Automobile unit 1 vehicle structure and engines.

Prepared by Mr. Rajesh K/AP Mech-RMKCET 1

 The term automobile or automotive stands for a
vehicle which can be moved by itself.
 The automobile is a self-propelled vehicle.
 It is used for the transportation of passengers and
goods from one place to the other on the ground.
 Examples: scooters,mopeds,cars,lorry,bus,jeep

 The invention of the automobile is not the product
of a single man, single generation in any company.
 The real history of automobiles was started during
15th century (i.e. during Leonardo Da Vinci’s
period.)
 Captain Nicholas Cugnot, a French engineer is
considered to be the father of “The Automoile”.

 In 1898, an American company imported three
“Oldsmobiles” cars into Bombay.
 One of which was sold to Janshedji Tata, an
industrialist.
 It was the first motor car in India.
 In 1903, an American company began to operate a
public taxi service with a feet of 50 cars.

 Premier Automobiles Ltd., Mumbai.
 Hindustan motors Ltd., Kolkata.
 Ashok Leyland Ltd., Chennai.
 Maruti Udyog Ltd.
 Tata Engg. & locomotive co., Ltd, (Telco)
Mumbai.

Based on purpose
Passenger vehicle
Goods carriers

Based on fuel used
➢ Petrol vehicles
➢ Diesel vehicles
➢ Gas vehicles
➢ Electric vehicles
➢ Solar vehicles
➢ Hybrid vehicles
➢ Bi-fuel vehicles

Solar Powered Electric vehicle
Hybrid vehicle

Based on capacity
➢ Heavy Motor Vehicles
➢ Light Motor Vehicles

Based on number of wheels
➢ Two wheelers
➢ Three wheelers
➢ Four wheelers
➢ Six wheelers
➢ Multi wheelers

Based on transmission
➢ Conventional
➢ Semi automatic
➢ Automatic
❖ Tata Nano.
❖ Maruti Suzuki Alto K10.
❖ Maruti Suzuki Celerio.
❖ Tata Zest.
❖ Ford Figo.
❖ Mahindra TUV300.
❖ Maruti Wagon R.
❖ Hyundai Creta.

1. The basic structure (frame, suspension
system, axle, wheels and tyres)
2. Power plant
3. Transmission system
4. The auxiliaries
5. The controls
6. The super structure

A complete vehicle without body is called
Chassis.
The following main components of the Chassis
are
1. Frame:
2. Engine or Power plant
3. Clutch
4. Gear Box
5. Propeller Shaft
6. Differential

Chassis of a Truck

Layout of Chassis

Classification of a vehicle chassis is based on the
position of the engine on the chassis.
1. Full forward
2. Semi Forward
3. Engine at centre
4. Engine at the back
5. Conventional chassis
Chassis also classified based on reference to drive
1. Rear wheel drive
2. Front wheel drive
3. Four wheel drive

Full Forward:
➢ Mostly power is given to the front wheels hence
reduces components
➢Problem of visibility & Costly because of
transaxle
➢Part of Chassis portion can not be utilized for
carrying passengers and goods

Semi Forward:
➢ Half portion of the engine is in the driver
cabin and remaining half is outside the cabin
such as in tata trucks
➢ In this arrangement a part of the chassis is
utilized for carrying extra passengers

Engine at Centre:
➢ Drive is given to the rear.
➢ Full space of the chassis floor can be used
(Royal tiger world master buses in Delhi)
➢ If used in cars it limits the car to be a two
seater.
➢ Luxury/Sports cars use this layout.

Engine at the rear/back:
➢ Reduced components
➢ Costly because of transaxle
➢ With elimination of propeller shaft the centre
of gravity lowered giving stable driving
➢ Better adhesion on road specially when
climbing hill.

Rear wheel Drive:
Good traction obtained while climbing the hill.
Good distribution of braking force.
Large bulge in the region of gear box and due to
propeller shaft.

Front wheel drive:
-Lighter in weight, because the driveshaft is
shorter, meaning better fuel economy.
-No floor hump in the passenger compartment,
for the same reason.
-Less weight in the drive train overall, resulting in
even more fuel economy.

