AUTOMOBILE ENGG LAB
Batch :- 3rd Year, B.E.
Department of Mechanical Engineering
ENGINEERING COLLEGE, BIKANER
26 August 2010
1. Valve refacing and valve seat grinding and checking for leakage of valves
2. Trouble sooting in cooling system of an automotive vehicle.
3. Trouble sooting in the ignition system , setting of contact breaker ponts and spark plug
4. Demonstration of steering system and measurement of steering geometry angle and
their impact on vehicle performance.
5. Trouble sooting in braking with specific reference to master cylinder, brake shoe,
overhauling of system and adjusting of the system and its testing.
6. Fault diagnosis in trans mission system including clutches, gear box assembly and
7. Replacing of ring and studying the method of replacing after repair
Experiment no:- 1
Object:- To study the engine valve and there maintenance.
Requirement:- sets of valve, there setting and accessories.
Poppet valve:- it’s main part are head and stem. The lower portion of the head which is called
valve face is ground to an angle of 300 or 450. 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 and
valve stem. The tappet slides vertically in it’s guide, which further actuates the valve
against the spring tension.
(2) Overhead valve mechanism:- in this system valve is mounted at overhead the engine
and 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
Valve seat insert:- there are simply rings pressed into the cylinder block or cylinder head to
reduce wear and to prevent leakage of the gases. In case of c.l. cylinder block or head, the inlet
valve seats are directly machined on the block because the working condition is almost the
Valve guide:-the up and down motion of the valve stem is supported and guided in the plain
hole booed in the boss of cylinder casing or cylinder head is called valve guide. The advantage
of this system is that, if the guide becomes wom.
Valve cooling:-the operating temperature of exhaust valve is more than 600 0c in engine.
therefore to save the valve lift, the cooling of the valve is necessary. Allthrough the cooling
water jackets are designed as near as possible to the valve but in case of heavy duty engines
this cooling not sufficient to cool the valve up the mark.
The melting point of sodium is about 1050 c where it becomes liquid. when the valve moves up
and down then the melted sodium is thrown upward into the hotter part of the valve where it
is absorbs that taken from the cylinder or head walls.
(1) Free type valve rotators:-to remove combustion product from the valve and ensure an
uniform wear as well as temperature between the valve face and seat, valve rotation is
necessary for each operation.
As the valve tappet moves up on the adjustment screw
pushes up on the tip air. Thereby lifting up the lock and spring retainer. In this action the
retainer takes the full pressure of the spring and valve becomes totally free. In this case engine
vibration are sufficient to rotates the valve in any direction, no external force is used on valve
(2) Rotacap valve radiator:- this type positives rotation of the valve by imposing a rotating
force on the valve stem each time the valve opens. The system consists of a sealing
cooler on which the valve spring is located. A retainer cap is mounted with help of split
collar on the end of the valve stem.
The retainer cap consists a ramp formed on it, a number
of spring and balls and a flexible washer is supported between retainer cap and sealing collar at
this section position the ball are kept at the top of ramp and retainer by return spring. when the
valve tappet is raised, the adjustment screw lift the valve thereby increasing the pressure on
sealing coller. Under this action the flexible easher tends to be flat thereby applying the force
on the balls and compressing the springs.
Valve service:-it includes adjustment of the valve tappet clearance, valve and valve seats
grinding 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
2:-they must be properly timed.
3:-the clearance between rocker arm and valve steam must be correct.
(1) Valve sticking:-the causes are:-
1:-due to gum or carbon deposited on the valve steam.
2:-due to insufficient ubrication.
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 seating of
valve, reasons are:-
1:-overheating of the valves causing due to clossed 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.
(4) Valve breaking:- the excessive tappet clearance causes heavy impact seating like a
hammer. 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 creats 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 particle 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 .
Valve train:-it includes cam shaft ,lifter, push rod , rocker arm, valve retainer and lock. Any fault
in valve train results in the following failure:-
(1) Cam shaft:-take out the cam shaft from the engine body carefully and then check
normal and abnormal cam wear in following manner
(a) Cam shaft arrangement:-use`v`block and dial indicator for this check,if abnormal replace
(b) Cam wear:-cams are made slightly tapered and lifter foots are slightly spherical.
