· PDF file . Made of either nodular iron, forged steel, or billet steel Crankshaft bearings: Known as friction or precision insert

Unit 1

VEHICLE STRUCTURE AND ENGINES ENGINE: Engine block assembly

Very sophisticated casting.

Made of cast iron or aluminum with cast iron cylinder liners.

A great deal of machining involved in the process of manufacturing.

Becomes the frame of the engine.

Bottom end parts:

Block

Crankshaft

Connecting Rod

Pistons, Rings, & Wrist Pin

Bearings (Main and Connecting rod)

Caps (main and Connecting Rod)

Fly Wheel and nuts and

bolts Cylinder block configurations:

Common cylinder configurations:

Vee, inline, opposed

And slant.

Number from farthest front

backwards Crankshaft:

Converts reciprocating motion into rotary motion.

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Made of either nodular iron, forged steel, or billet steel

Crankshaft bearings:

Known as friction or precision insert bearings.

Uses a steel backing with soft metal on crankshaft side.(lead, tin, copper,

silver, cadmium)

Oil clearance between crankpin and bearing very critical. (.001”)

Oil Clearance measured with plastigauge.

The flywheel (known as the flex plate when used with an automatic transmission) carries the engines inertia in between power strokes.

It is the powers take off for the engine. The clutch or torque converter bolts

to it. Lastly it has the starter motor’s ring gear Vibration damper:

The vibration damper smoothes the vibrations caused by the power strokes.

It has a pulley on it the run auxiliary systems.

It may contain timing marks or crankshaft timing sensors.

Balancer shafts:

Used to counteract the normal vibrations inherent to piston engines.

Found on 4 cylinder and 6 cylinder engines mostly.

Cover and pans:

Made of steel metal, aluminum, or plastic materials.

Usually use gaskets or seals

Gaskets seals and sealers:

Gaskets seal two stationary surfaces.

Seals do it when one surface moves.

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Many types of materials: rubber, paper, aluminum, steel, cork and more.

Sealers adhere gaskets to one of the surfaces.

Pistons:

Pistons harness the energy of the power stroke and transfer the force toward the crankshaft.

Head or crown

Ring grooves

Ring lands

Oil return holes

Skirt

Pin hole

Pin boss

Pin

offset Piston rings:

Rings seal the compression in the combustion chamber and the motor oil

in the crankcase.

Automotive engines use 3 rings: 2 compression and 1 multi-piece

oil ring Types:

Rings are usually made of cast iron

can be plated with chrome or molybdenum.

Help seal the ring to the cylinder wall.

Shapes of the ring vary to also help the ring seal better.

Piston pin:

Hollow polished steel pin.

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Attached in a variety of ways.

Pinned to piston.

Clamped to rod small end.

Snap ring free floating.

Press fit.

Connecting rods:

I-beam style rod use to transfer the pistons force to the crankshaft.

Small end contains the piston pin and the big end has a removable cap to

install it to the Crank.

Nuts and bolts are usually of a very high quality. Installation of pistons:

Cylinder number

Piston number

Notch to the front

Position ring gaps

Remove rod cap check bearing inserts

Cover bolts with fuel line if needed

Crankshaft at TDC or BDC

Install ring compressor

Oil piston, cylinder wall, & crank journal

Carefully tap in piston with hammer handle.

Properly replace rod cap

Automotive chassis: Introduction of Chassis Frame: Chassis is a French term and was initially used to denote

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the frame parts or Basic Structure of the vehicle. It is the back bone of the vehicle. A vehicle with out body is called Chassis. The components of the vehicle like Power plant, Transmission System, Axles, Wheels and Tyres, Suspension, Controlling Systems like Braking, Steering etc., and also electrical system parts are mounted on the Chassis frame. It is the main mounting for all the components including the body. So it is also called as Carrying Unit.

The following main components of the Chassis are 1. Frame: it is made up of long two members called side member riveted together with the help of number of cross members. 2. Engine or Power plant: It provides the source of power 3. Clutch: It connects and disconnects the power from the engine fly Wheel to the transmission system. 4. Gear Box 5.U Joint 6. Propeller Shaft 7. Differential 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 TYPES OF CHASSIS FRAMES: There are three types of frames 1. Conventional frame 2. Integral frame 3. Semi-integral frame

1. 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 are used 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

2. Integral Frame: This frame is used now 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.

3. 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.

