au mechanic slides year1 h4271e en 121080

8/12/2019 Au Mechanic Slides Year1 h4271e en 121080

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Mechanic Motor Vehicle 1st Year Transparencies


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Table of ContentsMechanic Motor Vehicle 1st Year Transparencies......................................................................................1

Vernier Caliper parts and principle.........................................................................................................1Reading of Vernier Caliper.....................................................................................................................2Micrometer parts and graduations..........................................................................................................3Micrometer reading.................................................................................................................................4Wheel alignment.....................................................................................................................................5Tyre wear Patterns and causes..............................................................................................................7

Clutch actuation(Hydraulic)....................................................................................................................7Types of gears........................................................................................................................................8Function of Universal joint and slip joint.................................................................................................9Hydraulic brakes...................................................................................................................................10Relationship between piston and flywheel movement..........................................................................12Four Stroke cycle operation (petrol).....................................................................................................12Four Stroke cycle operation (Diesel)....................................................................................................13Two stroke cycleoperation (Petrol)......................................................................................................14Bore dial gaugechecking ovality andtaper.........................................................................................15Overhead valve operating mechanism.................................................................................................17Cooling system.....................................................................................................................................18Fuel pump operation.............................................................................................................................19

Carburettor Function.............................................................................................................................20Float and starting circuit........................................................................................................................21Idling and main circuit...........................................................................................................................22Pump and Econostat circuit..................................................................................................................23Lubrication system (Engine oil circulation)...........................................................................................24Lubrication system (full flow and by pass flow oil filter)........................................................................25Ignition system......................................................................................................................................26

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Mechanic Motor Vehicle 1st Year Transparencies

Directorate General of Employment & Training, Ministry of Labour, Govt. of India.

Developed byCENTRAL INSTRUCTIONAL MEDIA INSTITUTEin collaboration with DEUTSCHE GESELLSCHAFT FUER TECHNISCHE ZUSAMMENARBEIT (GTZ)

Germany.P.O. Box 3142, 76, GST Road, Guindy, Madras 600 032. Phone: 234 5256, 234 5257, Fax: (009144) 234

2791

Vernier Caliper parts and principle

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Reading of Vernier Caliper

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49 Main scale divisions are divided into 50 vernier scale divisions

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ASSIGNMENTS:

Micrometer parts and graduations

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Micrometer reading

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MICROMETER GRADUATIONS

MICROMETER READING

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Example

ASSIGNMENTS:

Wheel alignment

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Tyre wear Patterns and causes

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figure

figure figure

figurefigure figure

WEARPATTERN

IDEAL At shoulders At center On one side Featherededge

Bald spots

CAUSE PERFECTCONDITION

Underinflation

Over inflation Excessive camber Incorrect toe Unbalancedwheel

Clutch actuation (Hydraulic)

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Action: The diaphragm spring(6)pushesthe pressure plate(5)against the clutchplate(4). Power flows from crankshaft(8)' flywheel(9)' pressure plate(5)' clutchplate(4)' and to primary shaft(10)

Action: The downward movement of the clutch pedal(1)pumps fluid from the master cylinder(2)to the slave cylinder(3)and pushes the release bearing(7)and the diaphragm(6)inwards. The pressure plate(5)and the clutch plate(4)moveaway from the flywheel(9). No power flows from the crankshaft(8)to the primary shaft(10)

Types of gears

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Spur GearsTeeth are straight and parallelOnly one tooth is in contact at a time.There is no axial thrustAPPLICATION Gear box

Worm GearsTeeth are at an angle and curvedMore teeth are in contact at a timeThere is axial thrustAPPLICATION Gear box.

Helical gearsTeeth are at an angleMore teeth are in contact at a timeThere is axial thrustAPPLICATION Gear box.

Rack and PinionTeeth are parallelOnly one tooth is in contact at a timeThere is no axial trust.Converts rotary motion into linear motion.APPLICATION Steering

Herring Bone GearsTeeth are straight at an angleMore teeth are in contact at a timeAxial thrust is neutralized

APPLICATION Gear box

Spiral Bevel GearsTeeth are curvedMore teeth are in contact at a timeProduces axial thrust

Transmits torque at 90APPLICATION Final drive differential

Function of Universal joint and slip joint

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Hydraulic brakes

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When the brake pedal(1)is pressed, the push rod forces the piston(3)of the Master Cylinder(2)forwardagainst the spring tension. The primary cup covers compensating port(4). The pressurised fluid is supplied tothe wheel cylinders(7)through the non return check valve(6). The wheel cylinder piston pushes the brakeshoes(8)towards the brake drum(9)and stops the rotation of the brake drum.

