Lesson Notes By Weeks and Term v4 - SHS 2
INTRODUCTION TO VEHICLE TECHNOLOGY
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INTRODUCTION TO VEHICLE TECHNOLOGY
Download the Lessonotes Mobile Ghana app for faster lesson access on Android and iPhone.
Subject: Applied Technology
Class: SHS 2
Term: 1st Term
Week: 6
Grade code: 2.1.2.LI.4
Strand code: 1
Sub-strand code: 2
Content standard code: 2.1.2.CS.1
Indicator code: 2.1.2.LI.4
Theme: AUTOMOTIVE TECHNOLOGY
Subtheme: INTRODUCTION TO VEHICLE TECHNOLOGY
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This lesson introduces the fundamental principles of vehicle suspension systems. In Ghana, we travel on all kinds of roads, from smooth highways to bumpy, untarred rural roads. The system that keeps our ride comfortable and safe by absorbing the shocks from these roads is the suspension system. Whether you are in a "trotro," a cargo truck carrying plantain, or a private car, the suspension is working hard. Understanding how it works is crucial for anyone interested in vehicle technology, maintenance, and safety. We will explore the three main types of suspension springs—leaf, coil, and air—and understand the critical role of the shock absorber.
A. What is a Suspension System? A vehicle's suspension system is a network of springs, shock absorbers, and linkages that connects the vehicle's body to its wheels. It has two main jobs: To support the vehicle's weight and absorb shocks: When a car hits a pothole or a "gallop" (speed bump), the suspension system compresses and rebounds, absorbing the impact energy. This prevents the shock from being transferred directly to the vehicle body and its occupants, providing a comfortable ride. To keep the tyres in firm contact with the road: For a vehicle to accelerate, brake, and steer effectively, its tyres must remain on the ground. The suspension system pushes the wheels down onto the road surface, ensuring maximum grip (traction) even on uneven surfaces.
The two most important components that achieve this are: Springs: These support the vehicle's weight and absorb initial shocks by flexing or compressing. They store the energy from the bump. Dampers (Shock Absorbers): These control the motion of the springs. Without them, a vehicle would continue to bounce up and down long after hitting a bump. They dissipate the energy stored in the spring. B. Types of Suspension Springs Leaf Spring Suspension Description: This is one of the oldest and simplest forms of suspension. It consists of several layers of long, flat steel strips, called "leaves," stacked on top of each other. The longest leaf at the top is called the "main leaf" and has its ends rolled into a circle to form an "eye." These eyes are used to attach the spring to the vehicle's frame. The leaves are held together in the middle by a centre bolt and on the sides by clips. How it works: One end of the spring is attached directly to the vehicle frame (the "hanger"), while the other end is connected via a pivoting link called a "shackle." The axle is bolted to the centre of the leaf spring stack. When the wheel hits a bump, the spring flexes upwards, getting flatter and longer. The shackle allows for this change in length. The steel's natural resistance to bending absorbs the shock. Common Applications in Ghana: You will find leaf springs on most heavy-duty vehicles due to their strength. Examples include: Pick-up trucks (Toyota Hilux, Nissan Hardbody) Commercial buses or "Trotros" (Ford Transit, Mercedes Sprinter, Benz 207) Cargo trucks (KIA Rhino, Man Diesel trucks) Advantages: Strong and Durable: Can support very heavy loads. Simple Design: Fewer parts make it cheaper to manufacture and easier to repair. Acts as a Locating Link: It holds the axle in place without needing extra linkages. Disadvantages: Stiff and Uncomfortable Ride: They are not very flexible, leading to a harsh ride, especially when the vehicle is empty. Heavy: The steel leaves add significant weight to the vehicle.
*Sketch:* ``` Vehicle Frame | (Shackle) (Hanger) / | / EYE---\_______/---EYE | ^ | |____|____| | (Axle) ``` Coil Spring Suspension Description: A coil spring is a heavy-duty torsion bar coiled into a helix (a spiral shape). It is made from a special steel rod that is heated and wound around a cylinder. How it works: The spring is typically placed between the vehicle's frame and a suspension control arm that holds the wheel assembly. When the wheel hits a bump, the spring compresses, storing the energy. When the bump is passed, the spring expands back to its original height. Unlike leaf springs, coil springs only support weight and absorb shocks; they do not locate the axle. Therefore, they must be used with other components like control arms and linkages. Common Applications in Ghana: Most modern passenger cars and SUVs use coil springs for a more comfortable ride. Saloon cars (Toyota Corolla, Camry, Honda Civic, Hyundai Elantra) SUVs (Toyota RAV4, Honda CR-V) Advantages: Comfortable Ride: They are much more flexible than leaf springs, providing a smoother ride. Compact and Lightweight: They take up less space and are lighter. Disadvantages: Lower Load Capacity: Cannot support the same heavy loads as leaf springs. More Complex System: Requires additional linkages (control arms, panhard rods) to position the wheel correctly. Air Suspension Description: This system replaces conventional steel springs (leaf or coil) with flexible, rubber-and-fabric bellows. These bellows are filled with compressed air, acting as the spring. The system includes an engine-driven or electric air compressor, an air storage tank, height sensors, and an electronic control unit (ECU). How it works: When the wheel hits a bump, the air inside the bellows is compressed, absorbing the shock. The ECU uses information from height sensors at each wheel to automatically adjust the air pressure in the bellows. It can add air to raise the vehicle or release air to lower it. This allows for a self-levelling system and an adjustable ride height. Common Applications in Ghana: Typically found in high-end luxury vehicles and large passenger buses. Luxury SUVs (Range Rover, some Mercedes-Benz models) Large Coaches (STC, VVIP, Neoplan buses) Advantages: Superior Ride Comfort: Provides the smoothest ride possible as the stiffness can be adjusted. Adjustable Ride Height: The vehicle can be raised for clearing obstacles or lowered for easy entry/exit and better aerodynamics at high speed. Load Levelling: The system automatically adjusts to keep the vehicle level, regardless of the load. Disadvantages: Very Complex: Many components can fail (compressor, air lines, bellows, sensors). Expensive: The initial cost is high, and repairs can be very costly. Potential for Leaks: Air leaks are a common problem, which can cause the vehicle to sag.
C. The Role and Testing of the Shock Absorber (Damper) Function: A spring, by its nature, will continue to oscillate (bounce) after being compressed. If a car only had springs, it would bounce down the road uncontrollably after hitting a single pothole. The shock absorber's job is to damp these oscillations. It is a hydraulic (oil-filled) device that resists motion, turning the kinetic energy of the bouncing into heat, which is then dissipated. It ensures the tyre returns to the road surface quickly and stays there, providing stability and control. Testing a Telescopic Shock Absorber for Serviceability: A worn-out shock absorber is a major safety hazard. It can increase braking distance, cause skidding on wet roads, and lead to a loss of control.