*DEFINITION

Automobile engineering is a branch of engineering which deals with everything about automobiles and
practices to propel them. Automobile is a vehicle driven by an internal combustion engine and it is used
for transportation of passengers and goods on the ground. Automobile can also be defined as a vehicle
which can move by itself.

Examples :

Car, jeep, bus, truck, scooter, etc.

*CLASSIFICATION OF VEHICLES

Automobiles or vehicles can be classified on different bases as given below :

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.

(c)Light motor vehicle (LMV), e.g. cars, jeeps, etc.

Wheels

(a)Two wheeler vehicle, 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 each having four wheels.

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)Steam vehicle, e.g. an engine which uses steam engine. These engines are now obsolete.

(e)Gas vehicle, e.g. LPG and CNG vehicles, where LPG is liquefied petroleum gas and CNG is compressed
natural gas.
Body

On the basis of body, the vehicles are classified as :

(a)Sedan with two doors

(b)Sedan with four doors

(c)Station wagon

(d)Convertible, e.g. jeep, etc.

(e)Van

(f)Special purpose vehicle, e.g. ambulance, milk van, etc.

Transmission

(a)Conventional vehicles with manual transmission, e.g. car with 5 gears.

(b)Semi-automatic

(c)Automatic : In automatic transmission, gears are not required to be changed manually. It is

automatically changes as per speed of the automobile.

Position of Engine

Engine in Front

Most of the vehicles have engine in the front. Example : most of the cars, buses, trucks in India.

Engine in the Rear Side.

Very few vehicles have engine located in the rear. Example : Nano car.

LAYOUT OF AN AUTOMOBILE CHASIS

 Figure : Chasis of a Passenger Car

It contains the source of power, i.e. engine, the frame, which supports the engine, wheels, body,
transmission, the braking system and the steering. It also gives support to suspension system and
springs. Besides these parts

*COMPONENTS OF THE AUTOMOBILE

The automobile can be considered to consist of five basic components :

(a)The Engine or Power Plant :It is source of power.

(b)The Frame and Chasis :It supports the engine, wheels, body, braking system, steering, etc.

(c)The transmission which transmits power from the engine to the car wheels. It consists of clutch,
transmission, shaft, axles and differential.

(d)The body.

(e)Accessories including light, air conditioner/hearer, stereo, wiper, etc.

FUNCTIONS OF MAJOR COMPONENTS OF AN AUTOMOBILE

Chasis and Frame

The chasis is formed by the frame with the frame side members and cross members. The frame is
usually made of box, tubular and channel members that are welded or riveted together. In addition to
this, it comprises of the springs with the axles and wheels, the steering system and the brakes, the fuel
tank, the exhaust system, the radiator, the battery and other accessories. Along with this the frame
supports the body.

Engine or Power Plant

The engine is the power plant of the vehicle. In general, internal combustion engine with petrol or diesel
fuel is used to run a vehicle. An engine may be either a two-stroke engine or a four-stroke engine.

An engine consists of a cylinder, piston, valves, valve operating mechanism, carburetor (or MPFI in
modern cars), fan, fuel feed pump and oil pump, etc. Besides this, an engine requires ignition system for
burning fuel in the engine cylinder.

Transmission System (Clutch and Gear Box)

The power developed by the engine is transferred to the wheels by transmission system. Transmission
system must do three jobs :

(a)It must provide varying gear ratios. Number of gear ratios are equal to number of gears in a vehicle.

(b)It must provide a reverse gear for moving vehicle in reverse direction.

(c)It must provide a neutral or disconnecting arrangement so that the engine can be uncoupled from the
wheels of the vehicle. In a conventional transmission system, there is a clutch, a manually operated
transmission (gear box), a propeller shaft and a differential or final drive.

Clutch

The purpose of the clutch is to allow the driver to couple or decouple the engine and transmission.
When clutch is in engaged position, the engine power flows to the transmission through it (clutch).
When gears are to be changed while vehicle is running, the clutch permits temporary decoupling of
engine and wheels so that gears can be shifted. In a scooter, the clutch is operated by hand where as in
a car the clutch is operated by foot. It is necessary to interrupt the flow of power before gears are
changed. Without a clutch, it will by very difficult.

Final Drive

Final drive is the last stage in transferring power from engine to wheels. It reduces the speed of the
propeller shaft (drive shaft) to that of wheels. It also turns the drive of the propeller shaft by an angle of
90o to drive the wheels.The propeller shaft has a small bevel pinion which meshes with crown wheel.
The crown wheel gives rotary motion to rear axles. 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. Final drive
is of two types, i.e. chain type and gear type.

