MODULE NO 1 :AUTOMOBILE ENGINEERING (MUMBAI UNIVERSITY )

2011-2012

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AUTOMOBILE ENGINEERING

TRANSMISSION SYSTEM | Mr. VAIBHAV VITHOBA NAIK

Automobile Engineering

MODULE NO 1 1. Introduction A. Classification of automobiles 2. Clutch A. Details B. Requirement of the clutches C. Types of Clutches and Clutch material D. Design of Clutch E. Fluid Coupling F. Trouble shooting and Remedies.

3. Transmissions a. Necessity of Gear box b. Types of gear box i.

Sliding mesh Gear box

ii.

Constant mesh Gear box

iii.

Synchromesh Gear box

iv.

Epicyclic Gear box

c. Overdrives and Hydrodynamic Torque converter d. Trouble shooting and Remedies.

4. Drive lines a. Propeller shafts and universal joints b. Types and construction c. Different and types of universal joints and constant velocity joints.

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Automobile Engineering

5. Live axle and differential a. Final drive ,Spiral ,Bevel ,Hypoid and Worm drives b. Types of live axles ,Semi, three quarter and full floating axles c. Necessity of the differential d. Conventional and non-Slip differential e. Trouble shooting and Remedies

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1. CLUTCH 1.1

Details of clutch

1.2

Types of clutch

1.3

Clutch material

1.4

Design of clutch

1.5

Fluid couplings

1.6

Trouble shooting and remedies

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Q.1: - What is CLUTCH? List the types of CLUTCH? Answer:  CLUTCH i. Clutch is a device which transmits the rotary motion of the engine to the transmission when required by the drivers. ii. Located between the engine and the gear box, it connects and disconnects the two units smoothly without shocks.  TYPES OF CLUTCHES Clutch may be classified as 1. Friction clutch a) Single plate clutch b) Multiplate clutch i. Dry and ii. Wet c) Cone Clutch i. Internal and ii. External 2. Semi centrifugal clutch 3. Centrifugal Clutch 4. Diaphragm clutch 5. Hydraulic Clutch 6. Electromagnetic Clutch

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Automobile Engineering

Q.2: - What is requirement of the CLUTCH? Answer:  REQUIRMENT OF CLUTCH 1. It should be able to transmit maximum torque of the engine. 2. It should engage gradually to avoid sudden jerk. 3. It should ne dynamically balance, for high speed engine. 4. It should be able to dissipate large amount of heat generated during the clutch operations. 5. Size should be small and occupies less space. 6. Lighter in weight. 7. Easy for operating so that it can operate by small effort of driver 8. It should have suitable mechanism for damp vibration and reduce noise during power transmission.

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Q.3: - List the component of the CLUTCH? Answer:  COMPONENT OF THE CLUTCH The main clutch components are 1. Clutch with draw mechanism. 2. Clutch plate. 3. Clutch lining. 4. Pressure plate. 5. Cover.

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Q.4: -Explain the construction CLUTCH PLATE? Answer: -CLUTCH PLATE

Figure :Clutch Plate 1) The clutch plate consists of steel plate with a splined central hub. 2) Annular friction facings are attached to the steel plate by rivets. 3) Special resins are also been used to bind the friction faces. 4) There is a provision of axial cushioning interposed between the clutch plate and friction facings. 5) The curved cushioning spring segments are attached rigidity to the centre plate and friction facings are riveted to the springs to these springs. 6) Apart from the cushioning, clutch plates are also provided with means of absorbing undesirable torsional vibrations. 7) The clutch plate for this purpose has to be made in two parts. 8) That is a central hub subassembly and outer facing ring assembly the two being torsionally flexible with respective each other.

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Automobile Engineering

Q.5: -List the requirement of the Clutch facing? List the types of Clutch facing? List the common clutch facing material? Answer: - CLUTCH FACING  Requirements of CLUTCH FACING 1) Good wearing properties 2) Presence of good binder 3) Cheaper 4) High coefficient of friction 5) High resistance to heat  Types of CLUTCH FACING 1) Millboard type 2) Moulded type 3) Woven a. Solid woven variety b. Laminated woven variety  COMMON CLUTCH FACING MATERIAL a. Leather b. Cork c. Fabric d. Asbestos e. Reybestos f. Ferodo g. Non asbestos clutch facing

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Automobile Engineering

Q.5: -Explain the principle of FRICTION CLUTCH? Answer: -PRINCIPLE OF FRICTION CLUTCH

1) The shaft A and disc C are revolving at some speed N rpm. 2) Shaft B and disc D are stationary initially when the clutch is not engaged. Now apply some axial force W to the disc D so that it comes in contact with disc C . 3) As soon as the contact is made, the force of friction between C and D will come into play and consequently the disc D will also start revolving. 4) If W is increased gradually, speed of D will increase correspondingly till the stage comes when the speed of D becomes equal to the C. 5) Then the clutch is said to be fully engaged. Let •

W=axial load applied

•

µ=coefficient of friction

•

T=torque transmitted

•

R=effective mean radius of the friction surface

Then,

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T = µw

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Vaibhav Vithoba Naik

Automobile Engineering

Q.6: -What are the various component of CLUTCH? Answer: -CLUTCH COMPONENTS: The main components of a friction clutch are: 1. Clutch plate 2. Clutch facing 3. Pressure plate 4. Springs 5. Bearing 1. Clutch plate: a. Clutch plate consists of steel plate with a splined central hub. Frictional facings are attached to the steel plate by rivets. b. The curved cushioning springs segments are attached rigidly to the center plate and the friction facings are riveted to these springs. c. The clutch plate is made in two parts i.e. a central hub assembly and outer facing ring assembly.

2.

Clutch facing: a. It is required to have good wearing properties and should have coefficient of friction and high resistance to heat. b. The commonly used clutch facing materials are: •

Leather

•

cork

•

fabric

•

asbestos

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•

3.

Rebates and freedom.

Pressure plate: a. High tensile gray iron is the most commonly used material for pressure plate. b. The pressure plate should be rigid enough to distort under pressure of clutch springs and also should have sufficient mass to absorb and conduct away the heat generated during disengagement.

