5th sem mode

7/31/2019 5th Sem Mode

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AUTOMOBILE ENGG LAB

3rd

Year, B.E.

Department of Mechanical Engineering

GOVT. ENGINEERING COLLEGE, AJMER


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Experiment no: - 1

Object: - To study of Valve refacing and valve seat grinding and checking for leakage of valves

Requirement: - sets of valve, there setting and accessories.

Poppet valve: - its main part is head and stem. The lower portion of the head which is calledvalve face is ground to an angle of 30

0or 45

0. Thereby matching the valves face in the head or

block the leakage of gas.

Valve actuating mechanism:-

(1)Side valve mechanism: - in this system the tappet is interpost between the cam andvalve stem. The tappet slides vertically in its guide, which further actuates the valve

against the spring tension.

(2)Overhead valve mechanism: - in this system valve is mounted at overhead the engineand also in opposite direction that if in case of valve side mechanism. Here the cam

operates the valve tappet which actuates the push rod provided vertically in the side of

crank case.

Valve service:- it includes adjustment of the valve tappet clearance, valve and valve seatsgrinding installing new seat inserts, cleaning and replacing valve guides, servicing camshaft and

its bearing, checking springs and timing the valves and finally tuning the engines.

Therefore valves are required to meet the following requirement:-

1:- all the valve must seat tightly and properly on there seat


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2:-they must be properly timed.

3:-the clearance between rocker arm and valve steam must be correct.

Valve trouble:-

(1)Valve sticking:-The causes are:-

1:-due to gum or carbon deposited on the valve steam.

2:-due to insufficient lubrication.

3:-warped stem, due to overheating, eccentric set and cocked springs or retainer.

4:-due to excessive valve steam clearance because its speeds up valve deposit.

(2)Valve burning:-the problem comes in the exhaust valves, it causes due to poor seatingof valve, reasons are:-

1:-overheating of the valves causing due to closed circulation of cooling system (water) around

the valve seat.

2:-due to overloading or overheating the engine.

3:-due to clean air fuel mixture.

4:-due to carbon deposit on the valve face and seats.

(3)Valve face wear:-the excessive tappet clearance or the dirt on the valve face or seat,wears the valve face. If the fuel air cleaner is not functioning properly then some of dirt

settles on valve seat and creates the trouble.


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(4)Valve breaking:- the excessive tappet clearance causes heavy impact seating like ahammer. If the valve seat is eccentric to its stream or if the valve spring or retainer is

cocked then the side pressure on the valve creates a fatigue in every operation.

(5) Valve deposit:- this may cause due to reason such as

--due to excessive amount of gum in the fuel.

--due to excessive rich mixture of fuel

--due to improper oil or dirt in oil

(6) Valve seat recession:-usually the engine heads and valve seat inserts are made of c.i.

therefore after certain period. The portide of iron flanking from the seat tend to stick on the

valve face. Gradually these particles embed in the valve face and build up into a cutting surface.

The valve seat is gradually cut Away .this is known valve seat recession.


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Servicing valves: - inspect the valve visual and if looks bad than discard for further use. Clean

the useable valve, polish the steams, now re-examine the valves which includes steam

straightness etc.

Valve face grinding: - if the valve is badly ridged or pitted. It should be refaced or trued with

the help of valve truing hand tool. This operation is operated manually by mechanic.

For efficient facing work is performed on grinding machine. This machine is consists of a

grinding wheel, a coolant delivering system and a chuck is hold the valve for grinding.

In some case to provide an interference angle between the two

faces makes the setting more leak proof. In this system valve is faced at an angle about 10

flatter than the seat angle.

Fig: - valve refacing and grinding

(2) Valve steam tip grinding:-for this purpose a special attachment is used on the valve grinding

machine. The valve stem is to be grind off as much from the tip as we ground off the valve face.


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Servicing valve guides:-they must be serviced before the valve seats are ground if desired the

nature of service depend upon the type of valve guide. They are of two types:-

(1) Integral type:-this type of valve guide is an integral part of engine block or head casting.If worn, ream it to a large size and install a valve with an oversize stem.

(2)Replaceable valve guide:-this type of valve guide is press fit into the cylinder block orhead casting .if worn, the old guide should be pressed out with the help of suitable press

or extractor.

Service of valve seat for not leakage: - to achieve better seating and sealing, the valve face

must be concentric with the valve stem, valve guide and seats. Valve guide are of two types:-

(A) Integral type

(b) Insert type

Different operation of valve seat service is as given under

(1) Replacing valve seat insert: - remove a badly worn out insert with a special puller.

Sometime inserts are drilled then they are removed in pieces with help of chisel and hammer.

(2) Grinding valve seats: - for this operation stone of proper shape is rotated on the valve seat

by many of concentric grinding. In this system the stone is kept concentric with valve slave seat

by pilot installer in guide.

(3) Checking valve seat concentricity: - after service the valve guide and seats, they are checked

for concentrically with help of dial gauge. The gauge is mounted on guide.

(4) Testing valve seating: - coat the valve face lightly with puission blue and put it in place turn

the valve with a light pressure. If blue appears all the way around the seat, it means valve seat

and guide are concentric.


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Experiment no.:- 2

Object: - to study the trouble shooting in cooling system of an automotive vehicle.

Requirement: - radiator, water body pump, fan, air cooling engine head, block etc.

Theory:-

Introduction: - out of total heat generated in an i.c. engine only 25% is converted into

mechanical energy, 35% losses through exhaust gases, 35% losses through the cylinder walls

and the remaining 5% passes through lubrication system. The dissipation of the heat from the

cylinder wall is done by means of cooling system of the engine.

Without cooling engine would result the pre ignition of the charge, burned up of lubricant

scoring of cylinder, binding of piston, bearing and warping of valves, the too much cooling of

the engine results decreased thermal efficiency, reduced vaporization of fuel, increased

viscosity of lubricant thereby decreasing overall efficiency of the engine.

Cooling system: - according to the need there are different cooling method as described

under:-

(1)Direct of air cooling: - this system is being used in light engine such as scooter, motorcycle, tractor and small aeroplane engine. The outer surface of the cylinder and cylinder

heads consist of fins which increases area of contact with the air thus radiated more

heat to the atmosphere. the rate of heat flow through the cylinder wall is expressed by

law which may be stated as:-

Q= KA T M/L

Where:-

Q=rate of heat transfer. Fig:- fins of engine

K= average thermal conductivity.


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A= surface heat transfer area.

T = temperature difference between the hot and cold surface.

M= mass flow rate of air.

L= length of heat flow path.

Advantages of air cooling:-

(a) As the air cooled engine does not consist of radiator, cooling jacket, coolant jacket,coolant etc. therefore it is lighter than other.

