Pondicheey University MEEE61 Automobile Engineering

1. Sri Ganesh College of Engineering and Technology
Department of Mechanical Engineering
MEE61-Automobile Engineering
2 MARK AND 11 MARK QUESTION AND ANSWERS
UNIT –I
PART A (2 MARKS)
1. Name few components of engine.
• Cylinder block
• Cylinder head
• Crankcase
• Cylinder
• Piston
• Connecting rod
• Crankshaft
• Camshaft
• Valves
• Spark plug (in the case of petrol engine)
• Fuel injector (in the case of diesel engine)
2. State the major types of automobiles according to the fuel used.
• Petrol Engines (SI engines)
• Diesel Engines (CI engines)
• Gas Engines (either SI or CI mode)
3. Classify automobiles with respect to the drive of the vehicle.
• Front wheel drive
• Rear wheel drive
• All four wheel drive
• Left hand drive
• Right hand drive
4. What are the two types of cylinder liners?
• Dry liners
• Wet liners
5. What are the functions of piston rings?
To provide a gas tight seal between the piston and cylinder liner to prevent the escape of gases
from top side of the piston to the underside.
6. What are the two types of piston rings?
• Compression rings
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2. • Oil rings
7. What are the different methods of engine cooling and its purpose?
Methods of Cooling Systems:
• Air cooling
• Oil (or) Water cooling
The purpose of cooling system is to cool the engine components in order to keep their temperature below
certain limit and thereby avoiding excessive thermal stress in those components.
8. State the difference between S.I and C.I engine.
Parameter SI Engine CI Engine
Type of fuel Petrol Diesel
Compression Ratio Low ( 6 to 10) High (12 to 24)
Operating cycle Otto cycle Diesel or Dual cycle
Thermal efficiency Low High
9. What is the purpose of ignition system in a petrol engine?
The purpose of an ignition system is to ignite the air-fuel mixture at the end of the
compression stroke.
10. What is the purpose of lubricating system? State its types.
The purpose of lubrication system is to supply the lubricating oil between the moving parts of the
engine in order to
0 Reduce the friction
1 Provide the cooling effect
2 carry away the deposits formed due to wear and tear
Types: -
2. Mist lubrication
3. Splash lubrication
4. Pressure feed lubrication
5. Combined splash & pressure feed lubrication
11. What is meant by turbo charging?
Increasing the density of inducted charge/air by using a compressor which gets its power from
exhaust driven turbine is known as Turbo charging.
12. What are the functions of frames in automobile?
1. To form the base for mounting engine and transmission system.
2. To withstand the engine and transmission thrust and torque stresses as well as
accelerating and braking torque.
3. To accommodate suspension system.
4. To carry the other parts of the vehicle and its passengers.
5. To resist the effect of centrifugal forces when cornering a curve.
6. To withstand bending and twisting stresses due to the fluctuating or rear and front axle.
13. List out the various loads acting on the chassis frame?
• Load of short duration
• Combined loads of moment any duration
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3. • Inertia loads
• Impact loads
• Loads due to road camber
• Loads due to wheel impact
• Static loads
• Overloads
14. What are the various resistances which effect the movement of an automobile?
Broadly the resistances can be categorized into the following categories:
• Aerodynamic drag
• Gradient resistance
• Rolling resistance
• Inertia
15. Write any four classifications of IC engine?
(a) Type of ignition
1. Spark Ignition engines
2. Compression Ignition engines
(b) Cycle of Operation
1. Otto cycle engine
2. Diesel cycle engine
3. Dual cycle engine
(c) Engine cycle per stroke
1. Four stroke cycle
2. Two stroke cycle
(d) Types of fuel used
1. Petrol engine
2. Diesel engine
3. Gas engine
UNIT-1
PART- B (11 Marks)
1. Explain four stroke petrol and two stroke Petrol engine with neat sketch with engine
components.
Basic Engine Components:
Even though reciprocating internal combustion engines look quite simple, they are highly complex
machines. There are hundreds of components that have to perform their functions satisfactorily to
produce output power. There are two types of engines, viz., spark ignition (S1) and compression-ignition
(CI) engine. Let us now go through the important engine components and the nomenclature associated
with an engine.
Engine Components The major components of the engine and their functions are briefly described
below.