VARIOUS LOADS ACTING ON THE FRAME:

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Various loads acting on the frame are 1. Short duration Load - While crossing a broken patch. 2. Momentary duration Load - While taking a curve. 3. Impact Loads - Due to the collision of the vehicle. 4. Inertia Load - While applying brakes. 5. Static Loads - Loads due to chassis parts. 6. Over Loads - Beyond Design capacity. STATE THE DIFFERENT BODIES USED IN AUTOMOBILES: The Automobile bodies are divided in two groups

Passenger Body

Commercial body

REQUIREMENTS OF BODIES FOR VARIOUS TYPES OF VECHILE: The body of the most vehicle should fulfill the following requirements: 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 color. 8. It should have uniformly distributed load. 9. It should have long fatigue life. 10. It should provide good vision and ventilation.

Unit 2

Engine Auxiliary systems Gasoline Electronic Fuel Injection System:

A modern gasoline injection system uses pressure from an electric fuel pump to spray

fuel into the engine intake manifold. Like a carburetor, it must provide the engine with

the correct air-fuel mixture for specific operating conditions. Unlike a carburetor,

however, PRESSURE, not engine vacuum, is used to feed fuel into the engine. This

makes the gasoline injection system very efficient.

A gasoline injection system has several possible advantages over a carburetor type of fuel

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system. Some advantages are as follows:

1. Improved atomization. Fuel is forced into the intake manifold under pressure that helps break fuel droplets into a fine mist. 2. Better fuel distribution. Equal flow of fuel vapors into each cylinder.

3. Smoother idle. Lean fuel mixture can be used without rough idle because of better fuel distribution and low-speed atomization.

* Lower emissions. Lean efficient air-fuel mixture reduces exhaust pollution.

* Better cold weather drivability. Injection provides better control of mixture enrichment than a carburetor.

* Increased engine power. Precise metering of fuel to each cylinder and increased air flow can result in more horsepower output. * Fewer parts. Simpler, late model, electronic fuel injection system have fewer parts than modern computer-controlled carburetors Types:

* single- or multi-point injection

* indirect or direct injection

The point or location of fuel injection is one way to classify a gasoline injection system. A

single-point injection system, also call throttle body injection (TBI), has the injector nozzles

in a throttle body assembly on top of the engine. Fuel is sprayed into the top center of the intake manifold .

A multi-point injection system, also called port injection, has an injector in the port (air-fuel

passage) going to each cylinder. Gasoline is sprayed into each intake port and toward each

intake valve. Thereby, the term multipoint (more than one location) fuel injection is used

System component:

Fuel tank

Electric fuel pump

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Fuel filter

Electronic control unit

Common rail and Pressure sensor

Electronic Injectors

fuel

line Fuel Tank:

is safe container for flammable liquids and typically part of an engine system in

which the fuel is stored and propelled (fuel pump) or released (pressurized

gas) into an engine.

Typically, a fuel tank must allow or provide the following:

Safe (UL Approved) fuel storage, there is some concern that UL (Underwriters Laboratories) is not the final arbiter of safety.

Filling (the fuel tank must be filled in a secure way) No Sparks.

Storage of fuel (the system must contain a given quantity of fuel and must avoid leakage and limit evaporative emissions)

Provide a method for determining level of fuel in tank, Gauging (the remaining

quantity of fuel in the tank must be measured or evaluated)

Venting (if over-pressure is not allowed, the fuel vapors must be managed through valves)

Feeding of the engine (through a pump)

Anticipate potentials for damage and provide safe survival potential.

Electronic fuel pump:

An electric fuel pump is used on engines with fuel injection to pump fuel from the tank to

the injectors. The pump must deliver the fuel under high pressure (typically 30 to 85 psi

depending on the application) so the injectors can spray the fuel into the engine.

Electric fuel pumps are usually mounted inside the fuel tank,

Some vehicles may even have two fuel pumps (a transfer pump inside the tank, and a

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main fuel pump outside).