4. Springs: a. The clutch springs are made from oil tempered spring steel wire or siliconchrome steel. 5. Bearing: a) This is either a thrust ball bearing which is packed with grease for lubrication or graphite impregnated one which does not require lubrication.

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Q.7: -Explain the mechanical operation the CLUTCH mechanism? Answer: -MECHANICAL OPERATION OF CLUTCH MECHANISM

1. On pressing the clutch pedal, the shaft A turns, which moves the fork lever and then through shaft B, actuates the release fork to press the thrust bearing. 2. This movement is further conveyed to clutch levers to disengage the clutch. 3. When the clutch pedal is pressed, the thrust bearing is not pressed immediately. 4. Rather a part of the pedal movement is purposely kept idle.

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Automobile Engineering

5. This is done to avoid a rapid wear of the thrust bearing and the clutch plates and is called clutch free pedal play. 6. Usually this is kept about 25mm at the pedal.

Q.8: -Explain the Hydraulic operation the CLUTCH? Answer: -HYDRAULIC OPERATION OF CLUTCH

Figure :Hydraulic operation of the Clutch 1. In heavy duty applications the force required to disengage the clutch become excessive. 2. This can be remedied by using hydraulic operation. 3. This type of operation is suitable for vehicles in which the clutch pedal and the clutch have to be located too far away from each other. 4. In this system, the clutch pedal operates the piston in the clutch master cylinder.

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Automobile Engineering

5. The hydraulic pressure thus produced is then transmitted through hydraulic lines to the slave cylinder containing the piston which is connected to the pressure plate. 6. This pressure moves the piston there by releasing the clutch. 7. The advantages of the system are complicated clutch linkages, vibration and wear of the linkages are eliminated. Q.9: -Explain the Vacuums operation the CLUTCH mechanism? Answer: - VACUUM OPERATION OF THE CLUTCH MECHANISM

Figure : Vacuum Operation of the Clutch mechanism 1) The partial vacuum existing in the engine manifold is put to use to operate the clutch. 2) A reservoir is connected to the engine manifold through a non return valve. 3) The reservoir is further connected to a vacuum cylinder through a solenoid operated valve.

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4) The solenoid is operated from the battery through a switch which is operated by a gear lever. 5) Vacuum cylinder contains a piston which is exposed to atmospheric pressure on one side. In the part throttle position, the vacuum in the engine manifold is collected inside the reservoir. 6) During operation the switch in the gear lever remains open and the solenoid operated valve remains in the bottom position. 7) When the driver changes the gear, the solenoid energizes which actuates the piston which further opens the vacuum from the reservoir to the vacuum cylinder. 8) The clutch used is an ordinary friction clutch.

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Automobile Engineering

Q.10: -Explain the working of SINGLE PLATE CLUTCH? Answer: -SINGLE PLATE CLUTCH Single plate clutch is most common type of the clutch used in motor vehicle. The simplified sketch of Single Plate Clutch is as shown in figure.

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Automobile Engineering

Figure :Single Plate Clutch 1. In a single plate clutch, the clutch plate is held between flywheel and pressure plate. 2. There are springs arranged circumferentially which provide axial force to keep the clutch in engaged position. 3. The friction plate is mounted on a hub which is splined from inside and thus it is free to slide over the gear box shaft. 4. Friction facing is attached to the friction plate on both sides to provide two angular friction surfaces for transmission of power. 5. A pedal is provided to pull the pressure plate against the spring force when ever it is required to disengage. 6. When the clutch pedal is pressed, the pressure plate is moved to the right against the force of the spring. 7. This is achieved by means of a suitable linkage and a throw out bearing. 8. With this movement of the pressure plate, the friction plate is reduced and the clutch is disengaged.  Advantages of Single Plate Clutch 1. Gear shifting is easier 2. More reliable  Disadvantages of Single Plate Clutch 1. Spring has to be stiffer. So greater force is required to be applied by the driver while disengaging.

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Automobile Engineering

Q.11: -Explain the working of MULTIPLATE CLUTCH? Answer:  MULTIPLATE CLUTCH

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Automobile Engineering

Figure :Multiplate Clutch The need of the Multiplate clutch arises due to either i. Space limitation such as in 2 wheelers. ii. Requirement of high torque transmission as in racing cars and on heavy transport vehicles. 1. Multi plate clutch has a number of clutch plates as compared to single plate. 2. The increase in number of friction surfaces increase the capacity of the clutch to transmit torque, size remains fixed. 3. During clutch engagement, spring pressure forces the pressure plate towards engine flywheel. This causes the friction plate and the steel driven plates to be held together. Friction locks them together tightly. 4. When the clutch get released, the movement of the pressure plate releases the spring pressure holding the driving and driven plates together.

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Vaibhav Vithoba Naik

Automobile Engineering

Q.12: -Explain the working of DIAPHRAGM CLUTCH? Answer: -DIAPHRAGM CLUTCH

Figure :Diaphragm Clutch 1. The diaphragm type clutch uses a diaphragm or a conical spring instead of coil spring to produce adequate pressure for engaging the clutch. 2. The clutch cover is secured to the engine flywheel. 3. The pivot rings are held in the clutch cover. 4. The outer rim of the diaphragm spring is in contact with the pressure plate. 5. In engaged position, the diaphragm spring keeps the pressure plate in firm contact with the flywheel. 6. To disengage the clutch, clutch pedal is pressed which causes the linkage to move the throw out bearing forward.

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Automobile Engineering

7. This causes the ring of the diaphragm spring move backward, which is away from flywheel. This happens because diaphragm spring is pivoted. Advantages 1. Does not have any release levers. 2. Less effort is required. 3. Compact in design. Q.13: -Explain the working of CENTRIFUGAL CLUTCH? Answer: CENTRIFUGAL CLUTCH

Figure :Centrifugal Clutch 1. In a centrifugal clutch, the springs are eliminated altogether. 2. Only the centrifugal force is used to apply the required pressure to keep the clutch in engaged position. 3. The advantage of centrifugal clutch is that no separate clutch pedal is required that is clutch is operated automatically depending upon engine speed. Module No 01

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4. As the speed increases, the weight flies there by operating the bell crank lever which presses the pressure plate. 5. This force is transmitted to the clutch disc by means of spring ‘a’. 6. The clutch disc containing friction lining is thus pressed against the flywheel there by engaging the clutch. 7. The spring ’b’ serves to keep the clutch disengaged at low speed. The stopper limits the amount of centrifugal force. Q.14: -Explain the working of SEMICENTRIFUGALCLUTCH? Answer: -SEMI CENTRIFUGAL CLUTCH

Figure :Semi-Centrifugal Clutch 1) In a semi centrifugal clutch, springs are designed to transmit the torque at normal speed, while for higher speed, centrifugal force assists in torque transmission.

