STATE ROAD TRANSPORT CORPORATION

The State Road Transport Corporation is a state owned subsidiary. It has its own fleet of Vehiles. The vehicles range from passenger bususes to Transport buses. The vehicles operation both in Intrastate as well as Inter State Routes. The famous routes are Srinagar to Delhi, Jammu, Leh and also some inter district routes.The workshop of SRTC is situated in Pampora and is a well managed through proper planning for maintaining resource allocations. It is situated on Left side of the National Highway on way from Srinagar. The employees of this workshop are well skilled and have good sense of Humour.

The workshop is divided into number of sections viz.,1. Engine Overhauling Sectiona. Dissembling Sectionb. Cleaning Sectionc. Inspection & Repaird. Assembling Section2. Gear Box Section3. Brake Section4. Lubrication Section5. Machine Shop6. Coach Repair Section etc

ENGINEAn engine is a device which transforms one form of energy into another form. However while transforming energy from one form to anither the efficiency of conversion plays an important role. Normally, most of the engines convert thermal energy into mechanical work and therefor they are called heat engines.Broader classification of heat engine

Basic Engine components:1. CYLINDER:It is a cylindrical vessel or space in which the piston makes reciprocationg motion.2. PISTON:It is a cylindrical componentfited into the cylinder forming the moving boundary of the combustion system.3. COMBUSTION CHAMBER:The space enclosed in the upper part of the cylinder, by the cylinder head & the piston top during the combustion process.4. INLET MANIFOLD:The pipe which connects the intake system to the inlet valve of the engine and through which charge is drawn into the cylinder.5. EXHAUST MANIFOLD:The pipe which connects the exhaust msystem to the exhaust valve of the engine and through which the products of combustion escape into the atmosphere.6. INLET & EXHAUST VALVES:Valves are commonly mushroom shaped popet type. These are the openings in the cylinder through which charge and the combustion products enters and leaves the engine cylinder respectively.7. SPARK PLUG:It is a component to initiate the combustion process in the spark ignition engines.8. CONNECTING ROD:It interconnects the piston and the crankshaft and transmits the gas forces from the piston to the crank shaft.9. CRANKSHAFT:It converts the reciprocating motion of the piston into the useful rotary motion of the output shaft. The crankshaft is enclosed in a crank case with balance weights for static and dynamic balancing of the rotating system.10. PISTON RINGS:These are fitted into the slots around the piston and provide a tight seal between the piston and the cylinder wall thus preventing leakage of the combustion gases.11. GUDGEON PIN:It forms the link between the small end of the connecting rod and the piston.12. CAM SHAFT:It along with its associated parts controls the opening and closing of the valves. The associated are push rods, rocker arms, valve springs and the tapets.13. CAM:These are made as integral parts of the cam shaft and their peculiar design regulstes the opening and closing of the valves.14. FLYWHEEL:It is the inertia mass attached to the output shaft which reduces the fluctuation in the torque. Multicylinder engines have smaller flywheels than single or double cylinder engines owing to their lesser fluctuation in the net torque at the output shaft.WORKING PRINCIPLE OF 4 STROKE DIESEL ENGINEDiesel engine works on diesel cycle the credit for whose invention goes to Rudolf Diesel (1892). The ideal sequence of operations for the 4 stroke CI Engine is as follows:1. SUCTION STROKE:Air alone is inducted into the cylinder during the stroke intake valve is open and exhaust valce is closed.2. COMPRESSION STROKE:The piston moves upwards from the BDC. The inlet and exhaust valves remain closed. The air is compressed in the cylinder with the high compression ratio of 10 22 and a high pressure of 40Kg/cm2 3. WORKING STROKE:The fuel injection starts nearly at the end of the compression. The rate of injection is such that the combustion maintains the pressure constant inspite of the piston movement on its expansion stroke. The heat is assumed to have been added at constant pressure. After the cutoff the products of combustion expand. Both the valves remain closed during the stroke.4. EXHAUST STROKE:The piston travelling from the BDC to TDC pushes out the products of combustion. The xhaust valve is open and intake valve is closed during the stroke.

