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Tamil Nadu HSE First Year Basic Automobile Engineering study materials
Tamil Nadu HSE First Year Basic Automobile Engineering study resources

Tamil Nadu HSE First Year Basic Automobile Engineering practice questions

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Question 1Workshop safety, hand tools and equipment

While using a bench grinder in the automobile workshop, which personal protective equipment is most important to protect the eyes from flying metal particles?

  1. A workshop apron tied at the waist
  2. Safety goggles with side shields Correct answer.
  3. A pair of cotton hand gloves worn on both hands
  4. A disposable dust mask covering the nose and mouth

Explanation

A bench grinder throws sparks, metal chips and abrasive fragments at high speed, so eye protection must resist impact from the front and side. Safety goggles with side shields are designed for this hazard. A mask, apron or ordinary glove does not protect the eyes.

Question 2Workshop safety, hand tools and equipment

A Phillips-head screw has a cross-shaped recess. Which tool should be selected to tighten it without damaging the slot?

  1. Flat chisel with a ground edge
  2. Allen key of the nearest available size
  3. Cross-head screwdriver of correct size Correct answer.
  4. Adjustable wrench with a wide jaw opening

Explanation

A cross-head screw has a cross-shaped recess that needs a driver with a matching cross-shaped tip. The correct size fills the recess so the torque is spread across the flanks and the slot is not chewed. A tool of the wrong shape cannot transmit torque properly in this recess.

Question 3Workshop safety, hand tools and equipment

When mounting a hacksaw blade in a standard frame, the teeth should point

  1. towards the handle so that the saw cuts only when the operator pulls it back
  2. away from the handle so that cutting occurs on the forward stroke Correct answer.
  3. sideways so that the blade rubs against the frame
  4. in either direction because the blade cuts on both strokes

Explanation

In a standard hacksaw frame the blade is fitted with the teeth pointing away from the handle. The saw then cuts on the forward push stroke, which lets the operator apply controlled pressure and keep the blade straight. Fitting the blade backwards makes cutting slow and can damage the teeth.

Question 4Workshop safety, hand tools and equipment

A hacksaw is to be used to cut a thin sheet-metal panel. Which blade pitch is most suitable to prevent the teeth from snagging?

  1. 18 teeth per inch
  2. 14 teeth per inch
  3. 24 teeth per inch
  4. 32 teeth per inch Correct answer.

Explanation

Thin sheet metal needs a fine-pitch blade, usually 32 teeth per inch, because several teeth then remain in contact with the thin section. This reduces snagging, tooth breakage and distortion of the sheet. Coarse blades catch on the thin edge and tear it.

Question 5Workshop safety, hand tools and equipment

An open-end spanner is marked 14 mm. This size refers to the

  1. thickness of the jaw measured at its strongest point
  2. diameter of the hole used for hanging the spanner
  3. distance across the flats of the nut it is designed to fit Correct answer.
  4. overall length of the spanner handle measured from the jaw to the end

Explanation

Spanner size markings give the width across the flats of the nut or bolt head the spanner is designed to fit. A 14 mm open-end spanner therefore fits a nut whose opposite flats are 14 mm apart. The handle length and jaw thickness are not the marked size.

Question 6Workshop safety, hand tools and equipment

A small petrol fire in the workshop is smothered with a fire blanket. This mainly removes which element of the fire triangle?

  1. Oxygen Correct answer.
  2. Heat
  3. Fuel
  4. Ignition source

Explanation

A fire blanket placed over a small petrol fire cuts off the air supply. Oxygen is therefore the element removed from the fire triangle. The fuel is still present and the hot metal can remain hot, so the blanket must be left in place until the fire is cool.

Question 7Workshop safety, hand tools and equipment

While filing a workpiece in a bench vice, a file with one safe edge is used mainly to

  1. cut faster on the forward stroke than on the return stroke of the file
  2. prevent the file from becoming clogged with metal chips
  3. remove pins from the file teeth while filing
  4. file a surface up to a shoulder without cutting the shoulder Correct answer.