(b)Power lost in the cooling water circulation pump is saved in this system.(c) The chances of freezing of water air omitted when used in cold place.(d)The air cooled engines are advantageous .there is scarcity of cooling water.(e) The cylinder and cylinder heads prepared under the system are cheaper than any other.

Disadvantage of air cooling:-

(a) Air cooled engines are less efficient than other because the coefficient of heat transferfor air is less than for water.

(b)As the cooling air cannot provide the even cooling around the cylinder, thereforedistortion in cylinder.

(c) As the air cooled engines do not consist of water jackets therefore they are soundinsulator.

(d)It needs a fast running as well as bulky fan which produce more noise and absorb morepower

(2) Indirect or water cooling: - in this system the cooling water flow through the jacketsmade around the cylinder, combustion chamber and valve parts. The heat from the

cylinder is absorbed by cooling water which is circulated through the radiator. From

radiator this heat is dissipated to atmosphere by means of fins provided on the radiator.

The water cooling system are of two types:-

(a) Thermosyphon system: - it has no water pump but the circulation of water through thejackets and radiator is maintained only by means of natural conversion which is called

thermosyphon. Its cooling rate is slow. It needs a particular level of water. It needs a big

size radiator.

(b)Pump circulation system: - the system consists of a water pump provided between thelower tank of radiator and water inlet of engine body. The pump is drive from the crank

shaft and water is forced for rapid cooling.


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Advantage of pump circulation system:-

(a) The size of the water passes and jacket can be reduced thereby obtaining a compactstructure of engine.

(b)Water can be circulated around the hottest spot of the engine such as sparking plug andvalve seat bosses.

(c) It needs less water and small size of radiator.(d)A rapid cooling is obtained by this system.(3)Liquid cooling: - in this system liquid such as glycerine and ethylene glycol is used as

coolant instead of water because they have higher boiling point. This increases heat

carrying capacity of the system, reduces the weight of coolant as well as size of radiator.

(4)Pressure sealed cooling: - the boiling point of water is 1000c, which can be raised due tohigher pressure by sealing the cooling system. Therefore reducing the weights of the

coolant and the radiator and increasing the thermal efficiency of the engine.

The pressure of the system can be raised by means of special radiator cap which maintains

pressure from 0.5 to 1 kg/cm2. The cap consists of a safety valve, vaccum valve, over flow pipe

and gasket for sealing purpose. When the pressure exceeds predetermined value then the

spring loaded pressure valve is opened automatically.

(5)Evaporative cooling: - the places where deficiency of soft water, this system of coolingis preferred. The system is similar to that for water cooling but the latent heat of steam

is considered in it.

This system consists of a radiator which acts as a condenser. The water is entered into the

engine block jacket from radiator by means of a pump. The steam formed at the engine flow

from top of block and enters at the bottom of radiator.

Components of a water cooling system:-

(1)Radiator:- it is made of copper or brass sheets and tubes which consists of a upper tankto the water outlet of the engine and lower tank which is connected to the water inlet

of the engine .water of the both the tank is connected by means of cores.The cores are of two types, the tubular type and cellular type. In case of tubular type the

cooling water passes through the vertical and zigzag tubes and air passes around them.

(2)Water pump: - the purpose of it is to increase the circulation of coolant in coolingsystem of engine. It consists of a casting which contains inlet and outlet ports of water.

The impeller which may be of rotor or disc type is mounted on the outer end of the

shaft by means of hub. When pulley gets drive from the crank shaft, then water


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available at the impeller is forced out through the outlet to the engine jackets. Fresh

water from the water lower tank of radiator away flows through the hose pipe of the

Pump.

fig:- water cooling system

(3)Cooling fans: - when the vehicle is moving under heavy load and low speed then thenatural air draft is insufficient to provide the desired engine cooling. Therefore the

system consists of a cooling fan which provides a powerful draft of air through radiator.

It is mounted behind the radiator on water pump shaft which is V belt driven. In modernvehicles to keep the cooling constant at different speeds and saving power in fans drive,

the cooling system are equipped with a thermostatically controlled power booster fan

that is driven through a liquid clutch which slips after reaching a set speed.

(4)Thermostat: - it is a valve provided in the cooling system which keeps a rigid controlover the cooling and maintains the cooling water temperature at the predetermined

value.

(a) Bellow type thermostat: - it consists of metallic bellowed filled with acetone liquid,a valve and its seat. The unit is suspended in hose and mounted at outlet of engine.

Initially the temperature of cooling water is low and the pressure of the acetoneinside the bellows is also reduced thereby retaining the valve on its seats and closing

the circulation of the water through the radiator. After start, when the engine is

working up and temperature reaches to predetermine value then the liquid inside

the bellows is converted into vapour thereby creating a pressure and opening the

valve.


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(b)Wax element thermostat: - it consists of copper leaded wax element. As the wax isheated. The wax of element expands. This movement of the element along the

plunger opens the valve against the return spring thereby flowing the water through

radiator and choosing through the bypass by means of side Sutter attached with the

valve.

Temperature gauge: - the engine temperature is indicated by means of a gauge mounted on

the dash board of the cab. If the temperature goes too high then driver at once stops the

vehicle and gets the engine to be cooled. Types of temperature gauge are bellow:-

(1)Bourden tube type temperature gauge: - it consist of two units, the engine unit anddash unit which are connected by means of a capillary tube filled with some volatile

liquid. The end towards the engine unit side of tube is closed and given a valve stop.

When temperature effect the engine unit then the volatile liquid filled in valve and

capillary tube expand thereby increasing the pressure inside the bourdon tube. Underthis condition the bourden tube tends to be straighten.

(2)Electrically operated temperature gauge: - it also consists of two units. The dash unitconsists of two coils, pointer, armature and a dial. The engine unit consists of a

resistance which is affected with the variation of engine temperature. As the

temperature of the engine increase, the value of resistance decreases thereby flowing

current through the A and increasing the emf built there.

Anti freezing solution: - in cold places the cooling water of the wheels attends a temperature

below of 40c where it tends to be frozen. As the frozen water requires more volume therefore

this expansion may cause the fracture of the radiator core, cylinder block water and pipes. Main

requirement of anti freeze are as given below:-

(a) They should be well mixable with water.(b)They should not have any corrosive and harmful action to any part of cooling system.(c) They should be sufficient cheap.(d)They should not deposit anything in jacket, hose pipe, and radiator cores.

The material such as wood, alcohol mixture, mixture of

glycerine, ethylene etc. are commonly used as anti freezes.

Cooling system trouble shooting: - the common fault occurring in the cooling systems

(1)Overheating:- it may be due to following reasons:- Engine fan belt slipping. Engine thermostate not opening properly. Engine pump impeller loose on shaft.