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Automobile Engineering

2) Three hinged and weighted levers are arranged at equal intervals. 3) At moderate speeds the pressure of the spring is sufficient to transmit the required torque. 4) However at higher speeds, the weight, due to the centrifugal force moves about fulcrum there by pressing the pressure plate. 5) The centrifugal force is proportional to the square of the speed so that enough pressure level is attained. Q.15: -Explain the working of ELECTROMAGNETIC CLUTCH? Answer: -ELECTRO MAGNETIC CLUTCH

Figure :Electromagenetic Clucth 1. The clutch has a conventional type of friction disc. 2. When battery current is supplied to the magnetic coil, an electromagnet in the flywheel gets energized. Module No 01

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Automobile Engineering

3. Now the armature is pulled by the electromagnet compressing the push off springs. 4. The pressure plate assembly moves towards the flywheel makes the clutch plate contact in between flywheel and pressure plate. 5. The electromagnetic clutch is best suited where remote operation is desired since no linkages are required to control its engagement. Q.16: -Short notes on FLUID FLYWHEEL ? Answer: -FLUID FLYWHEEL

Figure :Fluid Flywheel 1) The fluid flywheel or hydraulic coupling is normally used in automatic transmissions.

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Automobile Engineering

2) It consist of two members the driving and the driven. 3) The driving member is attached to the engine flywheel and the driven member to the transmission shaft. 4) The two members do not have any direct contact. The shell is always filled with fluid of suitable viscosity. 5) When the flywheel starts rotating the oil in the impeller (pump) starts moving. Due to the force of the rotation the oil impinges on the finds of the turbine and causes it to move. In this way the moving liquid transmits the engine power to any components to which the turbine is attached. 6) Theoretically the turbine speed becomes almost equal to that of the pump only under the best operating condition when the efficiency of the fluid coupling is highest. But usually turbine speed is less than that of the pump. The lag of the turbine behind the pump is known as slip. 7) For engine speed below about 500rpm percentage of slip is 100 which means the clutch is fully disengage. As the engine speed increases the percentage of slip rapidly falls below 10% beyond which the slip decreases gradually to a small value of about 2%. Advantages a. No wear on moving parts b. No adjustments to be made c. No maintenance necessary except oil level d. Simple design e. No jerk on transmission in the gear engagement. f. No skill required for operating g. Car can stop in gear and moved of.

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Automobile Engineering

Q.17: -Short notes on Clutch Adjustment? Answer:  CLUTCH ADJUSTMENT: 1) The only adjustment required for clutch is “CLUTCH FREEPEDAL PLAY”. 2) Due to continuous use of clutch or due to wear of Release (throughout) bearing or due to habit of driver by keeping foot continuously on pedal, there will be wear in friction having lining of clutch. 3) To avoid this, there should be free pedal play in clutch pedal so that for certain time the clutch will not be operated even though the pedal moves. 4) This adjustment may be varied along with the wear of clutch lining or release bearing etc. 5) It can be done by changing the linkage between the pedal and release fork. 6) It’s usual value is in between 30 and 35 mm.

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Automobile Engineering

Q .18: -Explain the trouble shooting and remedies of CLUCTH ? Answer: CLUTCH TROUBLE SHOOTING: The clutch may face most common troubles namely i. Clutch slip ii. Clutch drag iii. Clutch judder iv. Clutch rattle v. Knock Some of which are etc. discussed here: i.

Clutch slip:

1. Sometimes the clutch may slip while engagement. 2. In this condition, it fails to transmit the engine torque completely. 3. A large amount of heat generated which causes wearing and even burning of clutch plate. 4. The main reason for clutch slipping is a. Incorrect clutch linkage –which is to be adjusted. b. Oil or grease on friction linings –To clean the lining. c. Weak or broken clutch springs –Replace the springs. d. Incorrectly adjusted release levers and fingers to be adjusted. ii.

Clutch drag:

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1.

Some times when the clutch is to be disengaged, it is not disengaged

completely and it provides difficultly is changing the gears – which is called clutch drag. 2. The following are the reasons and remedies. a. Excessive free pedal play – to be adjusted. b. Incorrect adjustment of release levers – should be adjusted. c.

Pressure plate damaged – to be replaced. d. Clutch plate damaged – to be replaced. e. Clutch plate may be seized on clutch shaft splices – The splices may be cleaned and laminated.

iii.

Clutch judder: Some times as the clutch is engaged, a vibration or judder is produced instead of smooth gradual engagement. The following are the reasons and remedies





Loose or worn out clutch facings – clutch plate should be replaced. 

Loose rivets – Replace the clutch plate.



Misalignment of pressure plate with flywheel – to be adjusted.



Fly wheel may be loose on the crankshaft flange – to be tightened.

Bent splinted clutch shaft – may be straighten or to be changed.