An electric fuel pump is used on engines with fuel injection to pump fuel from the tank to

the injectors. The pump must deliver the fuel under high pressure (typically 30 to 85 psi

depending on the application) so the injectors can spray the fuel into the engine.

Electric fuel pumps are usually mounted inside the fuel tank,

Some vehicles may even have two fuel pumps (a transfer pump inside the

tank, and a main fuel pump outside).

Most newer vehicles use a "turbine" style fuel pump. A turbine pump has an impeller ring

attached to the motor. The blades in the impeller push the fuel through the pump as the impeller

spins. This type of pump is not a positive-displacement pump, so it produces no pulsations, runs

very smoothly and quietly. It is also less complicated to manufacture and is very durable. Some

aftermarket pump supplies use this type of pump to replace the older designs. Fuel Filter:

The fuel filter is the fuel system's primary line of defense against dirt, debris and small particles of rust that flake off the inside of the fuel tank.

Many filters for fuel injected engines trap particles as small as 10 to 40 microns in size.

Fuel filter normally made into cartridges containing a filter paper.

Electronic Control Circuit:

In automotive electronics, electronic control unit (ECU) is a generic term for any

embedded system that controls one or more of the electrical systems or

subsystems in a motor vehicle.

An engine control unit (ECU), also known as power-train control module (PCM), or

engine control module (ECM) is a type of electronic control unit that determines the

amount of fuel, ignition timing and other parameters an internal combustion engine

needs to keep running. It does this by reading values from multidimensional maps

which contain values calculated by sensor devices monitoring the engine. Working of ECU:

Control of fuel injection: ECU will determine the quantity of fuel to inject based on a

number of parameters. If the throttle pedal is pressed further down, this will open the

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throttle body and allow more air to be pulled into the engine. The ECU will inject

more fuel according to how much air is passing into the engine. If the engine has

not warmed up yet, more fuel will be injected.

Control of ignition timing: A spark ignition engine requires a spark to initiate

combustion in the combustion chamber. An ECU can adjust the exact timing of

the spark (called ignition timing) to provide better power and economy.

Control of idle speed: Most engine systems have idle speed control built into the

ECU. The engine RPM is monitored by the crankshaft position sensor which

plays a primary role in the engine timing functions for fuel injection, spark events,

and valve timing. Idle speed is controlled by a programmable throttle stop or an

idle air bypass control stepper motor. Common rail and Pressure sensor:

The fuel injectors are typically ECU-controlled. When the fuel injectors are

electrically activated a hydraulic valve (consisting of a nozzle and plunger) is

mechanically or hydraulically opened and fuel is sprayed into the cylinders at the

desired pressure. Since the fuel pressure energy is stored remotely and the injectors

are electrically actuated the injection pressure at the start and end of injection is very

near the pressure in the accumulator (rail), thus producing a square injection rate. If

the accumulator, pump, and plumbing are sized properly, the injection pressure and

rate will be the same for each of the multiple injection events.

The term "common rail" refers to the fact that all of the fuel injectors are

supplied by a common fuel rail which is nothing more than a pressure

accumulator where the fuel is stored at high pressure. This accumulator

supplies multiple fuel injectors with high pressure fuel. Electronic injectors:

The injectors can survive the excessive temperature and pressure of combustion by using the fuel that passes through it as a coolant

The electronic fuel injector is normally closed, and opens to inject pressurized

fuel as long as electricity is applied to the injector's solenoid coil.

When the injector is turned on, it opens, spraying atomized fuel at the combustion

chamber. Depending on engine operating condition ,injection quantity will vary. Fuel line:

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Fuel line hoses carry gasoline from the tank to the fuel pump, to the fuel filter, and

to the fuel injection system. While much of the fuel lines are rigid tube, sections of it

are made of rubber hose, which absorb engine and road vibrations.

There are two basic types of fuel hose: Fuel and oil hoses that meet the SAE

30R7 standard, and fuel injection hose that meets the requirements of SAE 30R9. Gasoline direct injection:

In internal combustion engines, gasoline direct injection is a variant of fuel injection

employed in modern two- and four- stroke petrol engines. The petrol/gasoline is

highly pressurized, and injected via a common rail fuel line directly into the

combustion chamber of each cylinder, as opposed to conventional multi-point fuel

injection that happens in the intake tract, or cylinder port. Gasoline direct injection:

When the driver turns the ignition key on, the power train control module (PCM)

energizes a relay that supplies voltage to the fuel pump. The motor inside the pump

starts to spin and runs for a few seconds to build pressure in the fuel system. A

timer in the PCM limits how long the pump will run until the engine starts.