Braking System
Brakes are used to slow down or stop the vehicle. Hydraulic brakes are generally used in automobiles,
where brakes are applied by pressure on a fluid. Mechanical brakes are also used in some vehicles.
These brakes are operated by means of leavers, linkages, pedals, cams, etc. Hand brake or parking brake
is usually a mechanical brake. These are used for parking the vehicles on sloppy surfaces and also in case

of emergency.
Gear Box
Gear box contain gearing arrangement to get different speeds. Gears are used to get more than one
speed ratios. When both mating gears have same number of teeth, both will rotate at same number
speed. But when one gear has less teeth than other, the gear with less number of teeth will rotate faster
than larger gear. In a typical car, there may be six gears including one reverse gear. First gear gives low
speed but high torque. Higher gears give progressively increasing speeds. Gears are engaged and
disengaged by a shift lever.

Steering System
In front wheels can be turned to left and right by steering system so that the vehicle can be steered. The
steering wheel is placed in front of driver. It is mechanically linked to the wheels to provide the steering
control. The primary function of the steering system is to provide angular motion to front wheels so that

vehicle can negotiate a turn. It also provides directional stability to vehicle when the vehicle moves
ahead in straight line. Now-a-days, many vehicles are equipped with power steering which uses pressure
of a fluid to reduce steering effort. When driver turns the steering wheel, a hydraulic mechanism comes
into play to provide most of the effort needed to turn the wheel. Front Axle Front axles are mounted at
the end of front axle. A part of the weight of vehicle is transmitted to the wheels through this axle. The
front axle performs several functions.

It carries the weight of the front of the vehicle and also takes horizontal and vertical loads when vehicle
moves on bumpy roads. When brakes are provided on front wheels, it endures bending stresses and
torsional stresses. It is generally made from steel drop forging. It is robust in construction.

Suspension System
Suspension system of an automobile separates the wheel and axle assembly of the automobile from its
body. Main function of the suspension system is to isolate the body of the vehicle from shocks and
vibrations generated due to irregularities on the surface of roads. Shock absorbers are provided in the
vehicles for this purpose. It is in the form of spring and damper. The suspension system is provided both
on front end and rear end of the vehicle. A suspension system also maintains the stability of the vehicle
in pitching or rolling when vehicle is in motion.

* Types of drives

There are mainly four different types of wheel drives that form the unique features of
automobile engineering.
These four types include
front wheel drive (FF),
rear wheel drive (RR),
rear mid – drive (MR) and
four wheel drive (4WD).
Front engine, front-wheel drive

The front-engine, front-wheel-drive layout (abbreviated as FF layout) places both the internal
combustion engine and driven wheels at the front of the vehicle. This is the most common layout
for cars since the late 20th century.

Front-wheel drive
Front-wheel drive (FWD) is a form of engine and transmission layout used in motor vehicles,
where the engine drives the front wheels only. Most modern front-wheel-drive vehicles feature a
transverse engine, rather than the conventional longitudinal engine arrangement generally found

The Front wheel drive layout is an arrangement of engine and transmission in which
engine drives only the front wheels of the vehicle. These vehicles are also known as FWD
vehicles. In addition, some people refer to these vehicles as 4X2 cars.

Technically, the term 4X2 means the following:

4: The number of axle-ends on a vehicle (2 at front + 2 at rear)

2: Number of wheels that directly receive power from the engine (The front two wheels)

A quick look at the history of the auto-world shows that front wheel drive cars were developed
mainly because of the fuel economy concerns. The mileage of these vehicles is better compared
to four-wheel drive vehicles because of the reduced number of driven wheels.
A typical Front Wheel Drive Layout

The above diagram depicts a typical FWD arrangement with the transversely mounted engine. In
these vehicles, the engine occupies space near the front axle. It later mates to transmission or the
'transaxle'. This is because of the fact that it combines the functions of transmission, driveshaft,
and differential. Thus, with the help of transaxle, the engine supplies power only to the front
wheels of the vehicle.

Possible configurations in FWD layout:

Depending upon the position of powerpack i.e. engine and transmission, FWD vehicles can have
the following arrangements:

1. Longitudinally mounted engine with front wheel drive

2. Transversely mounted engine with front wheel drive
3. Mid-mounted engine with front wheel drive

Front wheel drive advantages:

1. FWD cars have better traction while moving on the slippery roads like snow-covered roads
because the engine is mounted above or near the front axle.
2. These vehicles have compact design as the entire power-pack fits at the front of the vehicle.
 3. Due to the absence of propeller shaft and transmission tunnel, these cars have more interior
space.
4. Light-weight transmission reduces curb weight of the vehicle.
5. As the front wheels of these vehicles receive engine power, they 'pull' the vehicle instead of a
'push' from the rear. Thus, passengers feel more stability in these vehicles.