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Q.19: -Explain the function/purpose of transmission system ? Answer: FUNCTION /PURPOSE OF TRANSMISSION SYSTEM 1) Transmission system means the whole mechanism that transmits the power from the engine crankshaft to the wheels. 2) The transmission system consists of a clutch, gear box, propeller shaft, rear axle and differential gear between the driving wheels. 3) The functions of transmission system are a) To disconnect the engine from the road wheels when decide. b) Connect the engine to the wheels without shock. c) To vary the leverage between engine and drive wheels. d) Reduce the engine speed permanently in a fixed ratio e) To turn the drive through a right angle. f) To make provision such that the driving wheels may rotate at different speeds while taking turns. g) To make provision for the turning of the road springs which causes a relative movement between the engine and driving wheel

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Q.20: -Draw the neat sketch of transmission system in automobiles ? Answer: -

Figure: Transmission System in Automobiles

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Figure: Transmission System in Automobile Q.21:-What is the necessity of the gear box at all in the automobiles? Answer: -NECESSITY OF GEAR BOX 1) When the vehicle moves, the total resistance on vehicles does not remain constant but varies with speed. 2) To advance or propel the vehicle engine must vary with tractive effort with variation of total resistance. 3) If tractive effort is exceeding the sum of all the resistance, then the excess driving force will accelerate the vehicle. 4) If tractive effort is less than the sum of all the resistance, then the excess driving force will reaccelerate the vehicle. 5) Therfore, the variation of resistance and tractive effort of the vehicle at various speeds, the transmission system is necessary. Q.22: -List the type of the gear box used in the automobiles? Explain the function of gear box

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Answer: -TYPES OF GEAR BOX 1) Sliding mesh gear box. 2) Constant mesh gear box. 3) Synchromesh gear box. 4) Epicyclic gear box. Function of the gear box The main functions of a gear box are 1. To provide a means to vary the leverage or torque ratio between engine and road wheels. 2. To provide a neutral position so that the engine can be disconnected off the road wheels. 3. A means to reverse the direction of rotation of the drive. Q.23: -List and explain the various resistances acting on the vehicles? Answer: Various road resistances to the vehicles The total resistance to the vehicle motion is commonly 1. Resistance due to wind 2. Resistance due to gradient 3. Miscellaneous resistance The total resistance for same type of roads with different gradient may be represented by curves.

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The tractive effort of a vehicle at particular gear is minimum at initial point and increases with the speed, peaks at some optimum speed and decreases beyond that. The graph shows the tractive effort in first second and top gears respectively. Now consider the graph which is obtained by super imposing the above figures.

Here A is the stabilizing speed for gear 3 if a vehicle at gradient. If a vehicle at gradient 1 has a less speed B then the excess tractive effort which accelerates it to speed A. Similarly if the speed at any instant is C then the excess resistance decelerates it to A. If the vehicle has to move through gradient III then it has to be shifted to the next gear, since the stabilizing speed D.

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Q.24: -Explain the Sliding Mesh Gear Box? Answer: -SLIDING MESH GEAR BOX

Figure: Sliding mesh gear box 1) This is the simplest of gear boxes.

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2)

It consists of three shafts, a set of gears gear selector mechanism and gear shift lever.

3) The engine is coupled through the clutch to the clutch shaft or input shaft. 4) A lay shaft or counter shaft which is arranged parallel to the main shaft carriers gears of different size which are all fixed. 5) The input shaft gear meshes continuously with the driven gear on the lay shaft. 6) The main shaft is splined and gears can be slide to make it mesh with gears on the lay shaft. 7) The various gear reduction is obtained by sliding the appropriate gear on the main shaft to make it mesh with corresponding gear on the lay shaft. 8) Reverse gear is also provided by the help of idler gear which is provided in between the lay shaft gear and main shaft gear. Q.25: -Explain the Constant Mesh Gear Box? Give the advanatges? Answer: -CONSTANT MESH GEAR BOX

Figure :Constant Mesh Gear box

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1) In this type of gear box all the gears on the lay shaft are in constant mesh with the corresponding gears on the main shaft. 2) Gears on the main shaft are free to rotate (Bearing). 3) Dog clutches are provided which are free to slide on the main shaft. Gears on the lay shaft to are fixed. 4) When the left dog clutch is slide to the left by means of the selector mechanism, its teeth are engaged with those on the clutch gear and we get the direct gear. 5) The same dog clutch however when slide to right makes contact with the second gear and the second gear is obtained. 6) Similarly movement of the right dog clutch towards left result in low gear and towards the right in reverse gear.  Advantages 1) Helical gears can be used 2) Any damage that result from faulty engagement occurs only to the dog clutch. 3) Less noisy and reliable 4) All teeth are engaged at once.

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Q.26: -Explain the Double Declutching in Constant Mesh Gear Box? Answer: -DOUBLE DECLUCTHING IN CONSTANT MESH GEAR BOX 1. In the constant mesh gear box, for the smooth engagement of the dog clutch, it is necessary that the speed of the main shaft gear and the sliding dog must be equal. Therefore to obtain lower gear the speed of the clutch shaft, layshaft, main shaft must be increased. This is done by double declutching. 2. The clutch is disengaged and the gear is brought to neutral. Then the clutch is engaged and accelerator pedal is pressed to increase the speed of the main shaft gears. After this the clutch is again disengaged and the gear moved to the required lower gear and the clutch is again engaged. As the clutch is disengaged twice in the process this called double declutching. For changing the higher gear however reverse effect is decided; that is the driver has to wait with the gear in neutral till the main shaft speed is decreased sufficiently for a smooth engagement of the gear.

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OR 1. In constant mesh gear box, for smooth engagement of dog clutches it is necessary that the speed of main shaft and sliding dog clutch must be equal. 2. To obtain lower gear, the speeds of the clutch shaft, lay shaft and main shaft must be increased. This is done by double declutching. 3. The clutch is disengaged and the gear is brought to neutral. Then the clutch is engaged and accelerator pedal pressed to increase 4. The speed of the main shaft gears. Again the clutch is disengaged and the gear moved to the required lower gear and the clutch is again engaged. 5. As the clutch is disengaged twice, it is called double declutching.