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Abnormal clearance of impeller in pump housing. Cylinder head gasket improperly installed. Due to other mechanical reason such as clutch slipping, tight wheel bearing, dragging

brakes, use of heavy engine oil or any type of friction in transmission system.

(2)Water loss from cooling system:- reasons are:-

Radiator leakage. Water pump hose leakage. Leakage from the head gasket. Loose radiator upper tank baffle plate. Engine thermostate out of order. If looses occurs at high speed, it may be due to the leakage of air through the seal into

water pump.

(3)Water pump noises:- following cases are:- Pulley loose on pump shaft. Pump impeller loose on pump shaft. Impeller blades touching with pump housing.(4)Fan noises:- reason for this trouble are as given:- It may be due to fan belt troubles such as belt adjusted too tight or loose, incorrect

belts, belt badly warn out or misalignment of fan belt pulleys.

(5)Rapid wear of fan belt:- main causes are:- Excessive tight or loose adjustment of the belt. Use of incorrect type of belt. Oil on belt. Misalignment of belt pulley. Belt striking or rubbing on fan blades. Overload on belt.


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Fig: - battery ignition system

Components of battery ignition system:-

Metal-shell type ignition coil: - it is a transformer which steps up the 6 or 12 volts of battery to

the 6000 to 20000 volts, thereby obtaining a spark the electrodes of the plug.

It consists of metallic clad or case in which an iron core is placed. The inner

cylinder surface of the case in provided with a magnetic joke. In primary winding the coilcontains about 200 to 300 turns of copper wires of about 20 s.w.g. and the secondary winding

contains about 15000 to 20000 turns of copper wire of about 40 s.w.g.

First the secondary coil is wound over the core and then the primary coil is done over it. The

two terminal of primary winding are taken out from the case, one of which connects to battery

and other with contact breaker arm. Out of two ends of secondary winding one is connected to

spark plug through the distributor while the other end is earthed by means of interconnection

with the primary winding.

When the ignition switch is on and the contact breaker points are closed then the current from

the battery flows through the primary winding and which built up a magnetic field. When the

contact breaker in opened position then the magnetic field collapse, cut across the secondary

winding and introducing high voltage is supplied to spark plug. Which ignite the fuel mixture

already compressed in cylinder.


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Core type ignition coil:-in this type, the core is surrounded by primary winding, and then the

secondary winding is wounded on it. In this system heat is dissipates from the primary winding

to the secondary winding is controlled by means of providing a ballast resistor in the primary

circuit.

Ballast resistor: - since the primary winding is placed inside the secondary winding of the

system, therefore the length of the winding wire in primary winding is shorter than that of

secondary winding.

As the resistance is directly proportional to the length of the wire, it means:-

R proportional to L

It is known that I=V/R

Where:-

R is resistance of wire

L is length of wire

V is voltage

I is current passes through wire.

Since L is lesser therefore R introduces a large current I in the ignition coil, while cases

overheating remedy of which is to introduce on extra resistance in the primary coil. This

additional resistance is called ballast resistor.

Condenser: - as the collapsed magnetic field also cut across the primary winding when the

contact breaker points begin to open. This feedback of electrical energy is very harmful and

undesirable due to following reason. Following difficulties are overcome by condition which it

produces unnecessary arc across the contact breaker points which stores the whole feedback of

electric energy and immediately discharge it when the contact breaker points close. Thereby

passing the combine current from the battery and the condenser

Following difficulties are in condenser:-

(a) It produces unnecessary arc across be contact breaker point.(b)An arc across the points consumers most of the energy stored in the magnetic field

thereby reducing the voltage across the secondary winding and produce a weak spark at

spark plugs.


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A condenser consists of a numbers of long foils made of metal

which are insulated from each other by means of wanted paper .all the foils includes

papers are wound in the form of a cylinder which is placed in a metallic casing . All the

odd numbered conductors are inter connected to form one terminal which connected

to contact breaker.Similarly all the even numbered conductors are also interconnected to

form the other conducted which is earthed through the casing.

Contact breaker: - it is a cam actuated automatic switch for opening and casing primary

circuit at required instant. It consists of two points made of tungsten, one is stationary

or grounded point and other is mounted on a pivoted leaver or arm. Both the points

contact together by means of spring tension. The cam is mounted on the distributer

spindle which has the drive from the cam shaft. When the cam is rotated then the level

of leaver is moved up and down by lobe of cam. Thereby making and breaking the

contact between two points.

Alignment of breaker point:- after certain period the breaker points become dirty,

pitted, fail to correct gap and the ignition system becomes inoperative which result

failure the engine start. As for better results a spedfild gap between the points is

essential while arm is on the high lobe of cam. Similarly they should be close face to face

to make good contact with each other by means of spring tension. Therefore to

overcome this difficulty after certain good period of adjustment.

Cam or dwell angle:-the degree measured on the ignition cam, during which the contact

breaker points remain close is called cam or dwell angel. This angle should be so large

that it may allow magnetic saturation of primary coil.

A too small angle may be due to wide point gap, which results low

secondary voltage thus produce poor spark as well as misfiring of engine, similarly too

large cam angle may be due to small point gap, which results burning of condenser. The

point gap is generally maintained from 35 to 55 mm.

Distributer: - the main function of it is-

(a) To interrupt the flow of current is the primary winding than produces a high voltagesurge in secondary winding.

(b)To distribute is turn the high voltage surge to different flux at the right moment.It consists of a main housing, rotating shaft with a breaker cam, contact breaker,

condenser, rotor, ignition advice mechanism and a cap having provision to install the

high tension cables from ignition coil and the spark plugs. The distributer shaft posses

through the housing and gets drive from the camshaft by means of spiral gears. The


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lower and of shaft is connected to oil pump. The upper end is provided with a breaker

cam which has the same number of lobes as the engine has cylindered. A rotor is

provided above the cam and at top of shaft.

The rotor is made of Bakelite and having a nickel point

inserted in its top face. The contact breaker and the condenser are mounted on the

breaker plate which is fixed with the main housing.

The distributer cap which is also made of Bakelite contains the same number of

terminals as the number of cylinder as well as control contact to receive the high surge

from the ignition coil. The connection between the central terminals and the rotor point

is made of a spring loaded carbon brush. Other tap terminals are made of nickel.

Ignition advance: - in i.c. engine it has observed that a maximum energy is obtained

when the peak pressure occurs at about 50

to 120

after the top dead centre, thus if the

combustion space is decreased then the combustion pressure increase, similarly if the

spark is retared too long or combustion space is increased then combustion pressure

reduces. Since burning rate changes with change in engine speed therefore to obtain a

peak pressure at high speed the ignition timing is also shifted this is called ignition

advance. The factor which affects this are:-

(a) Engine speed(b)Type of fuel(c) Load on engine(d)Engine temperature

Methods of ignition advanced: - following are the method available for adjusting ignition

device advance.