Disadvantages of front wheel drive cars:

1. Tyre wear on these vehicles is uneven. Front tyres wear out faster compared to rear tyres
because of uneven weight distribution.
2. While driving on roads with high slopes or during sudden acceleration, front wheels may
experience loss of grip due to weight shift.

Front wheel drive cars in India:

The following are some of the FWD vehicles available in India:

Maruti Suzuki Alto 800 , Renault Kwid , Tata Bolt,Volkswagen Polo,Honda Amaze

Ford Figo Aspire.Maruti Suzuki Ciaz,Hyundai Elantra

The above diagram depicts a typical FWD arrangement with the transversely
mounted engine. In these vehicles, the engine occupies space near the front axle.
It later mates to transmission or the 'transaxle'. This is because of the fact that it
combines the functions of transmission, driveshaft, and differential. Thus, with
the help of transaxle, the engine supplies power only to the front wheels of the
vehicle.

Possible configurations in FWD layout:

Depending upon the position of power pack i.e. engine and transmission, FWD vehicles can have
the following arrangements:

1. Longitudinally mounted engine with front wheel drive

2. Transversely mounted engine with front wheel drive
3. Mid-mounted engine with front wheel drive.

Front wheel drive advantages:

1. FWD cars have better traction while moving on the slippery roads like snow-covered roads
because the engine is mounted above or near the front axle.
2. These vehicles have compact design as the entire power-pack fits at the front of the vehicle.
3. Due to the absence of propeller shaft and transmission tunnel, these cars have more interior
space.
4. Light-weight transmission reduces curb weight of the vehicle.

5. As the front wheels of these vehicles receive engine power, they 'pull' the vehicle instead of a
'push' from the rear. Thus, passengers feel more stability in these vehicles.

Disadvantages of front wheel drive cars:

1. Tyre wear on these vehicles is uneven. Front tyres wear out faster compared to rear tyres
because of uneven weight distribution.
2. While driving on roads with high slopes or during sudden acceleration, front wheels may
experience loss of grip due to weight shift.
UNIT - IV
torque converter
A torque converter is a type of fluid coupling which transfers rotating power from a prime
mover, like an internal combustion engine, to a rotating driven load. In a vehicle with an
automatic transmission, the torque converter connects the power source to the load. It is usually
located between the engine's flexplate and the transmission. The equivalent location in a manual
transmission would be the mechanical clutch.

The key characteristic of a torque converter is its ability to multiply torque when the output
rotational speed is so low that it allows the fluid coming off the curved vanes of the turbine to be
deflected off the stator while it is locked against its one-way clutch, thus providing the equivalent
of a reduction gear. This is a feature beyond that of the simple fluid coupling, which can match
rotational speed but does not multiply torque, thus reduces power.

Some of these devices are also equipped with a "lockup" mechanism which rigidly binds the
engine to the transmission when their speeds are nearly equal, to avoid slippage and a resulting
loss of efficiency

Advantages

 It produces the maximum torque as compared with the vehicle equipped with clutch.
 It removes the clutch pedal.
 It makes the job of driving a vehicle easier.

Disadvantages

 Its fuel efficiency is low as compared with the vehicle with manual transmission.

Application
  The torque converter is used in the vehicle that is equipped with the automatic
transmission. It is also used in industrial power transmission such as conveyer drives,
winches, drilling rigs, almost all modern forklifts, construction equipment, and railway
locomotives.
 It is used in marine propulsion systems

Emissions control methods

Engine efficiency has been steadily improved with improved engine design, more precise
ignition timing and electronic ignition, more precise fuel metering, and computerized engine
management.

Advances in engine and vehicle technology continually reduce the toxicity of exhaust leaving the
engine, but these alone have generally been proved insufficient to meet emissions goals.
Therefore, technologies to detoxify the exhaust are an essential part of emissions control.

Air injection

One of the first-developed exhaust emission control systems is secondary air injection.
Originally, this system was used to inject air into the engine's exhaust ports to provide oxygen so
unburned and partially burned hydrocarbons in the exhaust would finish burning. Air injection is
now used to support the catalytic converter's oxidation reaction, and to reduce emissions when an
engine is started from cold. After a cold start, an engine needs an air-fuel mixture richer than
what it needs at operating temperature, and the catalytic converter does not function efficiently
until it has reached its own operating temperature. The air injected upstream of the converter
supports combustion in the exhaust headpipe, which speeds catalyst warmup and reduces the
amount of unburned hydrocarbon emitted from the tailpipe.

Exhaust gas recirculation

In the United States and Canada, many engines in 1973 and newer vehicles (1972 and newer in
California) have a system that routes a metered amount of exhaust into the intake tract under
particular operating conditions. Exhaust neither burns nor supports combustion, so it dilutes the
air/fuel charge to reduce peak combustion chamber temperatures. This, in turn, reduces the
formation of NOx.

