BE SEM 8 AUTOMOBILE ENGINEERING NOTES

2011-2012

AUTOMOBILE ENGINEERING

MODULE NO 4 .ELECTRICAL SYSTEM

MECHANICAL ENGINEERING | Mr.Vaibhav V Naik

Automobile Engineering

Module no 4. Electrical system

1) Battery

2) Electronic ignition system

3) Charging system 

Dynamo



Alternator

4) Starting system

BATTERY

Module No 04

2

Vaibhav Vithoba Naik

Automobile Engineering

Q.1: - Describe the brief on the various types of the battery? Answer: BATTERY 1. Battery is one of the most important components of the entire electrical system of a vehicle. 2. The functions of a battery are a. To start the engine b. To act as a stabilizer c. To supply electrical energy to accessories .

TYPES OF BATTERY The types of battery are 1. Lead acid battery 2. Alkaline Battery a. Nickel iron type b. Nickel cadmium battery 3. Zinc-air battery

Module No 04

3

Vaibhav Vithoba Naik

Automobile Engineering

Q.2: - Explain the construction and working of lead acid battery?

Answer: LEAD ACID BATTERY The most widely used battery is the lead acid type. Other than lead acid battery, alkaline battery and zinc air battery is also used. The electrical energy generated by the charging system is converted into chemical energy and this chemical energy is stored in the battery. During discharging, the stored chemical energy is conv erted into electrical energy. The major components of a battery are 1) Container 2) Plates 3) Separators 4) Cell Cover 5) Electrolyte

1) Containers a. It is constructed in single piece and made of acid resistant of hard rubber or plastic or bituminous composition. b. It is divided by partitions into compartment for individual cell. c. Ribs are there at the bottom of each compartment. The battery plates rest on these ribs d. The space between the rib are provided on collect sediments. This minimizes the danger of short circuit due to se diments.

Module No 04

4

Vaibhav Vithoba Naik

Automobile Engineering

2) Grids and plates a. There are two types of battery plates, the positive and the negative. b. For each plate there is a supporting frame work or grid made of an alloy of lead and antimony.Maintenance-free batteries use about 0. 1% calcium instead of antimony. c. The function of grid is to hold the active materials and to carry current in the plates, which consists of horizontal & vertical ribs. d. The active materials in the positive plate grid are lead peroxide (PbO 2) and in negative spongy lead (Pb). e. A no of positive plates are lead burnt to a post strap to form a positive plate group, while the negative plate group contains one plate more than the positive group so that both sides of the positive plates can be utilized on which greater electron chemica l activity takes place.

3. Separators a. To avoid direct contact and thus short circuiting of positive and negative plates, thin sheets of some non -conducting materials are inserted between them. b. These sheets are called separators. c. These are made from treated wood, ebonite, sintered PVC. d. The materials of the separators must be sufficiently porous or perforate to allow diffusion of acid. e. 4. Cell cover a. Cell cover provides a ceiling for the cells. b. Each cell cover contains holes for the positive and negatives posts , a vent and filler openings. c. The vent allows the gases produced during battery charging to escape and are provided in the plugs to cover filler openings which are also used to check specific gravity of electrolyte. d. Cell covers are sealed in the containe r to form a leak proof joint.

Module No 04

5

Vaibhav Vithoba Naik

Automobile Engineering

5. Electrolyte a. Electrolyte used in lead acid battery is a solution of sulphuric acid. b. It contains approximately one part of sulphuric ac id, 2 parts of water by volume. c. Specific gravity of the electrolyte is kept under consistent observation to have a proper watch over the state of the battery. Fully charged

:

1.290

½ Discharged

:

1.200

Fully discharged :

1.110

d. Specific gravity also varies with temperature. As a rough guide, 18 points are added for every 25° excess of temperature above 15°C.

Module No 04

6

Vaibhav Vithoba Naik

Automobile Engineering

Q.3: - Write a note on Charging system Answer: A. CHARGING SYSTEM 1. Charging system is required to recharge the battery which is an important component of electrical system of an automobile. 2. Charging is required as the capacity of a battery to supply current is limited to the energy stored in it in the form of chemical energy. 3. Battery supplies the current to run the starting motor, various lights and horn, etc. 4. The charging system generates electricity to rech arge the battery and run other electrical components.  COMPONENTS OF A CHARGING SYSTEM

Charging system consists of :

1. Generator or Dynamo It converts mechanical energy into electrical energy.

2. Regulator It controls the generator output according to the need. It controls the current or voltage.

3. Relay It is used to control the flow of current between generator and battery. It acts as circuit breaker.

Module No 04

7

Vaibhav Vithoba Naik

Automobile Engineering

Battery Charging Procedure 1. Check the electrolyte level in the battery 2. Connect the positive and negative terminals to the respective terminal of the battery charger 3. Adjust the value of charging current 4. Keep a watch over the temperature of the electrolyte 5. Record the specific gravity and temperature hourly 6. In case several batteries have to be charged simultaneously, the same may be connected in series

Module No 04

8

Vaibhav Vithoba Naik

Automobile Engineering

Q.4: List the type of charging method. Explain them?

Answer:  CHARGING METHODS The charging methods are

A. Charging methods 1. Constant voltage charging 2. Constant current charging B. Types of Charging 1. Slow rate charging 2. Quick rate charging 3. Trickle charging 4. Dry Charging 1. Slow rate charging a. Ordinary batteries are charged by slow rate charging method. b. It takes 12 to 20 hours to complete and the charging current is equal to the number of positive plates per cell.

2. Quick rate charging a. In quick rate charging method, a high charging current (as high as 100A) is used till the battery comes to about 80% of charge level. b. The remaining charging process is finished by slow rate metho d.

Module No 04

9

Vaibhav Vithoba Naik

Automobile Engineering

3. Trickle Charging a. As the batteries left in the storage for long periods of time are subjected to self discharge, continuous charging at very low charging rate of about 5% of normal charging current has been employed for keeping in proper condition. b. Trickle charging is normally done on day time only. 4. Dry Charging a. Dry Charged Batteries do not contain any electrolyte, but their plates are already charged. b. The vent holes are closed by plugs so that no moisture enters the battery. c. The electrolyte is supplied in separate acid proof cartons. d. When the battery has to be used, electrolyte is filled and allowed to stand for 1 to 2 hours.

Module No 04

10

Vaibhav Vithoba Naik

Automobile Engineering

Q.5: - Write a note on Battery Capacity Answer: BATTERY CAPACITY 1) Battery capacity is a measure of the charg e stored by the battery, and is determined by the mass of active material contained in the battery. 2) The battery capacity represents the maximum amount of energy that can be extracted from the battery under certain specified conditions. 3) The most common measure of battery capacity is Ampere Hours (Ah), defined as the number of hours for which a battery can provide a current equal to the discharge rate at the nominal voltage of the battery.

