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Subject - AUTOMOBILE ENGINEERING ME 40041
Branch - Mechanical Engineering
Semester - 4th Semester
AUTOMOBILE ENGINEERING
UNIT-I: INTRODUCTION TO AN AUTOMOBILE
An automobile is a self-propelled vehicle that is used for transportation. It consists of various mechanical and electrical components that work together to generate motion and ensure the smooth running of the vehicle.
1.1 Classification of Automobiles
Automobiles can be classified into different categories based on various factors.
(a) Based on Fuel Type
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Petrol Vehicles – Powered by petrol engines (e.g., most cars and motorcycles).
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Diesel Vehicles – Use diesel engines, mainly used in trucks, buses, and some cars.
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Electric Vehicles (EVs) – Run on rechargeable batteries (e.g., Tesla, Nissan Leaf).
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Hybrid Vehicles – Combine an internal combustion engine with an electric motor (e.g., Toyota Prius).
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CNG/LPG Vehicles – Use compressed natural gas (CNG) or liquefied petroleum gas (LPG) as fuel.
(b) Based on Purpose
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Passenger Vehicles – Used for personal transportation (e.g., cars, buses, SUVs).
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Commercial Vehicles – Used for transporting goods or passengers for business (e.g., trucks, vans, taxis).
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Two-Wheelers and Three-Wheelers – Includes motorcycles, scooters, auto-rickshaws.
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Special Purpose Vehicles – Used for specific tasks (e.g., ambulances, fire trucks, military vehicles).
(c) Based on Drive Configuration
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Front-Wheel Drive (FWD) – Power is delivered to the front wheels.
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Rear-Wheel Drive (RWD) – Power is delivered to the rear wheels.
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All-Wheel Drive (AWD) or Four-Wheel Drive (4WD) – Power is distributed to all four wheels.
1.2 Chassis and Body
(a) Chassis
The chassis is the main supporting structure of a vehicle. It holds and connects all the major components, such as the engine, transmission, wheels, and suspension.
Types of Chassis Frames
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Ladder Frame – Used in trucks and SUVs; strong but heavy.
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Monocoque Frame – Used in modern cars; lightweight and provides better safety.
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Backbone Frame – Used in some sports cars; has a central tubular structure.
Diagram: Basic Chassis Structure
(Ladder frame vs. Monocoque frame)
(b) Body
The body of a vehicle is mounted on the chassis and provides safety, aerodynamics, and aesthetics.
Types of Car Body Styles
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Sedan – A four-door car with a separate trunk (e.g., Honda City).
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Hatchback – A small car with a rear door for cargo access (e.g., Maruti Swift).
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SUV (Sports Utility Vehicle) – A large, high-ground clearance vehicle (e.g., Toyota Fortuner).
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Convertible – A car with a retractable roof (e.g., Mercedes-Benz Cabriolet).
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Coupe – A two-door car with a sporty design (e.g., BMW M4).
1.3 Components of a Vehicle
A vehicle consists of the following major components:
(a) Power Unit (Engine)
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The engine converts fuel into mechanical energy.
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Types of engines: Petrol, Diesel, Electric, Hybrid.
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Common engine configurations: Inline, V-type, Boxer.
Diagram: Engine Components
(b) Transmission System
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Transfers power from the engine to the wheels.
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Types: Manual Transmission, Automatic Transmission, CVT (Continuously Variable Transmission).
Diagram: Transmission System
(c) Suspension System
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Absorbs shocks and provides a smooth ride.
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Types: Independent and Non-independent suspension.
(d) Braking System
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Slows down or stops the vehicle.
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Types: Drum Brakes, Disc Brakes, ABS (Anti-lock Braking System).
(e) Steering System
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Controls the direction of the vehicle.
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Types: Manual Steering, Power Steering.
(f) Electrical System
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Includes the battery, alternator, lights, sensors, and ECU (Electronic Control Unit).
(g) Fuel System
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Stores and supplies fuel to the engine.
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Components: Fuel Tank, Fuel Pump, Carburetor (for petrol engines), Fuel Injectors.
1.4 Layout of a Conventional Vehicle (Front Engine Rear-Wheel Drive Layout)
The front-engine rear-wheel drive (FR) layout is commonly used in trucks and sports cars.
Features
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The engine is placed at the front of the vehicle.
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Power is sent to the rear wheels through the driveshaft.
Diagram: FR Layout
Advantages
✔️ Good weight distribution
✔️ Better traction for heavy loads
✔️ Improved handling in performance cars
Disadvantages
❌ Heavier due to extra components like driveshaft
❌ Less fuel-efficient compared to front-wheel drive (FWD)
1.5 Vehicle Dimensions
Vehicle dimensions are important for design, safety, and performance.
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Overall Length – Distance from the front bumper to the rear bumper.
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Overall Width – Maximum width, including side mirrors.
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Overall Height – Height from the ground to the highest point of the vehicle.
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Wheelbase – Distance between the front and rear axles.
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Track Width – Distance between the left and right wheels.
Diagram: Vehicle Dimensions
1.6 Minimum Ground Clearance
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Ground clearance is the distance between the lowest part of the vehicle and the ground.
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Higher ground clearance is useful for off-road vehicles.
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Lower ground clearance improves stability and aerodynamics in sports cars.
Diagram: Ground Clearance
1.7 Minimum Turning Radius
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The turning radius is the smallest circular turn a vehicle can make.
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Smaller turning radius is better for city driving and parking.
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It depends on the wheelbase and steering system.
Conclusion
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Automobiles are classified based on fuel type, purpose, and drive configuration.
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The chassis provides structure, while the body ensures safety and aerodynamics.
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The conventional vehicle layout is front-engine rear-wheel drive.
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Vehicle dimensions, ground clearance, and turning radius affect performance and usability.
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