(c) Cam shaft bearing :-replace worn out bearing with the care that the oil holes in the
bearing should aligned with the oil holes in the block.
(d) Timing the valves:-the timing gear,sprockets,flywheel or vibration damper are marked
for proper position and correct valve timing.
(2) Lifter:-it has spherical foot ,if worn out then repair or replace. Always keep in order or
refit in the same order.
(3) Rocker arm;-if there tips are worn. They can be ground down on the valve refacing
machine or can be replaced.
(4) Push rod:- the straightmess of the push rods can be checked by rolling them on a flat
(5) Valve spring:-
(a) it is tested by a special fixer ,the pressure required to compress the spring to the
particular length is measured in this test is known spring tension.
(b) Spring squareness:- it is tested by a steel square, hold the spring near to it and rotate
the spring slowly on the flat surface and observe that the top turn of the coil should
not move away from the square more than 15 mm.
(6) Valve retainer and locks:- they are visual inspected worn and cracked retainer and locks
are discarded. There dislocation causes valve out of order and result account.
Servicing valves:- inspect the valve visual and if looks bad than discard for further use. Clean the
useable valve ,polish the steams , now reexamine the valves which includes steam straightness
(1) valve face grinding:- if the valve is badly ridged or pitted. It should be refaced or trued
with the help of valve truing hond tool. This operation is operated manually by
For efficient facing work is performed on grinding machine. This
machine is consist of a grinding wheel ,a coolant delivering system and a chuck is hold the valve
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 1 0
flatter than the seat angle.
(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.
Servicing valve guides:-they must be serviced before the valve seat are ground if desired the
nature of service depend upon the type of valve guide. They are of two type:-
(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 or
head casting .if worn, the old guide should be pressed out with the help of suitable press
Service valve seat:- 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 type:-
Different operation of valve seat service are 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.
Experiment no.:- 2
Object:- to study the trouble shooting in cooling system of an automotive vehical.
Requirement:- radiator, water body pump, fan, air cooling engine head, block etc.
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 preignition 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, motor
cycle, 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 deltaT M/L
Q= rate of heat transfer.
K= average thermal conductivity.
A= surface heat transfer area.
Delta 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 transfer
for air is less than for water.
(b) As the cooling air can not provide the even cooling around the cylinder, therefore
distortion is cylinder and cylinder heat ispossible.
(c) As the air cooled engine do not consist of water jackets therefore they are sound
(d) It needs a fast running as well as bulky fan which produce more noise and absorb more
(2) Indirect or water cooling:- in this system the cooling water flow through the jackets
made 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 the
jackets and radiator is maintained only by means of natural conversion which is called
thermosyyphon. Its cooling rate is slow. it needs a particular level of water. It needs a
big size radiator.
(b) Pump circulation system:- the system consist of a water pump provided between the
lower tank of radiator and water inlet of engine body. The pump is drive from the crank
shaft and water is forced for rapid cooling.
Advantage of pump circulation system:-
(a) The size of the water passes and jacket can be reduced thereby obtaining a compact
structure of engine.
(b) Water can be circulated around the hottest spot of the engine such as sparking plug and
valve 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 glycerin and ethylene –glycol are 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 to
higher 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 be opened automatically.
(5) Evaporative cooling:- the places where deficiency of soft water, this system of cooling is
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 tank
to 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 cooling system
of engine. It consists of a casting which contains inlet and outlet ports of water. The
impaller 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 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.
(3) Cooling fans:- when the vehicle is moving under heavy load and low speed then the
natural air draft is insufficient to provide the desired engine cooling. Therefore the
system consist 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 modern
vehicals 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) Thermostate:- it is a valve provided in the cooling system which keeps a rigid control
over the cooling and maintains the cooling water temperature at the predetermined
(a) Bellow type thermostate:- 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 acetone
inside 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 predetermined value then the liquid inside
the bellows is converted into vaipour thereby creating a pressure and opening the
(b) Wax element thermostate:- it consist of copper leaded wax element. As the wax is
heated. 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 chosing through the bypass by means of side sutter attechedwith the
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 vehical
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 and dash
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. Under this
condition the bourden tube tends to be straighten.