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4. Cylinder Block: The cylinder block is the main supporting structure for the various components. The
cylinder of a multicylinder engine is cast as a single unit, called cylinder block. The cylinder head is
mounted on the cylinder block. The cylinder head and cylinder block are provided with water jackets in
the case of water-cooling with cooling fins in the case of air-cooling. Cylinder head gasket is incorporated
between the cylinder block and cylinder head. The cylinder head is held tight to the cylinder block by
number of bolts or studs. The bottom portion of the cylinder block is called crankcase. A cover called
crankcase, which becomes a sump for lubricating oil is fastened to the bottom of the crankcase. The
inner surface of the cylinder block which is machined and finished accurately to cylindrical shape is called
bore or face.
Cylinder: As the name implies it is a cylindrical vessel or space in which the piston makes a
reciprocating motion. The varying volume created in the cylinder during the operation of the engine is
filled with the working fluid and subjected to different thermodynamic processes. The cylinder is
supported in the cylinder block.
Piston: It is a cylindrical component fitted into the cylinder forming the moving boundary of the
combustion system. It fits perfectly (snugly) into the cylinder providing a gas-tight space with the piston
rings and the lubricant. It forms the first link in transmitting the gas forces to the output shaft.
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5. FOUR STROKE PETROL ENGINE
Combustion Chamber: The space enclosed in the upper part of the cylinder, by the cylinder head and
the piston top during the combustion process, is called the combustion chamber. The combustion of fuel
and the consequent release of thermal energy results in the building up of pressure in this part of the
cylinder.
Inlet Manifold: The pipe which connects the intake system to the inlet valve of the engine and through
which air or air-fuel mixture is drawn into the cylinder is called the inlet manifold.
Exhaust Manifold: The pipe that connects the exhaust system to the exhaust valve of the engine and
through which the products of combustion escape into the atmosphere is called the exhaust manifold.
Inlet and Exhaust Valves: Valves are commonly mushroom shaped poppet type. They are provided
either on the cylinder head or on the side of the cylinder for regulating the charge coming into the cylinder
(inlet valve) and for discharging the products of combustion (exhaust valve) from the cylinder.
Connecting Rod: It interconnects the piston and the crankshaft and transmits the gas forces from the
piston to the crankshaft. The two ends of the connecting rod are called as small end and the big end.
Small end is connected to the piston by gudgeon pin and the big end is connected to the crankshaft by
crankpin.
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6. Crankshaft: It converts the reciprocating motion of the piston into useful rotary motion of the output shaft.
In the crankshaft of a single cylinder engine there is pair of crank arms and balance weights. The balance
weights are provided for static and dynamic balancing of the rotating system. The crankshaft is enclosed
in a crankcase.
Piston Rings: Piston rings, fitted into the slots around the piston, provide a tight seal between the piston
and the cylinder wall thus preventing leakage of combustion gases
Gudgeon Pin: It forms the link between the small end of the connecting rod and the piston.
Camshaft
The camshaft and its associated parts control the opening and closing of the two valves. The
associated parts are push rods, rocker arms, valve springs and tappets. This shaft also provides the drive
to the ignition system. The camshaft is driven by the crankshaft through timing gears.
Cams
These are made as integral parts of the camshaft and are designed in such a way to open the
valves at the correct timing and to keep them open for the necessary duration.
Fly Wheel
The net torque imparted to the crankshaft during one complete cycle of operation of the engine
fluctuates causing a change in the angular velocity of the shaft. In order to achieve
a uniform torque an inertia mass in the form of a wheel is attached to the output shaft and this wheel is
called the flywheel.
2. Explain two stroke Diesel and four stroke Diesel engine with neat sketch.
DIESEL ENGINE
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7. In a two stroke diesel engine, the cycle is completed in one revolution of the crankshaft. It has one
power stroke and one ideal stroke. In this cycle, the suction, compression, expansion and exhaust take
place during two strokes of the piston.
It has ports instead of valves; ports are cut in the cylinder wall. There are three ports namely Inlet
port, Transfer port and Exhaust port. The opening and closing of the port is obtained by the movement of
the piston which is made of particular shape to deflect the air upwards in the cylinder. Fuel injector is
provided in the cylinder to inject to fuel into the cylinder.