(a) Manual method: - turning the breaker plate fixed with the housing, in oppositedirection that of cam results advanced ignition and turning in same direction results

retard ignition. If this change is ignition timing is controlled by hand by means of a

leaver provided at the dash board then it is called manual method.

(b)Centrifugal advanced method: - the mechanism consists of an advance cam integralwith the ignition coil two advance weights, two springs and a plate which is fixed with adistributer shaft at low speeds all the parts of unit are in their set position, but as the

engine speed increases the two weight are thrown out due to centrifugal force against

the tension of spring and are pivoted on respective cams.

(c) Vacuum advance method: - this system consists of a vacuum advance unit which isfastened to the distributer the unit consist of a diaphragm which is link to a breaker

plate on which contact breaker is installed a return spring is provided on one side of


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diaphragm and other side is provided with a link which is further connected with the

breaker plate.

When the carburettor is at partly position a vacuum is created thereby moving the

diaphragm against tension of the return the spring this action

(d)Combination of centrifugal and vacuum advance: - as the centrifugal advance isproduced effected by the speed of engine and vacuum advance by the load conduction

of engine.

(e) Spark plug: - an element which is conduct the high potential from the ignition harnessinto the combustion chamber is called spark plug. It is provided with a gap across which

the high potential discharges thereby producing a spark and burning the charge in

combustion chamber.

The requirements of a good spark plug are given:-

It must have a high resistance so that current may be leaked thus produce spark.

It must maintain proper air gap between the two electrodes under allconduction.

It must be gas tight because leakage may cause the high temperature whichresults disintegration between the insulator and electrode.

It must have high resistance correction thereby maintaining a proper gapelength at high sparking potential.

It must have sufficient reach length. As the long reach plug reduces and theshort reach plug increase combustion space.

Classification of sparking plug: - maintain under:-

Detachable and non detachable type plug: - in the detachable plug two seatsare provided between the shell and insulator and the assembly is loaded by

means of a gland when the cleaning of inside of plug is necessary the gland can

be unscrewed individual component cleaned are reassembled in non detachable

type the centre assembly is retained by a swaged over lip forming part of body. a

permanent sealing is provided between the insulator.


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(a) Hot and cold type plug: - the hot plugs have a longer path of heat dissipation therebyrunning at higher temperature than the cold plug. A hot plug is generally used is

medium duty low speed and cold working operating conditions while the cold plug is

used in heavy duty high speed engines where high temperature are encountered.

(b)Special type of spark plug: - it is known as surface discharge plug consist ofsemiconductor material instead of air gap between two electrodes. Thereby producing

more intense and efficient spark than ordinary type.

Spark plug gap: - the factors, as the type of fuel mixture ratio and compression ratio effect theelectrical resistance of spark plug. Therefore to obtain best sparking results and adjustment of

air gap between two electrodes is essential according to varying conduction of charge. In

generally varies from 0.6 to 1 mm.


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Magneto ignition system: - in case of the battery ignition system a battery supplies the low

voltage to the primary circuit which in magneto ignition system a magneto serves the purpose

of the battery.

(a) Rotating armature type: - it consists of a permanent magneto having two pole shoes,which are mounted within the magneto housing made of aluminium or zinc alloy. An

armature containing primary and the secondary winding rotates between the two poles.

(b)Rotating magnetic type: - the working system of it is also similar as that of rotatingarmature type but difference is that in this system magnet rotates instead of armature.

All the winding condenser and contact breaker etc.

Ignition system trouble shooting: - following are the ignition trouble, there causes and

remedial action:-

(1)Low current and high resistance in primary circuit:- it may be causes due to anyfollowing reason :-

Dirty or burned breaker point. Loose wire connection. Ignition coil defective.

(2)Too high current or low resistance in primary circuit :- it may be due to any of thefollowing:-

Primary winding of the ignition coil is short circuited.


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Ballast resister if provided in primary circuit, short circuit.(3)Rapidly burning of breaker point:- these are- Condenser not earthed properly. Condenser is defective.

Oily breaker points. Point gap too small.

(4)Spark plug failure:- the causes are- Incorrect plug gap. Poor ignition and too much carbon deposited in the plug. Burned plug electrodes.

(5) Ignition cam angle changes with speed:- it may be due to following- Improper tension on breaker arm spring. Worn out breaker plate assembly. Worn out distributer shaft and bushing.

(6)Contact breaker heel wears quickly:- Breaker arm spring is too tight. Ignition is not being lubricated.

(7)Engine does not start in weather:-the cases are- Moisture on secondary wires. Moisture inside the distributer cap. Moisture on secondary terminal of ignition coil. Distributer cap cracked.

(8)Engine misfires at high speed:- the fault may be due to mechanical reason also butfollowing may be ignition causes-

Coil or condenser defective. Point gap too little. Worn out breaker plate assembly. Breaker points bounces.(9)Rough engine running:- causes are- Too advance ignition timing. Ignition advance mechanism not functioning properly.(10)Engine overheats: - it may be due to other reason such as cooling, lubrication, fuel and

break system etc. but the reason due to the ignition system is that retarded ignition timing.


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Experiment no: - 4

Object: - to study the steering geometry angles and their impact on vehicle performance

Requirement: - Beam axle, stub axle, steering linkage steering gears, power steering units and

linkage equipment to measure the camber angle castor angle, toe in, toe out etc.

Theory:-

1. Front and geometry: - The angular relationship between the front wheel, front wheel

attaching parts and vehicle frame are concerned with farm It consists the of the front wheel

from vertical king pin away from vertical and the toe in of front wheel

2. Front axle beam :- It is made of away steel with droop forging operation the ends of the axle

are given proper shapes to carry the stub axle and two states are made to attach the spring.

The downward Sioer is given to the axle beam at the central portion to keep a low chassisheight their.

3. Stub axle: - The front wheel hub rotates an antifrietm bearing on the stub axle which is

attached to the steering knuckle. Assembly is hinged is hinged on and of axle beam to permit

the wheel to the twined by steering gear.

4. Front wheel assembly: - The wheel hub rotates an ball bearing an a stab axle which is an

integer part of the steering knuckle. The bearing with stand Beth radial and side thrust the stub

axle is provided with a thrust bearing between the lower and of the beam axle and steering

knuckle lurk to reduce friction.

5. Front drive axle: - This system is provided with a shape single universal unit joint which

accommodates the steering motion of the stub axle. In this system an ordinary live axles is used

and the axle casing surrounding these components which are concerned it. At its outer and the

drive shaft is carried in bushed bearing.