(2) Electrically operated temperature gauge:- it also consists of two units. The dash unit
consists of two coils, pointer, armature and a dial. The engine unit consists of a
resistance which is effected 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 altends a temperature
below of 40c where it tend to be frozen. As the frozen water requires more volume therefore
this expantion 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
glycerin, thylene 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.
Abnormal clearance of impeller in pump housing.
Cylinder head gasket improperly installed.
Due to other mechanical reason such as cluch 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:-
Water pump hose leakage.
Leakage from thehead gasket.
Loose radiator upper tank baffle plate.
Engine thermostate out of order.
If looses occour at high speed, it may be due to the leakage of air through the seal into
(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.
Experiment no. :- 3
Object:- to study the trouble shooting in the ignition system, setting of contact breaker points
and spark plug gap.
Requirement:- battery 6 or 12 volts, ignition coil, ignition distributor, contact breaker,
cylindrical condencer, spark plug etc .
Introduction:- when a current of high ignition tension and high voltage is passed across the air
gap then it produces a spark there. When this spark is produced at the spark plug to ignite the
air fule mixture in the combustion chamber then it is called ignition system. The ignition system
are classified as (a) battery ignition system (b) magnet ignition system.
Qualities of good ignition system:-
(1) At synchronous time, it should provide a good spark at the electrodes of the plugs.
(2) It should work efficiently at low and high speeds of the engine.
(3) It should be light, effective and reliable in service.
(4) It should be compact and easy to maintain.
(5) It should be cheap and convenient.
(6) The interference produced at sparking plug should not effect the ratio and television
Battery ignition system:- the system consist of two circuit, the primery and secondary circuits.
In primary circuit a battery of 6 to 12 volts, ammeter, ignition switch, primary winding of
ignition coil, contact breaker and condencer. the secondary circuit contains secondary winding
of ignition coil, distributor and the sparking plug.
When the contact breaker point are in closed position then the current passes through the
primary circuits develops magnetic field in the ignition coil. As soon as the contact breaker
points are opened by means of cam system the magnetic field developed in the ignition coil is
collapsed suddenly, by which a high voltage source is produced in secondary winding .this high
voltage is led to each spark plug in turn by means of distributor thus produces a spark at the
electrodes of the plug. as per setting of ignition timing. Thereby ignition the compressed charge
inside the cyllnder.
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
cyllnder surface of the case in provided with a magnetic joke. In primary winding the coil
contains 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 connect to battery
and other with contect breaker arm. Out of two ends of secondary winding one is connected to
spark plug through the distributor while yhe oter 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 colleapse, cut across the secondary
winding and introducing high voltage is supplied to spark plug. Which ignite the fuel mixture
already compressed in cylinder.
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
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
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
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 begins to open. This feedback of electrical energy is very harmful and
undesirable due to following reason. Following difficulties are over come 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 condenoser
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 plags .
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 breakaer contact .
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 have 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 point.
Alignment of breker point:- after certain period the breker 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 condencor. The
point gap is generally maintained from 35 to 55 mm.
Distributer:- the main function of it are-
(a) To interrupt the flow of current is the primary winding than produces a high voltage
surge 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,
condencor, 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 spiril gears. The
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 bakallite and having a nickel point
inserted in its top face. The contact breaker and the condencer are mounted on the
breaker plate which is fixed with the main housing.
The distributer cap which is also made of bakallite 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 center, 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 which is called ignition
advance. The factor which effect 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
(a) Manual method:- turning the breaker plate fixed with the housing,in opposite direction
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 integral with
the ignition coil two advance weights, two springs and a plate which is fixed with a
distributer 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 is
fastened to the distributer the unit consist of a diaphgram which is link to a breaker
plate on which contact breaker is installed a return spring is provided on one side of
diaphragm and other side is provided with a link which is further connected with the
When the carborator is at partly position a vaccume is created thereby moving the
diaphgram against tension of the return the spring this action
(d) Combination of centrifugal and vaccume advance:- as the centrifugal advance is
produced effected by the speed of engine and vaccume advance by the load conduction
of engine .
(e) Spark plug:- an element which is conduct the high potential from the ignition harness
into the combustion chamber is called spark plug. It is provided with a gap across which
the high potential discharge thereby producing a spark and burning the charge in
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 electrode under all conduction.