Upward stroke:
During the first stroke, the piston moves upwards from the BDC to TDC. It uncovers the inlet port
and covers the transfer port and the exhaust port. At this time the air inside the engine cylinder is
compressed. At the end of compression, the pressure and temperature of the air is increased. Due to the
upward movement of the piston, a partial vacuum is created in the crank case and air is drawn into the
crankcase through the uncovered inlet port. Before the piston has reached the TDC, the fuel injector
injects the fuel into the cylinder. The fuel is mixed with high pressure and high temperature air in the
cylinder in a correct proportion and gets ignited. These two operations suction and compression are
completed in this first stroke.
Downward stroke: The combustion product expands and pushes the piston in downward direction. Due
to the piston movement, the inlet port is covered and the air-fuel mixture is partially compressed in the
crank case. It uncovers the exhaust port and transfer port. The exhaust gases are exhausted through the
uncovered exhaust port to the atmosphere. At the same time air which is already compressed in the
crank is forced into the cylinder through the transfer port. The top of the piston is made of deflected
shape. The entering air is deflected.
Four Stroke Diesel Engines:
The cycle of operation in a four stroke diesel engine is completed in two revolutions
of crankshaft or four strokes of piston using diesel oil as fuel. This engine works on diesel cycle.
1. Suction Stroke:
Starting of engine is done by an electric motor or manually. In both cases the energy
is supplied to the engine. In this stroke the inlet valve opens and the outlet valve remains closed.
Piston moves from T.D.C. to B.D.C. and in this way a vacuum is created in the cylinder. This
vacuum is filled by air alone and piston reaches to B.D.C.
2. Compression Stroke:
Both valves are closed. This time piston moves from B.D.C. to T.D.C. Air is
compressed in this stroke up to a compression ratio of 15:1 to 22:1 and a very high temperature is
produced due to high pressure. The high temperature is the only cause of combustion of the fuel.
The piston takes the power in this stroke from the flywheel. During this stroke the pressure and
temperature attain a high value of 40 to 60 bar and 600º C to 700º C.
3. Working / Power Stroke:
At the end of compression stroke or when the piston reaches the T.D.C. position, a
fine spray of diesel is injected in the cylinder through injector. The fuel burns by the heat of
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8. compressed air and due to its burning the power is produced. This power pushes the piston
downward i.e. from T.D.C. to B.D.C. The excess energy of the piston is stored in the flywheel of
the engine, which is further used for the remaining three strokes of the engine. The reciprocating
motion of the piston is converted into the rotary motion of the crankshaft by connecting rod and
crank. During expansion the pressure drops due to increase in volume of gases and absorption of
heat by cylinder walls.
4. Exhaust Stroke:
The exhaust valve begins to open when about 85% of the working stroke is
completed. The force of piston coming from B.D.C. to T.D.C. forces the burnt gases into the
exhaust manifold. Some of the gases are forced out due to higher pressure in the cylinder and the
remaining gases are forced out by the piston. Some of the burnt gases are however left inside the
clearance space. The exhaust valve closes shortly after T.D.C. The inlet valve opens slightly before
the end of exhaust and in this way the cycle repeats.
3. Compare Petrol engine with Diesel engine.
Comparison of petrol and diesel engine
Sl.No. Petrol engine Diesel engine
1 Intake: Air + fuel is admitted into the cylinder Air alone admitted into the cylinder
2 Fuel ignition: Spark ignition Compression ignition
3 Cycle: Otto cycle Diesel cycle
4 Compression ratio Low: (6:1) High(16:1)
5 Fuel admission: Through carburettor Through fuel injector
6 Engine Speed: High up to 5000 rpm Low up to 3500 r.p.m
7 Weight: Low up to 3kg per kW High up to 10kg per kW
8 Engine starting: Easy Difficult
9 Engine cost: Less More
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9. 10 Fuel Consumption: More Less
11 Fuel Cost: More Less
12 Maintenance cost: Less High
13 Space: Less More
14 Engine life: Less than 60,000 km More than 1,50,000 km
15 Vibration and Noise: Very less More
4. Compare four stroke and two stroke engine.
Comparison of four stroke and two stroke engine
S.N
o
Four stroke engine Two stroke engine
1 The cycle completed in four stroke of piston or two revolution
of crank
The cycle is completed in two
stroke of piston or one revolution
of crank
2 For every two revolution of crank shaft one power stroke For every one revolution crank
shaft one power stroke
3 Valves are required – inlet and outlet valves Ports are made in cylinder walls-
inlet, exhaust and transfer port
4 The engine is heavier and bulky The engine is light and compact
5 Volumetric efficiency is more Less
6 Thermal efficiency is high Low
7 Used in high vehicles (buses, trucks, etc.) Used in light vehicles (scooters,
motors, etc.)