1


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6 wheel alignments: - The purpose of wheel alignment is to position the front wheel and

steering meters to reduce the tyre wear, road shock, wheel wobbles and provide directional

stability and the vehicle can run straight down a read under condition and the entire road

i. camber :- the camber is the tilt of the front wheels from the vertical prone when the tilt is

outward at the top than the chamber is positive and when the tilt is inward at the top the

camber is called negative. The camber angle should net proceed. Excessive too less and unequal

camber tends to cause more rigid tyre wear.

ii. Kingpin inclination: - It is the inward tilt of the kingpin from the vertical plane. The

advantages of this inclination are:-

(a) It tends to keep the wheels straight ahead and helps the return of wheels to straightposition after as turn has been completed.

(b) It reduces tyre wear.(c) It reduces steering effort when the vehicle is stationary.(d)The kingpin inclination in combination with caster in used to provide direction stability

in vehicle. The amount of this inclination is generally kept 70

to 80

iii. included angle :- it is the sum of the sum of the camber and the kingpin inclination formed invehicle plane it determine the points of interdiction of the wheel and the kingpin centre lines

above on are below the road surface. Since the too opposite forces working on the wheel the

tractive force wits at the kingpin centerline for forward push and road resistance at the wheel

contact point at the road both should lie at the point of intersection just below the road surface

otherwise the wheel will tends to swing


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iv. Castor: - in addition to the side inclination the kingpin may be tilted forward or backward

from the vertical in the plane of wheel. The backward tilt from the vertical is called positive

castor and forward tilt is called negative castor. The positive castor provides directional stability

and tries to keep the wheel straight ahead. But more amount of positive castor increases the

effort required to steer.

v. Toe in: - The toe in is the turning in of the front wheels from the straight ahead position. The

purpose of it is to move the wheels perfectly straight ahead under running condition of the

vehicle to stabilize steering to prevent side supping and excessive wear of tyres.

vi. Toe out: - The steering system of a vehicle is designed to turn the inside wheel through a

larger angle than the outside wheel when making a turn. This action causes the front wheels to

toe out on turn

vii. Wheel balance:-the balancing of the front wheel is an important factor to make the steering

easier. The unbalance of the wheel may causes of uneven tyre wear. The wheel balance can be


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classified in two way static balance and dynamic balance. The wheel can be said statically

unbalanced if tilt weight is not evently distributed around the hub.

9 Steering characteristics: - when vehicle moves in a circular path the center of that path does

not coincides with the point of intersection of wheel axle. Under this condition the centrifugal

force acts on the wheel which matter with slip angle.

i. over steer :- If the slip angle for the rear wheels is greater than that for the front wheelsthere the radius of turn id decreased therefore the vehicles will turn more sharply into

the carve and the steering wheel has to be turned back to correct this tendency

therefore to keep the vehicle on the right path the wheels should a little less is

theoretical desired this condition of comering is called over steer

ii. under steer :- It the slip angle is greater for the front wheel than that for the rear theradius of turn is increased, therefore on turn the vehicles will tends to straighten out

this condition is called.

10. Steering linkage: - the motion of the steering wheel is transmitted through the leverage

between the steering wheel in order to overcame the friction opposing the turning of the road

wheel is minimized for proper ant rat the system is so designed that the steering wheel turns

through large angles than the stub at road the amount of leverage depends upon weight of

vehicle

11 steering connection:- far steering connection between drop arm and the stub axle the

angular motion in two pieces plane at connection is essential to winter the system properly but

in modern systems at steering the ball and socket joints are preferred

12 steering gears: - The steering mechanism which provides the necessary leverage may be of

several forms but the common types of them are as under


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i. rack and pinion steering gear :- the system insists of a rack housed is a fibular casingwhich is supported on the frame near the ends the ends if the rack are connected to the

track rods with the help of ball and socket joints the pinion shaft is carried in the plain

bearing, housed in caring the pinion is meshed with the rock and is given rotary motion

with the steering wheel

Fig: - rack and pinion steering gear

ii. worm and wheel steering gear :- The system consist of a worm wheel which in carriedis bearing is a cast iron the outer and of the worm wheel is freed to a drop arm fromwhere motion is farther transmitted to side rod steering arm and thon to stub axle. The

warm which is keyed on to a worm wheel.

iii. Screw and nut type steering gear: - in this system a screw is formed at the lower and ofthe steering shaft and the upper and is fixed to a steering wheel. The nut consists of

integral furnnions which pivot in the holes of the arm of the fork. The fork is connected

to the drop arm by a splined shaft. The upper and of the steering shaft is supported in

the steering column by a ball and socket joint so that shaft mag swing slightly

iv. Worm and roller steering gear :- this system consists of a roller having two teethfastened to the cross shaft by means with the threads of the worm gear the worm gear

is formed an the bottom and of the steering wheel shaft the outer and of the crossshaft is farmed in spindle to fir the drop arm

Fig:-Worm and roller steering gear


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13 Power steering: - It is a booster arrangement provided in steering system and is operated

when the steering wheel shaft is turned generally hydraulic pressure is used in the power

steering but some lines compressed air and electrical mechanism are also used in system a

pump is used in system which provide by hydraulic pressure when needed there are two kind

of power steering currently in use and are given as under

i. Integral power steeringii. Linkage booster power steering

Fig: - power steering

14 steering troubles shooting:-

i. Hard steering :- when the steering requires more effort than normal it is called hardsteering it may be due to the following reasons

- Uneven or low tyre pressure remedy is to in to correct reasons- Friction in steering gear linkage and at the king pin remedy is to lubricate the meshing

parts readjust or replace them if worm

- Disturbed alignment of the caster camber toe in and kingpin inclination etc remedy is tocheck the alignment and readjust if necessary

ii. Excursive play in steering system :- Die to following reasons- Loose wheel bearing, remedy is to readjust or replace the bearing- Loosenace is steering gear remedy is to readjust or replace the worm port- Warm steering knuckle parts, remedy is to replace the work partsiii.