When the brake pedal(1)is released, the pedal comes to its original position with the help of the pedal returnspring and shoes by the retracting springs. Wheel cylinder pistons are pushed inside and the fluid is sent backto master cylinder(2)by lifting the check valve(6)from its seat through the compensating port(4)and thetransfer port(5).

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Relationship between piston and flywheel movement

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Four Stroke cycle operation (petrol)

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A Suction Stroke B Compression Stroke C Power Stroke

Action:Inlet valve(1)opens and air fuelmixture enters inside the cylinder.

Action:Inlet valve(1)and exhaust valve(3)are closed. Air fuel mixture iscompressed.

Action:Valves(1)and(3)are closed. Sparfrom the spark plug(2)ignites themixture. Piston is forced down by thburnt gases.

Four Stroke cycle operation (Diesel)

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A Suction Stroke BCompression Stroke CPower Stroke DExhaust S

Action:Inlet valve(1)opens and only airenters inside the cylinder.

Action:Inlet valve(1)and exhaust valve(3)are closed. Air is compressed.

Action:Valves(1)&(3)are closed andInjector(2)sprays diesel. Dieselis ignited by hot compressed air.Piston is forced down by burntgases.

Action:Exhaust valve(gases are forcecylinder.

Two stroke cycle operation (Petrol)

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A Begining of Compression Stroke BSuction and Compression Stroke CPower

Action:All the ports1,2&4are closed. Air fuel mixture iscompressed above the piston.

Action:Inlet port(2)opens and the charge goes insidecrank case(3). Charge above the piston iscompressed and ignited.

Action:Piston is foport(1)opthe charge

Bore dial gaugechecking ovality and taper

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Overhead valve operating mechanism

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The flywheel(1)rotates in clockwise direction.

The crankshaft(2)and the gear(10)also rotate in clockwise direction.

The camshaft gear(3)and the camshaft(4)rotate in the anticlockwise direction at half of the crankshaftspeed.

The eccentricity of the cam lobe(11)pushes the tappet(5)and the push rod(6)in upward direction. The pushrod(6)pushes the rocker lever(7).

The rocker lever(7)swivels and the valve(9)is opened against the pressure of the spring(8).

Cooling systemTR 10 01 07 01 95

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Engine cold Engine hot

When the thermostat(5)is closed the bypassport(9)opens and water circulates in theengine itself and warms up quickly.

When the thermostat(5)is opened, the bypass port(9)closes. Water is circulated to the radiator through outlet(10)

Water flows frompump(1)' Engineblock(2)' Cylinderhead(3)' radiatoruppertank(4)throughthermostat(5)'Radiator core(6)'Lower tank(7)' and towater pump(1). Airpasses through theradiator cores with thehelp of a fan(8)

Fuel pump operation

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Suction Delivery

DETAILS: 6 8 6 8

When the rocker arm(1)is actuated by a cam lobe(2),diaphragm(3)is pulled down. The inlet valve(6)opensand the fuel is sucked in chamber(7).

When the diaphragm is pushed up by thespindle(4), the outlet valve(8)opens andthe fuel is sent to carburetor via outlet(5).

Idling

When the float chamber is full, back pressure keeps the diaphragm(3)down and the connecting link(9)doesnot move, only the rocker arm(1)moves. The spring(10)reduces the rattling noise.

Carburettor Function

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A Float circuit: When the needle valve(2)opens, fuel flows to the float chamber(4)throughthe inlet(5)and filter(6).

B Starting circuit: Petrol is drawn from the float chamber(4)through the starter jet(9)to thepassage(12).