OVERHAULING OF DIESEL ENGINEFollowing steps are taken during the overhauling of the engine:1. DISSEMBLING OF ENGINE:a. Remove the water pumo.b. Remove the exhaust manifoldc. Remove oil filter tubed. Remove the water outlet fittinge. Reove thermostatf. Remove the crankshaft pulleyg. Remove the oil pumph. Remove crankcase ventilation valvei. Remove rocker arm assemblyj. Remove cylinder headk. Remove oil panl. Remove piston and connecting rod assemblym. Remove timing gear covern. Remove front end plateo. Remove flywheel housingp. Remove clutchq. Remove flywheelr. Remove crankshafts. Remove exhaust valve and springst. Remove cam shaftu. Remove valve tapetsv. Remove oil gallery plugsCHECKING FOR TROUBLES1. Check the cylinder liners for scuffing and pitting2. Check the ylinder liner for allowed bore and thickness specification. If damaged beyond permissible linits change the damaged liners. If damage is not too serios the go for internal grinding, finishing and finally honing to abort the liner from removal.3. Check the cylinder body, water jacket for the proper flow of coolant water.4. Check the oil pump for the required flow of lubricating oil and flush the stainer (oil mesh filter) with high pressure water5. Crankshaft should be inspected for:a. Soundness to check cracksb. Roundness and wear of the journals ans crank pinsc. Balancingd. Alignment of crankpins and journalse. Cleanliness of oil galleries6. Check the connecting rod for bending and proper clearance at the big end between connecting rod cap and the bearings. To compensate for wear of the bearing and to secure the correct bearing clearance between the connecting rod and crankshaft, thin pieces of metal called shims are used.7. The piston rings should be checked for wear and gap. To check this gap, clean the carbon from the ends of the rinf and then check it with feeler gauges. The gap may be in the g=region 0.178 to 0.50mm governed by the diameter of the bore but if it exceed 1mm per 100mm of the bore diameter, new rings must be fitted.8. The gap between the ring and the groove in the piston should be checked by feeler gauges. The gap is usually 0.038 to 0.102mm for the compression rings and little less for the oil rings.9. Piston pin should be checked for the wear, cracking or pitting. Circlips should always be renewed and check they are not loose or cracked.10. Valve should be checked for proper clearance between cam and the valve tappet11. Valve seats should be checked for wear12. A slight clearance should bemaintained between the valve stem and the valve tappet =. This is known as valve tappet clearance or valve lash13. Cam shaft should be checked for proper alignmentASSEMBLYThe steps following during the disassembly should be followed in the reverse order. Further following should be noted carefully while assembling the engine.1. The connecting rods and caps are individually matched to each other and usually carry identifying numbers so that they may not be mixed after dissembled.2. The timing gear should be properly matched with the crankshaft.

TRANSMISSIONThe word transmission means the whole of the mechanism that transmits the power from the engine crankshaft to the rear wheels. However the transmission is also being used very commonly in the literature for mechanism which providesus with suitable variation of the engine torque at the road wheels whenever required.FUNCTIONS OF TRANSMISSION

The main functions that are performed by the transmission are:1. The torque or the tractive effort produced by the engine varies with the speed only within narrow limits. But the practical consideration for the running of automobile under different conditions demands a large variation of torque available at the wheels. The main purpose of the transmission is to provide a means to varythe leverage or torque ratio between the engine and the road wheels are required.2. The transmission also provides a neutral position so that the engine and the road wheels are disconnected even with the clutch in the engage position.3. A means to back the car by reversing the direction of rotation of the drive is alsoprovided by transmission.Generally two types of transmission are in use:1. Manually operated type2. Automatic typeThe manual transmission are commonly calle gear boxes.Here we are mainly concerned with manualled opeared gearbox.a. Removing the transmission:The procedure for removing the transmission of a 4 wheeled vehicle is as follows:1. Drain the transmission and the transfer case. Replace the trabsfer plugs.2. Remove the floor board inspection plate, shift lever, shift housing assembly and its gasket from the transmission.3. Remive the set screws from the transfer caseshift lever pivot pin. Remove the pivot pin shift levers and shift lever springs. If the vehiclenis equipped with power takeoff, remove the shift lever plate screws and lift out the lever.4. Disconnect the frint and rear propeller shafts from the transfer case.5. Disconnect the speedometer cable at the transfer case6. Disconnect the handbrake and cluctch control cable.7. Place jack under transmission and engine protecting the engine oil pan with a wooden block.8. Remove the nuts holding rear mounting to frame member.9. Remove the tranbsfer case snubbing rubber bolt nut at cross member.10. Remove the bolts holding frame center cross member to frame siderail and remove cross member.11. Remove bolts holding transmission to flywheel bell housing.12. Force transmission away from the clutch control lever tuv=be ball joint for disengagement.13. Lower jacks under engine and transfer case assemblies towards rear of vehicle until main drive gear shaft clears the flywheel housing.14. Lower jack under transmission. Remove transmission and transfer case as an assembly from under the vehicle.b. Separating transmission ans transfer case:The procedure for separating the transmission and transfer case is as follows:1. Remove the screws and lockwashers attaching the transfer case n=raer cover and remove the cover.2. Remove cotter pin nut and washer which holds the transfer case main drive gear on the rear end of the transmission main shaft. Also the main drive gear.3. Remove the transmission to transfer case screws.4. Separate the transmission from transfer case.