Catalytic converter

Main article: Catalytic converter

The catalytic converter is a device placed in the exhaust pipe, which converts hydrocarbons,
carbon monoxide, and NOx into less harmful gases by using a combination of platinum,
palladium and rhodium as catalysts.

There are two types of catalytic converter, a two-way and a three-way converter. Two-way
converters were common until the 1980s, when three-way converters replaced them on most
automobile engines. See the catalytic converter article for further details.

Types of alternative fuels used in automobiles

 Ethanol. An alcohol-based alternative fuel made by fermenting and distilling crops such
as corn, barley or wheat. ...
 Natural Gas. ...
 Electricity. ...
 Hydrogen. ...
 Propane. ...
 Biodiesel. ...
 Methanol.
 P-Series Fuels.

Bendix drive mechanism

A Bendix drive is a type of engagement mechanism used in starter motors of internal
combustion engines. The device allows the pinion gear of the starter motor to engage or
disengage the flywheel of the engine automatically when the starter is powered or when the
engine fires, respectively. It is named after its inventor, Vincent Hugo Bendix.

Operation

The Bendix system places the starter drive pinion on a helical drive spring. When the starter
motor begins turning, the inertia of the drive pinion assembly causes it to wind the spring forcing
the length of the spring to change, and allowing the pinion to engage with the ring gear. When
the engine starts, backdrive from the ring gear causes the drive pinion to exceed the rotative
speed of the starter, at which point the drive pinion is forced back and out of mesh with the ring
gear.

The main drawback to the Bendix drive is that it relies on a certain amount of "clash" between
the teeth of the pinion and the ring gears before they slip into place and mate completely; the
teeth of the pinion are already spinning when they come into contact with the static ring gear,
and unless they happen to align perfectly at the moment they engage, the pinion teeth will strike
the teeth of the ring gear side-to-side rather than face-to-face, and continue to rotate until both
align. This increases wear on both sets of teeth. For this reason the Bendix drive has been largely
superseded in starter motor design by the pre-engagement system using a solenoid.
clutches
Clutches for automobile. Clutch is a mechanical device that facilitates transmission of power
and motion from one component (the driving member) to another (the driven member) when
engaged, with a provision for disengagement whenever required.

Types of friction clutches:

 Cone clutch.
 Single plate clutch.
 Multi-plate cutch.
 Semi-centrifugal clutch.
 Centrifugal clutch.

single plate clutch

A single disc clutches , Disc Brake , electric clutch consisting of a clutch disk between the flywheel and a
pressure plate. Both the pressure plate and the flywheel rotates with the engine crankshaft or the
driving shaft. single disc clutch consists of a clock plate whose. both the sides are faced with a frictional
material clutch plate is mounted on.
Main Parts Of clutches :
 1) The driving members consist of a flywheel mounted on the engine crankshaft. The fly wheel
is bolted  to a cover which carries a pressure plate or driving disc, pressure springs and releasing
levers. Thus the entire assembly of the flywheel and the cover rotate all the times. The clutch
housing and the cover provided with openings dissipate the heat generated by the friction during
the clutch operation. 

2 ) The driven members consists of a disc or plate, called the clutch plate. It is free to slide
lengthwise on the splines of the clutch shaft. It carries friction materials on both of its surface.
When it is griped between the flywheel and the pressure plate, it rotates the clutch shaft through
the splines. 

3) The operating members consist of a foot pedal, linkage, release or throw-out bearing, release
levers and the springs necessary to insure the proper operating of the clutch.
Single plate clutch:
 It is the most common type of clutch used in motor vehicles. Basically, it consists of only one
clutch plate, mounted on the splines of the clutch shaft. The fly wheel is mounted on the engine
crankshaft and rotates with it. The pressure plate is bolted to the flywheel 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 is gripped between the flywheel and the pressure plate. The friction
linings are on both the sides of the clutch plate. Due to the friction between the flywheel, clutch
plate and pressure plate, the clutch plate revolves with the flywheel. As the clutch plate revolves,
the clutch shaft also revolves.

Single plate Clutch Working 

Clutch shaft is connected to the transmission. Thus the engine power is transmitted to the
crankshaft to the clutch shaft.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 flywheel and the
pressure plate. Thus, the flywheel remains rotating as long as the engine is running and the clutch
shaft speed 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 spring forces.

Multiplate clutch: 
Multiplate clutch consists of a number of clutch plates, instead of only one clutch plate as in the
case of single plate clutch. As the number of clutch plates are increased, the friction surface also
increase. 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 the gear box shaft.
They are firmly pressed by strong coil spring and assembled in a drum. Each of the alternate
plate slides in grooves on the flywheel and the other slides on splines on the pressure plate. Thus,
each alternate plate has inner and outer splines.