C Idling circuit: Petrol is drawn to the well(14)from the float chamber(4)through the main jet(20)

D Main circuit: Petrol is drawn from the float chamber(4)to the emulsion tube(21)throughthe main jet(20)

E Pump circuit: Petrol is drawn from the float chamber(4)to the pump chamber through thepump inlet valve(23)and to the pump jet(26)

F Econostat circuit: Petrol is drawn from the float chamber(4)to the econostat tube(31)throughthe jet(32)

Float and starting circuit

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B Starting circuit A Float circuit

When the dash board knob is pulled out, the starter valve lever(8)rotates the starter disc valve(10)and opens the fuel passage(12).Petrol is drawn from the float chamber(4)through the starter jet(9)tothe fuel passage(12). Air is drawn from the air jet(11). Air fuel mixturepasses through the passage(13)below the throttle(7).

When the fuel flows to various circuits, fuel level inthe float chamber(4)drops. The float(1)move doand the needle valve(2)opens. Fuel flows throughthe inlet(5)and the filter(6)to the float chamber(When the fuel level rises in the float chamber(4)thfloat(1)moves up and closes the needle valve(2)by the toggle(3).

Idling and main circuit

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D Main circuit C Idling ci

On further wide opening of the throttle valve(7), air velocity increasesacross the narrow passage and creates more vacuum. Petrol is drawn fromthe float chamber(4)through the main jet(20)to the emulsion tube(21).Vacuum draws petrol through the emulsion tube orifices and air throughchoke tube and the air correction jet(22).

When the throttle valve(7)is closed, thpetrol to flow from the well(14)to the piair bleeder(16). Both air and fuel mixturto run the engine at idling speed. Volumthe screw(19). When the throttle(7)is

orifice(18)discharges extra mixture req

Pump and Econostat circuit

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F Econostat circuit E Pump circuit

Under full load and full throttle opening at cruisingspeed, petrol is sucked from the float chamber(4)to the econostat tube(31)through the jet(32)andinjected by an injector(33)which providesmaximum fuel economy.

When the throttle(7)is closed, the diaphragm(25)is pushed back. Petrfrom the float chamber(4)to the pump chamber through the non return ivalve(23).Due to sudden wide opening of the throttle(7), the lever(24)pushes the(25)forward. Petrol passes through the pump jet(26)and opens the nonoutlet ball valve(27). The petrol is injected to the choke tube by the injec(28). This action supplies extra amount of fuel required for avoiding flat sspring loaded rod(29)is adjusted by a nut(30)for effective travel of the

Lubrication system (Engine oil circulation)

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Oil circulation

Oil flows from stainer(10)' Oilpump(1)' Filter(15)' Oilgallery(5)' Main bearings(4)'Connecting rod bearings(3)'and finally to sump.From main gallery(5)to 'Camshaft bearings(6)' rockershaft(7)' rocker arms(8)' andto sump.From main gallery to timinggear/chain(9)' and to sump.Excess pressure from pump(1)is relieved by the oil pressurerelief valve(2)

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Detail XA: oil under normal pressure Detail XB Oil pressuremore than specified limit

Relief valve plunger(11)closes the bypass port(12)and oil passes throughoutlet port(13)and to the oil filter(15)

The relief valve plunger(11)moves against the springpressure(14)and opens thebypass port(12). Excess ofpressurised oil escapesthrough bypass port(12)andto the oil sump.

Lubrication system (full flow and by pass flow oil filter)

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Type Full flow oil filter Type By pass flow oil filter

Function:From the oil pump(1)all the oil passes through the filter(2)to the mainoil gallery(5). By pass valve(4)provided in the filter allows oil to reach main oilgallery directly when the filter is chocked. Excess oil pressure is relieved by oilpressure relief valve(3).

Function:From the oil pump(1)only pagoes to the oil sump(6). The remaininggallery(5). Excess oil pressure is relieve

Ignition system

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FIRING ORDER: 1342

Function:Current flows from battery(A)' Ignition switch(B)' the primary windings of the Ignition coil(C)' CBpoints(E)' earth(D). Condenser(F)is fitted parallel to CB points(E). High tension current from coil(C)' Hightension wire(G)' Carbon rod(T)at the centre of the distributtor cap(R)' rotor(H)' distributor cap segments(W)' HT wires(K)' spark plug(L). The battery(A)the distributor(P)and the spark plug(L)are earthed atpoints(D)on the vehicle frame. Distributor(P)gets drive from the engine camshaft(M)through the screwgear(N)and rotates at half of the engine speed.

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au mechanic slides year1 h4271e en 121080

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