Q.6: - Write a note on Battery Ratings  BATTERY RATING a. Rating of a battery is determined by the current it can produce and the time for which it can sustain this current .

1) 20 Hour Rate It represents the rate of current a battery can deliver continuously for 20 hours after which the cell voltage should not drop below 1.75v

2) 20 Minute Rating It represents the rate of current a battery can deliver continuously for 20 minute after which the cell voltage not dropping below 1.5v 3) Reserve Capacity It is the time in minutes for which the battery can supply 25 Amperes at 25°C without the cell voltage falling below 1.75v

4) Cold Rating It represents the current in amperes which battery can supply continuously for 30 seconds without the cell voltage dropping below 1.4v .

Module No 04

11

Vaibhav Vithoba Naik

Automobile Engineering

Q.7: - Write a note on Battery efficiency?

Answer:  BATTERY EFFICIENCY The efficiency of a battery can be calculated either as the ampere hour efficiency or the Watt hour efficiency.

Ah efficiency = (A h discharging/A h charging) x 100% %Ƞ AH =[ Id Td/IcTc]×100 Id = Discharging Current Td =Discharging time Ic = Charging current Tc = Charging time

At the 20 hour rate the ampere hour efficiency can be about 90 percent. This efficiency figure is generally expressed as its reciprocal, called the charge factor. In this example the charge factor is about 1.1.

Watt Hour Efficiency=(Output in Watt hour/Input in Watt Hour)×100%

%ȠWH =[Vd Id Td/VcIcTc]×100 Vd=Average discharging voltage Vc=Average charging voltage Also %ȠWH =ȠAH ×[Vd /Vc]

Module No 04

12

Vaibhav Vithoba Naik

Automobile Engineering

Q.8: - Write a note on Alkaline Battery?

Answer: ALKALINE BATTERY Alkaline batteries are of two types, the Edison type or the nick el – iron type and the nickel – cadmium type. The construction of these is similar except for active materials. However, only the latter type is suitable for automobile service.

The basic construction of alkaline battery is similar to that of lead acid battery. In both the nickel -iron and nickel-cadmium type, the active material on positive plates is nickel hydroxide. On negative plates, it is metallic iron on nickel-iron cell and cadmium oxide on nickel -cadmium cell. The electrolyte used is potassium hydr oxide solution. The active material for positive as well as negative plates is contained in finely perforated steel tubes, which combine to form a plate. Due to this reason, even under severe jolts, no active material is lost from the plates and thus no se diment is produced.

The electrolyte does not take part in chemical reactions on charging or discharging, unlike in the lead –acid batteries .Its specific gravity remains, therefore, constant at about 1.20. For this reason, smaller quantities of the electrolyte are required. However due to the same reason, there is no indication of state of charge of the battery.  ADVANATGES The advantages of the alkaline battery over the lead acid type are: 1) Alkaline battery is lighter than lead –acid battery. 2) It is mechanically very strong & can stand very rough use. 3) The rate of charging can be much higher in case of alkaline battery.

Module No 04

13

Vaibhav Vithoba Naik

Automobile Engineering

4) The discharge rate when left standing is very low as compared to Lead acid type, since the active materials are insoluble in the elect rolyte .Therefore the battery has got much longer shelf life. 5) Comparatively longer life (10 -15 years )  DISADVANTAGES The disadvantages of the alkaline battery are:

1) The voltage of each cell in the alkaline battery is only 1.2 as compared to 2 volts for a lead acid cell. For this reason for a 6 volt battery 5 cells will be required as against 3 cells of the lead acid type . 2) Due to relatively higher internal resistance, the efficiency of the alkaline battery is slightly lower than that of the lead accumulato r. 3) Initial cost is higher compared to the lead acid battery.

Module No 04

14

Vaibhav Vithoba Naik

Automobile Engineering

IGNITION SYSTEM TYPES

 Convectional Ignition systems 1) Basically Convectional Ignition systems are of 2 types :

A. Battery or Coil Ignition System, and

B. Magneto Ignition System.

2) Both these conventional, ignition systems work on mutual electromagnetic induction principle.

3) Battery ignition system was generally used in 4 -wheelers, but now-a-days it is more commonly used in 2 -wheelers also (i.e. Button start, 2 -wheelers like Pulsar, Kinetic Honda; Honda-Activa, Scooty, Fiero, etc.).

In this case 6 V or 12 V batteries will supply necessary current in the primary winding.

4) Magneto ignition system is mainly used in 2 -wheelers, kick start engines. (Example, Bajaj Scooters, Boxer, Victor, Splendor, Passion, etc.).

5) In this case magneto will produce and supply current to the primary winding. So in magneto ignition system magneto replaces the battery.

Module No 04

15

Vaibhav Vithoba Naik

Automobile Engineering

A. BATTERY IGNITION SYSTEM

1. Figure shows line diagram of battery ignition system for a 4 -cylinder petrol engine. 2. It mainly consists of a 6 or 12 volt battery, ammeter, ignition switch, Auto-transformer (step up transformer), contact breaker, capacitor, distributor rotor, distributor contact points, spark plugs, etc.

Figure: Battery Ignition Syste m

Module No 04

16

Vaibhav Vithoba Naik

Automobile Engineering

3. The ignition system is divided into 2 -circuits :  Primary Circuit: a) It consists of 6 or 12 V battery, ammeter, ignition switch, primary winding it has 200-300 turns of 20 SWG (Sharp Wire Gauge) gauge wire, contact breaker, capacitor.  Secondary Circuit: a) It consists of secondary winding. Secondary winding consists of about 21000 turns of 40 (S WG) gauge wire. b) Bottom end of which is connected to bottom end of primary and top end of secondary winding is connected to centre of distributor rotor. c) Distributor rotors rotate and make contacts with contact points and are connected to spark plugs which are fitted in cylinder heads (engine earth).  Working: 1) When the ignition switch is closed and engine in cranked, as soon as the contact breaker closes, a low voltage current will flow through the primary winding. It is also to be noted that the contact beaker cam opens and closes the circuit 4-times (for 4 cylinders) in one revolution. 2) When the contact breaker opens the contact, the magnetic field begins to collapse. Because of this collapsing magnetic field, current will be ind uced in the secondary winding a nd because of more turns (@ 21000 turn s) of secondary, voltage goes up to 28000-30000 volts. 3) This high voltage current is brought to centre of the distributo r rotor. 4) Distributor rotor rotates and supplies this high voltage current to proper stark plug depending upon the engine firing order. 5) When the high voltage current jumps the spark plug gap, it produces the spark and the charge is ignited -combustion starts-products of combustion expand and produce power.