8 Lesser cooling is required Greater cooling is required
9 Lesser lubrication is required Greater lubrication is required
10 Heavier flywheel required Lighter flywheel required
11 Fuel consumption low High fuel consumption
12 Engine cost more Engine cost less
13 Less noisy More noisy
5. Explain the types of Automobiles in detail.
Types of automobiles
There are numerous types of automobiles found in different parts of the world. With respect to
different purposes, the various types of automobiles are classified as under:
With Respect to the Use
i. Auto-cycles and Mopeds
ii. Scooters and Motorcycles
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10. iii. Cars, Station wagons and Pick-ups
iv. Lorries (Buses) and Trucks
v. Tractors
With Respect to Capacity
i. H.T.V. or Heavy Transport Vehicles or Heavy Motor Vehicles: Bus, Coaches, Truck, Tractor.
ii. L.T.V. or Light Transport Vehicles, or Light Motor Vehicles: Cars, Jeeps, Motor cycles
iii. Medium Vehicles: Minibus, Station wagon
With Respect to Fuel Used
i. Petrol Vehicles: Jeeps, cars, Motor Cycles
ii. Diesel Vehicles: Truck, Bus, Tractor, Bulldozer, Mercedes
iii. Gas Vehicles- Coal gas, Gas turbine or Producer gas Vehicles.
iv. Electric Vehicles- Using electric storage batteries or accumulators to drive electric motors
attached to the front or rear wheels, e.g. Heavy cranes, battery truck, cars and forklifts.
v. Steam vehicles: Steam road rollers, it is now obsolete.
With Respect to Wheels and Axles
i. Two wheelers: Motor cycles
ii. Three wheelers: Tempos, Auto Rickshaws, Tricycles
iii. Four wheelers: Cars, Jeeps, Buses, Trucks (some buses and trucks have six tyres out of which
four are carried on the rear wheels for additional traction.
iv. Six axle wheelers (10 tyres) vehicles.
With Respect to the Motion
i. Reciprocating – piston engines
ii. Rotary – Wankel engine, Gas turbine
With Respect to the Suspension
i. Conventional – leaf spring
ii. Independent – coil, torsion bar, pneumatic.
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11. 6. Explain the General layout of Vehicle in details.
General layout
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12. Engine:
An engine is a device, which transforms one form of energy into another form. Normally, most of
the engines convert thermal energy into mechanical work and therefore they are called ‘heat engines’.
Heat engines can be broadly classified into two categories:
7. Explain the factors that affect the Resistance to Motion.
Resistance to motion
This is the resistance a vehicle faces while attempting to move from a stall condition or while
accelerating. This resistance must be overcome by the power plant of the engine in order to sustain
motion. When the power produced is smaller than the resistance to motion, the vehicle will gradually
slow down. We must have experienced the slowing down of bicycles if we stop pedalling. The bicycle
also slows down if we go uphill or if wind blows from front. A poorly inflated tire also causes the vehicle
to groan more and slow down. These are the resistances that force the vehicle to slow down under their
effect.
Broadly the resistances can be categorized into the following categories:
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13.  Air (or) wind resistance
 Gradient resistance
 Rolling resistance
 Inertia
All the above produce a restraining force working against the tractive force. The tractive force must
be greater than or equal to the resistive forces in order to maintain a sustainable motion. We can
balance them as
F = Freq = FA + FG + FR + FI
Where
FA= Force due to air resistance
FG = Force due to gradient of a slope
FR = Force due to rolling resistance
FI = Force due to moving or static inertia
The last one FI comes into the picture only when the vehicle accelerates or decelerates, while the first
three always offer a resistance even when the vehicle is moving at a constant speed
Air (or) wind resistance
The moving vehicle has to face air resistance. To reduce this air resistance the front bonnet and
mudguard are given slope. So that air can be easily turned apart. The air resistance depends upon.
• Vehicle speed
• Shape and size of the body
• Direction of wind
• Velocity of the wind.