Explanation

A safe edge on a file has no cutting teeth. It allows the file to run against a shoulder or corner while the toothed face cuts the required surface, so the shoulder is not damaged. It does not increase cutting speed or clear chips.

Question 8Workshop safety, hand tools and equipment

A torque wrench is used in engine assembly mainly to

  1. tighten a fastener to a specified torque without over-tightening Correct answer.
  2. loosen a seized nut by applying a long leverage
  3. check the hardness of a cylinder head bolt
  4. measure the length of a bolt before fitting

Explanation

A torque wrench is set to a specified torque and releases or signals when that value is reached. This gives a controlled clamp load and prevents over-tightening, which can stretch or break a bolt. It is not a breaker bar or a hardness tester.

Question 9Workshop safety, hand tools and equipment

Before mounting a new grinding wheel on a bench grinder, a worker suspends it and taps it lightly with a screwdriver handle. A clear ringing sound indicates that the wheel

  1. is free from cracks and is safe to mount Correct answer.
  2. needs to be dressed before the ring test
  3. has been used before and must be discarded
  4. is too hard for the work to be ground

Explanation

The ring test checks a grinding wheel for cracks before it is mounted. A clear, ringing note shows that the wheel is sound, while a dull thud suggests a crack or poor bond and the wheel must not be used. Tapping is done lightly with a non-metallic object.

Question 10Workshop safety, hand tools and equipment

A vehicle is to be raised for repair work under the chassis. Which practice is correct?

  1. Place the jack under the sump or fuel tank to get a flat lifting surface
  2. Raise the vehicle on soft ground so that the jack sinks slightly and grips
  3. Work under the vehicle while it is held only by the hydraulic jack
  4. Use the specified jacking point, chock the wheels and support on axle stands Correct answer.

Explanation

The vehicle must be on firm level ground, the wheels chocked and the jack placed only at the manufacturer's jacking point. After lifting, axle stands are placed under a strong chassis or axle point before anyone works underneath. A hydraulic jack alone can creep or fail.

Question 11Workshop safety, hand tools and equipment

A short circuit in a portable electric lamp in the automobile workshop starts a small fire in the wiring. Which extinguisher is most suitable to use on this live electrical fire?

  1. Dry sand
  2. Foam extinguisher
  3. Water-type extinguisher
  4. Carbon dioxide unit Correct answer.

Explanation

A carbon dioxide extinguisher smothers a live electrical fire and does not conduct current back to the user. It also leaves no powder residue that would damage wiring or instruments. Water and foam contain water and can conduct electricity, so they are unsafe on live equipment.

Question 12Workshop safety, hand tools and equipment

A mechanic needs to hold a tap squarely and turn it when cutting a new internal thread in a metal bracket. Which tool is designed for this task?

  1. Tap wrench Correct answer.
  2. Die stock
  3. Torque wrench
  4. Pipe wrench

Explanation

A tap wrench has adjustable jaws that grip the square shank of a tap and allow it to be turned squarely into a drilled hole. The long handles give control so the tap starts straight and is not bent. A die stock holds a die for cutting external threads, not a tap.

Question 13Workshop safety, hand tools and equipment

In engine maintenance, a feeler gauge is used mainly to measure the...

  1. diameter of a piston pin
  2. depth of a cylinder bore
  3. torque of a cylinder head bolt
  4. valve-stem-to-rocker clearance Correct answer.

Explanation

A feeler gauge is a set of thin steel leaves of known thickness, used to check small clearances such as valve clearance. The leaves are tried in the gap until the correct thickness is found. Diameters, depths and bolt torque need different instruments.

Question 14Workshop safety, hand tools and equipment

A ring spanner is chosen instead of an open-end spanner for loosening a tight, rusted nut on a chassis bracket mainly because the ring spanner...