Dissembly of transmission:The procedure for disassembling the transmission is as follows:1. Remove the shift housing and gasket from the top of the transmission case.2. Dissemble the shift housing by removing the shift rails and forks from the shift housing3. Remove the screws and washers attaching the front main drive gearbearing retainer to transmission. Remove the retainer and the gasket.4. Remove te socket head screws from the front end transmission case.5. Tap slightly on the front end of the counter shaft to loosen the lock plate. Remove the lock plate from the slots cut in the rear ends of the counter shaft and reverse idler shaft.6. Drive the counter shaft towards the rear of the case and remove it. Re ove the gears abd the bearings.7. Remove the main shaft rear bearing adapter8. Remove the main shaft from the case9. Drive the main drive gear into the case enough to remove the oil collector10. Remove the main drive gear11. Remive the counter shaft gear set, thrust washers, needle bearing rollers and spacers12. Remove the reverse idler shaft and gear by driving the shaft into the case.

Overhauling the TransmissionThe procedure for overhauling the transmission is as follows:1. Wash the transmission case thoroughly inside and outside with cleaning solvent2. Check bearing and shaft bores and clean them3. Check the case for cracks if cracks are found or the bores are not true replace the case.4. Check and clean all gears for cracks, chipped or cracked teeth or excessive wear of the teeth.5. Check all bushings and bearings for wear or damage6. Check the first and reverse sliding gear for freedom of movement on main shaft.7. Check the clutch for free sliding on the hub8. Check the condition of the bearing retainer oil seals.Reassembling the transmission:

Assemble the transmission in the reverse order of disassembly noting the following points:1. The idler gear is fitted correctly when the chamfered side is facing the sliding gear2. Better oil circulation is provided between the transmission and transfer case by addition of drilled passagesbetween two units.3. Assemble the spacer washer and countershaft needle roller bearing in the countershaft gear hub.4. The countershaft gear set when assemble in case have 0.31 to 0.45mm end play5. When assembling the main shaft gears the low and reverse sliding gear is installed with the shift shoe groove towards the front of the transmission6. Assemble the sunchronizer unit.7. When installing the main shaft see that the needle bearing rollers in the main drive gear are correctly positioned.8. Attach the transfer case to the transmission before the unit is installed in the vehicle.GEAR BOX TROUBLESThe most common troubles of gearbox and their causes are:

1. Grinding noise in neutral:a grinding noise occurs when the engine is running and vehicle is in neutral. Its major cause is geatbox not properlty aligned with the engine causing the shaft from the f;ywheel to the gear to bend.2. Noise in gear:when the vehicle is being driven or rear wheels turning off the ground noise is heard in gear. Its causes are:a. Dry rear bearing on main shaftb. Damaged speedometer drive gearc. The noises heard in neutral will also be heard in hgear but will be more pronounced.d. Noise occurring in rear end and in the clutch may also seem to come from the gear box3. Ahum or bowl in neutral:when the engine is running it occurs due to the following reasons:a. Lack of lubricationb. Too much backlash in geartrainc. Too much end play in gears or countershaftsd. Worn shafte. Gear chipped, burned, improperly matched or badly machinedf. Gear shift forks, rubbing in grooves causing gear interferenceg. Worn bearings4. Hard shifting, sticking in gear:it occurs due to the following reasonsa. Distorted splines of the main gearb. Too shport shifter lock springc. Improper clutch adjustmentsd. Battered gear teethe. Reote control shifting mechanism out of adjustment5. Oil linkage:oil leaks from the gear box due to the following reasonsa. Too high oil level in caseb. Damaged or improperly installed gaskets or oil sealsc. Loose cover boltsd. Cracked case or covere. Loose drain or filler plug6. Slipping out of geara. Too much clearance between teeth in meshb. Insufficient mesh or gearc. Worn gears of busings or bearing retainersd. Weak or broken shifter lock springe. Remote control shifting mechanism out of adjustmentf. Improper alignment of gear box with engine