Fuel is drawn into the pump through an inlet tube and mesh filter sock

The fuel then exits the pump through a one-way check valve and is pushed

toward the engine through the fuel line and filter.

The fuel filter traps any rust, dirt or other solid contaminants that may have passed

through the pump to prevent such particles from clogging the fuel injectors.

The fuel then flows to the fuel supply rail on the engine and is routed to the

individual fuel injectors. A fuel pressure regulator on the fuel rail maintains fuel

pressure, and recirculates excess fuel back to the tank.

The fuel pump runs continuously once the engine starts, and continues to run as

long as the engine is running and the ignition key is on. If the engine stalls, the

(PCM) will detect the loss of the RPM signal and turn the pump off.

Unit-3 11



Transmission systems Front wheel drive:

Most automobiles today have front-wheel drive

FWD car has transaxle

Drive axles extend to front wheels out of each side of transaxle

Each end of the drive axle is a CV joint

Transaxle can be either manual or automatic

Advantages

More efficient drivetrain

Better fuel economy

Combined with MacPherson struts: less unsprung weight for better handling

Transmission hump is eliminated

A few FWD engines have been mounted longitudinally

Most transaxles mounted sideways

Manual Transaxle:

Manual transaxles and transmissions

Use same kind of clutch

Three parallel paths for power flow

Input shaft located above intermediate shaft

Input shaft gears directly drive output shaft gears

Differential assembly

Gear shafts

Supported by larger ball, roller, or tapered roller bearings

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End play is controlled by thrust

washers Shift linkage:

Transverse transaxles

Shifted by cables or shift linkage

Two shift cables or rods

One moves a selector on transaxle

Other moves shift fork back and forth

Advantage

Engine shake is not transmitted back to driver’s hand on shift

lever Transaxle differential:

Allows wheels to turn at different speeds when rounding corners

Same as rear-wheel-drive differential

Ordinary helical gearset

Used instead of bevel gears

Power from differential side gears is transmitted to front drive axles through axle shafts

Transaxle power flow:

Five-speed power flow

Fixed gears for first, second, and reverse on input shaft

Fixed gears for third, fourth, fifth on intermediate shaft

Power flow leaves transmission intermediate shaft

Continues through drive pinion to axles

Engine is mounted sideways

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Axles run parallel to input shaft

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Automatic transaxle:

Combination of automatic transmission and differential

Same parts and operation apply

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Transverse engine

Power flow is through gears or sprocket and chain

Chain drive

Allows transaxle to be mounted slightly below and to the side of the engine

Front drive axles:

Difference between rear-wheel drive and front-wheel drive axles

Front-wheel drive axles have CV joints at ends

Axles driven at sharper angles

Allow steering front wheels during power transmission

Universal joint changes output speed twice in every revolution when run at an angle

Rear-wheel drive vehicle drive shaft turns very fast

Positioned before gear reduction of differential

Axle shaft parts:

Drive axle is called half shaft or axle shaft

Stub shaft (stub axle)

Short shaft at outside end

Splined to front hub so it can drive front wheels

CV joint classifications

Inboard and outboard

Fixed and plunge

Ball and tripod

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Axle shafts:

Characteristics

May be solid or hollow

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May have damper weights to absorb vibration

Turn much slower than rear-wheel drive shaft

Balance not as important

When different lengths: long one twists and lags before puts its

torque to the wheel

Torque steer is prevented by longer axle shaft of larger

diameter tubing

CV joint boots:

Boots at each end of axle contain grease

Protect joint from the elements

CV joint boot

Attached to axle and stub shafts with plastic or steel bands or straps

Made of natural rubber, neoprene, silicone, or urethane

Unit 4

Steering, Brakes and Suspension systems

Steering systems:

Any mode of transportation used by people must have some means of control.