Working Of Multi Plate Clutch

The multiple clutch works in the same way as the single plate clutch, by operating the clutch
pedal. The multiplate clutches are used in heavy commercial vehicles, racing cars and motor
cycles for transmitting high torque.
The multiple clutches may be dry or wet. When the clutch is operated in an oil bath, it is called a
wet clutch. When the clutch is operated dry, it is called dry clutch. The wet clutch are generally
used in conjunction with, or as a part of the automatic transmission.

Centrifugal Clutch
A centrifugal clutch is a clutch that uses centrifugal force to connect two concentric shafts, with
the driving shaft nested inside the driven shaft. It engages more at higher speeds.

The input of the clutch is connected to the engine crankshaft while the output may drive a shaft,
chain, or belt. As engine revolutions per minute increase, weighted arms in the clutch swing
outward and force the clutch to engage. The most common types have friction pads or shoes
radially mounted that engage the inside of the rim of a housing. On the center shaft there are an
assorted number of extension springs, which connect to a clutch shoe. When the central shaft
spins fast enough, the springs extend causing the clutch shoes to engage the friction face. It can
be compared to a drum brake in reverse. This type can be found on most home built karts, lawn
and garden equipment, fuel-powered model cars and low power chainsaws. Another type used in
racing karts has friction and clutch disks stacked together like a motorcycle clutch. The weighted
arms force these disks together and engage the clutch.

When the engine reaches a certain speed, the clutch activates, working somewhat like a
continuously variable transmission. As the load increases, the speed drops, disengaging the
clutch, letting the speed rise again and reengaging the clutch. If tuned properly, the clutch will
tend to keep the speed at or near the torque peak of the engine. This results in a fair bit of waste
heat, but over a broad range of speeds it is much more useful than a direct drive in many
applications.
Gear Box
Gear box has to provide torque multiplication.It has to provide the means to reverse a vehicle.It
has to provide neutral position.This means that the output shaft of a gearbox rotates at a slower
rate than the input shaft, and this reduction in speed produces a mechanical advantage,
increasing torque.

Types of Gearboxes

• Sliding Mesh Gear box

• Constant Mesh Gear Box

• Synchromesh Gear Box

• Transaxle Gear Box

• Sequential gear box

• Automatic Gear Box

Sliding Mesh Gearbox •

Normally 3 forward and 1 reverse gear ratios

• Spur gears are used

• Gear wheels on the main shaft engage with gear wheels on the lay shaft (counter shaft) by
sliding
 themselves.

• Not used in automobiles now 1.main drive gear 2.counter shaft 3.main shaft 4.I gear 5.II
gear 6.III gear 7.top speed engaging dogs

 Sliding Mesh Gearbox First gear position

 Second gear position

Third gear position

 Reverse gear position

 Constant Mesh Gearbox • All the gears are always in mesh • Gears on counter shaft are fixed
to it • Gears on main shaft are free to rotate • Dog clutches can slide on the main shaft and rotate
with it • Dog clutches engage with gears on the main shaft to obtain desired speed Advantages
over Sliding mesh Gearbox: • Helical and herringbone gear can be used in these gearboxes and
therefore, constant mesh gearboxes are quieter. • Since the gears are engaged by dog clutches, if
any damage occurs while engaging the gears, the dog unit members get damaged and not the
gear wheels.

Constant Mesh Gearbox Double declutching • Used for smooth downshifting

Synchromesh Gearbox

• Sliding sunchronizing units are provided to equalize the speeds of gear and dog before meshing
• The device works like a friction clutch • Equal speeds ensure smooth meshing • Normally not
used in 1st and reverse gear Working • Output shaft is always rotating (because it is positively
connected to the wheels) • Layshaft is connected to the engine, but it rotates freely when the
clutch is disengaged • Because the gears are meshed all the time, the synchro brings the layshaft
to the right speed for the dog gear to mesh. • The layshaft is now rotating at a different speed to
the engine. Now, the clutch gradually equalizes the speed of the engine and layshaft, either
bringing the engine to the same speed as the layshaft or vice versa depending on engine torque
and vehicle speed.

 Gear Selector Rod Ball & plunger prevents two gears engaging simultaneously

 Transfer Case • Normally used in 4 wheel drive vehicles • Two speed transmission having
‘low’ and ‘high’ gear ratios that can be engaged while in neutral position • Fixed after the
gearbox • Enables engagement and disengagement of 4 wheel drive

 Transaxle Gear Box • Has only 2 shafts • Used in vehicles with engine and drive on same
side – Front engine front wheel drive – Rear Engine Rear Wheel Drive • Most commonly used •
Gear Box and Differential in same housing
 24. Transaxles •Combination of transmission and differential in one unit is called transaxle.
•Transaxles are both automatic and manual. Advantages include: •Reduced drive train weight.
•Improved traction. •Smoother ride. •Quieter operation. •Increased passenger compartment
space.