CLUTCH AND ITS FUNCTIONS

Clutch is a device used in transmission system of a motor vehicle to engage and disengage the engine to the transmission. Thus the clutch is located between engine and transmission. When the clutch is engaged, the power follows from the engine to the drive wheels through the transmission system and vehicle moves. When the clutch is disengaged, the power is not transmitted to the drive wheels and the vehicle stops while the engine is still running. The clutch is disengaged when starting the engine, when shifting the gears, when stopping the vehicleand when idling the engine. The clutch is engaged only when the vehicle is to move and is kept engaged when the vehicle is moving. The clutch also permits the gradual taking up of the load.When properly operated, it prevents jerky motion of the vehicle.

MAIN PARTS OF THE CLUTCH1. Driving menbers2. Driven member3. Operating member

Driving menbers:consists of a flywheel mounted on the engine crankshaftDriven member:consists of a disc or a platecalled clutch plateOperating member:consists of a foot pedal, linkage, release or throughout bearing, release levers and the springs necessary to ensure the proper operation of the clutch

TYPES OF CLUTCHES:

1. Friction Clutcha. Single plate clutchb. Multiplate clutchc. Cone clutch2. Centrifugal clutch3. Semi centrifugal clutch4. Diaphgrahm clutch (conical spring clutch)5. Positive clutcha. Dog and spline slutch6. Hydraulic clutch7. Electromagnetic clutch8. Vacuum clutch

CLUTCH FAULTS:DIAGNOSIS AND REMEDYThe various symptoms, their causes and remedies are shown in a tabulated format:NOSYMPTOMSCAUSESREMEDY

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.Drag or Spin

Fierceness or snatch

Slip

Rattle

Tick or Knock

Abnormal facing wear

Difficukty in engaging gear after vehicle has been stored for the length of period.

Engine runs, but car doesnot move when in gear (propeller shaft not turning)

Clutch is noisy when pedal is all the way out and engine is running

Clutch noise when pedal is depressed

Noise (thud) when clutch is released engine running and transmission in gear

Grear griding while changing gear

Clutch pedal will not come all the way back[a] Oil or grease on the driven plate facings

[b] Misalignment between the engine and splined clutch shaft.

[c] Improper pedal adjustment not allowing full movement to release bearing

[d] warped or damaged pressure plate or clutch cover

[e] driven plate hub binding on splined shaft

[f] pilot bearing or bushing or clutch shaft binding

[g] Broken facing od driven plate

[h] Dirt of foreign matter in the clutch.

[a] Oil or grease on driven plate facing.

[b] Misalignment

[c] Binding of clutch plate mechanism.

[d] Worn out driven plate facings.

[a] Oil or grease on the driven plate facings.

[b] Binding of clutch mechanism.

[c] Improper pedal adjustment indicated by lack of the requisite free or unload foot pedal movements.

[d] Weak pressure springs.

[e] Incorrect setting of release lever.

[a] Damaged drivem plate i.e., broken springs etc

[b] worn parts in release mechanism.

[c] Excessive back lash in transmission.

[d] Wear in Transmission bearings.

[e] bent or worn splined shaft.

[a] Hub splines worn due to misalignment.

[b] Worn pilot bearing.

[a] Usually caused by overleading and the resiltant excessive slippage while starting.

[a] clutch plate stuck to flywheel or seized on transmission shaft splines

[a] clutch slipping or failed

[a] clutch linkage improperly adjusted.

[a] clutch release bearing worn or damaged.

[b] flywheel spigit bearing dry.