Module No 04

17

Vaibhav Vithoba Naik

Automobile Engineering

B. MAGNETO IGNITION SYSTEM

1. Magneto is a generator which is driven by engine to produce electric current. The magneto ignition system has self substantial source of electric current hence do not require bat tery. 2. A magneto when rotate at high speed by the engine is capable of generating high voltage requires to produce the spark. 3. It consists of armature built up of laminated of soft iron plate and woun with insulated copper wire and a laminated soft iron poll attached to permanent magnet.

Module No 04

18

Vaibhav Vithoba Naik

Automobile Engineering

4. Magneto system is of three types a. Rotating magneto type The armature is stationary and magnet rotates. b. Rotating armature type In this system armature rotates between the poles of magnet c. Polar type In this type both armature and magneto are stationary and the pole pieces rotate. 5. Rotating magneto type ignition system has the following main parts a. An electrical generator with permanent field magnets and rotating armature which produces alternating current. b. An induction coil with primary and secondary winding wound on armature. c. Contact breaker points to cut off the primary circuit and condenser. d. A distributor which distributes high tension current to spark plug.

 Working of Magneto ignition system

1) The operation of the mag neto ignition system is same as battery ignition system 2) In this system as magnet revolves and rapid change of magnetic flux in coil takes place. 3) Magneto flux varies from a positive maximum to negative maximum and back again. 4) This rapid variation of magnet ic field induces a current in primary winding of the coil. 5) When contact breaker point are opened the magnetic flux collapses producing high voltage spark in spark plug. 6) The contact breaker points are opened and closed with the help of cam.

Module No 04

19

Vaibhav Vithoba Naik

Automobile Engineering

 DRAWBACKS (DIS ADVANTAGES) OF CONVENTIONAL IGNITION SYSTEMS Following are the drawbacks of conventional ignition systems:

1) Because of arcing, pitting of contact breaker point and which will lead to regular maintenance problems.

2) Poor starting: After few thousands of kilometers of running, the timing becomes inaccurate, which results into poor starting (Starting trouble).

3) At very high engine speed, performance is poor because of inertia effects of the moving parts in the system.

4) Sometimes it is not possible to pr oduce spark properly in fouled spark plugs.

In order to overcome these drawbacks Electronic Ignition system is used.  ADVANTAGES OF ELECTRONIC IGNITION SYSTEM Following are the advantages of electronic ignition system :

1) Moving parts are absent -so no maintenance. 2) Contact breaker points are absent -so no arcing. 3) Spark plug life increases by 50% and they can be used for about 60000 km without any problem. 4) Better combustion in combustion chamber, about 90 -95% of air fuel mixture is burnt compared with 70-75% with conventional ignition system. 5) More power output. 6) More fuel efficiency.

Module No 04

20

Vaibhav Vithoba Naik

Automobile Engineering

 TYPES OF ELECTRONIC IGNITION SYSTEM

Electronic Ignition System is as follow :

1) Capacitance Discharge Ignition system

2) Transistorized system

3) Piezo-electric Ignition system

4) The Texaco Ignition system

Module No 04

21

Vaibhav Vithoba Naik

Automobile Engineering

A. Capacitance Discharge Ignition System (CDI)

1) It mainly consists of a) 6-12 V battery, ignition switch b) DC to DC convertor c) Charging resistance d) Tank capacitor e) Silicon Controlled Rectifier (SCR) f) SCR-triggering device g) Step up transformer h) Spark plugs.

Figure: Capacity Discharge Ignition System

2) A 6-12 volt battery is connected to DC to DC converter i.e. power circuit through the ignition switch, which is designed to give or increase the voltage to 250-350 volts. 3) This high voltage is used to charge the tank capacitor (or condenser) to this voltage through the charging resistance.

Module No 04

22

Vaibhav Vithoba Naik

Automobile Engineering

4) The charging resistance is also so designed that it controls the required current in the SCR. 5) The condenser is discharg e when SCR triggering device sends a pulse and high voltage spark is produced in the spark plug. 6) Depending upon the engine firing order, whenever the SCR triggering device, sends a pulse, then the current flowing through t he primary winding is stopped. and the magnetic field begins to collapse. 7) This collapsing magnetic field will induce or step up high voltage current in the secondary, which while jumping the spark plug gap produces the spark, and the charge of air fuel mixture is ignited.  Advantage of CDI system 1. It avoids the contact breaker point and its maintenance. 2. Better cold starting. 3. Performance increases with the speed. 4. It provides the constant voltage across the spark plug. 5. Secondary voltage remains constant with the speed of engine. 6. Eliminates the chance of misfiring.

Module No 04

23

Vaibhav Vithoba Naik

Automobile Engineering

B. Transistorized assisted contact (TAC system) ‘

Figure: Transistorized Assisted Contact (TAC system) ‘

1. The connected points are connected to base of transistor, which is further connected to the primary winding of igni tion coil through the ballast resistor. 2. The collector of transistor is connected to the battery. 3. When contact breaker point opens, the base circuit is distributed and current in the primary current decays causing the normal induction, which produces spark in the spark plug.

Advantages 1. The low breaker-current ensures longer life. 2. The smaller gap and lighter point assembly increase dwell time minimize contact bouncing and improve repeatability of secondary voltage. 3. The low primary inductance reduces primary inductance reduces primary current drop-off at high speeds. Module No 04

24

Vaibhav Vithoba Naik

Automobile Engineering

Disadvantages 1. As in the conventional system, mechanical breaker points are necessary for timing the spark. 2. The cost of the ignition system is increased. 3. The voltage rise-time at the spark plug is about the same as before.

C. Piezo-electric Ignition System 1) The development of synthetic piezo -electric materials producing about 22 kV by mechanical loading of a small crystal resulted in some ignition systems for single cylinder engines. 2) But due to difficulties of high mechanical loading need of the order of 500 kg timely control and ability to produce sufficient voltage, these systems have not been able to come up.

D. The Texaco Ignition System 1) Due to the increased emphasis on exhaust emission control, the re has been a sudden interest in exhaust gas recirculation systems and lean fuel-air mixtures. 2) To avoid the problems of burning of lean mixtures, the Texaco Ignition system has been developed. 3) It provides a spark of controlled duration which means that th e spark duration in crank angle degrees can be made constant at all engine speeds. 4) It is a AC system. This system consists of three basic units, a power unit, a control unit and a distributor sensor. 5) This system can give stable ignition up to A/F ratios as high as 24 : 1.

Module No 04

25

Vaibhav Vithoba Naik

Automobile Engineering

CHARGING SYSTEM

Q.1: - Explain the principle of operation of Dynamo? Ans: -DYNAMO 1. A dynamo is a machine used to convert mechanical used to convert mechanical energy into electrical energy. 2. When it is driven by the engine it produces electricity for running all the electrical circuits of the automobile and keeps the battery in charged condition. 3. This is the function of dynamo.

