Basics of automobile engineering

1. AUTOMOBILE ENGINEERING
UNIT-1

2. UNIT-1
• Introduction: Types of automobiles, vehicle construction and
layouts, chassis, frame and body, IC engines- components, function
and materials, Turbo charging- WGT, VGT and supercharging
Crankcase ventilation, Engine service, reboring, Decarburization,
Nitriding of crankshaft.
• Performance of automobiles: Taxable Power, Power and Torque
Curves, Resistances to a Moving vehicle, Rolling Resistance, Wind or
Air Resistance, Gradient Resistance, Total Resistance, Power required
to propel a vehicle.
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3. • Types of automobiles,
• Vehicle construction and layouts, chassis, frame and body,
• IC engines- components, function
• Turbo charging- WGT, VGT
• supercharging
• Crankcase ventilation,
• Engine service, reboring, Decarburization, Nitriding of crankshaft.
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4. Performance of automobiles:
• Taxable Power, Power and Torque Curves,
• Resistances to a Moving vehicle,
• Rolling Resistance,
• Wind or Air Resistance,
• Gradient Resistance,
• Total Resistance,
• Power required to propel a vehicle.
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5. Automobile or Vehicle
• An Automobile is a self propelled vehicle which contains the
power source for its propulsion and is used for carrying
passengers and goods on the ground, such as car, bus, trucks,
etc.
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6. On the Basis of Load
a) Heavy transport vehicle (HTV) or heavy motor vehicle
(HMV), e.g. trucks, buses, etc.
b) Light transport vehicle (LTV), e.g. pickup, station
wagon, etc.
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7. On the Basis of Load
c) Light motor vehicle (LMV), e.g. cars, jeeps, etc.
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8. On the Basis of Wheels
a. Two wheeler, for example: Scooter, Motorcycle, Scooty, etc.
b. Three wheeler vehicle, for example: Autorickshaw, three
wheeler scooter for handicaps and tempo, etc.
c. Four wheeler vehicle, for example: Car, jeep, trucks, buses, etc.
d. Six wheeler vehicle, for example: Big trucks with two gear axles.
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9. On the basis of Fuel used
a) Petrol vehicle, e.g. motorcycle, scooter, cars, etc.
b) Diesel vehicle, e.g. trucks, buses, etc.
c) Electric vehicle which use battery to drive.
d) Gas vehicle, e.g. LPG and CNG vehicles
e) Hybrid Vehicles, e.g. LPG/CNG and Gasoline
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10. On the basis of Transmission
a) Manual transmission
b) Semi-automatic
c) Automatic
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11. Drive
•Driven sitting towards right or left side
•Left hand drive
•Right hand drive
•Driving Axle
•Front wheel drive
•Rear wheel drive
•All wheel drive
- USA
- India
– Volkswagen Passat, Chevrolet Cruze,
Hyundai Sonata, Toyota Camry,……
– All Indian Vehicles
– Jeep
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12. a) Conventional: uses leaf springs
b) Independent: uses coil springs & torsion springs.
On the basis of Suspension System:
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13. Position of Engine
a) Engine in Front
• Most of the vehicles have engine
in the front.
• Example : most of the cars, buses,
trucks in India.
b) Engine in the Rear Side
• Very few vehicles have engine
located in the rear.
• Example: Volkswagen Beetle
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17. LAYOUT OF AUTOMOBILE & TYPES OF DRIVES OF
AUTOMOBILES
• The main parts of automobile are mounted on the chassis.
• The layout of these components on the chassis are different in different types
of vehicles, i.e., cars, jeeps, trucks, buses, etc.
• The main difference in the layout of this chassis is the position of the engine.
• The engine is located at the front of the vehicle, followed by a clutch, gear box,
propeller shaft, universals joints, differential, rear axle, etc.
• The radiator is located in front of the engine. Various other parts of the
vehicle are dynamo, horn, steering box, fan, timing gear, carburetor, air filter,
gear control, steering wheel, cylinder, petrol tank, rear axle, front axle. 17