  1. fits nuts of every size without any adjustment
  2. grips all six corners and resists slipping Correct answer.
  3. is lighter and can be swung quickly in tight spaces
  4. lets the handle be set at any offset angle

Explanation

A ring spanner encloses the nut and contacts all six corners, so the load is spread and the risk of rounding a rusted nut is lower. An open-end spanner contacts only two flats and can slip when high force is applied. The ring end is fixed, not adjustable, and does not fit every size.

Question 15Workshop safety, hand tools and equipment

Before drilling a hole in a steel plate, a centre punch is used to...

  1. enlarge the hole after the drill has passed through
  2. remove the burr from the drilled edge
  3. measure the drill diameter
  4. make a guide indentation for the drill point Correct answer.

Explanation

A centre punch makes a small conical indentation at the marked centre so the drill point does not wander when drilling starts. The indentation is made with a hammer after marking the position. It does not enlarge the hole or remove burrs.

Question 16Workshop safety, hand tools and equipment

A general-purpose high-speed steel twist drill for drilling mild steel in the workshop should have a point angle of approximately...

  1. 135°
  2. 90°
  3. 60°
  4. 118° Correct answer.

Explanation

A general-purpose twist drill for mild steel is ground to about 118° included angle. This angle gives a good balance between cutting efficiency and strength at the point. Softer materials may use a sharper angle, and harder materials a blunter 135° point.

Question 17Workshop safety, hand tools and equipment

A mechanic uses an impact wrench to remove the wheel nuts of a car. Which practice is correct?

  1. Start the nut with the impact wrench and finish by hand
  2. Use a standard chrome-plated socket with an adapter
  3. Wear eye protection and seat the socket fully Correct answer.
  4. Hold the socket by hand while the wrench is running

Explanation

An impact wrench delivers high torque and can spin a socket suddenly, so the socket must be fully seated and eye protection worn. The reaction force can injure hands, so the socket should not be held by hand while the tool runs. Impact-rated sockets, not ordinary chrome sockets, are required.

Question 18Workshop safety, hand tools and equipment

A metric micrometer screw gauge has a barrel reading of 5 mm and a thimble reading of 15 divisions. If its least count is 0.01 mm, the total reading is...

  1. 5.015 mm
  2. 6.5 mm
  3. 5.15 mm Correct answer.
  4. 15.5 mm

Explanation

The total micrometer reading is the barrel reading plus the thimble reading multiplied by the least count. Here 5 mm plus 15 × 0.01 mm gives 5.15 mm. The thimble divisions are not added as whole millimetres.

Question 19Workshop safety, hand tools and equipment

A ball bearing that is to be reused must be removed from a shaft. Which practice is correct?

  1. Grip the balls with pliers and twist the bearing off
  2. Hammer the outer race while the shaft is held in a vice
  3. Heat the bearing with a flame until it falls off
  4. Pull the inner race squarely along the shaft axis Correct answer.

Explanation

When a bearing is to be reused, pulling force must be applied to the inner race, which is the part press-fitted on the shaft. The puller screw should be aligned with the shaft axis so the bearing does not cock and damage the raceways. Hammering or heating the bearing can brinell or distort it.

Question 20Workshop safety, hand tools and equipment

A broken bolt is stuck in a threaded hole and its top is below the surface. Which sequence is correct for removing it with a screw extractor?

  1. Turn the extractor clockwise first, then drill the hole
  2. Drill a hole, tap in the extractor, and turn it anticlockwise Correct answer.
  3. Use a die to cut new threads on the broken bolt before extracting
  4. Drive the extractor into the bolt with a hammer and pull it straight out

Explanation

A screw extractor is used after drilling a pilot hole in the broken bolt. The extractor has left-hand threads, so it is tapped into the hole and turned anticlockwise to grip and unscrew the bolt. Turning it clockwise would tighten the extractor rather than remove the bolt.

Question 21Fundamentals of the automobile and chassis layout

Which part of an automobile chassis forms the structural base to which the engine, transmission and body are mounted?