For the automobile, two primary control systems are at the driver's disposal: (1)

the steering system, and (2) the braking system.

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The steering mechanism converts the driver's rotational input at the steering wheel into a change in the steering angle of the vehicle's steering road wheels.

For a car to turn smoothly, each wheel must follow a different circle. Since the

inside wheel is following a circle with a smaller radius, it is actually making a

tighter turn than the outside wheel. If you draw a line perpendicular to each

wheel, the lines will intersect at the center point of the turn. The geometry of the

steering linkage makes the inside wheel turn more than the outside wheel.

Steering behavior

The requirements in terms of steering behavior can be summarized as follows:

1. Jolts from irregularities in the road surface must be damped as much as

possible during transmission to the steering wheel. However, such damping

must not cause the driver to lose contact with the road.

2. The basic design of the steering kinematics must satisfy the Ackermann

conditions: the extensions of the wheel axes of the left and right front wheels,

when at an angle, intersect on an extension of the rear axle.

3. When the steering wheel is released, the wheels must return automatically

to the straight-ahead position and must remain stable in this position.

4. The steering should have as Iow ratio as possible (number of steering-wheel

turns from lock to lock) in order to obtain ease of handling. The steering forces

involved are determined not only by the steering ratio but also by the front

suspension load, the turning circle, the suspension geometry (caster angle, kingpin

angle, kingpin offset), the properties of the tire tread and the road surface.

The steering ratio is the ratio of how far you turn the steering wheel to how far

the wheels turn. For instance, if one complete revolution (360 degrees) of the

steering wheel results in the wheels of the car turning 20 degrees, then the

steering ratio is 360 divided by 20, or 18:1. A higher ratio means that you have

to turn the steering wheel more to get the wheels to turn a given distance.

However, less effort is required because of the higher gear ratio.

Generally, lighter, sportier cars have lower steering ratios than larger cars and trucks.

The lower ratio gives the steering a quicker response -- you don't have to turn the

steering wheel as much to get the wheels to turn a given distance -- which is a desirable

trait in sports cars. These smaller cars are light enough that even with the lower ratio,

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the effort required to turn the steering wheel is not excessive.

Some cars have variable-ratio steering, which uses a rack-and-pinion gearset

that has a different tooth pitch (number of teeth per inch) in the center than it has

on the outside. This makes the car respond quickly when starting a turn (the rack

is near the center), and also reduces effort near the wheel's turning limits.

Linkage steering system (worm) gear parts:

Steering Wheel – used by the driver to rotate a steering shaft that passes

through the steering column.

Steering Shaft – transfers turning motion from the steering wheel to the steering gearbox.

Steering Column – supports the steering column and steering shaft.

Steering gears are enclosed in a casing known as steering gear box.

A steering box must have the following qualities:

- no play in the straight-ahead position,

-low friction, resulting in high efficiency,

- high rigidity,

- readjustability.

For these reasons, two types have become established:

Rack and pinion streering:

Basically, as the name implies, the rack-and-pinion steering consists of a rack

and a pinion, The steering ratio is defined by the ratio of pinion revolutions

(steering-¬wheel revolutions) to rack travel. Suitable toothing of the rack allows

the ratio to be made variable over the travel. This lowers the actuating force or

reduces the travel for steering corrections.

Rack-and-pinion steering is quickly becoming the most common type of steering on

cars, small trucks. It is actually a pretty simple mechanism. A rack-and-pinion gearset is

enclosed in a metal tube, with each end of the rack protruding from the tube. A rod,

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called a tie rod, connects to each end of the rack.

The pinion gear is attached to the steering shaft. When you turn the steering wheel, the gear spins, moving the rack.

The rack-and-pinion gearset does two things:

It converts the rotational motion of the steering wheel into the linear motion

needed to turn the wheels.

It provides a gear reduction, making it easier to turn the wheels.

On most cars, it takes three to four complete revolutions of the steering wheel to make the wheels turn from lock to lock (from far left to far right).

