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UNIT 3, TRANSMISSION SYSTEM
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SYLLABUS:, Clutch: its need and types, Gearboxes: Types, of gear transmission, Shift mechanisms, Over, running clutch, Fluid coupling and torque, converters, Transmission universal joint,, Propeller shaft, Front and rear axles types,, Stub axles, Differential and its types, Four, wheel drive.
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INTRODUCTION TO THE TRANSMISSION, SYSTEMS IN AUTOMOBILE, • The power developed by the engine has to reach, the road wheels for moving the vehicle., Transmission system deals with this objective. It, transmits power to wheels as and when required, by varying speed and torque., • The most common transmission systems that, have been used for the automotive industry are:, 1. Manual transmission,, 2. Automatic transmission,, 3. Semi-automatic transmission,, 4. Continuously-variable transmission (C.V.T.)
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1. Manual Transmission, 2. Automatic Transmission, 3. Semi-automatic Transmission, 4. Continuously Variable Transmission (C.V.T.)
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Purpose of Clutch, • In vehicles with a manual transmission or, manual transaxle the power flows through a, clutch. This device engages and disengages the, manual transmission or transaxle and the, engine. When the driver pushes the clutch, pedal down, the clutch disconnects or, disengages from the engine flywheel. No engine, power can flow to the transmission or transaxle., When the driver releases the clutch pedal the, clutch engages. This allows power to flow to the, transmission.
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Functions of Clutch, 1. It can be disengaged. This allows engine cranking, and permits the engine to run freely without, delivering power to the transmission., 2. While disengaged it permits the driver to shift the, transmission into various gears., 3. While engaging, the clutch slips momentarily. This, provides smooth engagements and lessens the, shock on gears, shafts, and other drive train parts., 4. When engaged, the clutch transmits power from the, engine to the transmission. All slipping has stopped.
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Requirements of Clutch, 1. Torque transmission, 2. Gradual engagement, 3. Heat dissipation, 4. Dynamic balancing, 5. Size, 6. Vibration Damping, 7. Inertia, 8. Clutch free pedal play, 9. Ease of operation
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Types of Clutch, The following are the main types of clutches., 1. Friction clutches, 2. Fluid flywheel, Friction clutches are mainly classified into:, • Single plate clutch, • Multi plate clutch, • Centrifugal clutch, • Diaphragm spring clutch, • Semi centrifugal clutch
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Single Plate Clutch, 1. Thrust, Spring (Coil, Spring) Type:
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Diaphragm Spring Type Single Plate Clutch
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MULTI PLATE CLUTCH
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CENTRIFUGAL CLUTCH
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TYPES OF GEAR BOX:, The transmission can be classified into manual, and automatic types. The manual transmission is, conventionally called gear boxes. The following are, the important gear boxes used in automobiles:, 1. Sliding mesh gear box, 2. Constant mesh gear box, 3. Synchromesh gear box
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SLIDING MESH GEAR BOX, , Gears in Neutral
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First or, low shaft, gear
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Second, speed gear
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Third speed gear
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Fourth, speed, gear/ Top, or HighSpeed, Gear
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Reverse gear
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CONSTANT MESH GEAR BOX
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SELECTOR MECHANISMS: (SHIFT MECHANISMS)
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OVERRUNNING CLUTCH DRIVE
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FLUID FLYWHEEL
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TORQUE CONVERTER
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PROPELLER SHAFT
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UNIVERSAL JOINT, Hooke's Joint
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Types of Axles:, Following are the three different types of axles, • Rear Axles, • Front Axle, • Stub Axle
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Rear Axles
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Types of Rear axles:, Depending upon the methods of supporting the, rear axles and mounting the rear wheels, the three, types of rear axles are as follows:, • Semi-floating axle, • Full-floating axle, • Three quarter floating axle
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Semi-Floating Axle
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Full-Floating Axle
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Three-Quarter Floating Axle
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Front, Axle
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Types of Front Axles:, Usually, there are two main types of the front, axle:, • Live front axle., • Dead front axle.
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Stub Axle
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•, •, •, •, , Types of Stub Axle:, Following are the four types of the stub axle:, Elliot., Reverse Elliot., Lamoine., Reversed Lamoine.