  1. Clutch
  2. Frame Correct answer.
  3. Battery
  4. Radiator

Explanation

The frame is the rigid structural backbone of the chassis. It supports and locates the engine, gearbox, suspension and body, and it carries the loads transmitted from the road. Without a frame or an equivalent monocoque structure, these components would have no common mounting base.

Question 22Fundamentals of the automobile and chassis layout

What is the main function of the clutch in a vehicle's power train?

  1. To engage and disengage engine power smoothly Correct answer.
  2. To multiply engine torque before it reaches the wheels
  3. To keep the road wheels aligned in a straight line
  4. To change the direction of rotation of the propeller shaft

Explanation

The clutch sits between the engine flywheel and the gearbox. It engages and disengages engine power smoothly so the vehicle can start from rest and gears can be changed without shock. It does not multiply torque or change shaft direction.

Question 23Fundamentals of the automobile and chassis layout

An axle that transmits driving torque to the road wheels is known as a:

  1. Stub axle
  2. Live axle Correct answer.
  3. Steering axle
  4. Dead axle

Explanation

A live axle both supports the road wheels and transmits driving torque to them, so it is used at the driven end of the vehicle. A dead axle supports wheels but does not drive them, while a stub axle is a short axle that carries a single wheel and is commonly used for steering.

Question 24Fundamentals of the automobile and chassis layout

In a front-engine rear-wheel-drive (FR) layout, the propeller shaft performs which function?

  1. It transmits drive to the differential Correct answer.
  2. It houses the clutch plates inside the gearbox casing
  3. It supports the front road wheels through hub bearings
  4. It carries the engine crankshaft and flywheel assembly

Explanation

In an FR layout the engine and gearbox are at the front, while the rear wheels are driven. The propeller shaft is the rotating shaft that carries drive from the gearbox output to the differential at the rear axle. It is not part of the engine, front hub or clutch housing.

Question 25Fundamentals of the automobile and chassis layout

What is the main purpose of the differential in a rear-wheel-drive vehicle?

  1. To transfer the braking force mainly to the front wheels
  2. To allow the wheels to turn at different speeds in a turn Correct answer.
  3. To increase the engine speed before the gears are engaged
  4. To lock both rear wheels together when driving straight

Explanation

When a vehicle turns, the outer wheel travels a longer path than the inner wheel. The differential lets the two driven wheels rotate at different speeds while still transmitting torque to both. This prevents tyre scrub and allows smooth cornering.

Question 26Fundamentals of the automobile and chassis layout

The steering gear box in a vehicle is used to:

  1. maintain battery charge while the engine is running
  2. absorb road shocks before they reach the chassis frame
  3. multiply the engine torque delivered to the rear axle
  4. change steering wheel rotation into wheel movement Correct answer.

Explanation

The steering gear box is placed between the steering wheel and the steering linkage. It converts the rotary motion of the steering wheel into angular movement of the front wheels and usually provides a gear reduction that makes steering easier. It does not multiply engine torque or absorb road shocks.

Question 27Fundamentals of the automobile and chassis layout

Leaf springs are commonly used in the suspension system mainly to:

  1. transmit engine torque to the road wheels
  2. reduce the turning radius of the vehicle
  3. support the load and absorb road shocks Correct answer.
  4. keep the wheel alignment fixed at all loads

Explanation

Leaf springs are flexible steel strips that support the vehicle load and absorb road shocks. They also locate the axle, but their main functions are load carrying and springing. Transmission of engine torque is a drive-line function, not a suspension function.

Question 28Fundamentals of the automobile and chassis layout

In a sliding-mesh gearbox, how is a gear engaged?

  1. By changing the effective length of the propeller shaft
  2. By sliding a gear wheel along its shaft into mesh Correct answer.
  3. By pressing a brake shoe against the gearbox drum
  4. By varying the hydraulic oil pressure inside the gearbox

Explanation

In a sliding-mesh gearbox, gears are mounted on splined shafts and a gear wheel is slid along its shaft until it meshes with the corresponding gear. This direct sliding action selects the gear ratio. Oil pressure and propeller-shaft length are not used to engage gears.