The primary components of the rack and pinion steering system are:

Rubber bellows

Pinion

Rack

Inner ball joint or socket

Tie-rod

Rubber Bellows:

This rubber bellows is attached to the Rack and Pinion housing. It protects the

inner joints from dirt and contaminants. In addition, it retains the grease

lubricant inside the rack and pinion housing. There is an identical bellows on

the other end of the rack for the opposite side connection. Pinion:

The pinion is connected to the steering column. As the driver turns the

steering wheel, the forces are transferred to the pinion and it then causes

the rack to move in either direction. This is achieved by having the pinion in

constant mesh with the rack. Rack:

The rack slides in the housing and is moved by the action of the meshed pinion into the

teeth of the rack. It normally has an adjustable bush opposite the pinion to control their 22



meshing, and a nylon bush at the other

end. Inner ball or socket:

The inner ball joint is attached to the tie-rod, to allow for suspension movement and slight changes in steering angles

Tie rod:

A tie rod end is attached to the tie-rod shaft. These pivot as the rack is

extended or retracted when the vehicle is negotiating turns. Some tie-rods and

tie-rod ends are left or right hand threaded. This allows toe-in or toe-out to be

adjusted to the manufacturer's specifications. Toe:

Toe is defined as the difference of the distance between the leading edge of the

wheels and the distance between the trailing edge of the wheels when viewed

from above. Toe-in means the front of the wheels are closer than the rear; toe-

out implies the opposite. Figure 7.20 shows both cases.

For a rear-wheel-drive vehicle, the front wheels normally have a slight amount of toe-

in.. When the vehicle begins to roll, rolling resistance produces a force through the

tire contact patch perpendicular to the rolling axis. This force produces a torque

around the steering axis that tends to cause the wheels to toe-out. The slight toe-in

allows for this, and when rolling, the wheels align along the axis of the vehicle.

Conversely, front-wheel-drive vehicles require slight toe out. In this case, the tractive

force of the front wheels produces a moment about the steering axis that tends to toe

the wheels inward. In this case, proper toe-out absorbs this motion and allows the

wheels to parallel the direction of motion of the vehicle. Power rack and pinion:

When the rack-and-pinion is in a power-steering system, the rack has a slightly

different design.

Part of the rack contains a cylinder with a piston in the middle. The piston is

connected to the rack. There are two fluid ports, one on either side of the piston.

Supplying higher-pressure fluid to one side of the piston forces the piston to

move, which in turn moves the rack, providing the power assist. Re- circulating ball streering:

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The forces generated between steering worm and steering nut are transmitted via a low-friction recirculating row of balls. The steering nut acts on the steering shaft via gear teeth. A variable ratio is possible with this steering box,

Recirculating-ball steering is used on many trucks and SUVs today. The linkage that turns the wheels is slightly different than on a rack-and-pinion system.

The recirculating-ball steering gear contains a worm gear. The first part is a block of metal with a threaded hole in it. This block has gear teeth cut into the outside of it, which engage a gear that moves the pitman arm (see diagram above). The steering wheel connects to a threaded rod, similar to a bolt, that sticks into the hole in the block. When the steering wheel turns, it turns the bolt. Instead of twisting further into the block the way a regular bolt would, this bolt is held fixed so that when it spins, it moves the block, which moves the gear that turns the wheels.

Instead of the bolt directly engaging the threads in the block, all of the threads are filled with ball bearings that recirculate through the gear as it turns. The balls actually serve two purposes: First, they reduce friction and wear in the gear; second, they reduce slop in the gear. Slop would be felt when you change the direction of the steering wheel -- without the balls in the steering gear, the teeth would come out of contact with each other for a moment, making the steering wheel feel loose.

Power steering in a recirculating-ball system works similarly to a rack-and-pinion system. Assist is provided by supplying higher-pressure fluid to one side of the block.

Power steering helps drivers steer vehicles by increasing steering effort of the steering wheel. Hydraulic or electric actuators add controlled energy to the steering mechanism, so the driver needs to provide only slight effort regardless of conditions. Power steering helps considerably when a vehicle is stopped or moving slowly. As well, power steering provides some feedback of forces acting on the front wheels to give an ongoing sense of how the wheels are interacting with the road; this is typically called "rοad feel"·

Representative power steering systems for cars increase steering effort via an actuator, a hydraulic cylinder, which is part of a servo system. These systems have a direct mechanical connection between the steering wheel and the linkage that steers the wheels. This means that power-steering system failure still permits the vehicle to be steered using manual effort alone.