 Transaxle Gear Box

Sequential Gearbox

Manual transmissions use the standard "H" pattern in the shifter. The manual transmission in a
motorcycle is different. In a motorcycle, gears are shifted by clicking a lever up or down with
toe/heel. It is a much faster way to shift. This type of transmission is called a sequential gearbox
or a sequential manual transmission. The only difference is the way the control rods are
manipulated. The "H" pattern is eliminated and replaced with a different motion. Fool proof
system – Impossible to select wrong gear Race cars use sequential gearboxes

 Continuously Variable Transmission The Continuously Variable Transmission (CVT) is a

transmission in which the ratio of the rotational speeds of two shafts, as the input shaft and
output shaft of a vehicle or other machine, can be varied continuously within a given range,
providing an infinite number of possible ratios. Continuously variable transmission allows the
relationship between the speed of the engine and the speed of the wheels to be selected within a
continuous range rather than in steps. This provides even better fuel economy if the engine is
constantly running at a single speed. The transmission provides better user experience without
much rise and fall in speed of an engine, and eliminates the jerk felt when changing gears.

Epicyclic Gearbox

•Epicyclic gear trains are used to get the various gear ratios. •At least one wheel not only rotates
about its own axis but also rotates about some other axis • Automatic gearboxes typically use one
or more compound planetary gear sets having two sun gears and two sets of intermeshing planet
gears. • There is still only one ring gear.

Automatic Transmission Epicyclic Gearing or Planetary Gearing are as used in an automatic

transmission. An Automatic transmission will select an appropriate gear ratio without any
operator intervention. They primarily use hydraulics to select gears, depending on pressure
exerted by fluid within the transmission assembly. Rather than using a clutch to engage the
transmission, a fluid flywheel, or torque converter is placed in between the engine and
transmission. It is possible for the driver to control the number of gears in use or select reverse,
though precise control of which gear is in use may or may not be possible. For certain
applications, the slippage inherent in automatic transmissions can be advantageous; for instance,
in drag racing, the automatic transmission allows the car to be stopped with the engine at a high
rpm (the "stall speed") to allow for a very quick launch when the brakes are released
Automatic Transmission Cutaway view of a typical 3-speed automatic transmission

Working • If the car is in overdrive (on a four-speed transmission), the transmission will
automatically select the gear based on vehicle speed and throttle pedal position. • When we
accelerate gently, shifts will occur at lower speeds than if accelerate at full throttle. • When we
floor the pedal, the transmission will downshift to the next lower gear. • When we move the shift
selector to a lower gear, the transmission will downshift unless the car is going too fast for that
gear. If the car is going too fast, it will wait until the car slows down and then downshift. • When
we put the transmission in second gear, it will never downshift or upshift out of second, even
from a complete stop, unless we move the shift lever.

Advantages
Advantages of Automatic Transmission over Manual Transmission: • Better fuel efficiency • No
loss of torque transmission from the engine to the driving wheels during gear shifts • Very
smooth gear-shift operations • Appeals to drivers due to overall fast shifts and rapid responses,
along with the latest technology

Disadvantages
Disadvantages of Automatic Transmission over Manual Transmission: • Mechanical
efficiency is less than that of a manual transmission type.

• It requires a specialized transmission fluid/lubricants which is expensive and need to be

changed regularly.

• It is expensive to manufacture.

• It is heavier than an conventional manual transmission gearbox.

• It has much higher rate of failure due to complexity.

Propeller Shaft
A drive shaft, driveshaft, driving shaft, tailshaft (Australian English), propeller shaft (prop
shaft), or Cardan shaft is a mechanical component for transmitting torque and rotation, usually
used to connect other components of a drive train that cannot be connected directly because of
distance or the need to allow for relative movement between them. As torque carriers, drive
shafts are subject to torsion and shear stress, equivalent to the difference between the input
torque and the load. They must therefore be strong enough to bear the stress, while avoiding too
much additional weight as that would in turn increase their inertia.

To allow for variations in the alignment and distance between the driving and driven
components, drive shafts frequently incorporate one or more universal joints, jaw couplings, or
rag joints, and sometimes a splined joint or prismatic joint.

Hotchkiss drive
The Hotchkiss drive is a shaft drive form of power transmission. It was the dominant means for
front-engine, rear-wheel drive layout cars in the 20th century. The name comes from the French
automobile manufacturer Hotchkiss, although other makers, such as Peerless, used similar
systems before Hotchkiss.
During the early part of the 20th century chain-drive power transmission was the main direct
drive competitor of the Hotchkiss system, with the torque tube also popular until the 1950s.