Four wheel drive:
 Traction is nearly doubled compared to a two-
wheel-drive layout
 Handling characteristics in normal conditions
can be configured to emulate FWD or RWD
 4WD systems require more machinery and
complex transmission components

It is the foundation on which the power
plant and the body are carried and which in
turn is supported on the wheels through
axles and springs

Cross sections of Frame
Cross Section of Frame:
a. Channel Section - Good resistance to bending
b. Tabular Section - Good resistance to Torsion
c. Box Section - Good resistance to both bending
and Torsion

• The various steels used for conventional pressed frame
are mild steel, carbon sheet steel and sheet nickel alloy
steel
•Carbon - 0.25-0.35%
•Manganese -0.35-0.725%
•Silicon -0.30% (maximm)
•Nickel -3%
•Phosphorous -0.05% (max.)
•Sulphur -0.5% (max)

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

There are three types of frames
1. Conventional frame
2. Semi-integral frame
3. Integral frame

Conventional Semi Integral
Integral

 Body is the super structure for all the vehicles it
may either be constructed separately and bolted
to the chassis or manufactured integral with the
chassis.
 It consists of windows and doors engine cover,
roof, luggage cover etc.

 Weight of the body is 40% for car and 60 to 70%
of total weight of the buses. Therefore reduction in
body weight is important.
 If we reduce the weight of the body which also
improves the fuel economy. (i.e., Mileage)

Body Panels

1. Air Resistance
2. Gradient resistance (Vehicle weight but depend on
the speed of the vehicle)
3. Rolling Resistance
4. Miscellaneous resistance
a. Road charecteristics
b. vehicle speed
c.Tyre charecteristics

AERODYNAMICS
It is a branch of dynamics concerned with
studying the motion of air, particularly when it
interacts with a solid object, such as
an Automobile, airplane wing, etc.

FORCES ACTING ON VEHICLE :
Drag force (Fx)- Along the vehicle direction
Profile drag, interference drag, skin friction,
cooling and ventilation system drag.
Cross wind (Fy)- along side or lateral direction
Assymetric flow of air around the vehicle body
Lift force(Fz) – vertical force acting from the bottom of
the vehicle
Because of pressure difference between top and
bottom of the vehicle.

MOMENTS DUE TO FORCES:
Moments created by forces acting on the vehicle
Pitching moment – Created by drag or lift
force about y-axis and reduces the traction in
the wheels
Yawing moment- Created by cross wind about
z-axis
Rolling Moment – Created by cross wind
about x-axis

Forces and moments acting on a vehicle

1. To provide necessary torque to move the vehicle from
standstill position
2. To provide different speeds to the driving wheels
3. To disconnect engine from the driving wheels
4. Helps to connect engine with the wheels smoothly and
without shock.
5. Provides relative motion between the engine and the
drivig wheels due to flexing of road springs.
6. Provide means to transfer power in opposite direction.
7. Enable diversion of power flow at right angles.
8. Bear the effect of torque reaction , driving thrust and
braking effort effectively.
9. Provide a varied leverage between the engine and the
drive wheels

 Combustion of fuel with oxygen of the air occurs
within the cylinder of the engine.
 An engine is the prime mover and it is the heart of
the automobile.
 It is used to convert the heat energy obtained from
fuel into useful mechanical work.
 Nowadays I.C Engines are commonly used in
automobiles

Four stroke engine
Two stroke engine

Horizontal engine

ENGINE

o This is the main block of the engine.
o This contains the cylinder and provides housing for the
crank, crank shaft and other engine parts.
o This is the basic frame for the engine and the parts fitted
on it.
o Material: Hard Grade cast iron or Aluminium alloys

 This is the top most part of the engine which
covers the cylinder.
 It is bolted with the engine block at the top.
 Provides combustion chamber, and mounting areas
for spark plugs and valve parts
 Material: Hard Grade cast iron or Aluminium alloys

 Gasket are used so that a gas tight joint is
formed.
 These joints will withstand high pressure
and heat developed in the combustion
chambers.
 This is usually cast as a single piece.
 Material: Soft copper and asbestos sheet

 Used to guide and seal piston and to mount
cylinder assembly to head.
 It contains gas under pressure during
combustion


 Material: Chromium plated mild steel

o The piston is the most active part of the engine.
o The movement of the piston changes the volume
inside the cylinder and provides combustion space.
o Material : cast iron, aluminium alloy, nickel-iron
alloy, cast steel, etc.

