INTRODUCTION
The term automobile or automotive stands for a vehicle which can be moved by itself.
Therefore, an automobile is a self-propelled vehicle. It is used for the transportation of passengers, goods from one place to another on the ground. A vehicle producing Power within itself for its- propulsion is known as self-propelled vehicles. Example. scooters, mopeds, cars, lorry, bus, jeep, tractors, ship, airplanes, helicopters, rockets etc.
Automobile vehicles differ from aeronautical vehicle .such as ships, airplanes, helicopters, rockets etc., which fly in air and from marine vehicles such as motor boat which sail in water.
Modern automobiles are produced by using complex components of machineries and therefore it requires a careful attention for making it to perform the task in a safe, economical and efficient way. It is made up of a frame supported by the body and power producing units and power transmitting units. These units are further-supported by tyres and Wheels are connected by springs and axles. In general, the power is produced by internal combustion engines. This power intern is transmitted to rear wheels through various transmission systems such , as clutch ,propeller shaft, gear box, differential units etc.
The various units are held together in a proper position and arranged on the frame. The automobile is propelled through the friction between tyre and ground. The super structure or body of the automobile provides protection and comfort to the passenger. The essential parts of Truck is shown in figure.
Requirements of an Automobile
The following requirements must be fulfilled for an automobile.
1. It should develop power by itself.
2. The rate of power development must be easily controlled.
3. There should be an arrangement to transmit developed power to wheels.
4. An arrangement must exist to continue and discontinue power flow to wheels.
5. It should be possible to control or vary the torque.
6. The driving thrust should successfully be carried in the vehicle.
7. It must have a directional control.
8. An arrangement must exist to stop the vehicle while it is running
All above requirements are fulfilled by the following arrangements.
1. The power is developed by the engine.
2. The rate of power development is controlled bv an accelerometer.
3. The power developed by the engine is transmitted to wheels by transmission system.
4. The gear box is provided for varying or changing the torque.
5. The driving thrust is carried to the chassis frame through the suspension system.
6. Directional control is maintained through the steering.
7. The moving vehicle is stopped by means of brakes
DIFFERENT LAYOUTS OF A CAR
Front Engine Front Wheel Drive
The majority of light vehicles have the engine at the front of the vehicle with the driving power being transmitted to front wheels. In the arrangement shown in Figure. The engine and transmission units are placed transversely at the front of the vehicle. So, they are at right angles to the main axis of the vehicle.
No propeller shaft is used in the front engine front wheel drive and differentials are included in the same assembly. This layout provides an optimum body-luggage space and a flat front line resulting a transverse longitudinal engine position. A good road adhesion is provided by the large proportion of vehicle's weight acting on driven wheels.
List of some cars having front engine front wheel driving system
- Maruti Suzuki Alto.
- Chevrolet Beat.
- Hyundai Verna.
- Hyundai i10.
- Honda City.
- Honda Civic.
- Toyota Corolla.
- Mitsubishi Outlander.
Advantages:
1. Because the engine and transmission system are placed over the front wheels the road holding is improved especially in wet and slippery conditions.
2. Good steering stability is achieved because the driving force at the wheels is in the
direction that the vehicle is being steered. There is also a tendency for front-wheel drive vehicles to understeer which can improve drivability when cornering.
3. Passenger and cargo space~are good because there is no need for a transmission shaft to the rear axle.
4. Good road adhesion is obtained due to a large part of the vehicle weights are carried
on driving wheels under normal conditions,
5. Under steady conditions, this drive is preferred by many drivers.
6. Lower flat floor line is provided due to dispensing with the propeller shaft resulting
less centre of gravity.
7. The engine clutch, gear box and final drive are combined similar to a rear engine car.
It provides a more comfortable drive due to final drive spring.
Disadvantages:
1. Complicated drive shafts are needed for constant velocity Joints.
2. Acceleration is affected because the load transfer to rear of the vehicle lightens the
load on the drive axle at the front.
3. The turning circle radius is limited by the angle through which a constant-velocity
joint can function.
4. Due to the combination of steered and driven wheels with short shafts, special
universal joints and more complicated assembly are required.
5. To prevent the rear wheels from skidding under heavy brake, the required weight at
the rear usually necessitates a special arrangement.
6. The tractive effort is reduced which is mostly required on steep gradients and during
acceleration.
Front Engine Rear Wheel Drive
In this layout, a front mounted engine-clutch-gear box unit drives a beam type rear
axle suspended on leaf springs through a propeller shaft with two universal joints. With
the help of coil springs, the front wheels are independently sprung.
This layout is one of the oldest layouts which remain unchanged for many years.