Most shaft-drive systems consist of a drive shaft (also called a "propeller shaft" or Cardan shaft)
extending from the transmission in front to the differential in the rear. The differentiating
characteristic of the Hotchkiss drive is the fact that it uses universal joints at both ends of the
driveshaft, which is not enclosed. The use of two universal joints, properly phased and with
parallel alignment of the drive and driven shafts, allows the use of simple cross-type universals.
In contrast, a torque tube arrangement uses only a single universal at the end of the transmission
tailshaft, typically a constant velocity joint.

In the Hotchkiss drive, slip-splines or a plunge-type(ball and trunnion u-joint) eliminate thrust
transmitted back up the driveshaft from the axle, allowing simple rear-axle positioning using
parallel leaf springs. In the torque-tube type this thrust is taken by the torque tube to the
transmission and thence to the transmission and motor mounts to the frame. While the torque-
tube type requires additional locating elements, such as a Panhard rod, this allows the use of coil
springs.

TORQUE TUBE DRIVE

A torque tube system is a drive shaft technology, often used in automobiles with a front engine
and rear drive. The torque tube consists of a large diameter stationary housing between the
transmission and rear end that fully encloses a rotating tubular steel or small-diameter solid drive
shaft that transmits the power of the engine to a regular or limited-slip differential. Its use is not
as widespread in modern automobiles as is the Hotchkiss drive. The torque tube system is also
used for other types of vehicles and machinery.

Construction

The "torque" that is referred to in the name is not that of the driveshaft, along the axis of the car,
but that applied by the wheels. The design problem that the torque tube solves is how to get the
traction forces generated by the wheels to the car frame. The "torque tube" transmits this force by
directly coupling the axle differential to the transmission and therefore propels the car forward
by pushing on the engine/transmission and then through the engine mounts to the car frame. In
contrast, the Hotchkiss drive has the traction forces transmitted to the car frame by using other
suspension components such as leaf springs or trailing arms.

A ball and socket type of joint called a "torque ball" is used at one end of the torque tube to allow
relative motion between the axle and transmission due to suspension travel. Later American
Motors Rambler models (1962 through 1966) used a flange and cushion mount in place of the
ball and socket Since the torque tube does not constrain the axle in the lateral (side-to-side)
direction a panhard rod is often used for this purpose. The combination of the panhard rod and
the torque tube allows the easy implementation of soft coil springs in the rear to give good ride
quality.

In addition to transmitting the traction forces, the torque tube is hollow and contains the rotating
driveshaft. Inside the hollow torque ball is the universal joint of the driveshaft that allows
relative motion between the two ends of the driveshaft. In most applications the drive shaft uses
a single universal joint which has the disadvantage that it causes speed fluctuations in the
driveshaft when the shaft is not straight. The Hotchkiss drive uses two universal joints which has
the effect of canceling the speed fluctuations and gives a constant speed even when the shaft is
no longer straight.

The torque tube design is typically heavier and securely ties the rear end together, thus providing
for a rigid rear and assuring good alignment under all conditions. However, because of the
greater unsprung weight of the torque tube and radius rods there may be a "little hopping around
of the rear end when cornering fast or on washboard roads"

UNIVERSAL JOINT
A universal joint (universal coupling, U-joint, Cardan joint, Spicer or Hardy Spicer
joint, or Hooke's joint) is a joint or coupling connecting rigid rods whose axes are
inclined to each other, and is commonly used in shafts that transmit rotary
motion. It consists of a pair of hinges located close together, oriented at 90° to
each other, connected by a cross shaft. The universal joint is not a constant-
velocity joint.

When axes of the shaft in vehicle are inclined to each other by some angle,
universal joints shaft are used to transmit torque and rotational motion from one
shaft to another. In the transmission of the vehicle, Universal joints are
incorporated to perform some basic functions.

A universal joint is a positive, mechanical connection between rotating shafts, which are usually
not parallel, but intersecting. They are used to transmit motion, power, or both. The simplest and
most common type is called the Cardan joint or Hooke joint. A universal joint allows driving
torque to be carried through two shafts that are at an angle with each other. Because of this, two
universal joints are used in a vehicle, one between the gear box and the propeller shaft and
other between the propeller shaft and the differential pinion shaft.

Differential
A differential is a gear train with three shafts that has the property that the rotational speed
of one shaft is the average of the speeds of the others, or a fixed multiple of that average.