Question 29Fundamentals of the automobile and chassis layout

A rear-engine rear-wheel-drive (RR) layout is preferred in some small cars mainly because it:

  1. provides a long propeller shaft to the rear wheels
  2. places engine weight over the driven rear wheels Correct answer.
  3. requires a large floor tunnel through the cabin
  4. increases the load carried by the front wheels

Explanation

In a rear-engine rear-wheel-drive layout the engine sits over the driven rear wheels. This places more weight on the driven wheels, which can improve traction under acceleration. It also avoids a long propeller shaft, but it does not create a long shaft or a large floor tunnel.

Question 30Fundamentals of the automobile and chassis layout

Which characteristic is a direct advantage of a front-engine front-wheel-drive (FF) layout?

  1. It avoids a long propeller shaft and floor tunnel Correct answer.
  2. It always provides a 50:50 front-to-rear weight distribution
  3. It gives a heavy rear axle for better hill climbing
  4. It requires a separate differential on the front axle

Explanation

In an FF layout the engine, clutch, gearbox and final drive are grouped at the front, so drive goes directly to the front wheels. This removes the need for a long propeller shaft and the floor tunnel that usually accompanies it. It does not guarantee a 50:50 weight distribution.

Question 31Fundamentals of the automobile and chassis layout

In motor-vehicle classification, the designation 4×2 means that the vehicle has:

  1. four axles and two differentials
  2. four wheels, two of them driven Correct answer.
  3. four driven wheels and two steered wheels
  4. four forward gears and two reverse gears

Explanation

The first numeral denotes the total number of road wheels and the second denotes the number of driven wheels. A 4×2 vehicle therefore has four road wheels, with two receiving engine torque, as in a typical front-wheel-drive car.

Question 32Fundamentals of the automobile and chassis layout

In a front-wheel-drive car, the rear axle supports the rear wheels but receives no engine torque. Such an axle is called a:

  1. dead axle Correct answer.
  2. live axle
  3. driving axle
  4. fully floating axle

Explanation

An axle that merely carries part of the vehicle weight and does not transmit driving torque is a dead axle. In a front-wheel-drive car the rear axle is normally of this type, while the driven front wheels receive torque through the front driveline.

Question 33Fundamentals of the automobile and chassis layout

In automobile terminology, the chassis normally includes the frame, power plant, transmission, running gear and controls, but it does not include the:

  1. body shell Correct answer.
  2. suspension springs
  3. engine
  4. gearbox

Explanation

The chassis is the complete working assembly that supports and moves the vehicle, often called the rolling chassis when the body is absent. The body shell is mounted on the chassis and provides accommodation for passengers or goods, so it is not part of the chassis itself.

Question 34Fundamentals of the automobile and chassis layout

A slip joint is provided in the propeller shaft of a rear-wheel-drive vehicle mainly to:

  1. disengage the drive when the clutch is pressed
  2. allow the shaft length to vary as the axle moves Correct answer.
  3. increase engine torque before the final drive
  4. turn the drive through 90 degrees at the rear axle

Explanation

The rear axle moves up and down with the suspension, so the distance between the gearbox and the final drive changes. The slip joint permits the propeller shaft to slide while still transmitting torque, preventing damage to the shaft and bearings.

Question 35Fundamentals of the automobile and chassis layout

A universal joint is used at the gearbox end of a propeller shaft to:

  1. vary the speed ratio between gearbox and final drive
  2. permit angular movement between the two shafts Correct answer.
  3. transmit drive only when the wheels are straight
  4. allow the propeller shaft to lengthen and shorten

Explanation

The gearbox output and the propeller shaft are not always in a straight line because the rear axle moves with the suspension. A universal joint transmits torque while allowing the shaft to operate through a small angle.