It must be gas tight because leakage may cause the high temperature which
results disintegration between the insulator and electrode.
It must have high resistance correction thereby maintaining a proper gape
length at high sparking potential.
It must have sufficient reach length. As the long reach plug reduces and the
short reach plug increase combustion space.
Classification of sparking plug:- maintain under:-
(a) Detachable and non detachable type plug:- in the detachable plug two seats are
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.
(b) Hot and cold type plug:- the hot plugs have a longer path of heat dissipation thereby
running 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.
(c) Special type of spark plug:- it is known as surface discharge plug consist of
semiconductor material instead of air gap between two electrode. 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 the
electrical resistance of spark plug. Therefore to obtain best sparking results and adjustment of
air gap between two electrode is essential according to varying conduction of charge. In
generally varies from 0.6 to 1 mm.
Magneto ignition system :- in case of the battery ingiotion 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 consist 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 rotating
armature 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
(1) Low current and high rasistance in primary circuit:- it may be causes due to any
following 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 the
Primary winding of the ignition coil is short circuited.
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 but
following 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.
Experiment no :- 4
Object:- to study the stearing geometry angles and their impact on vehicle performance
2. 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.
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 chassis
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
6 wheel alignment:- The purpose of wheel alignment is to position the front wheel and
steering meters to reduce the tyre wear, read sheck, wheel wobbes and provide directional
stability and the vehicle can run straight down a read under condition and all the road
i. chamber :- 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 isc 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
advantage of this inclination are:-
(a) it tends to keep the wheels straight abead and helps the return of wheels to straight
position 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 in
vehicle 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
iv. caster :- 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
stoblehty 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
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.
Viii. comering power :- viewing from the top the wheels rotating plane makes an angle with the
direction of the motion of the vehicle is called slip angle. therefore the side force that can be
sustained is proportional to magnitude of of slip angle. The ratio between side force sustained
and slip angle is called the comering power. which depends upon the instruction of the tyre
vertical force between the tyre and road sire of tyre extent of any tilting of the wheel and
inflation pressure. The wheel rotates in its own plane and tends to bring it in the travelling
direction then the torque is called selfrighting torque and it decreases with the bad on wheel.
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 wheels
there 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 the
radius 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
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 type of them are as under
i. rack and pinion steering gear :- the system insists of a rack housed is a fibular casing
which 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
ii. worm and wheel steering gear :- The system consist of a worm wheel which in carried
is bearing is a cast iron the outer and of the worm wheel is freed to a drop arm from
where 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 of
the 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. Pinion and sector steering gear :- in these system the lower and of the steering shaft is
formed to pinion where as the upper and is fixed with steering wheel the steering shaft
pinion is having a mast with the internal teeth of a sector the sector is made riged with
gear arm whose stem pivots in the bracket
v. Helical grooved cam steering gear :- in this system helical groove is farmed at the
bottom and of the steering wheel shaft the helical groove engages the projected pin of
the drop wum spindle lever by a joint the to and fro motion is obtained at the drop arm
when the steering wheel shaft is turned.
vi. Warm and roller steering gear :- this system consists of a roller having two teeth
fastened 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 cross
shaft is farmed in spindle to fir the drop arm
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 steering
ii. Linkage booster power steering
14 steering troubles shooting :-
i. Hard steering :- when the steering requires more effort than normal it is called hord
steering 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 renedy 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 to
check 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
- Looseance is steering gear remedy is to readjust or replace the worm port
- Warm steering knuckle parts, remedy is to replace the work parts
iii. Vehical 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 if
- Looseness in steering gear linkage and it king pin remedy is to adjust or replace the
worn 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
- 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
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 absorber
vi. 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 parts
vii. 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 pingear remedy is to readjust or replace the worn part
Viii. Front wheel trampel 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
- To much wheel ran out, remedy is to repair or replace the shock absorbers if necessary
ix. 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 speed carfre. it may be due to over inflation remedy is to inflate to
- 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
Experiment No : 5
To study the demonstration of steering system and measurement of steering geometry angle
and their impact on vehicle performance.
when we drive the vehicle the torque of the engine produce tractive effort at the periferi 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 are as given in engg to bring the vehicle are as
given to rest in shortcut possible distance.