Q.27: -Explain the Synchromesh Gear Box? Give the advantages? Answer: -SYNCHROMESH GEAR BOX

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Automobile Engineering

1) The synchromesh devices are used to simplify the operation of changing gear. 2) This device helps unskilled drivers to change gear without the occurrence of clashes and damages. 3) By this device the members which ultimately are to be engaged are 1st brought into frictional contact and when the friction has equalized their speeds, the positive connection is made. 4) The synchronizer is free to slide on splines. 5) On the main shaft it has conical portions to correspond with the conical portions on the gear box shaft pinion and on the wheel that rotate freely on the main shaft. 6) The synchronizer unit carries a sliding sleeve. In neutral position the sliding sleeve is held in place by the spring loaded ball. 7) When a shift starts the spring loaded balls cause the synchronizing drum and sliding sleeve as an assembly to move towards the selector gear. 8) The first contact is between the synchronizing cones on the selection gear and the drum. 9) This contact brings both to rotate at the same speed. 10)When the speeds of the two have become equal a slightly greater pressure on the gear over comes the resistance of the balls. 11)Further movement of the shift fork forces the sliding sleeve towards the selector gear. 12) The internal splines on the sliding sleeve match the external splines on the selector gear. 13)Now the dog teeth are locked up or engaged. Thus positive connection is made. 14) Special modifications are made in synchromesh gear boxes to allow sufficient time for smooth operation otherwise a clash will result.

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15)Guide bars are provided so that the gear will not be engaged positively before velocity equalization has been made.

Q.28: -Explain the Selector Mechanism used in gear box? Answer: -SELECTOR MECHANICSM

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Figure: Selector Mechanism 1) There are many mechanisms which have been used for selecting the desired gear and sliding the same to engage with the corresponding gear on the lay shaft. 2) This can be divided into i. Shifting mechanism mounted on transmission case ii. Shifting mechanism mounted on steering column iii. Shifting mechanism mounted on floor with remote control linkage. 3) The lower end of the selector lever fix into slots (Selector gates) in the selector rods. 4) For each selector sleeve separate selector rods are provided. 5) The selector rod can slide but just to avoid unwanted engagement of gears, slots are made on selector rods and are provided with spring loaded balls. 6) An interlocking mechanism which ensures that one gear can be engaged at a time is also used. 7) When particular gear is to be engaged the corresponding selector rod is moved in the desired direction. Q.29: -List the types of Transmission used in Automobiles Answer:  Transmission types 1. Manual 2. Semi automatic 3. Automatic •

Manual Transmission a) Sliding mesh gear box b) Constant mesh gear box c) Synchromesh gear box.

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•

Automatic Transmission a) Semi automatic : b) Fully Automatic

Q.30: -Explain the working of Torque Convertor in Automatic Transmission? Answer:  TORQUE CONVERTER

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Figure :Torque Converter. 1. It is the initial component of an automatic transmission. It increases the torque in a ratio of about 2:1 to 3:1. 2. A torque convertor consists of the three main parts. a) Impeller or the driving member which is connected to the engine. b) The turbine or the driven member which is connected to the road wheels through the transmission gears c) Stator fixed to the frame through a free wheel 3. Oil under pressure is maintained inside the torque converter. 4. When the engine is started the impeller starts rotating. 5. The oil having taken high kinetic energy from the engine through the impellers hits the outer edge of the turbine. 6. This force increases with the increase of engine speed. 7. The turbine blade angle is such that, when the oil comes out of the turbine, its direction is effectively back ward. It will push the impeller in the opposite direction and will cause a loss of power.

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8. To avoid this dragging the fluid is made to strike on stator, which change its direction suitably. The repeated pushing of oil on the turbine blades causes the torque on the turbine to increase, the phenomena is called torque multiplication 9. When the turbine speed has increased 85% to 90% of impeller speed, the coupling point is reached and the oil leaves the turbine in the forward direction, hitting back the stator blade. 10. To avoids the stator to become a hindrance, It is mounted on a free wheel which allows it to rotate in the direction of turbine or impeller.

Q.31: -Explain the working of Planetary gear unit in Automatic Transmission?

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Automobile Engineering

Answer: - PLANETARY GEAR UNIT

Figure :Planetary Gear unit 1) An epicyclic gear box consists of two three or even four planetary gear sets. 2) A simple planetary gear unit consist of four main components namely ring gear, pinion or planet gears, carrier, and sun gear. 3) The planets turn around sun gears. These plants gears are carried by a carrier and shaft and are also in mesh internally with ring gear. 4) Different torque ratios and speed ratios are obtained by making anyone of the parts i.e. the sun gear, carrier or the ring gear stationary. 5) The drive is given to the second member and a varied output is taken from the third. 6) 7 possible speed variations can be obtained from a single planetary gear unit a. Forward, past output speed, sun gear is stationary - carrier is idle and ring is driven b. Forward slow output speed sun gear stationary ring gear driving, carrier driven c. Reverse slow output speed carrier stationary, sun gear driving, ring gear driven d. Reverse fast output speed carrier stationary, ring gear driving, sun gear driven e. Forward, very slow output speed, ring gear stationary, sun gear driving, carrier driven

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f. Forward, very fast output speed, ring gear stationary carrier driving, sun gear driven g. Forward, direct drive giving drive to any two members.

Q.32: -Explain the working of an Over Drive

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Automobile Engineering

Answer:  OVER DRIVE 1) It consist of an epicyclic gear train in which sun gear is free to rotate in the engine shaft which is spline while the carrier can be slide. 2) A free clutch is also fitted on the input shaft. 3) The ring gear is in mesh with the casing of the output shaft. 4) When the sun gear is locked with the casing, it becomes stationary, the speed of the output shaft increase hence says as overdrive is engaged. 5) When the sun gear is locked with the carrier or ring gear, solid drive through the gear train is obtained. 6) Thus depending upon the locking of sun gear with casing or carrier the overdrive or direct drive is obtained.

Figure :Overdrives 7) There is another possible control of the mechanism there is a direct drive through the free wheel clutch when the engine develops the power.

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Automobile Engineering

8) When the accelerator pedal is brought to zero position and engine is idling, the output shaft tends to override the input shaft. 9) The roller of free wheel no longer remains wedge and the vehicle freewheels. 10)Thus for gear changing driver has to life his foot off the accelerator pedal, clutch need not be operated.  Advantage. 1) It gives higher top gear ratios for better fuel economy. 2) It reduces the engine wear and tear because of driven road speed ,the engine speed is less. 3) It is easy for engagement and disengagement. 4) A quarter running is provided by reduced engine speed.

Q.33: -Explain the function of the Propeller shaft with a neat sketch?