Question 36Fundamentals of the automobile and chassis layout

In a Hotchkiss-drive rear suspension, the driving thrust and braking torque from the rear axle are transmitted to the chassis mainly by the:

  1. torque tube
  2. propeller shaft
  3. leaf springs Correct answer.
  4. shock absorbers

Explanation

In the Hotchkiss arrangement, the leaf springs are clamped to the axle and attached to the frame, so they locate the axle and carry thrust and torque. A torque tube is used in a different arrangement, where it encloses the propeller shaft and takes the reaction.

Question 37Fundamentals of the automobile and chassis layout

In a four-wheel-drive vehicle, the transfer case is fitted mainly to:

  1. split torque between the front and rear axles Correct answer.
  2. reduce wheel speed independently at each road wheel
  3. operate the clutch and gearbox as one unit
  4. change the angle between two propeller shafts

Explanation

The transfer case takes drive from the gearbox and divides it between the front and rear axles. Many transfer cases also include a low-range gear, which gives extra torque reduction for rough terrain or heavy loads.

Question 38Fundamentals of the automobile and chassis layout

The final drive of a rear-wheel-drive vehicle usually consists of a crown wheel and pinion because this arrangement:

  1. permits the propeller shaft to change length
  2. allows the rear wheels to rotate at different speeds
  3. gives fixed speed reduction and a 90-degree turn Correct answer.
  4. disengages the drive when reverse gear is selected

Explanation

The crown wheel and pinion form the final reduction gear, lowering shaft speed and increasing torque before drive reaches the axle shafts. Their bevel arrangement also turns the drive through a right angle from the propeller shaft to the axle.

Question 39Fundamentals of the automobile and chassis layout

A propeller shaft has two universal joints. Why are they normally fitted so that their yokes are in phase?

  1. To make the shaft rotate opposite to the gearbox
  2. To cancel cyclic speed variation from each joint Correct answer.
  3. To lock the rear axle against suspension movement
  4. To increase the shaft's length under heavy torque

Explanation

A single universal joint running at an angle makes the driven shaft speed up and slow down twice per revolution. With two joints correctly phased, the fluctuations cancel and the output speed remains nearly uniform, reducing vibration.

Question 40Fundamentals of the automobile and chassis layout

If a vehicle's final drive ratio is made numerically higher, what is the most likely effect?

  1. Higher road speed for the same engine speed and less wheel torque
  2. No change in torque or speed, because the gearbox controls both
  3. Greater wheel torque and lower road speed for the same engine speed Correct answer.
  4. Lower engine speed at a given road speed and reduced fuel consumption

Explanation

A numerically higher final drive ratio means more reduction: the propeller shaft turns more times for each turn of the road wheels. This multiplies torque at the wheels but lowers the vehicle speed for a given engine speed, so acceleration improves while top speed may fall.

Question 41Fundamentals of the automobile and chassis layout

Camber is defined as the angle between the wheel plane and the vertical, viewed from the front of the vehicle.

  1. Camber is the difference in distance between the front and rear of the road wheels.
  2. Camber is the angle between the steering axis and the vertical, viewed from the side of the vehicle.
  3. Camber is the angle between the wheel plane and the vertical, viewed from the front of the vehicle. Correct answer.
  4. Camber is the angle between the wheel plane and the longitudinal axis of the vehicle, viewed from above.

Explanation

Camber is the inward or outward tilt of the wheel plane from the vertical when the vehicle is viewed head-on. Positive camber tilts the top of the wheel outward, while negative camber tilts it inward, and both affect tyre wear and cornering stability.

Question 42Fundamentals of the automobile and chassis layout

In a front-engine front-wheel-drive car, the gearbox and final drive are often combined in a single unit called a:

  1. transaxle Correct answer.
  2. transfer case
  3. differential carrier
  4. propeller shaft

Explanation

A transaxle integrates the transmission and the final drive in one housing, and it drives the front wheels through half shafts. This arrangement removes the need for a long propeller shaft between a front-mounted engine and a rear axle.