In other power steering systems, electric motors provide the assistance instead of hydraulic systems. As with hydraulic types, power to the actuator (motor, in this case) is controlled by the rest of the power-steering system.

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Some construction vehicles have a two-part frame with a rugged hinge in the

middle; this hinge allows the front and rear axles to become non-parallel to

steer the vehicle. Opposing hydraulic cylinders move the halves of the frame

relative to each other to steer. Hydraulic power assisted steering:

Energy source

The energy source consists of a vane pump (generally driven by the engine) with

an integral oil-flow regulator, an oil reservoir and connecting hoses and pipes.

The pump must be dimensioned so that it generates sufficient pressure to

enable rotation of the steering wheel at a speed of at least 15 m/s even when

the engine is only idling.

The compulsory pressure-limiting valve required on hydraulic systems is usually integrated. .

The pump and the system components must be designed such that the

operating temperature of the hydraulic fluid does not rise to an excessive level

(<100°C) and such that no noise is generated and the oil does not foam. Control Valve:

All power steering pumps have a flow-control valve to vary fluid flow and power

steering system pressures. A pressure relief valve prevents excessive pressures

developing when the steering is on full-lock, and held against its stops. The flow

control valve is located at the outlet fitting of the pump.

During slow cornering, or when parking, pump speeds are normally low. There is less

demand for fluid flow, but to provide the required assistance, high pressure is needed.

Discharge ports direct the fluid to the outlet, and then to the steering gear. The outlet

fluid pressure is slightly lower than the internal high pressure coming from the pump. Pump:

The hydraulic power for the steering is provided by a rotary-vane pump. This

pump is driven by the car's engine with a belt and pulley. It contains a set of

retractable vanes that spin inside an oval chamber.

As the vanes spin, they pull hydraulic fluid from the return line at low pressure and

force it into the outlet at high pressure. The amount of flow provided by the pump

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depends on the car's engine speed. The pump must be designed to provide

adequate flow when the engine is idling. As a result, the pump moves much

more fluid than necessary when the engine is running at faster speeds.

The pump contains a pressure-relief valve to make sure that the pressure does not get

too high, especially at high engine speeds when so much fluid is being pumped. Rotary Valve:

A power-steering system should assist the driver only when he is exerting force on the

steering wheel (such as when starting a turn). When the driver is not exerting force

(such as when driving in a straight line), the system shouldn't provide any assist. The

device that senses the force on the steering wheel is called the rotary valve. Electric power assisted with pull drift :

Pull-Drift Compensation starts with EPAS technology, which replaces the traditional

hydraulic-assist powersteering pump with an electric motor. This increases fuel economy

because the electric motor operates only when steering assistance is required.

Sensors constantly measure steering wheel torque applied by the driver to

maintain the vehicle’s path. Continuous adjustments are made as the system resets to

adapt to changing road conditions or maneuvers, such as the vehicle turning a corner.

When the system detects a pulling or drifting condition, such as a

crowned road surface, it provides torque assistance to help make steering easier.

For drivers, this assistance is seamless and imperceptible.

EPAS technology can be fine-tuned by engineers to fit the driving

characteristics of varying products, whether it’s a luxury sedan or sporty compact SUV.

Unit-5

ALTERNATIVE ENERGY SOURCES

Alternative fuels:

As the cost of conventional fuels goes up, the interest in other fuel sources increase. 26



In some cases, alternative fuels are more environmentally friendly. Some alternative fuels are more energy efficient

Types of alternative fuels:

Ethanol

Natural gas

Propane

Hydrogen

Biodiesel

Electricity

Methanol

Ethanol:

Ethanol is an alcohol-based alternative fuel produced by fermenting and

distilling starch crops or cellulose that have been converted into simple sugars

Ethanol is most commonly used to increase octane and improve the emissions quality of gasoline.

Ethanol can be blended with gasoline to create E85, a blend of 85% ethanol and 15% gasoline.