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Automobile Engineering

Answer: PROPELLAR SHAFT Function of propeller shaft:This is a shaft which transmits the drive from the transmission system (gear box) to the rear axle through differential. 1. Transmit the power from gear box top final dive. 2. To compensate the change in length. 3. Transmit motion at an angle which is varying frequently

Figure: Propeller Shaft Construction:It consists of the following components. 1) Shaft: a) It is made of steel tube with suitable diameter & length to withstand torsional stress developed by torque transmission. b) It is made up of strong steel tube, but light & well balanced so that vibration will not occur. 2) Universal joints:-

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Automobile Engineering

a) The gear box is attached to the chassis & rear axle is attached to the frame by spring. This spring compress or expand & is in continuous movement due to road irregularities. This results in vibration of angle drive between gearbox & differential. b) Hence the propeller shaft is required to transmit the power between the two points at varying vertical & horizontal distance. Thus two universal joints are necessary in propeller shaft to take care of variation in the angle of drive. 3) Sliding joint:a) Due to road irregularities, the effective length of transmission is also changing. To take care of this slight variation in length of drive, sliding joint is provided. b) General propeller shaft is as shown in figurec) It consists of two universal joints & one sliding joint. At one end of shaft universal joint is attached & another end external splines are made to slide in to internal splines of sliding sleeve having attached second universal joint.

Q.34: -Short Note on Propeller shaft ?

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Automobile Engineering

Answer:  PROPELLAR SHAFT 1) This is the shaft which connects the gear box output shaft to the pinion shaft of differential. 2) The propeller shaft carries the power from the engine clutch and transmission unit to the driving wheels of the vehicle through the final drive. 3) It mainly consist of 3 parts i. Shaft ii. Universal joints iii. Slip joint 4) The propeller shaft is manufactured in thin walled steel tubes. 5) Tubular section makes them lighter and stronger than a solid shaft of same size. It is also less expensive. 6) If the distance between transmission shaft and differential is more, one or more intermediate shafts are connected to the gear box main shaft and other end to the main propeller shaft. 7) The intermediate propeller shaft is supported in a bearing unit.

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Functions of propeller shaft 1. Transmit the power from gear box top final dive. 2. To compensate the change in length.

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Automobile Engineering

3. Transmit motion at an angle which is varying frequently

Q.35: -Short note on UNIVERSAL JOINT or HOOK JOINT? Answer: - UNIVERSAL JOINT or HOOK JOINT

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Automobile Engineering

1) Universal joints are incorporated at the ends of the propeller shaft. 2) Universal joints take care of the variation in inclination of the propeller shaft. 3)

Universal joint consist of two ‘Y’ shaped yoke and a cross shaped member called spider.

4) The four arms of the spider are assembled into needle bearing housed in the lug of the yokes. 5) The needle bearing consist of steel sleeve and a set of thin needle rollers. 6) Special glands keep the lubricant from flowing out.

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Automobile Engineering

Figure: Universal Joints 7) When the two shaft are an at an angle the bearing in the yoke permit the yoke to swing on the spider with each rotation of the shaft. 8) The universal joints have one defect that is the speed of the driven shaft does not remain uniform depending up on the angle of inclination of the shaft. 9) The driven shaft speed under goes cyclic variation.

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Automobile Engineering

10)The variation is zero in zero angle of inclination but its magnitude become considerable when the angle is large. 11)In order to limit the fluctuation in speed of the joint angle is limited to 1820% 12)The above mentioned speed variations can be overcome by using two separate universal joint connected to the propeller shaft. 13)With this arrangement the velocity variation at the second joint is equal and opposite to that which occurs at the first joint so that both cancels. 14)This will be valid only when angles on the both joints are exactly equal.

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Automobile Engineering

Q.36: -List the types of Universal Joints and explain any one of them? Answer:  UNIVERSAL JOINTS 1. An universal joints is used where two shafts are connected at to transmit torque. 2. In the transmission system of the motor vehicle ,the transmission main shaft,propellar shaft and the pinion shaft are not in one lies hence the coincide between them are made by the universal joint are used to.  TYPES OF UNIVERSAL JOINTS 1. Cross type or spider and two yoke 2. Pot type joint 3. Ball and treunion type 4. Constant velocity type 5. Flexible ring Universal Joint 1. CROSS TYPE OR SPIDER AND TWO YOKE a. It consists of two Y-shaped yokes and a cross piece (spider). b. One yoke is connected to driving shaft and other is connected to driven shaft. c. The cross-piece has four-arms which are known as trunnions and are attached to the ends of yokes. d. Four needle bearings are provided – one for each arm of cross-piece. e. These bearings allow the yoke to swing around the trunnion when driving and driven shaft remove together at an angle.

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Automobile Engineering

A simple cross-type universal joint is shown in Figure .

Figure: Cross-type Universal Joint f. This is a variable velocity joint, i.e. the driving and driven shaft do not rotate at the same speed throughout a revolution. However, their rpm is same. g. This happens because both shafts are not in straight line. h. Ring and trunion type and cross ball type designs also come in this category of universal joints. 2. POT TYPE JOINT a. A pot type of joint is another kind of the universal joints. b. Figure gives the general arrangement of this type of joints.

Figure: Pot type Universal Joint

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Automobile Engineering

c. The end of the one shaft is specially shaped and carries two hemispherical shaped block attached to it by means of a pin d. These blocks slides in the pot,the pot itself os carried by the second shaft. e. This arranged axial movements.

3. Ball and Trunnion Joint a. This type of joint consists of a ball type head which is fastened to one end of the propeller shaft. b. A pin is also pressed through this end of shaft. c. Two steel balls are fitted at the end of this pin. The joint facilitates rotary motion through ball and pin. d. The balls can also move axially. e. Ball and trunnion joint is also a variable velocity joint.

4. Constant Velocity Universal Joint a. This type of joint permits movement of both driving and driven shafts at constant velocity. b. Because, two joints in this case operate at same angles. c. These joints are generally used when the automobile in a front wheel (axle) drive. Because speed variation between driving and driven shaft will introduce difficulty in steering and excessive tyre wear.