Principle of Dynamo

“When a conductor moves in a magnetic field, current is produced in it. The direction of current is determined by Fleming’ s right hand rule”. Fleming’s Right Hand Rule “If thumb, fore finger and middle finger of right hand are stretched so that they are mutually perpendicular to each other, if the fore finger indicates the direction of magnet ic field and the thumb shows the direction of motion of the conductor, then middle finger will indicat e the direction induced current.” This is called Fleming’ s right hand rule. A magnetic field acts between north and south poles of magnets. There are lines of forces between two poles. When the conductor moves such that lines of force are cut, current is induced in the conductor. This current can be used to run any electrical components, e.g. lights and charging system, etc. The current induced in the condu ctor depends upon a. The rate at which force lines are cut and b. Strength of magnetic field, etc.

Module No 04

26

Vaibhav Vithoba Naik

Automobile Engineering

2. Explain construction and working of Dynamo? Ans:-DYNAMO Construction of Dynamo 1. Dynamo consists of a round oute r casing with two stationary electromagnets knows as field magnets , opposite to each other. 2. Between the magnets, armature is placed generally consisting 28 separate coils of wire. 3. The ends of each coil are joined to copper segments that make up commutator. 4. The armature is mounted on bearing and is driven by fan belt. 5. In contact with commutator is stationary carbon bushes are used.

Working of Dynamo 1. When small amount of current is passed through the stationary filed windings, the magnetic field is induced. 2. As armature revolved induced ma gnetic field, current is generated in the armature winding. 3. This DC current leaves the winding through the commutator and the carbon brushes in contact with it. 4. One brush receives positive charge and other negative charge. 5. The amount of the current generated depends on speed at which the armature is turning and strength of field magnets. 6. When Dynamo is charging low voltage battery or when head light and other high current consuming components, it can take more than half of HP.

Module No 04

27

Vaibhav Vithoba Naik

Automobile Engineering

Q.3: - Explain the principle of operation of Alternator? Ans: - ALTERNATOR OR AC GENERATOR FUNCTION “An alternator generates alternating current (AC) unlike a dynamo which generates direct current (DC)”. Modern automobiles which require more electric loads are fitted with alternators instead of dynamos. These vehic les require more electrical power because they have power steering, power windows, electrical system for automobile transmission, etc. A rectifier is required to convert AC to DC as all electrical equipments use DC. PRINCIPLE The principle of working of al ternator differs from that of dynamo in the manner in which the conductor and magnetic field move relative to each other. In an alternator the conductor remains stationary but the magnetic field is rotated. However, conductor rotates and magnetic field rem ains stationary in case of a dynamo. In an alternator, a rotating bar magnet produces magnetic field which is cut by a stationary conductor.

Figure shows the working principle of an alternator. The north pole of rotating magnet is shown at top and south pole at the bottom in Figure (a). If this magnet is rotated by half revolution such that north pole comes down and south pole takes upper position. During this the current in the upper leg of conductor flow s in one direction.

Module No 04

28

Vaibhav Vithoba Naik

Automobile Engineering

Figure (b) shows the north pole of magnet at bottom and south pole at top. When the magnet is now rotated by another half revolution, the direction of current in the wire is reversed. Therefore, with the revolution of magnet, the current reverses its direction after each half revolution. Thus, an alternating current flows. This is the principle of working of an alternator.

Module No 04

29

Vaibhav Vithoba Naik

Automobile Engineering

Q.4: - What are the components of Alternator? Ans: -COMPONENTS OF ALTERNATORS Alternator consist of the following 1. Frame : a. The frame of housing is made up of cast aluminum in two pieces which encloses the completely assembly of alternator. b. The front part of know as drive end has ball bearing and back part is known as end frame has roller bearing.

2. Rotor : a. Magnetized Rotor turns inside the stator. It is also called Armature. b. It is mounted on the bearing and placed inside the stator. c. The main parts of rotor are Rotor coil, interlocking finger and slip rings. d. The rotor contains an iron core around the rotor shfat.Many turns of the copper wire coated with varnish are wound over the core. e. Their ends of the wire are connected to two separate slip rings. f. The current drawn the battery passes through the slip rings to the coil and in turn into magnet. g. One of the ends becomes North Pole and other end becomes South Pole.

3. Stator : a. Stator is internally slotted, laminated iron core. b. Three set of windings are usually wound around the stator core. c. Each winding has one of its end connected to the common y junction. d. Positive diode rectifier a nd negative diode rectifier is connected to each of its end converts AC current to DC current.

Module No 04

30

Vaibhav Vithoba Naik

Automobile Engineering

4. Rectifier a. It converts AC into DC. b. Alternator changes circuit six silicon diode rectifiers are used to change AC current to DC. c. An insulated die cast aluminum h older known as heat sink is connected to three positive polarities. d. The positive rectifiers are joined to the battery terminals of the generator.

5. Brushes It is used to make contact with slip rings.

6. Pulley Wheel It is driven by fan belt to drive rotor.

7. Outer Case It is protective covering in which all the component are housed.

Module No 04

31

Vaibhav Vithoba Naik

Automobile Engineering

Q.5: - Explain the working principle & construction of the alternator. Explain rectification? Ans: -COMPONENTS OF ALTERNATOR 1. An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current. 2. Most alternators use a rotating magnetic field but linear alternators are occasionally used. 3. In principle, any AC electrical generator can be called an alternator, but usually the word refers to small

rotating

machines

internal

driven

by

automotive

and

other

combustion engines. 4. Alternators in power stations driven by steam turbines are called turbo- alternators.  WORKING PRINCIPLE-

1. Alternators generate electricity by the same principle as DC generators,

namely, when

the

magnetic

field

around

a

conductor changes, a current is induced in the conductor. Typically, a rotating magnet called the rotor turns within a stationary 2. Set of conductors wound in coils on an iron core, called the stator. The field cuts across the conductors, generating an induced EMF, as the mechanical input causes the rotor to turn. 3. The rotating magnetic field induces an AC voltage in the stator windings. Often there are three sets of

stator windings,

physically offset so that the rotating magnetic field produces three phase currents, displaced by one-third of a period with respect to each other.

