1. Linear Actuation: Many mechanical systems require linear motion for specific tasks, such as moving objects along a straight path, lifting or lowering loads, or controlling linear positioning. Converting rotary motion to linear motion allows for the creation of linear actuators, devices that produce linear movement in response to rotational input.
2. Precision and Control: Linear motion is often more precise and controllable in certain applications than rotary motion. Converting rotary motion to linear motion enables engineers to achieve precise movements and positioning in machinery, robotics, and other systems.
3. Space Constraints: In situations where space is limited or where linear motion is more practical, converting rotary motion becomes essential. Linear motion systems can be more compact and efficient in confined spaces compared to rotational systems.
4. Transmission of Forces: Linear motion is useful when the transmission of force in a straight line is required. This is common in applications like pressing, stamping, or other processes where a linear force is needed.
5. Conveyor Systems: Many conveyor systems require linear motion to transport materials efficiently from one point to another. Converting rotary motion to linear motion is often used in designing conveyor belts and similar systems.
6. Piston Engines: In internal combustion engines, the reciprocating motion of pistons is a result of converting the rotary motion of the crankshaft into linear motion. This linear motion is essential for driving the engine's power cycle.

EVALUATION: 1. What is rotary motion?

2. Identify and discuss the types of rotary motions you know.
3. Why is it necessary to convert rotary motion to linear motion?

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively