JSS 3. After Mid-Term.TOPIC7: MOTION IN ENGINEERING SYSTEMS.

Definition:
Motion can be defined as the movement of a body (object) from one point to another with the application of force.

                                                                 Types of Motion

At this level, the two types of motion to be considered are Linear Motion and Rotary Motion.

Linear Motion: This is the motion of a body moving in a straight line. For instance, a push-pull link mechanism is a simple machine that operates with linear motion. E.g.

 Rotary Motion: This is motion of a body moving in a circular form. Examples of circular motion is the rotation of a fan, vehicle tyres, the handle of the clock, etc. e.g.

                                                             Transmission of Motion

For any engine to function, motion must be transmitted from one part of the engine to other parts. For instance, in a car, motion is often transmitted from the car engine to the wheels. This is possible because of the motion transmission system in the car.
The transmission system in a car includes the gearbox and the clutch.

Function of the Clutch: The function of the clutch is to disconnect two shafts running at different speeds, that is, the engine crankshaft and the gearbox shaft.

                                                             Types of Car Engines

1.Front- Engine Rear-Wheel Drive: This is an engine that consists of a clutch, a gear box, a propeller shaft and a rear axle. Most cars in Nigeria operate on this type of engine.

2. Front-Engine Front Wheel Drive: In this type of engine, every other parts mentioned in 1 above is present except for the propeller shaft. Transmission is directly from the gearbox to the rotating wheels.

3. Rear-Engine Rear-Wheel Drive: In this type of engine, there is no propeller shaft also. The clutch, engine, gearbox are all engineered at the back of the car. Example is Volkswagen cars.

4. Front-Engine 4-Wheel Drive: This is a more recent technological advancement in the engineering of cars. There is no propeller shaft and most times no mechanical gearbox. The gear system is a hydraulic system. This car contains of the brake and the accelerator only, with all 4 wheels connected to the gear box.

e.g. Mechanical Gear System and Hydraulic Gear System.

                                             Control of Rotary Motion-Brakes
Brakes are meant to bring bicycles and cars in motion to a stop. Kinetic energy in a moving object is absorbed by the brake. This produces heat on the brake as kinetic energy is converted into potential energy. As the brake absorbs heat, the vehicle slows down until it finally comes to a stop.

                                                      How Brakes Work
There are different types of brakes. However, the principle of how the brake works is the use of friction. If the brake in a car or bicycle is pressed against the rotating drum or disc or wheel, the resulting friction between the pad and the drum or wheel slows down the rotating wheels, until they eventually come to a stop. E.g.

A Bicycle Brake.

A Disc Brake.

  

                                   Conversion of Rotary Motion to Linear Motion

In some machines, it is necessary for a change from one form of motion to another along it’s line of operation. For instance, a sewing machine will need to convert linear motion from the moving pedal to rotary motion at the wheel and finally to linear motion again at the needle.

The piston-crank mechanism of a car engine is another example of converting rotary motion at one point of an engine to rotary motion at another point of the same engine. (teacher will explain more). E.g.

Other examples of machines involved in converting one form of energy to another are;
Screw jack, Rack and piston steering system, Crankshaft and cylinder, Metalwork table vice, Woodworker’s vice, Pipe vice, G-clamp, etc. 

Class Work.

(i) define motion
ii. list the two types of motions
iii. explain how to convert one form of motion to another
iv. explain machines that make use of motions.

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