Piston designs

 To provide a good sealing fit between the
piston and cylinder.
 There are two type of rings
1. COMPRESSION RINGS - Prevents gases
leaking from combustion chamber. These
rings are located at the top of the piston
2. OIL RINGS - prevents lubricant entering
into the combustion chamber.
Too much oil film and the engine will use
excessive oil and too little oil causes heat and
insufficient lubrication
Material: cast iron, alloy steels, etc

 The link between the crankshaft and the piston
 The connecting must withstand heavy thrust
 Cross section is an “H” or “I”
 It has passage for transfering lubricating oil
from the big end bearing to the small end
bearing. Dynamic Dampers can be mounted to
the crankshaft to reduce vibration

 Changes reciprocating motion of pistons into
rotating motion to drive propeller
 The propeller mounts to the front of the
crankshaft using a spline, taper, or flange
 The crankshaft rotates within the crankcase and
is supported by main bearing journals
 Dynamic Dampers can be mounted to the
crankshaft to reduce vibration

 Counterweights are also used to reduce
vibration
 Counterweights and dampers are used in piston
engines because the power pulses and
movement of the pistons create large amounts of
vibration
 The engine is also mounted in rubber bushings
to absorb vibration
 Material: Plain carbon steel, Al alloy, nickel
alloy steelsPrepared by Mr. Rajesh K/AP Mech-RMKCET 87

 Turns at 1/2 the speed of the crankshaft
 Must be mechanically coupled to the
crankshaft for timing purposes (gears, belts,
chains)
 The camshaft consists of bearing journals and
lobes spaced along the shaft
 Each lobe is positioned to open and close a
valve at a specific time
 Material: Plain carbon steel, Al alloy,
nickel alloy steels

 Valves control the flow of gases inside the engine
 Poppet valves are the most common and get their
name from the popping open and closed during
operation
 Intake valves are chrome steel and are cooled by
the incoming air and fuel mixture
 Exhaust valves are also alloy steel but are often
filled with metallic sodium for cooling. Valve
faces may be coated with Stellite to reduce wear
and corrosion
 Valve faces are ground to 30 degrees for intake
(airflow) and 45 degrees (cooling) for exhaust

1290 degrees F
(typical)

 May be solid, roller, or hydraulic
 The lifter follows the cam lobes and pushes on
the pushrod
 Solid and roller lifters require adjustable
rocker arms
 Hydraulic type lifters fill with oil and lengthen
to compensate for any clearances in the valve
system

 Transmits push of lifter up to rocker arm
 Hollow to allow oil to flow to the top of the
cylinder for valve part lubrication
 Length can be varied to adjust valve clearance
 Valve clearance is the space between the top of
the valve stem and the rocker arm.
 valve clearance increases as the engine
operates due to cylinder expansion (solid lifters)
 Hydraulic lifters have a “0” clearance in
operation

Valve clearance adjustment
Valve clearance measurement

 Adjustable in solid lifter
 One end rests on the valve stem and the
other on the pushrod
 Rocking motion opens and closes the valves

 Must be able to withstand forces inside an
engine with minimal friction and heat build-up.
Must accept radial and thrust loads
Plain Bearings
 A steel insert with babbitt (lead alloy) bonded
to the bearing surface
 Plain bearings are keyed to keep them in place
 A lip or flange allows the plain bearing to
accept thrust loads
 Commonly used as crankshaft and rod
bearings in opposed engines

Plain bearing

Roller Bearings (antifriction)
 Hard steel rollers captured between an inner and
outer “race” and held in alignment by a “cage”
 May be tapered to absorb radial and thrust loads
or straight to absorb radial loads only