Gradient resistance:
When a vehicle travels uphill, a component of its
weight, works in a direction opposite to its motion. If
some energy is not supplied to overcome this
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14. backward force, then the vehicle would slow down, stall and roll backwards. If the vehicle is trading uphill
at a slope of θ, then the weight of the vehicle, W has two components: one perpendicular to the road
surface (with a value W·Cos θ) and the other along the road surface (with a value W·Sin θ). The
component along the road surface is the one that tries to restrict the motion.
The gradient resistance is given by: FG = W·Sin θ
Rolling resistance
When a vehicle rolls, it rolls with its tires in contact with the road surface. The relative motion of
two hard surfaces produces a friction. Further, neither the road, nor the tires are perfectly rigid. Hence,
both flex under the load slightly. As there is a gradual deformation at the contact between the road and
the tire, greatest at the bottom most point and least at the entry and exit points, the slip of the tire w.r.t.
the road produces another type of loss of energy which results in a resistance.
Rolling resistance is composed of the following components:
• Tire Rolling resistance: FR,T
• Road rolling resistance: FR,Tr
• Resistance due to tire slip angle: FR,α
• Resistance due to bearing friction and residual braking: FR,fr
Hence the rolling resistance offered may be written as:
FR = FR,T + FR,Tr + FR,α + FR,fr
The tire rolling resistance FR,T is a result of the resistance due to flexure of the tire, air resistanceon the
tire and friction of tire with the road. These three can be summed up and written as:
FR,T = FR.T.flex + FR.T.A + FR.T.fr.
In a simplified manner the total rolling resistance can be related to the vertical load on the wheels and
can be written as:
Co−efficient of rolling friction, kR = FR/FZ.w
UNIT-2
PART A (2 MARKS)
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15. 1. What is the function of clutch?
The function of the clutch is to connect and disconnect the engine with road wheels. The clutch
has to be disengaged during gear shifting, idling etc.
2. What are the types of clutch?
Friction clutches
• Single plate clutch
• Multi plate clutch
• Cone clutch
• Semi centrifugal clutch
Centrifugal clutch
Fluid clutches
• Flywheel
3. What is the function of gear box? State its types.
The functions of the gearbox are
0 To provide the vehicle motion at different speeds
1 To provide the neutral position
2 To provide a means to reverse the vehicle.
Types
• Sliding mesh gearbox
• Constant mesh gearbox
• Synchromesh gearbox
• Automatic gearbox – Planetary, Torque converter
4. What is a universal joint? What are its types?
Universal joint is a type of flexible joint between two shafts who axes intersect and may
15

16. assume different inclinations at different times. It is used to transmit power even at inclined angles
of the shaft.
Types
• Yoke joint
• Single cardan joint
• Double cardan joint
• Rag joint
• Canfield joint
5. State the functions of a slip joint.
The function of a slip joint is to accommodate the propeller shaft length variations, when a
vehicle is moving over a bump or bit.
6. What is the necessity of a propeller shaft?
The propeller shaft is used to transmit the power from the gearbox to the final drive. It is also
used to cover the span between these two components.
7. What is Hotchkiss drive and Torque Tube drive?
In Hotchkiss drive, the loads such as vehicle weight, driving torque, braking torque and side
thrust all are taken by leaf springs. Two universal joints and one slip joint are must needed.
In Torque tube drive, the driving torque and braking torque are taken by torque tube while the
vehicle weight and side thrust are taken care of by leaf springs. One universal joint is just sufficient.
8. What is the function of differential unit?
The function of a differential unit is to permit the vehicle turns without wheel skidding. It
permits higher speed for outer wheels and reduced speed for inner wheels during turning. It gives
higher gear reduction ratio with 90 degree drive direction change.
9. What is a fluid coupling?
Fluid coupling is device which transmits torque due to the kinetic energy of the moving
fluid. In a fluid coupling, two members namely impeller and turbine are present.
10. What is the use of torque convertor?
The torque converter is device which provides a varying torque ratio using fluid energy. In a
torque converter, three members namely impeller, turbine and stator are present.
11. State the forces act on the rear axle
• Shear force due to vehicle weight
• Bending moment due to vehicle weight
• Driving torque
• Shear force due to side thrust
12. What are the different types of rear axles?
• Semi floating rear axle
• Full floating rear axle
• Three quarter floating rear axle
13. What is the difference between fluid coupling and torque converter?
Fluid coupling is used for transfer torque at high speed to wheel while torque
converter converts torque at low speed. They both consist two rotors while torque converter also
consist stator with two rotors.