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19. FUNCTIONS OF THE CHASSIS FRAME:
1. To carry load of the passengers or goods carried in the body.
2. To support the load of the body, engine, gear box etc.,
3. To withstand the forces caused due to the sudden braking or
acceleration
4. To withstand the stresses caused due to the bad road condition.
5. To withstand centrifugal force while cornering
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20. TYPES OF CHASSIS FRAMES:
There are three types of frames
• Conventional frame
• Integral frame
• Semi-integral frame
Conventional frame: It has two long side members and 5 to 6 cross members
joined together with the help of rivets and bolts. The frame sections used are
generally.
a. Channel Section - Good resistance to bending
b. Tabular Section - Good resistance to Torsion
c. Box Section - Good resistance to both bending and Torsion
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22. Integral Frame:
• This frame is used now a days in most of the cars.
• There is no frame and all the assembly units are attached to the body.
• All the functions of the frame carried out by the body itself.
• Due to elimination of long frame it is cheaper and due to less weight most
economical also.
• Only disadvantage is repairing is difficult.
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24. Semi - Integral Frame:
In some vehicles half frame is fixed in the front end on which engine gear box and
front suspension is mounted. It has the advantage when the vehicle is met with
accident the front frame can be taken easily to replace the damaged chassis frame.
This type of frame is used in FIAT cars and some of the European and American
cars.
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25. VARIOUS LOADS ACTING ON THE FRAME:
 Short duration Load - While crossing a broken patch.
 Momentary duration Load - While taking a curve.
 Impact Loads - Due to the collision of the vehicle.
 Inertia Load - While applying brakes.
 Static Loads - Loads due to chassis parts.
 Over Loads - Beyond Design capacity.
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26. The Automobile bodies are divided
in two groups
1. Passenger body
2. Commercial body
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27. REQUIREMENTS OF BODIES FOR VARIOUS TYPES OF VECHILE:
1. The body should be light.
2. It should have minimum number of components.
3. It should provide sufficient space for passengers and luggage.
4. It should withstand vibrations while in motion.
5. It should offer minimum resistance to air.
6. It should be cheap and easy in manufacturing.
7. It should be attractive in shape and colour.
8. It should have long fatigue life
9.It should provide good vision and ventilation.
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28. Vehicle Layout
Rear engine / rear wheel drive Mid engine / four wheel drive
Front engine / front wheel drive Front engine / rear wheel drive 28

29. Front engine / rear wheel drive 29

30. All / four wheel drive 30

31. Front Engine - Rear Wheel Drive
This layout is one of the oldest layout which remained unchanged for many years.
some of the advantages provided by this system are :
(a) Balanced weight distribution between the front and the rear wheels.
(b) Easy front wheel steering.
(c) Behind the rear seats, large luggage space is available.
(d) Accessibility to various components like engine, gearbox and rear axle is better
in comparison to other layouts. The control linkages-accelerator, choke, clutch and
gearbox are short and simple.
(e) Full benefits of the natural air stream created by vehicle’s movement is taken by
the forward radiator resulting in reduced power losses from a large fan. 31