Ethanol can degrade quickly in water, therefore, posing less environmental harm than oil in the case of a spill

Ethanol is an excellent, clean-burning fuel, potentially providing more

horsepower than gasoline. In fact, ethanol has a higher octane rating (over

100) and burns cooler than gasoline

One acre of corn can produce 300 gal. Of ethanol per growing season.

So, in order to replace that 200 billion gal. Of petroleum products,

American farmers would need to dedicate 675 million acres, or 71 percent

of the nation's 938 million acres of farmland, to growing feedstock. Natural gas:

27



Natural gas is produced either from gas wells

Or in conjunction with crude oil production.

Because of the gaseous nature of this fuel, it must be stored onboard a vehicle in either a compressed gaseous state or in a liquefied state

A natural gas vehicle can be less expensive to operate than a comparable

conventionally fueled vehicle depending on natural gas prices.

The United States has vast natural gas reserves across the country

Vehicles tend to cost $3500 to $6000 more than gasoline

powered ones Propane:

Propane or liquefied petroleum gas (LPG) is a

Popular alternative fuel choice for vehicles because there is already

an infrastructure of pipelines, processing facilities, and storage for

its efficient distribution.

LPG produces fewer vehicle emissions than gasoline.

Propane is produced as a by-product of natural gas processing and crude oil refining.

Propane vehicles can produce fewer ozone-forming emissions than vehicles powered by reformulated gasoline

The cost of a gasoline-gallon equivalent of propane is generally less than that of gasoline, so driving a propane vehicle can save money.

Hydrogen, a gas, will play an important

role in developing sustainable transportation

In the United States, because in the future it may be produced in virtually unlimited quantities using renewable resources.

Hydrogen:

Hydrogen and oxygen from air fed into a proton exchange membrane fuel cell

produce enough electricity to power an electric automobile, without producing

28



harmful emissions. The only byproduct of a hydrogen fuel cell is water.

Currently there are no original equipment manufacturer vehicles available for sale to

the general public. Experts estimate that in approximately 10-20 years hydrogen

vehicles, and the infrastructure to support them, will start to make an impact. Bio diesel:

Biodiesel is a domestically produced, renewable fuel that can be manufactured

from vegetable oils, animal fats, or recycled restaurant greases.

Biodiesel is safe, biodegradable, and reduces serious air pollutants

such as particulates, carbon monoxide, hydrocarbons, and air toxics.

Biodiesel can also be used in its pure form but it may require certain

engine modifications to avoid maintenance and performance problems

and may not be suitable for wintertime use.

Pure biodiesel, B100, costs about $3.50--roughly a dollar more per gallon than petro diesel.

Need to heat storage tanks in colder climates to prevent the fuel from gelling

Like E85, biodiesel began with farm co-ops and local entrepreneurs.

High fuel prices affect farmers, too, and here was an opportunity to

make money from otherwise fallow farmland Electricity:

Electricity can be used as a transportation fuel to power battery electric

and fuel cell vehicles. When used to power electric vehicles, electricity

is stored in an energy storage device such as a battery.

EV batteries have a limited storage capacity and their electricity must

be replenished by plugging the vehicle into an electrical source.

EVs have lower "fuel" and maintenance costs than gasoline-powered vehicles.

Vehicles that operate only on electricity require no warm-up, run almost

silently and have excellent performance up to the limit of their range.

Also, electric cars are cheap to "refuel." At the average price of 10 cents

per kwh, it costs around 2 cents per mile. Pure electric cars still have

limited range, typically no more than 100 to 120 miles. 29



Methanol:

Methanol, also known as wood alcohol, can be used as an alternative fuel in flexible fuel vehicles that run on M85

It is not a commonly used fuel at this time as methanol produces a high amount of formaldehyde in emissions.

The benefits include lower emissions, higher performance, and lower

risk of flammability than gasoline. Methanol can easily be made into

hydrogen for hydrogen fuel cell vehicles in the future

Methanol is extremely corrosive, requiring special materials for delivery and

storage. Methanol, in addition, has only 51 percent of the BTU content of

gasoline by volume, which means its fuel economy is worse than ethanol's.

Methane also can be produced by processing biomass such as grass clippings, sawdust and other cellulose sources.



· PDF file . Made of either nodular iron, forged steel, or billet steel Crankshaft bearings: Known as friction or precision insert

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