Vehicle wander - due to following reasons- Uneven of les pressure remedy is to inflate to correct pressure

- Steering gear and linkage binding remedy is fore adjust or replace the warm parts ifnecessary

- Looseness in steering gear linkage and it king pin remedy is to adjust or replace theworn part uneven lead in vehicle remedy is to readjust the lead

iv. Vehicle pulls to one side

- Uneven tyre pressure remedy is inflate to correct pressure


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- In correct or uneven caster remedy is to check alignment and adjust as necessary- Tight front wheel bearing reined is to readjust and replace the defective leaver and

parts

v. Steering kickback :- if may be due to following reason- Looseness in steering gear remedy is to adjustor readjust or repair the warm gear- Looseness or repair the warm gear- Looseness in linkage remedy is to readjust or replace the warm parts- Shock absorbers calefactive remedy is to replace or replace shock absorbervi. Wheel wobble :- it may be due to following reasons :-- Ball joins worm out remedy is to replace their- Wheel bearing or steering gear bearing loose remedy is to readjust or replace them- Caster is excess remedy is to replace the damaged partsvii. Front wheel shimmy at low speed :- the following factor may covey this trouble- Unequal or infract camber remedy is to readjust the camber- Irregular tyre thread remedy is to match treads or replace worn tyres- Loose kingpin linkage or steering pin gear remedy is to readjust or replace the worn partViii. Front wheel trample or high speed shimmy

- Any cause listed under shimmy at low speeds remedies are stated above- Wheels out of balance remedy is to rebalance the whets- Too much wheel ran out, remedy is to repair or replace the shock absorbers if necessaryix. Improper tyre wear: - reasons are

- Rapid wear from speed remedy is to dirt the Vehicle at normal speed for longer tyre life.- Wear at tread. it may be due to over inflation remedy is to inflate to correct pressure- Wear at one treads side if may due to excessive camber remedy is to adjust camber- Feather edge wear it may be due to excising toe in and toe out on turn


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Experiment No: - 5

Object: -to study of Trouble shooting in braking with specific reference to master cylinder,brake shoe, overhauling of system and adjusting of the system and its testing.

Theory:-

Introduction:-

When we drive the vehicle the torque of the engine produce tractive effort at the periphery of

the driving wheel. When the brakes are applied the braking torque produces a negative tractive

effort at peripheral of the braking wheel.

Purpose of brakes:-

The main purpose fitting brake on motor wheel is as given in engg to bring the vehicle are as

given to rest in shortcut possible distance.

To control the vehicle when it is descending along the hills.

To full fill the above needs, two independent braking system are provided in the vehicle

a) Service brake: - which is operated by foot pedal in regular operation.b) Emergency brake: - which is operated by hand lever while parking the vehicle.

Requirement of brake:-

1. Brake must be strong enough to stop the vehicle within the desired distance. This is possible

only if no skidding and drive has proper control.

2. The brake pedal and operative effort should be within response and of drive. So that under

fatigue can be avoided.

Force acting on the brake drum and ground:-

Let be the

Wb = normal force on brake shoe

Ub =coefficient of friction between drum and shoe


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Fb = force of friction on brake drum

Rb = radius of brake drum

Wt = normal force on tyre

Ut = coff of friction between tyre and ground.

Ft = force of friction between tyre and ground

Rt = radius of tyre

So, retarding force on brake drum

Fb = Ub *Wb

Retarding torque= Fb * Rb

Retarding force provided at the point of control of tyre on ground

Ft = Ut * Wt but, Ft * Rt = Fb * Rb

Or, Ft = Fb * Rb / Rt

Factor affecting the coff of friction:-

The value of u can be unity but practically it is less than unity. It depends upon the following factor:-

I. Condition of road-dry wet muddy snowy etc.II. type of tyre trade

III. Tyre inflation- correct, over, under.

Application on duty:-

Foot brake or service brake or running brake

Hand brake or parking brake or emergency brake

Conventional: - drum brake, disk brake

Method of power employed:-


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Mechanical brake, hydraulic brake, electrical brake, vacuum brake, air brake.

Drum type brake:-

They are of two types, one is internally operating and other is externally operating drum brake.

a. Internal expending drum brake:-

It is formed by mounting the shoe to role against inside the surface of drum. The system consists of brake

drum, stationary plate, two shoes hinged at the anchor pins, cam system to expand the shoe and a retracting

spring.

fig:- internal expanding drum brake

b. External contracting drum brake:-

The type of brake is used as parking brake in motor vehicle. The system consist of drum, band with lining,

operating lever with adjusting lever and push rod with returning spring.

Disk Type brake:-


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These brake consist of a metal disk instead of a drum and a pair of paid, instead of the curved shoe pressure

on the friction pad may be actuated by pull rod or by hydraulic system. In case of rear wheel brake assembly

is attached to the axel housing, while in the case of front wheel brake

fig:- disk brake

Different types of brake are:-

1. Lever operating disc brake 2.caliper type disc brake 3.disc brake servo system 4. Swing cylinder disc

brake 5.sliding calliper disc brake.

Mechanical brake:-

When efforts from the pedal is transmitted to the wheel brake by means of cables, rod or shaft then this

system is mechanical brake.

a. Leading and trading shoe:- The shoe which drag along the drum and oppose the rotation and createmore thrust or friction against the brake drum is called leading shoe.

b. Floating cam brakes: - This system consists of a floating cam instead of a fixed on the back plate.There by equal force are applied on both the shoe and a greater braking torque is provided by a

given effort.


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c. Brake with leading shoe: - the system consists of two fixed cam which expands to the individualshoes. In this system both the shoes act as leading shoe, this increasing braking torque.

Hydraulic brakes:-

when a fluid enclosed in a pipe is used to transmit the pedal effort to rod wheel instead of the rod or cable

the system is called hydraulic brake ,the system consist of a master cylinder and piston.

1. Master cylinder 2. Wheel cylinder 3. Hydraulic two leading shoe brake 4.tandom master cylinder

Bleading of brake:-

The procedure of removing air out of the hydraulic braking system is called bleeding. The system consists of

a bleader valve which is to be provided at the highest point of the wheel cylinder.

Wheel cylinder vatchest type adjuster:-

The system consists of a wheel cylinder body having two adjuster wheel fitted at each end of the cylinder

body. There are two vatchest teeth on the adjuster, there are two screw structures.


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Hill holder:-

When a vehicle is going uphill and is stopped in neutral gear by applying the foot brakes.

Brake trouble shooting:-

The general complaints and troubles attributed to the brakes are usually classified as given under

1. low brake pedal :- In case of mechanical brake more oil cables conducts2. cam brocks worn out3. spring and clips broken

Spring brake pedal:-

1. In a conical brake link rod straight and cables stretched remedy is to repair or replace them.2. shaft incorrectly set

Brake noise:-

1. loose wheel bearing2. Brake lings loose on brake shoe.

Erratic brakes:-

1. linkage loose and greasy2. cam levers set wrong3. Brake plate loose and shift under braking efforts.4. Drums weak and change shape when hot.

Brake drag:-

Dragging means that the brakes remains applied pressing the pedal.

Vehicle pulls to one side:-

1. low tyre pressure


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2. loose wheel bearings3. unequal camber4. Loose spring v bolts, back plates and steering.