Module No 04

32

Vaibhav Vithoba Naik

Automobile Engineering

4. The rotor magnetic field may be produced by induction (in a

"brushless" alternator), by permanent magnets (in very

small machines), or by a rotor winding energized with direct current through slip rings and brushes. The rotor magnetic field may even be provided by stationary field winding, with moving poles in the rotor. Automotive alternators invariably use a rotor winding, which allows control of

the

alternator

generated

voltage by varying the current in the rotor field winding. Permanent magnet machines avoid the loss due to magnetizing current in the rotor, but are restricted in size, owing to the cost of the magnet material. Sincethe permanent magnet field is constant, the terminal voltage varies directly with the speed of the generator. Brushless AC generators are usually larger machines than those used in automotive applications. 5. According to the construction of rotor alternators are classified into two types. 1) Salient pole alternator 2) Cylindrical pole alternator(Non salient pole alternator)  Construction of stator: 1. A stator for a dynamoelectric machine, comprising: a stator core having a generally cylindrical shape, the stator core having a plurality of circumferentially spaced slots, a stator winding including a plurality of conductors, each conductor having a plurality of straight segments interconnecting a plurality of end loop segments 2. The plurality of conductors organized into at least a first filar and a second filer, the plurality of conductors organized into multiple phases defined by a circumferential pitch, each phase having a conductor in the first filar and a conductor in the second filar; the plurality of conductors organized into layers

Module No 04

33

Vaibhav Vithoba Naik

Automobile Engineering

 RECTIFICATION-

1. A rectifier is an electrical device that converts alternating current (AC) to direct current ( DC), a process known as rectification. 2. Rectifiers have many uses including as components of power supplies and as detectors of radio signals. 3. Rectifiers may be made of solid state diodes, vacuum tube diodes, mercury arc valves, and other components. 4. A device which performs the opposite function (converting DC to AC) is known as an inverter. 5. When only one diode is used to rectify AC (by blocking the negative or positive portion of the waveform), the difference between the term diode and the term rectifier is merely one of usage, i.e., the term rectifier describes a diode that is being used to convert AC to DC. 6. Almost all rectifiers comprise a number of diodes in a specific arrangement for more efficiently converting AC to DC than is possible with only one diode. Before the development of silicon semiconductor rectifiers, vacuum tube diodes and copper(I) oxide or selenium rectifier stacks were used.

Module No 04

34

Vaibhav Vithoba Naik

Automobile Engineering

Q.6: - Short notes on Alternators? Ans: -ALTERNATORS 1. In Alternators, alternator has stationary soft iron ring known as stator and armature or rotor is mounted on bearing inside the stator, driven by fan belt. 2. The armature contains one winding of coil having its ends connected to the slip ring. 3. The current is fed to slip ring through stationary carbon brush a nd when current flows through the armature coil it get magnetized forming one north pole and other south through the armature coil it get magnetized forming one north poles and other south poles. 4. Its turning magnet generates current in alternators stationa ry winding. As armature or rotor rotates the current produced is alternating current . 5. Alternator consist of the following A. Stator a. Stator consists of laminated soft iron core on which windings are wound. b. A positive diode rectifier and negative diode rectifie r is connected to each of its ends to convert AC to DC.

B. Rotor a. Magnetized Rotor turns inside the stator. b. The main parts of rotor are Rotor coil, interlocking finger and slip rings. C. Rectifier – converts AC into DC a. Alternator changes circuit six silicon diod e rectifiers are used to change AC current to DC. b. An insulated die cast aluminum holder known as heat sink is connected to three positive polarities. c. The positive rectifier are joined to the battery terminals of the generator.

Module No 04

35

Vaibhav Vithoba Naik

Automobile Engineering

D. Brushes b. It is used to make contact with slip rings.

E. Pulley wheel a. It is driven by fan belt to drive rotor.

F. Outer case a. It is protective covering in which all the component are housed.

Module No 04

36

Vaibhav Vithoba Naik

Automobile Engineering

Q.7: - Short notes on CUT OUT?

Ans: -CUT OUT CUT OUT is an automatic s witch connected between the generator and battery.

Function a. It ensures the correct coupling of battery and generator. b. It connects the battery only when the generator speed is such that its voltage is more than that of battery and is capable of charging the battery, otherwise it will open and disconnect the two units when generator voltage falls below than that of battery.

Construction 1. It consists of a pair of contact held by spring and can be closed magnetically. 2. The contact should open when engine is stationary or running slowly. 3. It consist of two windings namely a. Shunt winding of many turns of fine wire. b. Series winding of comparatively few turns of speaker wire.

Module No 04

37

Vaibhav Vithoba Naik

Automobile Engineering

4. Shunt winding is connected across generator terminal and se ries winding is connected to battery terminal. 5. Shunt winding controls the generator emf and battery circuit. The increases of generator speed increases the flow of current through the shunt winding and at a particular moment, the contact point close. 6. As the generator speed decreases its output falls down to a value lesser than battery voltage. 7. A reverse flow current from the battery to shunt winding weakens the magnetic field and contact points opens to stop the flow of reverse current.

Module No 04

38

Vaibhav Vithoba Naik

Automobile Engineering

Q.7: - Compare or Difference between the Alternator and dynamo?

Answer: -

No Alternator

DC generator /Dynamo

1

Develops AC current

Develops DC current

2

Produces enough current during

It produces very little charge

idling speed of the engine.

during idling..

3

Simple and robust in construction.

It is not very robust.

4

High output weight ratio.

Low output weight ratio.

5

Run upto a very high speed

Run upto 9000 rpm only

(20,000 rpm)

6

Less maintenance

Frequent maintenance

7

The alternator charges the battery The generator does not change at low engine speed.

the battery at low idle speeds.

8

9

Module No 04

39

Vaibhav Vithoba Naik

Automobile Engineering

Q.8: - Explain with the neat sketch of bendix drive? Ans: -BENDIX DRIVE 1) Bendix drive is starting system deals with starting the engine by cranking and disconnect the system when engine starts idling. Bendix drive is used to engage and disengage the starting motors with engine flywheel. 2) Now when the engine has started it is necessary to disconnect the motors otherwise engine will rotate with very high speeds. Drive head is usually keyed to the end of armature shaft.

3) When current is passed to the motor, armature starts rotating with full speed. This turning effect is transmitted through the head and spring to threaded sleeve. 4) Pinions turns slowly till engaged flywheel. When the pinion strikes the collar, it starts rotating with same speed of armature shaft. When engine starts running starting motor disengages.

Module No 04

40

Vaibhav Vithoba Naik

Automobile Engineering

STARTING SYSTEM Q.1: - Write a note on Starting system? Ans: -STARTING SYSTEM The starting system of an automobile is used to start the internal combustion engine. Both SI and CI engines cannot start by itself. These engines need to be cranked by a starting motor. This motor is also called a starter or cranking motor. Cranking of any engine means rotating its crank shaft. Rotation of crank shaft causes the piston to reciprocate. When piston reciprocates, suction, compression, expansion and exhaust strokes of engine are completed. Thus, engine completes its working cycle and it starts running. Starting motor produces necessary torque to rotate the engine wheel (crank shaft)through a suitable gear (one pinion on motor and other ring gear around engine wheel).