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• The Elliot stub axle is attached to the front axle by placing in the yoke end with a, kingpin and cotter to join the two together., • In Reversed Elliot type stub axle, the arrangement is reversed. In Lamoine type stub, axle, instead of yoke type hinge, an L-shaped spindle is used as shown in the figure.
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DIFFERENTIAL, • Purpose:The differential gear box has following functions:, • Avoid skidding of the rear wheels on a road, turning., • Reduces the speed of inner wheels and increases, the speed of outer wheels, while drawing a curve., • Keeps equal speeds of all the wheels while, moving on a straight road., • Eliminates a single rigid rear axle, and provides a, coupling between two rear axles.
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Types of Differentials in Cars and Trucks, • Open Differential
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Limited-Slip Differential
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Locking Differential
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Torque-Vectoring Differential
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How a Differential Works, • Front Engine / Rear-Wheel Drive (FR) Type:, • Engine → Transmission → Drive Shaft → Rear, Differential → Axle Shaft → Rear Wheels
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Front Engine/Front-Wheel Drive (FF) Type, • Engine → Transaxle & Built-in Front Differential →, Front Wheels
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4-Wheel Drive Type, • Engine → Transmission → Transfer Case → Front & Rear, Drive Shaft → Front & Rear Differential → Front Drive Shaft, & Rear Axle Shaft → Front and Rear wheels
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Four Wheel Drive
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• TERMINOLOGY Four-wheel drive (4WD) is often designated as, “4 × 4” and refers to a vehicle that has four driven wheels., ■ The first 4 indicates that the vehicle has four wheels., ■ The second 4 indicates that all four wheels are driven., • A vehicle will have more pulling power and traction if all of its, wheels are driven. This requires a drive axle at each end of, the vehicle, another driveshaft, and a transfer case or power, transfer unit to drive the additional driveshaft and drive axle., The transfer case is normally attached to the rear of the, transmission. It has a single input shaft from the transmission, and two output shafts, one to the front drive axle and one to, the rear drive axle. Some transfer cases are two-speed and, include a set of reduction gears for lower-speed, highertorque operation., • Four-wheel drive can be built into, ■ A front-engine rear-wheel drive, ■ A front-engine front-wheel drive, ■ A rear-engine rear-wheel drive
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Fig. Three major, 4WD, configurations. The, traditional form (a), uses a transfer case, to split the torque, for the front and, rear drive axles., Both (b) and (c) are, typical AWD, configurations.
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ALL-WHEEL DRIVE, • All-wheel-drive (AWD), also called full-time four-wheel, drive, vehicles are four-wheel-drive vehicles equipped, with a center (inner-axle) differential so they can be, operated on pavement in four-wheel drive. Full-time, four-wheel drive is another name for all-wheel drive., All-wheel drive vehicles are designed for improved onroad handling., • There will be one differential in each drive axle, assembly plus a differential between the two drive, axles. The inter-axle differential allows the front-to-rear, wheel speed differential. Because all wheels are driven,, these vehicles are excellent for use in rain and snow, where added control is needed.
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Four-Wheel Drive Advantages, • 4WD improves traction in dangerous driving, conditions, such as snow, ice, rocks, and other, scenarios that can make control difficult. By, engaging both sets of wheels, traction and control, improves., • Additional weight contributes to better grip on the, road., • 4WD is great for those who like off-roading
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Four-Wheel Drive Disadvantages, • The main disadvantage of 4WD is added cost for purchase,, maintenance, and fuel. The extra equipment (differentials,, transfer case, etc.) adds complexity and weight to the vehicle,, increasing initial market value, tire wear, and the cost of, repairs and maintenance., • The added power and weight of 4WD and AWD systems, require more fuel, making them less efficient than their 2WD, counterparts., • Added weight improves traction and control, but it also, increases the braking distance required to make a complete, stop. Lighter vehicles can avoid collision easier than heavier, vehicles., • 4WD and AWD can cause overconfidence in drivers, ironically, leading to more situations where you can become stuck., • Although 4WD improves traction, slow down and use, extreme caution on icy, snowy, and slick roads., Overconfidence can lead to dangerous accidents.
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Thank You, ?