Free play in rear axle

Cluctch not operating correctly

Fault in linkageFit new clutch plate

Check and correct the alignment

Correct pedal adjustment

Renew defective parts

Clean splines and lubricate with small quantity of high melting point greaseRenew or lubricate pilot bearing

Fit new clutch plate

Dismantle clutch from flywheel and cleen the unit. See that all working parts are free.

CAUTION: Never use petrol or paraffin for cleaning clutch.

Fit new plate and eliminate possible ingress of oil or grease. Check and correct the alignment.Free and lubricate journals.Change clutch plate.

Fit new plate and eliminate oil leak

Free and lubricate journals

Correct pedal adjustment and/or clearances.

Fit new springs

Reset the levers.

Fit new parts as necessary

Check and correct alignment and then fit new driven plateRenew pilot bearing

Avoid overloading and excessive slippage.

Jack up driving wheels, start engine in gear, press clutch pedal and apply brake. If not successful, clutch will have to be dismantled and freed off.Check for correct free play

Adjust the linkage

Replace release bearing

If particularly annoying, lubricate or release but this will entail stripping the clutch

Correct the play

Check and correct

Check and adjust

BRAKES

IntroductionOnce the vehicle is started, it must be stopped somewhere. Brakes are applied on the wheels to stop the vehicle. Brakes serve the following functions in a vehicle1. To stop and slow down the vehicle in the shortest possible distance in emergency.2. To control the vehicle to be retained when decending the hill.CLASSIFICATION OF BRAKES:Automobile brakes can be classified on various basis1. With the respect to applicationa. Foot brakeb. Hand brake2. With respect to the number of wheelsa. Two wheel brakesb. Four wheel brakes3. With respect to brake geara. Mechanical brakesb. Power brakes4. With respect to nature of power employeda. Vacuum brakesb. Air brakesc. Hydraulic brakesd. Hydrostatic brakese. Electric brakes5. With respect to the method of braking contacta. Internal expanding brakesb. External contracting brakes

MECHANICAL BRAKES

In a motor vehicle the wheel is attached to an auxillary wheel called drum. The brake shoes are made to contact this drum. In most designs two shoes are used with each drum. The brake shoes have brake linings on their outer surfaces. The shoes are generally mounted to rub against the inside surface of the drum. The shoes are held at a pivot and are fastened to a retractor spring for the braking action. When the brake pedal is pressed, the brake linkage makes the shoes to expand against the drum.

DISC BRAKE

The motor vhicles are now being fitted with the disc brakes. A disc brake consistes of a rotating disc and two friction pads which are actuated by four hydraulic wheel pistons contacining in two halves of an assembly called caliper. To apply the brake the hydraulic pressure is applied to the fluid inlet tube due to which wheel cylinder pistons force the friction pads against the rotating discs.

HYDRAULIC BRAKES

These are applied by liquid pressure. The pedal force is transmitted to the brake shoe by means of a confined liquid through a system of force transmission. The system is based upon pascals principle which states that the confined liquids transmit pressure without loss equally in all directions. The system consists of master cylinder and wheel cylinder. The master cylinder is connected by tubing to the wheel cylinders. The system is filled with the liquid called brake fluid, which is usually a mixture of glycerine and alcohol or caster oil, denatured alcohol and some additives. When the brake pedal is pressed to fluid from the master cylinderto the wheel cylinders which in turn due to high pressure pushes the brake drum against the wheel drum, thereby stopping the wheels.

BRAKE SERVICE

Following is the procedure to service the brakes:1. Check the fluid level in the master cylinder2. Check brake pedal adjustment3. Check brake pedal travel4. If the brakes pull to the one side after adjustment, check tyre pressure. Check brake linings for fpreign material and clean as required.5. Check the brake system for leaks by applying a steady pressure on the brake pedal. If the pedal falls away the brake system hs the leak somewhere. Find the leak points and remove them.6. A spongy brake pedal indicates the presence of air in the hydraulic system. The condition must be corrected by b;leeding the brakes.7. If the brakes become locked, the brakes must be released by opening the bleeder screw on any one of the wheel cylinders.