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Automobile Engineering

Q.37: -List the types constant velocity Joints and explain any one of them? Answer: -CONSTANT VELOCITY JOINTS 1) Constant velocity joints are used where the front axle are being driven, regulation of rotation and transmission of torque at large indication are vital. 2) In these vehicles the inclination between the shafts may assume a large varying (400). 3) The speed of shaft connected by these joints is absolutely equal.  TYPES OF CONSTANT VELOCITY JOINTS Types of CV joints are given above a. Rzeppa joint b. Tripod joint c. Rzeppa plunging CV joint d. Closed tulip plunging CV joint e. Open tulip plunging CV joint 1. RZEPPA JOINT

a. The first CV joint is the Rzeppa joint. b. In this 6 spherical ball are held in a precise geometrical position midway between 2 shafts.

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Automobile Engineering

2. TRIPOD JOINT

a. Another CV joint is tripod joint which are 3 roller bearing attached to arms at the end of the driving shaft further modified with plunging capability. b. This permits driving and driven shaft move towards away from each other.

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Automobile Engineering

Q.38: -What is Final Drive and list its function? Ans: -FINAL DRIVE 1.

In most automobile vehicles the final driver is embodied in rear axle.

2.

But in various popular vehicles with front wheel drive and a few

special purpose vehicles with four wheel drive, it becomes necessary to consider final drives as units dependent of their positions.



FUNCTIONS OF FINAL DRIVE: In a motor vehicle the final drive has two purposes.

1)

To provide a permanent speed reduction. For motor cars the reduction is

usually about 4:1 and 10 :1 in heavy vehicle. 2)

To turn the drive through 90~ so that the torque may be transmitted from

propeller shaft to the rear axle.

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Automobile Engineering

Q.39:-Explain the construction of the FINAL DRIVE? Ans:  CONSTRUCTION OF THE FINAL DRIVE 1) The final drive consist of a bevel pinion and crown wheel (ring gear )as shown in the figure. 2) The bevel pinion is mounted on the shaft which is 3) From the crwon wheel ,the drive goes to the rear axle through the diffrential. 4) There are three types of the final drive gearing a. Straight Bevel gears b. Sprial Bevel Gears c. Hypoid Gears 5)

Figure: Final Drive Module No 01

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Automobile Engineering

1) Final drive is the last stage in transferring power from engine to wheels. 2) It reduces the speed of the propeller shaft (drive shaft) to that of wheels. 3) It also turns the drive of the propeller shaft by an angle of 900 to drive the wheels. 4) The propeller shaft has a small bevel pinion which meshes with crown wheel. The crown wheel gives rotary motion to rear axles. 5) The size of crown wheel in bigger than that of bevel pinion, therefore, the speed of rear axles (or crown wheel) in lower than the speed of pinion. 6) Final drive is of two types, i.e. chain type and gear type. 7) For final reduction in speed two types of gears can be used. 8) One of them may be use of level gears and another may be worm and worm wheel. 9) Worm and worm wheel combination provides large reduction without employing larger gears. It is strong also.

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Automobile Engineering

Q.40: -List and explain the various force acting on the rear axle ? Answer: REAR AXLE Various forces and torques experienced by rear axle can be identified as follows. 1. Weight of the body The rear axle may be considered a beam supported at ends loaded. This weight causes shear force and bending movement in the axle shaft. 2. Driving Thrust The driving torque produced in the engine causes the thrust to be produced in the road wheels which has to be transmitted from the axle casing to chassis frame and the body of the vehicle. 3. Torque reaction If the road wheels are prevented from rotation from the propeller shaft rotating, it is seen that bevel pinion with tends to roll down to crown wheel. This tendency is also present when the vehicle is running. Thus there is a force on axle casing to rotate. This called torque reaction. 4. Side Thrust Often the rear axle experiment side thrust or pulls due to any side load on the wheel.

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Automobile Engineering

Q.41: -List and explain the various force acting on the rear axle? Ans: -REAR AXLE: Almost all the vehicles have live axles as rear axles. The Axle housing completely remain stationary, do not move with the wheels. The rear axle should carry the following loads. 1)

The total rear weight of the vehicle causing both bending and shearing

actions. 2)

Side thrust on the wheels when cornering, which imposes bending load

and an end thrust or a pull. 3) Driving torque.

The commonly used rear axle drives are 1. Hotch kiss drive 2. Torque tube drive

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Automobile Engineering

Q.42: - Explain the Hotchkiss drive and Torque tube drive with the help of neat sketches? Ans: 1. HOTCH KISS DRIVE

Figure :Hotchkiss drive a) This is the simplest and most widely used type of rear axle drive. b) In this case the springs besides taking weight of the body also take the torque reaction, driving thrust and side thrust. c) The propeller shaft is provided with two universal joints also a sliding joint. d) The springs is fixed rigidly in the middle to the rear axle. e) The front end of the spring is fixed rigidly on the frame while the rear end is supported in the shackle.

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Automobile Engineering

2. TORQUE TUBE DRIVE

Figure :Torque tube drive a. In this type of drive the spring takes only the side thrust besides supporting the body weight. b. The torque reaction and driving thrust are taken by another member which is called torque tube. c. One end of the torque tube is attached to the axle casing, another end which is in spherical shape fixed in the cup fixed to the frame. d. The torque tube encloses the propeller shaft since the torque tube takes the torque reaction the centre line of the bevel pinion shaft will not shift. e. So that no sliding joint is required and one universal joint is enough.

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Automobile Engineering

Q.43:- Explain with line diagram, the principal of differential. Ans: PRINCIPAL OF DIFFERENTIAL 1) When a vehicle travels in a straight-line, the two rear wheels turn on road exactly at same speed & there is no relative movement between the rear wheels. 2) But when vehicle takes a turn, the outer wheel turns on a longer radius than inner wheel. The outer wheel turns faster than inner wheel i.e. there is relative movement between two rear wheels. 3) If the two rear wheels are rigidly fixed to a solid rear axle, the inner wheel will slip, which will cause rapid tire wear, steering difficulties & poor road holding. 4) Therefore there must be some mechanism in the rear axle which should reduce the speed of inner wheels & increase the speed of outer wheels while taking turns. 5) It should be at the same time keep the speeds of all the wheels same when going straight ahead. Such a device which serves the above function is called as differential.