32. Rear Engine-Rear Wheel Drive
• This arrangement eliminates the necessity for a propeller shaft when the engine
is mounted adjacent to the driven wheels.
• The engine-clutch-gear box-final drive form a single unit in this layout..
• Compared to FWD it has a simpler drive shaft layout. Further, the weight of rear
engine on the driving wheels provides excellent traction and grip.
• very effective rear wheel braking is possible.
• Due to the absence of the propeller shaft the obstructed floor space is reduced.
The front of the vehicle can, therefore, be designed for good visibility and
smooth air flow.
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33. • Natural air cooling is not possible, it requires a powerful fan.
• Long linkage required for the engine, clutch and the gear box controls.
• The rearward concentration of weight causes the vehicle to be more affected by
side winds at high speeds. this makes the vehicle unstable resulting in over
steering and turning very sharply into a curve.
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34. Front Engine-Front Wheel Drive
• This layout provides optimum body-luggage space and a flat floor
• Provides good grip and good road holding on curves due to major weight at the
front and chance of skidding on slippery surface is very much reduced.
• when the vehicle is to be ‘steered in’ to the curve, it provides ‘understeer’
characteristics always preferred by drivers.
• This requires special universal joints and a more complicated assembly.
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35. Four Wheel Drive/ All Wheel Drive
• Offer Excellent traction - both on dry pavement and in poor weather
• Offer double the traction that is offered by 2WD systems
• More weight and cost
• Requires special service and maintenance
• Braking distance is more because of more weight
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36. Types of engines: Mainly engines are of two types.
External Combustion Engines: The External Combustion Engines are those in
which the combustion takes place outside the engine cylinder. E.g.: Steam Engine.
Internal Combustion Engines: In the Internal Combustion Engines the combustion
of fuel takes place inside the engine cylinder. E.g.: All Automobile Engines.
Functions of I.C. Engine: Engine is that kind of prime mover which converts
chemical energy of fuel into mechanical energy. The fuel on burning changes to
gas which impinges upon the piston and pushes it to change into reciprocating
motion. The reciprocating motion of piston is then converted to rotary motion of
crank shaft with the help of slider mechanism involving connecting rod and crank
shaft.
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37. Classifications of I.C. Engines
The I.C. Engine can be classified on the basis of
1. Working cycle:
a. Otto cycle Engine or Spark Ignition Engine (S.I. Engine)
b. Diesel Cycle Engine or Compression Ignition engine (C.I. Engine)
2. Number of strokes:
a. Two Stroke engine, b. Four Stroke engine.
3. Fuel used:
a. Liquefied petrol engines, b. Diesel engines, c. Gasoline or petrol,
b. d. Compressed Natural gas engines, e. Methane or ethanol engines.
4. Fuel supply system:
a. Fuel supply through carburetor, b. Fuel injected by Fuel injecting pump. 37

38. 5. Method of ignition:
a. battery or coil ignition, b. Magneto ignition, c. Electronic ignition
6. Method of cooling:
i) Air cooled, ii) Water cooled
7. Cylinder Arrangement:
i) in line type, ii)V type, iii) Opposed cylinder type, iv)Radial type
8. Valve operating system:
i) Overhead, ii) Side valve type
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39. Materials used, function and Constructional details of Petrol Engine Components
Engine consists of the following parts.
1. Cylinder block
2. Cylinder head
3. Crankcase
4. Piston
5. Piston Rings
6. Piston Pin
7. Connecting Rod
8. Crankshaft
9. Flywheel
10. Valves and valve mechanism
11. Rocker Arm
12. Camshaft
besides the these components engine contain so many
accessories like air cleaner, oil filter, automatic chokes,
automatic heat controls, spark plug, ignition devices,
carburetors, manifolds, vibration damper etc. 39

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41. Cylinder block
The main function of cylinder is to guide the piston.
Material :
Grey cast iron or Aluminium alloy
oCylinder
oCylinder liners
oDry liner
oWet liner
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42. Cylinder head
The main function of cylinder head is to seal the cylinder block and not to permit
entry and exit of gases on cover head valve engine.
Material :
Grey cast iron or Aluminium alloy
Pistons
Functions:
• To transmit the force of explosion to the crankshaft.
• To form a seal so that the high pressure gases in the combustion chamber do not
escape in to the crankcase.
• To serve as guide and a bearing for small end of the connecting rod.
Material:
• Cast iron and aluminium alloy (Aluminium – silicon)
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44. Piston rings
Functions:
• Prevention of leakage of gas into the crank case.
• Prevention of lubricating oil film
• Prevention of lubricant entry into the combustion chamber above the piston head.
• Easy transmission of heat from piston to cylinder wall.
•
Piston rings are made of cast iron of fine grain and high elastic material which is
not affected by the working heat. Sometimes it is made by alloy spring steel.
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46. Connecting rod
The function of connecting rod is
to convert the reciprocating motion
of the piston in to the rotary motion
of the crankshaft.
Material:
• Drop forging of steel or
duralumin.
• Malleable or Spheroidal graphite
cast iron. 46