Some examples of this layout are
- Maruti Suzuki Eeco. Maruti Suzuki Eeco (Versa) | The National Passenger Carrier.
- Mahindra Quanto/Nuvosport. Mahindra Quanto.
- Mahindra TUV300.
- Mahindra Bolero.
- Mahindra Scorpio.
- Tata Safari Storme.
- Toyota Innova.
- Ford Endeavour.
Advantages:
I. It is reasonably balanced weight distribution between front and rear wheels providing good handling characteristics.
2. For easy front wheel steering movement, the engine occupies the reduced width
between arches.
3. Behind the rear seats, a large luggage space is available by providing the increased
carrying capacity as well as space for easy body movement.
4. Accessibility to various components such as engine, gear box and rear axle are better
compared to other layouts.
5. The control linkages such as accelerator, choke, clutch and gear box are short and
simple.
6. For the full benefits of the natural air stream created by vehicles, the movement is
taken by the forward facing radiator in reduced power losses from a large fan.
Disadvantages:
1. A single or split propeller shaft with universal joints and supporting bearings between front mounted gearbox and rear axle may generate vibration, drumming, howl and other noises under certain operating conditions.
2.The floor tunnel is necessary to provide a clearance for the operation of a propeller shaft system and it may interfere with passenger leg-room.
3. In case of a rigid casing for the axle and final drive, more weight is not supported by
the suspension system so that the quality of the suspension ride may be reduced.
4. Additional universal joints and drive shafts are required for independent rear suspension.
5. A rear-wheel-drive vehicle when stuck in mud, tends to plough further into the ground
when attempts are made to drive away.
Rear Engine Rear Wheel Drive
This arrangement eliminates the necessity for a propeller shaft when the engine is
mounted adjacent to driven wheels. The engine-clutch-gearbox-final drive forms a single unit in this layout. In order to reduce the 'overhang' distance between wheel centres and the front side of the engine, the final drive is generally placed between clutch and gear box.
List of cars having this type of layout
- Benz Patent-Motorwagen.
- BMW 600, 700, and i3.
- Chevrolet Corvair.
- Davrian.
- DMC DeLorean.
- Dune buggies such as the Meyers Manx.
- Fiat 500, 600, 850, 126 and 133.
- FMR Tg500.
Advantages:
1. Short drive line because the engine, gearbox and final drive can be built into a single unit.
2. A majority of weight at the rear of the vehicle gives improved traction during hill climbing and acceleration.
3. It has a simple drive shaft layout compared to a front wheel drive.
4. Effective rear wheel braking is possible with this layout.
5. Due to the absence of the propeller shaft, the obstructed floor space is reduced.
6. The exhaust gases, fumes, engine heat and noises are carried away from
passengers.
7. The drive arrangement results a compact layout and short car.
8. The front of the vehicle can be designed for good visibility and smooth air flow.
Disadvantages:
1. The rearward concentration of weight causes the vehicle to be more affected by side winds at high speeds. It makes the vehicle unstable resulting over-steering and turning very sharply into a curve.
2. It is difficult to accommodate the liquid cooling of the engine.
3. It is difficult to accommodate the fuel tank in a safe zone of the vehicle.
4. Space for luggage is reduced.
5. Steering is difficult in slippery conditions.
6. It has a restricted luggage compartment due to narrow front which houses the fuel tank also.
7. Natural air cooling is not possible because it requires a powerful fan.
8. Long linkages are required for the engine, clutch and gear box controls
Four-Wheel Drive
To increase the effective use of the vehicle required to travel on rough unconstructed
roads and trucks, a special arrangement known as four wheel drive is provided. Due to all four
wheels getting driven, the whole weight of the vehicle is available for traction.
The system is provided in jeeps which are known as 4x4 wheel drive or all-wheel drive vehicles.
These vehicles are also called off-road vehicles as it is constructed mainly for the purpose of unformed or off-road driving conditions.
Example:
Mahindra Scorpio, Maruti Suzuki Gypsy,Tata Safari, Toyota Fortuner, Mitsubishi Pajero, Mahindra Bolero etc.
Advantages:
1. The increased traction is obtainable from four driven wheels which is especially
useful on soft or slippery ground.
2. If the front wheel drops into a ditch, they tend to climb out with a rear wheel drive
3. Wear of tyres and other driveline components are more evenly shared
Disadvantages:
1. It increases weight and bulk.
2. It increases cost.
3. It increases fuel consumption.
4. It increases maintenance due to complexity of transmission system.
5. It is possibly difficult to accommodate an anti-locking brake system.
This is my first post and I hope this will be beneficial for you.
Thankyou....
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