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Automobile Engineering

To understand the principle on which differential works consider figure. 1. To the crown wheel of the final drive is attached a cage, which carries a cross-pin where two planet pinions are employed. 2. Two sun gears mesh with the two planet pinions. Axle half shafts are splined to each of these sun gears. 3. When the vehicle is going straight , the cage & inner gears rotate as a single unit & two half shafts revolve at same speed . In this situation, there is no relative movement among the various differential gears. 4. To understand what happens when the vehicle is taking turn, assume that the cage is stationary. Then turning any one sun gear will cause other to rotate in the opposite direction. 5. This means that if the left sun gear rotates “n” times in a particular time, the right gear will also rotate “n” in the same period, but of course in opposite direction. 6. Thus for example, consider a vehicle with wheel speed “N” r.p.m. going straight. When it takes turn towards, there will be resistance to the motion of right wheel & as a result differential action; if the right wheel rotates back at “n” rpm, then left wheel will rotate forwards at “n” rpm. This will give resultant speed of left wheel as (N+n) and that of right wheel as (N+n) rpm.

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Automobile Engineering

Q.44.-What is the different type of the differential used in automobiles? Ans: TYPES OF DIFFERENTIAL There are three types of differential: 1. Conventional type, a. Non-slip or self locking type, and b. Double reduction type. 1) Conventional Type a) Conventional type differential described delivers same torque to each rear wheel. b) If any of the wheels slips due to any reason the wheel does not rotate and vehicle does not move.

2) Non-slip or Self Locking Type a) Non-slip or self locking type differential overcomes this drawback. b) It construction is similar to that of conventional type differential. c) But, two sets of clutch plates are provided additionally. d) Also, the ends of planet shafts are left loose in notches provided on the differential cage. 3) Double Reduction Type a) Double reduction type differential provides further speed reduction by additional gear. b) This type of differential is used in heavy duty automobiles which require larger gear reduction between engine and wheels.

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Automobile Engineering

Q.45:- What is Rear Axle? List the various load acting on the Rear live axle half shaft? List the types of rear axle supports Ans: REAR AXLE 1. Rear axle transmits power from differential to the wheels so that vehicle may move. 2. Rear axle is not a single piece but it is in two parts which are connected by the differential. 3. Each part of rear axle is called the half shaft. 4. Outer end of the rear axle carries the wheel while inner end is connected to sun gear of the differential. 5. In vehicles which employ rear wheel drive, rear wheels are driving wheels. However, in front wheel drive vehicles, front wheels are driving wheels. 6. Rear axles and differential are completely enclosed in a housing to protect them from dust, dirt, water and any possible damage.  Functions of Rear Axle A. To transmit power from differential to the wheels. This is main function. B. To carry weight of automobile.  Load on Rear live axle half shaft The various loads on rear live axle half shaft are a. Shaft force due to vehicle weight b. Bending moment on accountant of the offset of vehicle load applied through spring seats and road wheels. c. End thrust carried by side forces d. Bending moment caused by end thrust and its reaction offered by tyres e. Driving torque

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Automobile Engineering

 Types of Rear Axle Support Rear axles differ on the basis of method of supporting them and mounting of rear wheels. On this basis, these axles can be classified into three types: (a) Half floating axle (b) Three-quarter floating axle (c) Fully floating rear axle.

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Automobile Engineering

Q.46:- Discuss the Semi-floating type rear axle with neat sketch? Ans: SEMI FLOATING TYPE REAR AXLE

Figure : Semi floating axle.

1) An axle in which the shaft has to take the entire load is called semi or non floating axle. 2) In this wheel hub is directly connected to the axle. 3) The inner end of the axle shaft is splined and is supported by the final drive unit where as outer end is supported by a single bearing inside the axle casing. 4) In this type all the loads are taken by the axle shaft. 5) The whole load acts on the shaft and shaft has a tendency to shear at the point A. 6) The semi floating axle is the simplest and cheapest but for a given torque they have to be of larger dia. for the same torque transmitted compared to the other type of rear axle supports.

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Automobile Engineering

Q.47:- Discuss the Fully floating type rear axle with neat sketch? Ans: FULL FLOATING TYPE REAR AXLE

Figure : Full floating axle. 1) This type is very robust and is used for heavy vehicle. 2) The axle shafts have flanges at the outer end which are connected to the flanged sleeve by means of bolts. 3) There are two tapper roller bearing supporting axle casing in the hub which take up any side load. 4) Thus the axle shaft carry only the driving torque. So their failure or removal does not affect the wheels.

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Automobile Engineering

Q.48:- Discuss the Three quarter floating type rear axle with neat sketch? Ans: THREE QUARTER FLOATING TYPE REAR AXLE

Figure :Three quarter floating axle. 1) This type of axle is a combination of full and semi floating bearing. 2) In this bearing is locating between the axle casing and hub axle shaft do not have to withstand any shearing or bending action due to the weight of the vehicle, which are taken up by the axle casing through the hub and bearing. 3) However it has to take the end loads and driving torque.

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Automobile Engineering

Q.48:- Short Notes on a. Differential lock b. Self locking different Ans:a. Differential Lock: 1) The torque transmitted by the bevel gear differential to each of the rear wheels remains equal even when they are rotating at different speeds. 2) Due to this reason if one wheel in on a slippery surface, mend, lose dirt or sand the wheel on the solid ground will not be driven while the other spins around idly. 3) When the differential lock is applied, the differential action is stopped and the whole torque is then applied to the wheel which is gripping on the road. b. Self Locking Differential: 1) A self locking differential consists of two clutches, one on each side, to lock the side gears and axles to the differential cage, when the differential action is not desired. 2) The mechanism consists of four differential pinion gears mounted on two cross shafts at right angles to each other. 3)

When the differential cage is driven by the rear axle gears, the turning

resistance causes the cross shafts to move up the ramps and push the shafts apart. 4)

This action forces the pinions on each shaft to bear against the side gear

rings in order to apply the clutch which locks both axle shafts and force them to turn at the same speed.

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Automobile Engineering

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