47. Crank shaft
The function of crank shaft is receives the efforts or thrust supplied by piston to the
connecting rod and converts the reciprocating motion of piston into rotary motion
of crankshaft
Material:
• Forging steel • Spheroidal graphitic
• Nickel alloy castings
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48. Crankcase (or) Oil sump (or) Oil pan
The main body of the engine to which the cylinder are attached and which
contains the crankshaft and crankshaft bearing is called crankcase.
Function:
• To store the oil for the engine lubricating system.
• To collect the return oil draining from the main bearings or from the cylinder
walls.
• To serve as a container in which any impurities or foreign matter.
• To provide for cooling of the hot oil in the sump by transfer of heat to the
outside air stream.
Material:
• Pressed steel sheet or Aluminium alloy
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49. Turbo charging and Super charging
Super Charger
• A supercharger is a device which increases the pressure of the air fuel mixture
from the carburetor before it enters the engine.
• It is connected between the carburetor and the cylinder in the way of intake
manifold.
• It is usually driven by the engine through suitable gears and shafts.
• There are 3 types of superchargers.
1. Centrifugal type
2. Vane type
3. Roots air blower type.
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50. Purpose of supercharging
• To reduce the weight per horsepower of the engine.
• To minimize the space occupied by the engine.
• To maintain the power of the engine even at high altitudes.
• To improve power in a racing car.
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51. Effects of Supercharging
• A supercharger produces better mixing of the air-fuel mixture.
• The temperature of the charge is raised as the charge is compressed
in the supercharger.
• The higher temperature tends to lessen the density of the charge.
Also, the chances for detonation are highly increased.
• Power is required to drive the supercharger. This power is usually
supplied by the engine. Therefore, some of the gain in power due to
supercharging is utilized by the supercharger.
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52. • It consists of an impeller which
rotates at a very high speed, about
10000 RPM.
• The air fuel mixture enters the
impeller at the centre and after
passing through the impeller and
diffuser vanes goes out of the
casing to the engine cylinder.
• The simple construction leads to
advantages of lightweight and
compact size. Therefore it is easy to
be fitted to existing production cars
as aftermarket device.
Centrifugal type super charger
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53. • The Roots supercharger consists of two rotors,
usually with 3 lobes each.
• They rotate in counter direction to pump the air from
inlet to outlet.
• This motion does not compress the air inside the
supercharger.
• However, as the supercharger supplies air faster than
what the engine can consume, high pressure is built
up in the intake manifold.
Roots type super charger
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57. The vane type super charger, in its simplest form,
consists of a cylindrical casing. A cylindrical rotor
carrying protruding vanes is mounted eccentrically in
the casing so that the space between rotor and the casing
has been divided into a number of compartments. The
volume of these compartments varies as the rotor turns.
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59. Turbo charger
A Turbocharger is a device that is used to increase the power of the engine or one
can say efficiency of engine by increasing the amount of air entering into the
combustion chamber. More air into the combustion chamber means more amount
of fuel will be admited into the cylinder and as a result one will get more power
from the same engine if the turbocharger are installed in it.
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60. • A turbocharger mainly consists of two main sections: the turbine and the
compressor.
• The turbine consists of turbine wheel and the turbine housing whose purpose is to
guide the exhaust gases into the turbine wheel.
• The kinetic energy of the exhaust gases gets converted into the mechanical
energy after striking the turbine blades.
• The exhaust outlet helps the exhaust gases to exit from the turbine.
• The compressor wheel in turbocharger is attached to a turbine with the help of
steel shaft.
• As the turbine turns the compressor wheel, it draws the high-velocity, low
pressure air stream and convert it into high-pressure, low –velocity air stream.
• This compressed air is pushed into the engine with the more quantity of fuel and
hence produce more power.
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63. TURBOCHARGER Vs SUPERCHARGER.
The function of the supercharger is same as that of turbocharger but the
supercharger is driven mechanically by the engine, often with the help of belt
connected to the crankshaft, whereas turbocharger is powered by a turbine
driven by the engine’s exhaust gases. Turbocharger is considered more
efficient than the superchargers as they are using the waste exhaust gases
energy for its power source.
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64. Engine lubrication
Objects of lubrication
1. To reduce friction between the moving parts.
2. To reduce wear of the moving parts.
3. To act as cooling medium for removing heat.
4. To keep the engine parts clean
5. To form a good seal between piston rings and cylinder walls.
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65. CRANK CASE VENTILATION
• The products of combustion contain mainly nitrogen, water and carbon dioxide,
sulphuric acid (due to sulphur content in the fuel)
• It is quite possible that the product of combustion may leak through the piston
rings into the crankcase oil by slipping past the piston rings.
• Thus the lubricating oil in the crankcase becomes dilute when mixed with water
and gasoline which leak past the piston rings. The acid causes corrosion of the
crankcase metals as water does.
• If either or both are allowed to enter and remain in the crankcase, the crankcase
ventilation removes all these unwanted particles from the crankcase, which leak
past the piston rings.
• It prevents the lubricating oil from becoming dilute and corrosion of crankcase
metals due to acid formation.
• Road draught crankcase ventilation system
• Induction manifold positive crank case ventilation system 65