]


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Experiment No- 06

Object: -

To study fault diagnosis in transmission system including clutches, gear box assembly anddifferential

Theory:-

Clutch: - It is a device being used for connecting or disconnecting the transmission of power at

wheel from one shaft to another shaft, whose axes are connecting.

Requirement of clutch:-

1.

Gradual engagement: - the clutch should be engaged gradually so that occurrence of sudden jerks

avoided.

2. Size: - the size of clutch should be small so that it should occupy minimum space.3. Torque transmission: - the clutch should be designed that maximum torque of the engine can be

transmitted through it.

4. Heat dissipation:-Due to friction occurring in this system a large system of heat is generated. Thereforethe design the clutch should ensure adequate dissipation of heat.

5. Dynamic balancing: - for high speed clutch, the dynamic balancing is necessary.Types of clutch:-

1. Cone clutch:-when the clutch is engaged position, the power is transmitted from engine side femalecone to male cone further through the spline shaft to the gear box. When the clutch system is

disengaged the male cone is pulled out thus the surfaces of faces are separated out.

Fig: - Cone clutch


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2. Single plate clutch: - the friction plate is held in between the flywheel and pressure plate. Axial pressureis applied on pressure plate by means of six helical springs. To increase the friction surfaces the friction

surfaces the friction lining are provided on both side of the clutch plate.

Fig: - Single plate clutch

3. Multiple plate clutches: - the construction is clear out from simplest sketches. It consists of two set offrictional plate one set of plate slide on spline provided on the flywheel.

fig:- Multiple plate clutches

4. Semi centrifugal clutch:- In case of heavy duty vehicle to escape the driver from the fatigue of heartclutch, the help is taken from centrifugal force by keeping some weight on eccentric position.


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Fig: - Semi centrifugal clutch

5. Centrifugal clutch: - in the purely centrifugal type of clutch, the clutch pedal and the spring areeliminated along only and only the centrifugal force of weight is used to apply required pressure on

floating plate as well as pressure plate for keeping the clutch in engaged position. In this system the

operation of the clutch is automatic and depends on the engine speed.

Fig: - Centrifugal clutch

6. Electromagnetic clutch:-clutch is clear from the simple sketch. The flywheel incorporating the windingwhich is supplied electricity from battery or dynamo. When the electric current is supplied to the

winding it is energised and attracts the pressure plate thus pressing the clutch plate b/w two surfaces

and there by engaged the clutch.

Fig: - Electromagnetic clutch


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7. Vacuum clutch: - In this system of clutch plate as well as plate of pressure are the same as of theordinary clutch. Pressure is exerted on the clutch plate by means of helical spring. The only difference is

this that the clutch disengagement and engagement rod is moved by the vacuum system.

Fig: - Vacuum clutch

8. Hydraulic clutch: - this system consists of an oil reservoir from which the oil is pumped in to theaccumulator tank. The pump is driven by the engine itself. Then the oil under pressure sent through the

control valve to cylinder. The control valve is electrically operated by a switch connected with gear

change lever.

Fig: - Hydraulic clutch

Fluid coupling: - the operation of the can be understood from the simplified sketch. Which shown driven

input shaft having a two bladed paddle mounted within a casing filled with oil of a medium viscosity and the

casing is integrate with the o/p shaft.


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Fig: - Fluid coupling

Clutch trouble shooting:-

1. clutch slipping:- this may be caused bya. Facing of the worn out remedy is either replace facing or new clutch plate should be

installed.

b. Clutch adjustment may be faulty remedy is just adjacent the clutch.c. Pressure lever may blind, remedy is just adjust them properly.d. Clutch plate be blinding or hitting against floor board, remedy is just adjust it.

2. Clutch dragging:- this is caused bya. clutch disengagement being too tight remedy is that it should be releasedb. clutch pedal improperly adjusted remedy is adjust properlyc. Misalignment remedy is to correct it, with the help of dial indicator.

Clutch grabbing:- It may be caused by

a.

clutch pedal sticking remedy is to adjust the clutch

b. Imperfect alignment , remedy is to make necessary corresponds and properly lining up of motorclutch and transmission

c. Pressure plate or clutch plate badly warped, worm out or damaged.


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Sliding mesh gear box:- this system consist of a counter shaft having gear on it in fixed and reducing

diameter from and always having mesh with clutch gear.

Fig: - Sliding mesh gear box

Constant mesh gear box:- It is similar to the sliding mesh gear box only diff is that all the gear are in constant

mesh with corresponding gear on counter shaft.

Fig: - Constant mesh gear box

Free wheel unit: - In some vehicle a free wheel unit is fitted to the main shat behind the gear box which allow

the drive from main shaft to propeller shaft but prevent drive being transmitted from the propeller shaft to

main shaft.


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Fig: - Free wheel unit

Gear box trouble shooting: - the common fault on gear box and their cause are as given under

a. transmission noisy in neutralb. transmission noise in gear while drivingc. transmission leaksd. transmission difficult shifting into geare. transmission sticking in gearf. transmission slipping out of gear

Propeller shaft: - propeller shaft transmit power from gear box to the rear axle. It consist of main parts

shaft, universal joints, slip joints

fig:- Propeller shaft and Universal joint

Universal joint: - a universal joint is a form of mechanical connection b/w two shafts giving a positive drive

while following angular movement of one and both of shafts.


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Propeller shaft trouble shooting: - vibration, squeak, metallic rathe, cleak or grow, lubricant loose at joint.

Axle and Differential trouble shooting: -

1. Noise - same when in drive as when vehicle is coasting

1. Road noise. No corrective action available.

2. Tire noise. Inspect tires and check tire pressures

3. Front wheel bearings loose, worn or damaged

4. Insufficient differential oil

5. Defective differential.

Fig: - Axle and Differential

2. Knocking sound when starting or shifting gears


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1. Defective or incorrectly adjusted differential

3. Noise when turning

1. Defective differential.

4. Vibration

1. See probable causes under Driveshaft. Proceed under the guidelines listed for the driveshaft. If problem

persists, check the rear wheel bearings by raising the rear of the vehicle and spinning the wheels by hand.

Listen for evidence of rough (noisy) bearings. Remove and inspect.

5. Oil leaks

1. Pinion oil seal damaged.

2. Axle shaft oil seals damaged

3. Differential covers leaking. Tighten mounting bolts or replace the gasket as required.

4. Loose filler plug on differential

5. Clogged or damaged breather on differential.


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Experiment No: 07

Object: - To study the piston, piston rings their repair and replacement.

Piston:-

It is cylindrical plug that moves up and down in engine cylinder. It is attached to the

small end of the connecting rod by means of a piston pin. Its diameter is slightly smaller

than that of the cylinder. The space between the cylinder wall and the piston is called

piston clearance. The purpose of the clearance is to avoid seizing of the piston in

cylinder and to provide a film of lubricant between piston and cylinder wall.

