Automobile Chassis Components and Drive System
Figure 1.13 shows the front and top views layout of the typical chassis. In this layout, the engine location is at the front end of the vehicle. The engine is connected to the gearbox through clutch. The drive of the engine can be connected or disconnected from the gearbox by using clutch assembly. The clutch pedal provided at the vicinity of the driver facilitates to engage or disengage the clutch with gearbox whenever required. From gearbox, power is transmitted to the differential through a propeller shaft and universal joints and finally to the wheels via rear axles. The radiator is placed at the front side of the engine.
Components and Drive Systems in Chassis
Frame is the foundation for carrying the engine and body of the vehicle. It also carries steering, power train etc. by means of springs, axles, rubber pads etc. The frames are made of box, tubular, channel or U-shaped section, welded or riveted together. In order to make them rigid to withstand shocks, blow twists and vibration mats, cross-bracing or cross members are used. When the engine, wheels, power trains, brackets and steering systems are fitted on the frame, the assembly is known as chassis. Frame bends upward in a shape at the rear to provide space for rear springs. It is tapered at the front to provide space for turning front wheels when steered.
2. Suspension systems:
Suspension systems are used in vehicles. to insulate the wheel and axles from the frame in order to avoid the transmission of road effects to passengers while travelling on uneven road to provide a comfortable ride to passengers and to avoid additional stresses in the motor car frame.
3. Steering system:
The function of the steering system is to enable the driver to accurately control the direction taken by the vehicle under all operating conditions. The system must be light and easy to operate, free from shock and vibration as direct as possible. The steering system also helps to convert the rotary motion of the driver’s steering wheel into the angular turning front wheels as well as to multiply the driver’s effort with the leverage or mechanical advantage of turning wheels.
4. Braking system:
The most vital factor in running and controlling the modern vehicle is the braking system. In order to bring the moving motor vehicle to rest or slow down in a shortest possible time, the energy of motion possessed by the vehicle must be converted into some other form energy. Brake is a friction device for converting the power of momentum or kinetic energy moving vehicle into heat.
5. Internal combustion engines:
In internal combustion engines, the combustion takes place within the engine unlike steam engines which work using steam which has externally been raised in a boiler. In all Internal Combustion (IC) engines, the air is supplied along with a measured quantity of fuel. This fuel burns within the engine and it produces a high pressure and high temperature gas.
It is a friction type uncoupling device. It consists of a single steel disc faced with suitable friction material. It is clamped between two surfaces directly driven by the engine. For disengagirtg the clutch, the two surfaces are ^positively separated by pressing the clutch pedal. The main function of the clutch is to take up the drive smoothly from the engine and to release or disengage whenever desired. The disengagement of clutch is reauired while changing the gear or bringing the vehicle to rest.
It consists of various types of gears which are constantly in mesh. The gear change takes place by sliding the dogs. The main function of the gear-box is to provide the necessary variation to the torque applied by the engine to the road wheel according to the operating conditions. The necessary variations are provided due to the presence of different gear ratio among various meshing gears.
8. Propeller shaft:
The function is to transmit the power from the rear end of the gear-box to the final reduction gear in the axle. The vertical movement of the rear axle relative to the frame is also accommodated. It is an ordinary Hooke’s joint. The small and limited angular displacement in the rubber joints is advantageous in damping out torsional vibrations.
9. Universal joint:
Due to the flexibility of road springs, the rear axle is constantly moving up and down. The propeller shaft fitted to the rear axle must also be free to move up and down. To permit the turning of the propeller shaft, this movement takes place and universal joints are fitted at each of its ends. Therefore, the relative movement between engine and driving wheel is maintained by the universal joint.
The differential gear carries the power from propeller shaft to rear wheel axles. It helps two rear wheels to turn at different speeds when rounding a curve. The outer wheel must over- run than the inner wheels when taking a turn. The differential gear also ensures that the final output torque is equally distributed between two wheels without any consideration of their relative speeds.
Springs are fitted between frame and wheel to prevent the upward movement of the frame along with up and down movement of the wheel. A spring is a reservoir of energy which is stored in steel springs by bending them or by twining them. When the spring resumes to its normal state, this energy is released.
12. Front axle:
It is used for steering front wheels carried on stub axles swiveling upon kingpin’s axle extremities. Steering arms and track rod link, two stub axles are together used for swiveling them by a steering wheel about kingpins. The steering wheel linked to one of the stub axle by shaft, a gear box and suitable linkage are operated by the driver’s hand wheel. An axle in which one-piece beam is used to support the vehicle through springs (axle and spring arrangement) was previously used. Now, an arrangement known as independent front suspension replaces the axle and spring arrangement. Under the control of springs, wheels are free to rise and fall independently in the vertical direction to each other.
13. Rear axle:
Rear axle or driving axle is a tube such as shaft enclosing driving shafts with suitable bearings for rotating the wheels. It is used for fixing the rear wheels. It is enlarged at the centre for enclosing the final drive gears used for providing main speed reduction between engine and driving wheels. The change of direction from the line of propeller shaft to the transverse line of the axle shafts is also provided by the rear axle.
In reality, the battery is the heart of the electrical system of a motor vehicle. It supplies current to the cranking motor and ignition system. The function of the battery is to store electrical energy which can be used whenever required. Battery may be called nerve- centre of the whole installation because it supplies electrical energy for operating all electrical devices and other units except the charging device. It also supplies the electricity for operating the various electrical devices when the vehicle is not operating or running slowly and generator
speed is insufficient to meet the full load requirements.
15. wheel :
The wheels are fitted below the chassis to support the load of the vehicle and passengers. They are fitted with hollow rubber tyres filled with air in rubber tubes under sufficient pressure necessary for carrying the load. The shocks caused by road irregularities are absorbed by them. By fitting springs between wheels and vehicle to allow the vertical movement of the wheels in relation to vehicle, a greater part of unevenness of road surfaces is taken care of.
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