Question 43Fundamentals of the automobile and chassis layout

In a conventional ladder-type chassis frame, the cross members are provided mainly to:

  1. carry the radiator and front body panels only
  2. increase torsional rigidity and prevent distortion of the side members Correct answer.
  3. permit the side members to twist independently along the whole frame
  4. shorten the wheelbase without changing the overall length

Explanation

Cross members connect the two side members and brace the ladder frame against twisting and parallelogram distortion. They help the frame carry engine, suspension and body loads while keeping the side members in correct alignment.

Question 44Fundamentals of the automobile and chassis layout

While a vehicle negotiates a turn, the inner front wheel must follow a smaller-radius path than the outer front wheel. In a conventional steering system, this condition is met by:

  1. locking the rear differential while the vehicle is turning
  2. setting both rear wheels with equal negative camber during the turn
  3. inclining the steering arms so their projections meet near the rear axle centre Correct answer.
  4. giving both front wheels exactly the same steering angle through one common track rod

Explanation

In the Ackermann layout, the steering arms are angled so that their projected centre lines intersect near the centre of the rear axle. This geometry turns the inner front wheel through a larger angle than the outer wheel, allowing both wheels to roll without excessive sideways scrub.

Question 45Engine construction and working principles

During which stroke of a four-stroke petrol engine is the air-fuel mixture drawn into the cylinder?

  1. Exhaust stroke
  2. Compression stroke
  3. Intake stroke Correct answer.
  4. Power stroke

Explanation

The intake stroke begins with the piston near top dead centre and moving downward. The descending piston lowers the cylinder pressure, and the open inlet valve allows the air-fuel mixture to be drawn in. Compression, power and exhaust strokes follow in that order.

Question 46Engine construction and working principles

Which engine component converts the reciprocating motion of the piston into rotary motion?

  1. Camshaft
  2. Crankshaft Correct answer.
  3. Flywheel
  4. Pushrod

Explanation

The piston is linked to the crankshaft through the connecting rod. As the piston moves up and down, the offset crankpin forces the crankshaft to rotate. The crankshaft then delivers torque to the flywheel and transmission.

Question 47Engine construction and working principles

In a two-stroke engine, how many revolutions of the crankshaft are needed to complete one working cycle?

  1. One Correct answer.
  2. Three
  3. Two
  4. Four

Explanation

A two-stroke engine completes the full sequence of intake, compression, power and exhaust in a single up-and-down movement of the piston. That corresponds to one revolution of the crankshaft. A four-stroke engine, by comparison, needs two revolutions.

Question 48Engine construction and working principles

What is the main function of the flywheel in a reciprocating engine?

  1. Smooth out torque fluctuations Correct answer.
  2. Raise the compression ratio
  3. Operate the valve train
  4. Atomise the fuel charge

Explanation

The flywheel stores kinetic energy during the power stroke and releases it during the other strokes. This keeps the crankshaft turning smoothly between power impulses and reduces speed fluctuation under load. It does not change the compression ratio or prepare the fuel charge.

Question 49Engine construction and working principles

Why is tappet clearance provided in the valve mechanism of an engine?

  1. To seal combustion gases inside the cylinder
  2. To lubricate the rocker arm during operation
  3. To allow for thermal expansion of valve stem Correct answer.
  4. To increase the maximum valve lift obtained

Explanation

Valve stems become longer when they are heated during engine operation. A small clearance prevents the expanded stem from holding the valve off its seat, which would cause compression loss and valve burning. The clearance is set to the manufacturer's specification when the engine is cold.

Question 50Engine construction and working principles

A four-cylinder four-stroke engine fires in the order 1-3-4-2. When cylinder 1 is on its power stroke, which cylinder is on its compression stroke?

  1. Cylinder 2
  2. Cylinder 4
  3. Cylinder 1
  4. Cylinder 3 Correct answer.

Explanation

In this firing order each cylinder begins its power stroke 180 degrees after the previous one. Cylinder 3 is the next to fire, so at the instant cylinder 1 is on power, cylinder 3 is completing compression. Cylinders 4 and 2 are on intake and exhaust respectively.