66. • To remove gases and vapors from the crankcase and prevent their
release into the environment.
• such as unburned fuel and blow-by gases, can leak past the
piston rings and enter the crankcase. These gases can contain
harmful substances like hydrocarbons, carbon monoxide,
and nitrogen oxides.
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68. • In a positive crankcase ventilation, the
crankcase vapor are returned to the engine
through the intake manifold, instead of
being exhausted into the atmosphere.
• The crankcase outlet tube is connected to
the manifold just beneath the carburetor.
• So that the vapors are drawn into the intake
manifold and utilized into the cylinder
during the operation.
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69. SERVICING OF ENGINE
• Engine servicing is a method of engine reconditioning. In this method the old
and worn engines are dismantled completely, repair and reassemble all the parts,
Rebuild the engine, rebore the cylinders etc., and refit the engine.
• For Servicing of an Engine, the following points are to be attended.
1. Cleaning the Engine, Reconditioning of Engine by Valve Servicing, Cylinder
reboring, Crankshaft turning etc.
2. Servicing of Cooling System
3. Servicing of Lubrication System
4. Servicing of Fuel Supply System etc
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70. • Degreasing /cleaning
• A layer of oil, grease and dirt gets coated to the engine parts with passage of time
and usage. The unwanted layer of grease dist etc., should be removed.
• This can be done by hand cleaning or by means of certain cleaning methods.
• For degreasing of smaller parts, the parts are being brushed or scrubbed with a
stiff bristle brush to get rid of hard deposits.
• Other dirty parts are placed in a large perforated tray or wire basket and exposed
within a tank to the vapour of the heated Trichloroethylene.
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71. • Decarbonization
• Carbon is deposited in the cylinder due to rich mixture supply, use of wrong grade
oil, unnecessary idling, poor fitted piston and piston rings.
• Deposition of carbon causes Engine knockings,burnt value resulting in loss of
power.
• These are in general three methods of decarbonizing or decoking.
1) Scrapping method
2) Oxygen decarbonizing method
3) Chemical method of decarbonizing
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72. Scrapping method :
• The scrapping of the carbon is done by hand scrapping with the help of tools.
• To remove the carbon quickly, carbon removing brushes may be fixed in the
chuck of an electric portable drill.
• To clean valve grinder, valve stems etc., special wire brushes may also be used.
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73. Oxygen De-carbonizing method:
• It is the process of removing carbon from the inside of the cylinder and head of
the piston without removing cylinder head by means of an oxygen flame.
• The equipment consists of an oxygen tank fitted at an initial pressure of 156
kg/cm² and an adjustable reducing valve for bringing the pressure down to 0.7 to
1.4 kg/cm².
• The oxygen is applied to the combustion space by inserting a flexible delivery jet
through a valve by slightly bending it.
• The oxygen flame will burn away all the carbon deposits completely.
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74. Chemical Method of De-carbonizing:
• A special chemical is injected into the spark plug or injector hole in liquid form.
The engine should be in warm condition so that the liquid can act more efficiently.
• After twelve hours the carbon in loosened, so that upon starting the engine it is
blown out of the exhaust pipe.
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75. Chemical Cleaning:
• Chemical cleaners can be used to dissolve carbon deposits in the
engine.
• These cleaners are typically added to the fuel or sprayed directly into