To control the vehicle when it is decending 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 responce 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
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 depents upon the following factor:-
I. condition of road-dry wet mudddy 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:-
mechanical brake, hydraulic brake ,electrical brake, vaccum brake, air brake.
1.Drum type brake:-
they are of two type , 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 consist of brake
drum, stationary plate,two shoes hinged at the ancor pins, cam system to expand the shoeand a retracting
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.
these brake consist of a metal disk in stead of a drum and a pair of paids, 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 different type of brake are:-
1.lever opereting disc brake 2.caliper type disc brake 3.disc brake servo system 4. swing cylinder disc brake
5.sliding caliper disc brake.
when efferts from the peddal is trasmittted to the wheel brake by means of cables, rod or shaft then this
system is mechanical brake.
a. Fixed expender brake:- the system consist of a cam or toggeld fixed the back plate. when cam or
toggle slightly roteted by means of pedal, liver and linkage its expand both shoes against brake drum.
b. Leading and trading shoe:- The shoe which drag along the drum and oppose the rotation and create
more thrust or friction against against the brake drum is called leading shoe.
c. Floating cam brakes:- This system consist of a floating cam insted 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
d. Brake with leading shoe:- the system consist of two fixed cam which expands to the individual shoes .
In this system both the shoes act as leading shoe , this incresing braking torque.
Grinding mechanical brake:-
this system consist of a conical wedge pulled by pull rod instead of cam expanding system of the shoe.
Expand unit:- It consist of a mechanical wedge which is provided with steel roller on the side the shoe
plungers are rested on the side of the steel roller.
when a fluid inclosed in a pipe is used to transmit the peddal effort to rod wheel instead of the rod or cable
the system is called hydraulic brake ,the system consist of a master cyllinder and piston.
1.master cylinder 2. wheel cyllinder 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 consist of a
bleader valve which is to be provided at the heighest point of the wheel cylinder.
Wheel cylinder vatchet type adjuster:-
the system consist of a wheel cylinder body having two adjuster wheel fitted at each end of hte cyllinder
body. there are two vatchest teeth on the adjuster , there are two screw structure.
when a vehicle is going up hill 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 conducts
2. cam brocks worn out
3. spring and clips broken
Spring brake pedal :-
1. In an conical brake link rod straight and cables streched remedy is to repair or replace them.
2. shaft incorrectly set
3. shoe no contered on drums
1. loose wheel bearing
2. brake lings loose on brake shoe.
1. linkage loose and greasy
2. cam levers set wrong
3. Brake plate loose and shift under braking efforts.
4. Drums weak and change shape when hot.
dragging means that the brakes remains applied pressing the peddal.
Vehicle pulls to one side :-
1. low tyre pressure
2. loose wheel bearings
3. unequal camber
4. loose spring v bolts, back plates and steering.
we have successfully study about breaking system and and types of brake, and also test the braking system.
Experiment No- 06
To study faultdiagnosis in trans mission system including clutches, gear box assembly and
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 connnecting.
Requirement of clutch:-
1. Gradual engagement:- the clutch should be engaged gadually so that occcurance of sudden jurks
2. Size:- the size of clutch should be small so that it should occupy minimum space.
3. Torque transmission:- the cluch should be designed that maximum torque of the engine can be
transmitted through it.
4. Heat dissipation:-Due to friction occuring in this system a large system of heat is generated. therefore
the 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 ingaged position , the power is transmitted from engine side femail cone
to male cone furthur through the spline shaft to the gear box. when the clutch system is dis ingaged the
male cone is pulled out thus the surfaces of faces are saperated out.
2. Single plate clutch:- the friction plate is held in between the flywheel and pressure plate. axial pressure
is applied on pressure plate by means of six helical spring. To increase the friction surfaces the friction
surfeces the friction lining are provided on both side of the clutch plate.
3. Diaphragm type clutch:- it is similar to single plate clutch but here the diaphragm type spring is used
instead of helical spring. To disingaged the clutch effort is applied to press the through out bearing it
and then pressure plate is released to make free the friction disc between the surfaces.
4. Multiple plate clutch:- the construction is clear out from simplest sketches. It consist of two set of
frictional plate one set of plate slide on spline provided on the flywheel.