Module No 04

41

Vaibhav Vithoba Naik

Automobile Engineering

1) Starting system is the heart of electrical system in automobile s. It consists of battery, starter motor, solenoid, neutral safety switch and ignition switch. 2) When the key is inserted to ignition switch and turned to start position ,a small amount of current is passes through the neutral safety switch to starter relay or started solenoid. 3) Starter solenoid allows high currents to flow through the battery cables to the starter motor. 4) The starter motor then cranks the engine so that the piston moving downward can create a suction that draws air fuel mixture into the cylinder. By creating spark by ignition system, mixture is ignited. 5) If the compression in engine is high enough and all th is happens at the right time, the engine will start.  COMPONENTS OF STARTING SYSTEM Starting system consist of the following components. 1. Staring system : Staring motor to produce the rotation of crankshaft.

2. Drive mechanism: Drive mechanism to transfer rot ary motion of starter to the crank shaft of the engine.

3. Ignition switch: The ignitions switch to start the motor.

Module No 04

42

Vaibhav Vithoba Naik

Automobile Engineering

Module No 04

43

Vaibhav Vithoba Naik

2011-2012

MECHANICAL ENGINEERING

MODULE NO 5. BODY ENGINEERING

AUTOMOBILE ENGINEERING | Mr. Vaibhav V Naik

BODY ENGINEERING

Automobile Engineering

MODULE NO5. BODY ENGINEERING 1. BODY DESIGN a. Importance of body design b. Material for body construction c. Styling forms d. Coach and bus style e. Layout of passenger cars, bus and truck bodies.

2. Aerodynamic of the vehicle a. Aerodynamic drag b. Aerodynamic lifts and pitching moment c. Side force d. Yawing moments and rolling moments

3. Basic dimension a. Geometrical relations to driver seat b. Dimension of foot and pedal control, c. Passenger seats d. Vehicle dimension and visibility

4. Overall criteria for vehicle comparison 5. Chassis types and structure types : a. Open , b. Semi integral and c. Integral bus structure 6. Frame : a. Function and types of Frames b. Load on the frames c. Load and distribution of structure d. Location of power plant

BE.MECHANICAL

2

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

BODY DESIGN a. Importance of body design b. Material for body construction c. Styling forms d. Coach and bus style e. Layout of passenger cars, bus and truck bodies.

BE.MECHANICAL

3

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q.1: - What are the main features of the automobile body?

Ans: Main feature of automobile body are

1. Torsional stiffness : To avoid the flexing of body on bad roads, it must resist twisting between the front and back.

2. Beam stiffness Body should not get sagged in the middle of vehicle resulting jamming of the door

3. Resistance to side impact Side member and doors of vehicle should be sufficient stong to resist t he side impact.

4. Safety glasses The glass used for front and rear vision and in door is provided with lamination

5. Less resistance to overflowing wind Vehicle should have minimum resistance to wind , therfore the vehicle body is provided with aerodynamic sha pe.

6. Safe guarding components from weather The components of engine and other systems are safeguarded from weather by automobile body

BE.MECHANICAL

4

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q.2: - What are the requirements of Bodies for various types of vehicles?

Ans: REQUIREMENTS OF BODIES FOR VARIOUS TYPES OF VECHILE: The body of the most vehicles 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 colour. 8. It should have uniformly distributed load. 9. It should have long fatigue life 10. It should provide good vision and ventilation.

BE.MECHANICAL

5

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q.3: - State the different bodies used in automobiles: Ans: The Automobile bodies are divided in two groups BODY

Passenger Body

Commercial Body

Figure: Types of Layout

BE.MECHANICAL

6

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

B. According to Chassis design the body can divided into 1) Conventional Type 2) Integral Type 3) Semi- Integral Type C. According to other usage: 1) Light vehicle Bodies - cars, jeeps 2) Heavy vehicle Bodies – Busses, Lorries 3) Medium vehicle Bodies - Vans, Matadors

BE.MECHANICAL

7

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q.4: Explain various safet y features in body, which can be incorporated during design Ans:1) Crashworthy Crashworthy systems and devices prevent or reduce the severity of injuries when a crash is imminent or actually happening. Much research is carried out using anthropomorphic cra sh test dummies.

2) SEATBELTS Seatbelts limit the forward motion of an occupant, stretch to slow down the occupant's deceleration in a crash, and prevent occupants being ejected from the vehicle.

3) AIRBAGS Airbags inflate to cushion the impact of a vehicle oc cupant with various parts of the vehicle's interior.

4) LAMINATED WINDSHIELDS Laminated windshields remain in one piece when impacted, preventing penetration of unbelted occupants' heads and maintaining a minimal but adequate transparency for control of the car immediately following a collision. Tempered glass side and rear windows break into granules with minimally sharp edges, rather than splintering into jagged fragments as ordinary glass does.

5) CRUMPLE ZONES Crumple zones absorb and dissipate the force of a collision, displacing and diverting it away from the passenger compartment and reducing the impact force on the vehicle occupants. Vehicles will include a front, rear and maybe side crumple zones (like Volvo SIPS) too.

BE.MECHANICAL

8

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

6) SIDE IMPACT PROTECTION B EAMS.

7) Collapsible universally jointed steering columns , (with the steering system mounted behind the front axle - not in the front crumple zone), reduce the risk and severity of driver impalement on the column in a frontal crash.

8) Pedestrian protection systems. Padding of the instrument panel and other interior parts of the vehicle likely to be struck by the occupants during a crash.

BE.MECHANICAL

9

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

2. AERODYNAMIC OF THE VEHICLE a. Aerodynamic drag b. Aerodynamic lifts and pitching moment c. Side force d. Yawing moments and rol ling moments

BE.MECHANICAL

10

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q1. Explain Aerodynamic drag and aerodynamic lift with moments acting on the vehicle? Ans:- AERODYNAMIC DRAG AND AERODYNAMIC LIFT 1) A breakdown of the factors causing aerodynamic dra g. 2) Aerodynamic drag of rotating wheels may be omitted in the consideration of utilitarian or utility vehicles as it only gives a component of drag without considering at speeds a bove 150km/h (93 mph). 3) The total aerodynamics drag of a vehicle includes many factors such as profile drag, induced drag, skin friction drag, interference drag & cooling and ventilation system drag. 4) The total aerodynamic drag can be written in usual form:

Px = Cx .ρ.v2.A/2

where Cx = dimensionless drag coefficient, ρ = air density V = velocity of the vehicle & A = cross-sectional area of the vehicle (When viewed from front)

Skin friction drag 1. Drag due to tangential stress exerted on the surface of the body as the viscous fluid 2. Slips as a body (i.e.), the drag caused due to the friction between the aircraft’s outer surface & air. 3. Friction forces between an object & air through which it is moving produces skin friction drag. 4. The magnitude of skin friction drag depends on surface area of the Aircraft. 5. The whole surface of the aircraft experience s a surface (or) skin friction drag as it moves through the air