UNIT-II
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17. PART-B
PART- B (11 Marks)
1. Explain the single plate clutch with neat sketch.
Single plate Clutch:-
It is the most common type of clutch used in motor vehicles. It consists of only one clutch plate, mounted
on the spines of the clutch shaft. The fly wheel is mounted on the engine crane shaft and rotates witch it.
The pressure plate is bolted to the fly wheel through clutch springs, and is free to slide on the
clutch shaft when the clutch pedal is operated. When the clutch is engaged, the clutch plate, having
friction linings on its both sides, is gripped between the fly wheel and pressure plate.
Due to the friction between the flywheel, clutch plate and pressure plate revolves; the clutch shaft
which is connected to the transmission system also revolves. When the clutch pedal is pressed, the
pressure plate moves back against the force of the springs, and the clutch plate becomes free between
the fly wheel and pressure plate.
Thus, the flywheel remains rotating as long as the engine is running and the speed of the clutch
shaft reduces slowly and finally it stops rotating. As soon as the clutch pedal is pressed, the clutch is said
to be disengaged, otherwise it remains engaged due to the force of springs.
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18. 2. Explain the Multi plate clutch with neat sketch.
Multiplate clutch
Multi plate clutch consists of a number of clutch plates. As the number of clutch plates increased, the
friction surfaces also increased. The increased number of friction surfaces obviously increases the
capacity of the clutch to transmit torque. The plates are alternately fitted to the engine shaft and gear box
shaft.
One set of plates slides in grooves on the flywheel and the other set slides on spines on pressure
plate hub. They are firmly pressed by strong coil springs and assembled in a drum. Each of the alternate
plate slides in grooves on the flywheel and the other slides on spines on the pressure plate. Thus each
alternate plate has inner and outer spines. The construction is similar to single plate type except that all
the friction plates in this case are in two sets, one set of plate’s slides in grooves on the flywheel and the
other one slides on splices on the pressure plate hub.
These clutches are used in heavy commercial vehicles, racing cars and motor cycles for
transmitting higher torque. Beside these clutches are used in scooters and motor cycles where space
available is limited.
3. Explain the Gearbox with neat Diagram.
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19. Constant mesh gear box
In this type of gearbox, all the gears of the main shaft are in constant mesh with corresponding
gears of the countershaft. The gears on the main shaft which are bushed are free to rotate. The dog
clutches are provided on main shaft.
The gears on the lay shaft are, however, fixed. 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.
The same dog clutch, however, when slide to right makes contact with the second gear and
second gear is obtained. Similarly movement of the right dog clutch to the left results in low gear and
towards right in reverse gear. Usually the helical gears are used in constant mesh gearbox for smooth
and noiseless operation.
Neutral gear:-
When engine starts, the clutch gets rotate. If rotates clutch gear and lay shaft gear, all the gears
on main shaft also get rotate because the no one dog is engage to the gear.
Reverse gear:-
As the driver wand’s to move the vehicle back he shifts the first dog towards digger gear which is
engages to the idler gear. As the dog engages its start rotate with the gear in reverse or opposite
direction and tends to rotate the main shaft in reverse direction.
4. Explain Synchromesh Gear box with neat Diagram.
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20. Synchromesh gearbox
In modern cars, helical gears and synchromesh devices are used in gear boxes to synchronize
the rotation of gears that are about to be meshed. This gear box is provided with synchromesh devices
by which two gears to be engaged are first brought into frictional contact which they are engaged
smoothly.
When the gear lever is moved, the synchronizer cone meets with a similar cone on the pinion.
Due to the friction, the rotating pinion is made to rotate at the same speed as the synchromesh unit.
To give a positive drive further movement of the gear lever enables the coupling to override
several spring loaded balls and the coupling engages with the dog on the ride of the pinion. Since both
pinion and synchromesh unit are moving at the same speed, this engagement is done without noise or
damage to the dogs. This type of gearbox is similar to the constant mesh type gearbox.
Instead of using dog clutches here synchronizers are used. The modern cars use helical gears
and synchromesh devices in gearboxes, that synchronize the rotation of gears that are about to be
meshed.
(a) Disengaged position (b) Engaged position
Synchronizing Unit Arrangement
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21. 6. Write short notes on the torque converter in detail.