Type of pistons:-

Based on specific requirement of a particular engine and other considerations of thepiston are designed in different forms and shapes are following:

1. Deflection head piston:

The head of the piston is raised upward. It consists of two regions A and B. The fresh

charge of air-fuel mixture enters at A and is deflected upward within the cylinder during

suction stroke.

Fig: - Deflection head piston

2. Combustion chamber type piston:


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This type of piston has a cavity on the top which serves as a portion for combustion

chamber. Profile of cavity provides turbulence of air-fuel mixture.

Fig: - Combustion chamber type piston

3. Domed and depression heated piston:

This type of piston is provided with cavities in their head to accommodate the valves

during the operation. The head of the piston may be flat or domed shaped.

Fig: - Domed and depression heated piston

Piston Clearance:-

The piston clearance is made of aluminium alloy whereas the material used for all the

cylinder is cast iron. The two different metals have unequal coefficient of expansion

which causes engine slip. So, following are the methods to maintain proper clearance.

(i)Providing head dam: to keep the heat away from the piston, a groove is cut near the

top of the piston. This groove is known as Heat Dam.


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(ii)Provide slots in the piston: these slots may be horizontal, vertical or T-type. They

reduce the path for heat travelling from the piston head to the piston skirt.

(iii)Cam ground piston: Due to providing the bushes for mounting the piston pin in the

wall of the piston, there is unequal thickness or the amount of the metal with piston

wall. When heated there will be unequal expansion in the piston diameter whichproduce engine knock.

(iv)Wire-wound piston: few pistons such as split or cam ground type are provided with

the bond of steel wire between the piston and the oil controlled ring grove.

(v)Bi-metal piston: this piston is made from two metals aluminium and steel. The skirt is

made of steel in which aluminium is casted to form the boses. The steel has very small

expansion when heated thereby obtaining smaller clearance of the piston.

(vi)Piston with special alloy: with greater clearance the engine produces more noise in

cold conditions. A fine clearance may be used without risk of seizure by use of special

alloys.

(1)Lo-Ex alloy (2) Invar alloy

(vii)Special pistons: the surface of the modern pistons are anodized or treated with a

coating of tin or ZnO2. The special construction control clearance as well as the

expansion of piston in addition to its own advantage:

(a) Oil cooled piston

(b) Inserted rings carries piston

(c) Offset piston

(d) Heat shielded piston

(e) Two piece piston

Fig: - piston parts

Piston Ring:-


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A. Function of piston ring:-

To prevent leakage of the compressed and expanding gases above the pistoninto the crank.

To control and provide the lubricating oil between the piston and cylinderwall.

To scrap out the unnecessary particles and excessive lubricating oil from thecylinder.

B. Piston ring gap: - To maintain the seat between the piston and the cylinder walls aslight radial pressure is necessary which is produced to provide slightly greater

diameter of the ring than the bore in which they work. Therefore to mount the ring

into piston, a gap is essential.

C. Piston ring points: - Rings for automotive engines usually have butt-joint, but insome cases the joints may be lapped, angled or of the scaled type. While placingrings into piston the joints should be staggered so that the compression from

combustion chamber may be prevented to be leaked by piston skirt.

D. Piston ring materials: - A ring should have excellent heat wear resisting and elasticqualities. Therefore fine grained alloys of cast iron provide superior to any other

metal used for this purpose.

E. Types of piston rings: - A piston consists of a set of piston rings. There may be twothree or four number of rings in a set. Actually there are two types of piston rings as

described under:

(a)Compression or gas rings: The top two rings are called compression rings, they

prevent the leakage of the gases which are under pressure from the combustion

chamber to the crank case.

(b)Oil regulation rings: The bottom ring in case of three rings set or the two bottom

rings in a four set of piston rings are called oil regulation rings. They scrap the excess

of lubricating oil from the cylinder wall and deliver it through the ring slot and piston

oil drain holes to oil pan.

Service pistons and rings:-

After separating the pistons and rods, the rings are removed from the pistons with the

help of special ring expander services of these parts include piston cleaning, piston

inspection, ring grove repair, attaching rods and pistons.

(i)Piston cleaning: - It is possible to reverse the piston thereby its surface should be

cleaned carefully. Avoid the use of wire bush and caustic solutions because they may

spoil the surface of the piston.


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(ii)Piston Inspection: - check the piston for crank wear, scuff scored, skirts, ring loud, pin

bosses, head and worn rings groove. If there is a major defect discard the piston. Worn

ring grooves can be repaired for which oversized rings can be recommended.

(iii)Piston groove repair:-If the piston is in good condition only the tap groove has work

out due to high tank and pressure, then it can be repaired.(iv)Selection of new piston:-The pistons are made avoidable in a number of sizes. With

use of oversize the respective cylinder are only finished accordingly.

(v)Service Piston rings:-The ring once used should be discarded because the old rings

will not seat properly to provided scaling. If the rings are sticking in the grove, a special

compound can be sprayed into the running engine through carburettor.

If the cylinder wall are only slightly tampered are out of round then standard size rings

can be used. Theses rings should have greater tension and flexibility so that they may

follow the changing contours of the walls and provide desired scaling.

(vi)Fitting Piston Ring:-Ring are fitted to the cylinder as well as to the piston. They are

available in different standard and oversize which are packed with intrusion in sets. First

step is to fit the ring in the cylinder and push it down to the lower limit of travel and

measure the ring gap with seller gauge. If the ring gap is wrong it means the rings are of

wrong size packed in the set. Avoid filling the ring ends because it can remove some of

the ring coating and cause early failure.

After testing the rings in the cylinder check them in the grooves of piston. The rings

should roll completely in the grooves without binding. If they are tight the radial

pressure will be impaired. If too slack, oil pumping will be inevitable result. If still tight

them rub-down on the side of the ring with fine energy paper on surface plate.

(vii)Attaching rods and pistons:-Before fitting the rings attach the rods and pistons by

means of piston rings be sure that parts match as in the original assembly. Arrange the

piston in the correct position in the rod.

If the rod and piston are provided with lock bolt system, put the piston through the

piston rod and lock the pin by tightening the bolts.

(viii)Reinstalling piston and rod assemblies: - After attaching the rod and piston and

installing the rings presuming the cylinder bore is already true, set the rings in their

proper position and dip the assembly in lubricating oil. Compress the rings into the

groove with a piston ring compressor. Cover the rod bolts with rubber hose and push

the piston down into the cylinder.

Now strike the piston head with the wooden handle of a hammer and gets the piston

slid in. Check the direction of the piston with help of a mark provided on piston head. Be

sure that the big end of the rod is seating on the crank pin.


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5th sem mode

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