BE.MECHANICAL

11

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

INDUCED DRAG 1. The drag caused due to induced lift. 2. Induced drag is a bi-product of lift and is closely related to the angle of attack. 3. Induced drag is separate from the parasite drag. 4. Due to the development of lift a wing will have both induced and parasite drag. 5. Actually induced drag is directly proportional to lift and inversely proportional to speed. Effects of induced drag: 1. Induced drag increases with increase in weight 2. Induced drag decreases with wing span i.e., high aspect ratio reduces induced drag 3. Speed increases, induced drag decreases

INTERFERENCE DRAG 1) It is caused by interference (i.e.) a term applied to the aerodynamic influence of bodies & parts of an aircraft on one anoth er. 2) When the aircraft parts are far apart the interference drag effect will be less. 3) If gap between a biplane wing decreases then interference increases. 4) Total drag is greater than the sum of the drag on the individual parts of the aircraft. 5) This is due to the flow interference at the junction of various surface, such as the wing, fuselage junction, tail fuselage ju nction or engine wing junction. 6) This Flow interference creates additional drag which is interference drag. 7) It is not directly associated with production of lift i.e., it is a parasite drag. Suitable fairing and streamlining of shapes to control local pressure gradient that can minimize interference drag. 8) Fairing is a part of the skin of an aircraft added to encourage streamline flow, thereby reducing eddies. 9) Hence, decreasing drag.At zero speed, there is no relative motion be tween the aircraft and the air.

BE.MECHANICAL

12

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

10)Therefore there is no parasite drag. As the speed inc reases skin friction drag, formdrag and interference drag increases about half the p arasite drag on aircraft due to the wing.

BE.MECHANICAL

13

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

3. BASIC DIMENSION a. Geometrical relations to driver seat b. Dimension of foot and pedal control, c. Passenger seats d. Vehicle dimension and visibility

BE.MECHANICAL

14

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q.1: - Short notes on Visibility and Blind Spots? Answer: A. Visibility 1. In transport, driver visibility is the maximum distance a t which the driver of a vehicle can see and identify prominent objects around the v ehicle. 2. Visibility is primarily determined by weather condition s (see visibility) and by a vehicle's design. 3. The parts of a vehicle that influence visibility include the wi ndshield, the dashboard and the pillars. 4. Good driver visibility is essential to safe road traffic. 5. Good all round visibility is one of the main requirements of the body design. It depends upon the size of the window opening and their position relative to the occupants.

BE.MECHANICAL

15

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

B. Blind spots 1. Blind spots may occur in the front of the driver when the A -pillar (also called the windshield pillar), side-view mirror, and interior rear -view mirror block a driver's view of the road. 2. Behind the driver, there are additional pillars, headrests, passengers, and cargo that may reduce visibility. 3. Blind spots are affected directed by vehicular speed, since they increase substantially the faster one goes.

A-pillar blind spot

Forward visibility 1. This diagram shows the blocked view in a horizontal -plane in front of the driver. 2. The front-end blind spots caused by this can create problems in traffic situations, such as in round about, intersections, and road crossings. 3. Front-end blind spots are influenced by the following design criteria: a. Distance between the driver and the pillar b. Thickness of the pillar c. The angle of the pillar in a vertical plane side view d. The angle of the pillar in a vertical plane front view e. the form of the pillar straight or arc -form f. Angle of the windshield g. Height of the driver in relation to the dashboard h. Speed of the opposite car

BE.MECHANICAL

16

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Effects of A-pillar angle on visibility 1. Most passenger cars have a diagonal pillar as shown in this side view. 2. The angle between the horizon and A -pillar is approximately 40 degrees with a straight pillar that is not too thick. 3. This gives the car a strong, aerodynamic body with an adequately sized front door.

40° angle A-pillar bar blind spots

Vertical A-pillar having small blind spots

BE.MECHANICAL

17

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q.2: - Short notes on Ergonomics Ans: Ergonomic 1. Ergonomics is the study of designing equipment and d evices that fit the human body, its movements, and its cogn itive abilities. 2. The International Ergonomics Association defines ergonomics as follows:

Ergonomics (or human factors) is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system, and the profe ssion that applies theory, principles, data and methods to design in order to optimize human well-being and overall system performance.

3. Ergonomics is employed to fulfill the two goals of health and productivity. 4. It is relevant in the design of such thing s as safe furniture and easy-to-use interfaces to machines. 5. Proper ergonomic design is necessary to prevent repetitive strain injuries, which can develop over time and can lead to long -term disability.

BE.MECHANICAL

18

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q.3: - Short notes on Drivers seat geometry Answer: Driver’s seat geometry

1. A correct driving position is important in the vehicle layout and the seat position in relation to the steering wheel, foot controls and other secondary control is of fundamental importance in body des ign. 2. Seating position has an influence not only on the drivers comfort but also on road safety. 3. The driver’s seat should be adjustable -45mm horizontally and 30mm vertically. Inclination of the steering column has a direct influence on the forces which can be applied by the driver. 4. A vertical steering column allows the driver to use the maximum force because the whole body is involved in the work of turning the wheel, not just the shoulders, as is the case when steering column is horizontal. 5. Forces of varying magnitude can be exerted on the foot pedals, depending on the angles α and β of the inclination of the seat and the back rests. 6. The distance between the floor and seat also has some influence on these forces. It should also be noted that harder seat allow the driver to use more force when controlling the vehicles. 7. These facts influence the design of controls and seating layout for different categories of vehicle. 8. Trucks have control which requires large forces and it is therefore usual vertical steering columns and a seating position that allows the driver to exert his full weight on the pedals. 9. Large fore are not acceptable in passenger cars and in consequence the controls are designed for the comfort.

BE.MECHANICAL

19

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

CHASSIS a. Types and structure types : b. open , c. semi integral and d. integral bus structure

BE.MECHANICAL

20

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

CHASSIS

Chassis is a French term which is now denotes the whole vehicle except body in case of heavy vehicles. In case of light vehicles of mono construction, it denotes the whole vehicle except additional fittings in the body.

“Chassis consists of en gine, power train, brakes, steering system and wheels mounted on a frame .”

BE.MECHANICAL

21

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q.1: - Draw the layout of the CHASSIS? List the main components of the Chassis? Answer: -LAYOUT OF CHASSIS AND ITS MAIN COMPONENTS:

Figure: Layout of chassis The following main components of the Chassis are 1. Frame: it is made up of long two members called side members 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 and Differential

BE.MECHANICAL

22

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q.3: - List the various load acting on the CHASSIS? Ans:- LOAD ACTING ON THE CHASIS Various loads acting on th e frame are 1) Short duration Load - While crossing a broken patch. 2) Momentary duration load – while taking a curve 3) Impact loads –Due to collision of the vehicle 4) Inertia loads –While applying the brakes 5) Static loads-load due to chassis parts 6) Over loads – beyond design capacity.