Torque converter:-
The torque converter is also a kind of fluid flywheel (drive) but change in the torque by providing
variable gear ratio. Additional part that is stator is used, so that its gear ratio is maximum when starting
from rest and decreases as the vehicle gets speed.
Construction:-
It uses
1. Stator.
2. A driving pump impeller.
3. Turbine.
Torque converter
The fluid fitted in the torque converter is oil circulates under part to the other. The housing from
one oil float B charged by the stationary blade B such way that the oil return that pump impeller after
passing through the turbine as the vehicle picks up the speed the blade being to turn along with the other
member so the torque multiples thus the power from engine crank shaft transfer to the turbine.
7. Write short notes on Fluid flywheel in detail.
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22. Fluid fly wheel
The net torque imparted to the crankshaft during one complete cycle of operation of the engine
fluctuates causing a change in the angular velocity of the shaft. In order to achieve a uniform torque an
inertia mass in the form of a wheel is attached to the output shaft and this wheel is called the flywheel.
The fluid fly wheel or hydraulic coupling has been used in cars employing automatic
transmission. It consists of two members, the driving and driven. The driving member is attached to the
engine fly wheel and the driven member to the transmission shaft. The driven member is free to slide on
spines on the transmission shaft.
8. Explain the types of Differential in detail.
Types of differential:
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23. Differential is of the following types:
1. Conventional.
2. Power-lock or Non-slip or Limited Slip
3. Double reduction type.
Conventional Type
Final Drive Conventional type differential delivers same torque to each rear wheel. If any of the
wheels slips due to any reason the wheel does not rotate and vehicle does not move.
Non-slip or Self Locking Type
Non-slip or self locking type differential overcomes this drawback. It construction is similar to that
of conventional type differential. But, two sets of clutch plates are provided additionally. Also, the ends of
planet shafts are left loose in notches provided on the differential cage.
Double Reduction Type
Double reduction type differential provides further speed reduction by additional gear. This type
of differential is used in heavy duty automobiles which require larger gear reduction between engine and
wheels.
9. Write short notes on Drive Axle.
Drive/Rear Axle
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24. It is that axle through which drive goes to the wheels. It is also known as live axle since power
flows through it. It serves the following purposes.
1. It acts as a beam to support the weight of the body.
2. It acts as an axis for the wheel
3. It transmits power to the wheels
1. It acts as housing at support for the final drive, differential and half shafts.
Forces acting on rear axle
1. Shear force due to vehicle weight.
2. End thrust by the side forces (while cornering, side wind)
3. Driving Torque
4. Bending moment due to vehicle load and end thrust.
Types of Rear Axles
Depending upon the methods of supporting the rear axles and mounting the rear wheels, the rear
axles are of three types
1. Semi-floating axle
2. Full floating axle
3. Three quarter floating axle.
1. SEMIFLOATING AXLE:
In semi floating type of rear axle, all the load of rear portion of the vehicle is carried by the axle shaft.
Therefore, it needs to be of a large size, for the same torque output, than any other type. The inner end of the
axle shaft is splined and is supported by the differential side Gear, whereas the outer end is supported by a
single bearing inside the axle casing. In this type of axle the wheel hub is directly fitted on the axle shaft.
In this, the axle shaft takes the vehicle load as well as the driving thrust. It is simplest and cheapest of
all other types and widely used in cars.
2. FULL FLOATING AXLE:
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25. This type is very robust one and is used for heavy vehicles. It has two deep-groove ball (or)
taper roller bearings, located between the axle casing and wheel hub. The outer of the axle is made
flanged to which the wheel hub is bolted. With this arrangement, the axle shaft may be removed from
the housing without disturbing the wheel by removing the hub cap and the coupling.
The vehicle load is taken by the axle casing. The axle shaft takes only the driving thrust. For this
reason, it is called full floating
3. THREE QUARTER FLOATING AXLE:
The three quarter floating axle is shown in fig. In this axle the single bearing is located
between the hub and the axle casing. Thus the weight of the vehicle is transferred to the axle casing,
and only the side thrust and driving torque are taken by the axle. The axle shaft is keyed rigidly to the
wheel hub. This arrangement provides the driving connection and maintains the alignment of the
wheel. The construction at the inner end of the axle shaft is the same as with the semi floating type.
Although the three quarter floating axle is more reliable but it is not as simple as the semifloating axle.
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