MAINTENANCE OF BRAKES1. There should be no oil or grease between the drum and the brake.2. Care should be taken to see that the excessive amount of the lubricant is not put into the rear axle bearings or the front hubs or the differential.3. Keep the grease retainers in good condition.4. Glazed surface (if any) of the brake lining may be removed by stiff wire brush.5. The drum surface should be clean. In extreme cases it may be refaced.6. Rattles in the brakes occur due to improper tension in the return springs of the brakes. This may be avoided if the springs holding the shoes are kept at proper tension.

ENGINE COOLINGMETHODS OF ENGINE COOLING

There are four methods of engine cooling:1. Air cooling2. Water cooling3. Liquid cooling4. Steam coolingMost automatic engines uses air cooling and water cooling methods. Liquid cooling and steam coling are rarely used in actua practice

AIR COOLINGIn this method of cooling, the heat is dissipated directly to the air after being conducted through the cylinder walls. Fins and flanges on the outer surfaces of the cylinders and heads serve to increase the area exposed to cooling area, raise the rate of cooling. The basic principle involved in this method is to have a current of air flowing continuously over the heated surface of thew engine from where heat is to be removed. The amount of heat dissipated depends upon the following factors:1. Surface area of the metal in contact with air.2. Rate of air flow3. Temperature difference between heated surfsace and the air4. Conductivity of the metal.

WATER COOLINGIn this method of cooling, water is circulated through water jacket around each of the combustion chamber, cylinders, valve seat and valve stems. The circulsated water, when passes through the engine jackets in the block and cylinder head, takes heat of combustion. When it passes through the radiator, it is cooled by air drawn through the radisator by fan and by air flow developed by the forward motion of the vehicle. After passing through the water the radiator the water again goes in the engine jackets.

MAINTENANCE OF THE COOLING SYSTEMThe proper operation of the cooling system gives satisfactory performance of the engine. The cylinder bores are completely surrounded by a water jacket which presents distortion of the cylinder walls, direct cooling and large water holes, properly placed in the cylinder head gasket cause more water to flow past the valve seat and carry the heat away from the valves giving positive cooling of the v alves and seats.It is recommended that the cooling system be flushed twice a year, preferably in the fall before antifreeze is added and in the spring when the antifreeze is drained. Additional flushing will aid great in rmevong rust and scale especially when used with a pushing solution. A cleaning solution should be used to loosen the rust and scale in additional flushing of the cooling system.

Flushing is accompanied through the system in a direct opposite to the normal coolant flow. The action causes the water to get behind the corrosion deposits and force them out. To do this, remove the upper and lower radiatpor hoses. Then attach a drain hose at the top of the radiator. Attach a new piece of hose to the radiator outlet at the bottom and insert the flushing gun. Connect the water hose of the flushing gun to the water line and the air hose to the air line. Turn on the water and when the radiator is full apply the air in the short blasts. Continuw=e thus flushing operatoion until the water runs clear through the top hose.COOLING SYSTEM TROUBLESS.NoTROUBLESPOSSIBLE CAUSES

1.

2.

3.

4.

5.

6.External leakage

Internal Leakage

Water loss

Poor circulation

Corrosion

Overheating[a] Loose hose clips.[b] Defective rubber hose.[c] Damaged radiator seams.[d] Excessive wear in the water pump.[e] Loose core plugs.[f] Damaged Gaskets.

[a] Defective cylinder head gasket.[b] Cracked cylinder wall.[c] Loose cylinder head bolt.

[a] Boiling.[b] External or Internal Leakage.[c] Restricted radiator or inoperative thermostat.

[a] Restriction in system.[b] Insufficient coolant.[c] inoperative water pump.[d] loose fan belt.[e] Inperative thermostat.

[a] Excessive impurity in water.[b] Infrequent flushing & draining of system.[c] Incorrect antifreeze mixture.

[a] Poor circulation due to any reason.[b] Dirty oil and sludge in the engine.[c] Radiator fins choked.[d] Incorrect ignition timing.[e] Incorrect valve timing.[f] Low oil level

COACH REPAIR WORK

1. Check an attend passenger seat cushions and upholstery, driver seat cushions.2. Check up items such as destination boards, vision mirrors, bulb horn, conductor call bell.3. Check passenger door, driver door for proper functioning and locking arrangements.4. Attend to any defector damages observed etc.5. Check for any broken window pans, if any replace with new ones.