BE.MECHANICAL

23

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

FRAME Frame: a. Function and types of Frames b. Load on the frames c. Load and distribution of structure d. Location of power plant

BE.MECHANICAL

24

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q.1: - List out the types of Chassis frame? Explain them? Ans: TYPES OF CHASSIS FRAMES : A. CONVENTIONAL FRAME : 1. It has two long side members and 5 to 6 cross members joined together with the help of rivets and bolts. 1) 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 B. Integral Frame: 1) This frame is used now days in most of the cars. 2) There is no frame and all the assembly units are attached to the body. 3) All the functions of the frame carried out by the body itself. 4) Due to elimination of long frame it is cheaper and due to less weight most economical also. Only disadvantage is repairing is difficult. C. Semi - Integral Frame: 1) In some vehicles half frame is fixed in the front end on which engine gear box and front suspension is mounted. 2) It has the advantage when the vehicle is met with accident the front frame can be taken easily to replace the damaged chassis frame. 3) This type of frame is used in FIAT cars and some of the European and American cars.

BE.MECHANICAL

25

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q.2: - State the function of the CHASSIS FRAME? Ans:- 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 .

BE.MECHANICAL

26

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q.3: - Short notes on FRAME ? Ans:-FRAME

1. It is structure to furnish supports for transmission system ,th e body and other units such as shock absorber ,spring and shackles.etc 2. It also maintains the correct relationship between the other related parts in order to perform their normal functions and freedom from strain. 3. It takes all static and dynamic loads with out undue twist and deflection. 4. The frame is the main part of the chassis on which remaining parts of chassis are mounted. 5. The frame should be extremely rigid and strong so that it can withstand shocks, twists, stresses and vibrations to which it is subje cted while vehicle is moving on road. It is also called underbody. 6. The frame is supported on the wheels and tyre assemblies. 7. The frame is narrow in the front for providing short turning radius to front wheels. 8. It widens out at the rear side to provide la rger space in the body.

Load coming on the frame 1. Weight of vehicle and passengers, which causes vertical bending of the side members. 2. Vertical loads when vehicle comes across a bump or pot hole of road. 3. Inertia load due to sudden application of sudden br akes. 4. Engine torque and braking torque. TYPES OF FRAME There are three types of frames: 1. Conventional frame, 2. Semi-integral frame, and 3. Integral frame (or unit frame)

BE.MECHANICAL

27

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

A. CONVENTIONAL FRAME 1. It is non-load carrying frame. 2. The loads of the vehicle are tra nsferred to the suspensions by the frame. 3. This suspension in the main skeleton of the vehicle which is supported on the axles through springs. 4. The body is made of flexible material like wood and isolated frame by inserting rubber mountings in between. 5. The frame is made of channel section or tubular section of box section. Example: This type of frame is used for trucks.

B. SEMI-INTEGRAL FRAME 1. In this case the rubber mountings used in conventional frame between frame and suspension are replaced by more s tiff mountings. 2. Because of this some of the vehicle load is shared by the frame also. 3. This type of frame is heavier in construction. Example: Popular in European and American car.

C. INTEGRAL FRAME OR FRAME -LESS CONSTRUCTION 1. In this type of construction, th ere is no frame. 2. It is also called unitized frame -body construction. 3. In this case, the body shell and underbody are welded into single unit. 4. The underbody is made of floor plates and channel and box sections welded into single unit. This assembly replaces the frame. 5. This decreases the overall weight compared to conventional separate frame and body construction.

BE.MECHANICAL

28

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q.4.List the advantage and disadvantages of frame less construction?

Ans:- The advantage and disadvantages of frame less construction  Advantages of frame less construction 1. Reduced weight of vehicle. 2. Lower manufacturing cost. 3. Shock absorbing capacity of vehicle increases, which improves the safety of passengers. 4. Stability of vehicle increases due to lower position of vehicles.  Disadvantages of frame less construction 1. Reduction in strength and durability. 2. Increased cost of repairs in case of damage due to accidents. 3. Topless cars are difficult to provide frame less construction. 4. Economical only in case of mass production.

BE.MECHANICAL

29

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q5.Give the classification of motor vehicle on the basis of location of power plant Solution:

CLASSIFICATION OF MOTOR VEHICLE ON THE BASIS OF LOCATION OF POWER PLANT

The engine is typically placed in one of three locations. In the vast majority of vehicles, it is located as the front of the vehicle, in front of the passenger compartment. Front -mounted engines can be positioned either longitudinally or transversely with respect to the vehicle The second engine location is a mid -mount position between the passenge r compartment and rear suspension. Mid -mount engines are normally transversely mounted. The third, and least common, engine location in the rear of the vehicle. The engines are typically opposed -type engines. Each of these engine locations offers advantages and disadvantages:1. Front Engine Longitudinal a. In this type of vehicle, the engine, transmission, front suspension, and steering equipment are installed in the front of the body, and the differential and rear suspension are installed in the rear of the b ody. b. Most front engine longitudinal vehicles are rear -wheel drive. c. Some front-wheel-drive cars with a transaxle have this configuration, and most four-wheel-drive vehicles are equipped with a transfer case and have the engine mounted longitudinally in the front of the vehicle. d. Total vehicle weight can be evenly distributed between the front and rear wheels with this configuration. e. This lightens the steering force and equalizes the braking load. f. With this design, it is possible to independently remove and install the engine, propeller shaft, differential, and suspension. g. Longitudinally mounted engines require large engine compartments. h. The need for a rear-drive propeller shaft and differential also cuts down passenger compartment space.

BE.MECHANICAL

30

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

2. Front Engine Transverse a. Front engines that are mounted transversely sit sideways in the engine compartment. b. They are used with transaxles that combine transmission and differential gearing into a single compact housing, fastened directly to the engine. c. Transversely mounted engines reduce the size of the engine compartment and overall vehicle weight. d. Transversely mounted front engines allow for downsized, lighter vehicles with increased interior space. e. However most of the vehicle weight is toward the front of the vehicle.Th is provides for increased traction by the drive wheels. f. The weight also places a greater load on the front suspension and brakes

3. Mid-engine Transverse a. In this design, the engine and drive train are positioned between the passenger compartment and rear axl e. b. Mid-engine location in used in smaller, rear -wheel-drive, highperformance sports cars for several reasons. c. The central location of heavy components results in a center of gravity very d. near the center of the vehicle. e. This vastly improves steering and handling. Since the engine is not under the hood, the hood can be sloped downward, improving aerodynamics and increasing the driver’s field of vision. f. However, engine access and cooling efficiency are reduced. g. A barrier is also needed to reduce the transf er of noise, heat, and vibration to the passenger compartment.

BE.MECHANICAL

31

Vaibhav Vithoba Naik

BODY ENGINEERING

Automobile Engineering

Q6.Explain the various loads acting on the chassis frame ? Ans: 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.

BE.MECHANICAL

32

Vaibhav Vithoba Naik