5. Semicentrifugal clutch:- In case of heavy duty vehicle to escape the driver from the fatigue of heart
clutch, the help is taken from centrifugal force by keeping some weight on eccentric position.
6. Centrifugal clutch:- in the purely centrifugal type of clutch , the clutch pedal and the spring are
eliminatedalong 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.
7. of the pressure plate and other slide in grooves
8. Electromagnetic clutch clutch is clear from the simpled sketch. the flywheel incorporating the winding
which is supplied electricity from battery or dynamo. when the electric current is supplied to the
winding it is energiged and attaracts the pressure plate thus pressing the clutch plate b/w two surface
and there by engaged the clutch.
9. Vaccum clutch:- In this system of clutch plate as well as plate of pressure are the same as of the ordinary
clutch. pressure is exerted on the clutch plate by means of helical spring. the only difference is this that
the clutch disengagement and engment rod is moved by the vaccume system.
10. Hydraulic clutch:- this system consist of an oil reservoir from which the oil is pumped in to the
accumulator tank. the pump is driven by the engine itself. then the oil under pressure sent through the
control valve to cylinder. the contol valve is electricaly operated by a switch connected with gear change
1. clutch with drow mechanism
2. clutch plate 3. clutch lining
Fluid coupling:- the operation of the can be understood from the simplified sketch. which shown driven input
shaft having a two bladed padddle mounted within a casing filled with oil of a medium viscosity and the
casing is integrate with the o/p shaft.
Clutch trouble shooting:-
1. clutch slipping:- this may be caused by
a. facing of the worn out remedy is eigther replace facing or new clutch plate should be
b. clutch adjustment may be faulty remedy is just adjecent 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 draging:- this is caused by
a. clutch disingagement being to tight remedy is that it should be released
b. clutch pedal improperly adjusted remedy is adjust properly
c. mis alignment 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 motor
clutch and transmission
c. pressure plate or clutch plate badly warped , worm out or damaged.
Sliding mesh gear box:- this system consist of a counter shaft having gear on it infixed and reducing diameter
from and always having mesh with clutch gear.
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.
Torque convertor:- In torque converter fluid motion gives torque.
Free pedal 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
Gear box trouble shooting:- the common fault on gear box and their cause are as given under
a. transmission noisy in neutral
b. transmission noise in gear while driving
c. transmission leaks
d. transmission difficults shifting into gear
e. transmission sticking in gear
f. transmission slipping out of gear
Propeller shaft:- propeller shaft transmit power from gear box to the rear axel . It consist of main parts –
shaft , universal joints , slip joints
Universal joint:- a universal joint is a form of mechanical connection b/w two shaft giving a positive drive
while following angular movement of one and both of shaft.
Propeller shaft trouble shooting:- vibration, squeak , metallic rathe , cleak or grow , lubricant loose at joint.
Rear axel trouble shooting:- axel noisy , excessive hash
We have successfully studies faults in transmission system .
11. :- The construction and the principle of this
Experiment No : 07
To study the piston ,piston rings, their repair and replacement.
It is cylindrical plug that moves up and down in engine cylinder. It is attached to the
small end of the connecting rodby 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 the
piston 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
2. Combustion chamber type piston:
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.
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.
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.
(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 thepiston,there is unequal thickness or the amount of the metal with piston wall.
When heated there will be unequal expansion in the piston diameter which produce
(iv)Wire-wound piston: few pistons such as split or camground 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
(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
(d)heat shielded piston
(e)two piece piston
A. Function of piston ring:-
To prevent leakage of the compressed and expanding gases above the piston
into the crank.
To control and provide the lubricating oil between the piston and cylinder
To scrap out the unnecessary particles and excessive lubricating oil from the
B. Piston ring gap:- To maintain the seat between the piston and the cylinder walls a
slight 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 in
some cases the joints may be lapped, angled or of the scaled type. While placing
rings 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 elastic
qualities. 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 two
three or four number of rings in a set. Actually there are two types of piston rings as
(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 ina four set of piston ringsare 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.
(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 size. 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 carburater.
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
mayfollow 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 coatingand 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 sideof the ring with fine energy paper on surface plate.
(vii)Attaching rods and pistons:-Before fitting therings 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 pistonwith help of a mark provided on piston head. Be
sure that the big end of the rod is seating on the crank pin.
on the crank pin.