the intake manifold or combustion chamber.
• The chemicals react with the carbon, breaking it down and allowing it
to be burned off during normal engine operation.
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76. RECONDITIONING OF CYLINDER:
• After prolonged usage of the engine, the cylinder of the engine will get maximum
taper wear and ovality wear.
• The Taper and Ovality wear will occur only after 40000 to 60000 kms run.
• Generally the maximum permissible ovality is specified as 0.01 mm and taper as
0.25 mm.
• Cylinder bores with less than 0.01 mm Ovality need not be rebored. They should
only be Honed.
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77. CYLINDER REBORING:
• Reboring is done by the reboring machine in which a single point cutter which
is set to exact diameter required with special micrometer.
• The cutter blade shaft is mounted inside a column which moves up and down its
housing in the fixed part of the machine for tool feeding purpose.
• The top surface of the cylinder block is thoroughly cleaned and the boring bar
set at one of the cylinder bores.
• After completing boring the cylinder must be washed thoroughly to remove all
abrasive particles.
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78. CYLINDER REBORING
MACHINE
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79. CYLINDER HONING METHOD:
• After Reboring, Honing is required to finish the bore to smooth finish.
• It removes minor imperfections and glaze. A hone consists of four or six narrow,
narrow graded grinding stones mounted in cage around a spindle which rotated
by an electric motor.
• Place the Hone in the cylinder and expand the stones until the assembly can just
be turned by hand and machine started.
• Move the Hone up and down slowly with the first cut rough Hone up and down
slowly with the first cut rough stones, but more rapidly with the finish cut five
stones.
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80. Honing
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81. Nitriding of crank shaft
• It is a surface modification processes developed industrially to improve the wear,
corrosion and fatigue resistance of a steel.
• Machine components such as crankshaft are subjected to alternating stresses
and thus there is a requirement of good toughness but very hard and wear
resistant surface.
• To achieve this a process known as Nitriding is performed in which Nitrogen
content is increased on the surface and hard nitrides are formed
• The component is exposed to nitrogenous atmosphere or dipped into Nitriding
salt bath
• Some notable characteristics of the process are
• No quenching is required
• The component is needed to be heat treated before Nitriding is performed
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82. • The cleaned crankshaft is placed in a sealed chamber, often referred
to as a nitriding furnace or retort, which is capable of providing a
controlled atmosphere for the process.
• The crankshaft is heated to an elevated temperature, typically in the
range of 500 to 600 degrees Celsius (932 to 1112 degrees
Fahrenheit), in the presence of a nitrogen-rich atmosphere. This
temperature range promotes the diffusion of nitrogen into the
surface layer of the crankshaft material.
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83. • During the heating process, nitrogen atoms diffuse into the surface
layer of the crankshaft material. The nitrogen reacts with certain
alloying elements, such as chromium and aluminum, present in the
material, forming nitrides. These nitrides contribute to the increased
hardness and wear resistance of the treated surface.
• After the desired nitriding time has elapsed, the crankshaft is slowly
cooled to ambient temperature within the nitriding chamber.
Controlled cooling helps prevent distortion or cracking of the
component.
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