The differential is a device that splits the engine torque two ways, allowing each
output to spin at a different speed. The differential is found on all modern cars
and trucks, and also in many all-wheel-drive (full-time four-wheel-drive)
vehicles. An open differential (OD) is the most common type. ... In four-wheel
drive vehicles using open differentials (usually standard from the factory), only
one wheel on each axle powers the vehicle. Advantages include seldom breaking
an axle, less tire wear, and they are free as most new vehicles come with open
differentials.
The automotive differential is designed to drive a pair of wheels while allowing
them to rotate at different speeds. In vehicles without a differential, such as karts,
both driving wheels are forced to rotate at the same speed, usually on a common
axle driven by a simple chain-drive mechanism.

Here is how a differential looks like inside

1 .flange. (attaches to drive shaft) 2 .pinion gear. 3 .side gears. 4 .ring gear. 5 .left axle shaft.

6 .right axle shaft. 7 .pinion (spider) gears.

Ackermann steering Mechanism

Ackermann steering geometry is a geometric arrangement of linkages in the steering of a car or
other vehicle designed to solve the problem of wheels on the inside and outside of a turn needing
to trace out circles of different radii.

Advantages

The intention of Ackermann geometry is to avoid the need for tires to slip sideways when
following the path around a curve. The geometrical solution to this is for all wheels to have their
axles arranged as radii of circles with a common center point. As the rear wheels are fixed, this
center point must be on a line extended from the rear axle. Intersecting the axes of the front
wheels on this line as well requires that the inside front wheel be turned, when steering, through
a greater angle than the outside wheel.

Rather than the preceding "turntable" steering, where both front wheels turned around a common
pivot, each wheel gained its own pivot, close to its own hub. While more complex, this
arrangement enhances controllability by avoiding large inputs from road surface variations being
applied to the end of a long lever arm, as well as greatly reducing the fore-and-aft travel of the
steered wheels. A linkage between these hubs pivots the two wheels together, and by careful
arrangement of the linkage dimensions the Ackermann geometry could be approximated. This
was achieved by making the linkage not a simple parallelogram, but by making the length of the
track rod (the moving link between the hubs) shorter than that of the axle, so that the steering
arms of the hubs appeared to "toe out". As the steering moved, the wheels turned according to
Ackermann, with the inner wheel turning further. If the track rod is placed ahead of the axle, it
should instead be longer in comparison, thus preserving this same "toe out".

Design and choice of geometry

A simple approximation to perfect Ackermann steering geometry may be generated by moving

the steering pivot points inward so as to lie on a line drawn between the steering kingpins and the
center of the rear axle. The steering pivot points are joined by a rigid bar called the tie rod which
can also be part of the steering mechanism, in the form of a rack and pinion for instance. With
perfect Ackermann, at any angle of steering, the center point of all of the circles traced by all
wheels will lie at a common point. Note that this may be difficult to arrange in practice with
simple linkages, and designers are advised to draw or analyse their steering systems over the full
range of steering angles.

Modern cars do not use pure Ackermann steering, partly because it ignores important dynamic
and compliant effects, but the principle is sound for low-speed maneuvers. Some racing cars use
reverse Ackermann geometry to compensate for the large difference in slip angle between the
inner and outer front tires while cornering at high speed. The use of such geometry helps reduce
tire temperatures during high-speed cornering but compromises performance in low-speed
maneuvers.
STEERING GEOMETRY

CASTER ANGLE

The caster angle or castor angle is the angular displacement of the steering axis
from the vertical axis of a steered wheel in a car, motorcycle, bicycle, other
vehicle or a vessel, measured in the longitudinal direction. It is the angle between
the pivot line (in a car an imaginary line that runs through the center of the
upper ball joint to the center of the lower ball joint) and vertical. In automobile
racing, the caster angle may be adjusted to optimize handling characteristics for
a particular venue.
CAMBER ANGLE

Camber angle is the angle made by the wheels of a vehicle; specifically, it is the angle between
the vertical axis of the wheels used for steering and the vertical axis of the vehicle when viewed
from the front or rear. It is used in the design of steering and suspension. If the top of the wheel
is farther out than the bottom (that is, away from the axle), it is called positive camber; if the
bottom of the wheel is farther out than the top, it is called negative camber.

Toe – in and Toe -out

In automotive engineering, toe, also known as tracking, is the symmetric angle that each wheel
makes with the longitudinal axis of the vehicle, as a function of static geometry, and kinematic
and compliant effects. This can be contrasted with steer, which is the antisymmetric angle, i.e.
both wheels point to the left or right, in parallel (roughly). Negative toe, or toe out, is the front of
the wheel pointing away from the centerline of the vehicle. Positive toe, or toe in, is the front of
the wheel pointing towards the centerline of the vehicle Toe can be measured in linear units, at
the front or rear of the tire, or as an angular deflection..