Ball Bearings (antifriction)
 Used for both radial and thrust loads
 Deep grooves in races allow thrust loads
OUTER RACE
INNER RACE
CAGE
BALL

 It is the process of altering the timing of a valve lift
event, and is often used to improve performance, fuel
economy or emissions.
 It is increasingly being used in combination
with variable valve lift systems.
 The aim was to improve volumetric efficiency,
decrease NOx emissions, and decrease pumping losses.
* VTEC (Variable Valve Timing and Lift Electronic Control)

The variable cam system used on some Ferraris

 Late intake valve closing (LIVC) The first variation of continuous variable valve timing involves
holding the intake valve open slightly longer than a traditional engine. This results in the piston
actually pushing air out of the cylinder and back into the intake manifold during the compression
stroke. The air which is expelled fills the manifold with higher pressure, and on subsequent
intake strokes the air which is taken in is at a higher pressure. Late intake valve closing has been
shown to reduce pumping losses by 40% during partial load conditions, and to decrease nitric
oxide (NOx) emissions by 24%. Peak engine torque showed only a 1% decline, and hydrocarbon
emissions were unchanged.
 Early intake valve closing (EIVC) Another way to decrease the pumping losses associated with
low engine speed, high vacuum conditions is by closing the intake valve earlier than normal. This
involves closing the intake valve midway through the intake stroke. Air/fuel demands are so low
at low-load conditions and the work required to fill the cylinder is relatively high, so Early intake
valve closing greatly reduces pumping losses. Studies have shown early intake valve closing
reduces pumping losses by 40%, and increases fuel economy by 7%. It also reduced nitric oxide
emissions by 24% at partial load conditions. A possible downside to early intake valve closing is
that it significantly lowers the temperature of the combustion chamber, which can increase
hydrocarbon emissions.
 Early intake valve opening Early intake valve opening is another variation that has significant
potential to reduce emissions. In a traditional engine, a process called valve overlap is used to
aid in controlling the cylinder temperature. By opening the intake valve early, some of the
inert/combusted exhaust gas will back flow out of the cylinder, via the intake valve, where it
cools momentarily in the intake manifold. This inert gas then fills the cylinder in the subsequent
intake stroke, which aids in controlling the temperature of the cylinder and nitric oxide
emissions. It also improves volumetric efficiency, because there is less exhaust gas to be
expelled on the exhaust stroke.
 Early/late exhaust valve closing Early and late exhaust valve closing can also reduce
emissions. Traditionally, the exhaust valve opens, and exhaust gas is pushed out of the cylinder
and into the exhaust manifold by the piston as it travels upward. By manipulating the timing of the
exhaust valve, engineers can control how much exhaust gas is left in the cylinder. By holding the
exhaust valve open slightly longer, the cylinder is emptied more and ready to be filled with a
bigger air/fuel charge on the intake stroke. By closing the valve slightly early, more exhaust gas
remains in the cylinder which increases fuel efficiency. This allows for more efficient operation
under all conditions.Prepared by Mr. Rajesh K/AP Mech-RMKCET 110

TYPES
 Air cooling
 Water cooling

 Method of cooling an engine by the use of
atmospheric air is called air-cooling.
 Generally the two stroke engines are air-cooled.
 The heat from the cylinder is spread over a large
area of the outer surface of cylinder head and
cylinder by providing fins.

 Light in weight.
 No coolant is used.
 Warming up is faster.
 Less efficient.
 Noisy operation.

 In water cooling, water is used for cooling the
engine by circulating it through water jackets
around each combustion chamber cylinder,
cylinder head, valve and valve sheet.
 By absorbing heat, water will become hot.

WATER COOLING SYSTEMS

 In an IC engine heat is generated between the
moving parts due to friction. This heat produces
wear and tear of the moving parts.
 To reduce the power loss and wear and tear, a
foreign substance called lubricant is introduced in
between the rubbing surfaces.

 It reduces the friction between the moving parts.
 It reduces wear and tear.
 It provides cushion effect.
 It produces cooling effect.
 It reduces noise

LUBRICATION SYSTEM

Automobile unit 1 vehicle structure and engines.

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