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The correct choice is (c) Vibration dampers

The best explanation: Vibration damper is also CALLED a harmonic balancer. It is mounted on the front END of the CRANKSHAFT. It CONSISTS of a damper flywheel-cum- crankshaft pulley and a driving FLANGE connected with a rubber ring in between.

The correct CHOICE is (C) 1.35-1.6

The best explanation: A TYPICAL cast STEEL for crankshaft has a carbon composition of 1.35-1.6 percentage. ALONG with carbon the stew contains chromium in 0.05-0.5 percentage, silicon 0.85-11 percentage, manganese 0.6-0.8 percentage etc.

Right choice is (c) 600

For explanation I would SAY: The ultimate tensile strength of the crankshaft material is about 600 MPA. The crankshaft must be ADEQUATELY strong, tough, hard, and should POSSESS HIGH fatigue strength. As such proper material has to be selected for the construction.

The correct choice is (b) 2

The best explanation: The CRANKSHAFT are generally of TWO types, they are ONE piece and BUILT up. In the built-up CONSTRUCTION the crankpins and journals are bolted to crank arms, which also serves as flywheels. One-piece construction is almost universally used for automotive crankshaft.

The CORRECT CHOICE is (c) Water pump

To explain: The main components of a crankshaft are the main journal, crankpins, crank webs, counterweights, and oil holes. WHEREAS the water pump has no ROLE in the crankshaft construction. The main journal is supported in the main bearing in the CRANKCASE.

The CORRECT option is (a) Cast steel

Easy explanation: The crankshaft was initially forged but LATER on casting of the crankshaft has ALSO become quite common. The cast crankshaft both steel as WELL as S.G iron have been used. The S.G iron has a high strength cast iron in which carbon is in the form of spherical modules of GRAPHITE.

Right choice is (C) Belt

To explain: The vibration damper REDUCES the torsional vibration UTILIZING the dragging effect produced by the inertia of damper FLYWHEEL. Engines with belt-driven CRANKSHAFT do not need vibration damper. The belt acts as a damper.

Correct choice is (c) 20

To explain: The DESIGN features of a crankshaft is that the crankpin length is at least 30% of its diameter,which itself USUALLY not less than 60% of the cylinder CORE. The THICKNESS of the crank web is usually about 20% of the cylinder bore size.

Right answer is (d) Blow-by

Easiest explanation: Blow bye is the condition wherein the exhaust GASSES escape from the combustion chamber and ENTER into the CRANKSHAFT and contamination of the oil TAKES place. To avoid this crankcase ventilation is provided.

Right CHOICE is (d) Flywheel

Best explanation: The flywheel ABSORBS EXCESS energy during the power stroke and GIVES out the absorbed energy during the other three STROKES. Thus it is the flywheel that keeps the crankshaft rotating at the uniform speed throughout despite uneven power impulses of engine cylinders.

Right answer is (b) Crank web

To explain: The DISTANCE between the axis of the MAIN JOURNAL and the crankpin center lines is exactly one half of the engine stroke and is CALLED crank-throw which determines the crankshaft turning EFFORT.

Correct OPTION is (a) To withstand the twisting and bending loads

To ELABORATE: The crankwebs should be ADEQUATELY STRONG to withstand the twisting and the bending loads. However increasing their size excessively would increase the inertia which would TEND to wind and unwind the crankshaft when the engine is running.

The correct CHOICE is (c) Big end

For explanation: In splash type lubrication a split is ATTACHED to the big end of the connecting ROD and set at an angle to the AXIS of the rod. The spout DIP into the sump of lubricating oil during the downward motion of the connecting rod and splashes the oil as the connecting rod moves up.

The correct option is (d) 0.35-0.45

The best explanation: The material used for the connecting ROD is either MEDIUM CARBON STEEL or alloy steel. The medium carbon steels contain 0.35-0.45 percentage carbon. The alloy steel includes nickel-chromium or chromium-molybdenum steels.

The CORRECT answer is (c) FORCE=(π×D^2/4)×maximum GAS pressure

Best explanation: The correct relationship the force acting on the PISTON is found using Force =(π×D^2/4)×maximum gas pressure where D is the cylinder bore,maximum gas pressure is in the range of MPa or N/mm^2.

Correct ANSWER is (a) Critical BUCKLING load = factor of SAFETY ×force on connecting rod

The explanation is: The correct relationship between the Critical buckling load and the force acting on the connecting rod is Critical buckling load = factor of safety ×force on connecting rod where critical buckling load is in terms of NEWTON and factor of safety is usually 5 to 6.

Correct answer is (d) Steel

To EXPLAIN: The connecting rod is generally made up of drop forging of steel or DURALUMIN. However, with the technology these days cast from MALLEABLE or spheroidal graphite cast iron. Forged connecting rods are comparatively CHEAPER and have LESS strength.

The correct answer is (b) Bending stress due to INERTIA

The best explanation: The small end of the connecting rod is subjected to TRANSLATION motion and the big end is subjected to pure rotary motion. The intermediate point moves in an elliptical orbit. The LATERAL oscillation induces inertia that acts all along the LENGTH. This TYPE of action is called whipping. The bending stress due to the inertia force is called whipping stress.

Correct answer is (d) Axial and bending stresses

For explanation I would SAY: A combination of axial and bending stresses acting on the connecting rod in operation. The axial stresses are produced DUE to CYLINDER GAS pressure and the inertia force arising on account of reciprocating motion, whereas bending stress CAUSED due to centrifugal.

Correct choice is (a) Piston and CRANKSHAFT

For explanation I would SAY: The connecting rod converts the LINEAR MOTION of the piston into rotary motion of the crankshaft. The connecting rod CONNECTS the piston and the crankshaft. The tensile strength of the connecting rod is in the range if 1034MPa.

Right option is (c) Small end to big end of the CONNECTING ROD

The explanation is: For lubrication, a rifle HOLE is drilled from the small end of the connecting rod to the big end of the connecting rod. The oil is lifted from the crankcase with higher PRESSURE and lubricates cylinder through oil rings.

Correct answer is (C) CONNECTING rod

The best EXPLANATION: BUCKLING can be experienced in a connecting rod and not in other COMPONENTS. The buckling is the deflection of the connecting rod therefore the buckling stress is found out for each material that is being used for the connecting rod.

The correct option is (c) Drop forging

The best explanation: A CONNECTING rod is drop forged COMPONENT wherein a heavy HAMMER is DROPPED from a height of 1-1.5 meters, on to a hot workpiece kept on an anvil. The force of the BLOW varies from 10-3000 Newtons.

The correct choice is (B) LENGTH between the small end and big end AXIS

To explain: The length of the connecting rod is the length from the small end axis and the big end cap axis of the connecting rod. This length also contains the shank length in it thus the length of the connecting rod is CALCULATED.

The correct answer is (a) Scavenging ratio

The explanation: The various factors necessary to select a ring for an ENGINE are dimensions of the engine block, piston design, piston DISPLACEMENT, piston SPEED, bore to stroke ratio, cooling capacity, crankcase pressure whereas scavenging ratio has no main role in piston ring selection.

Right choice is (c) 2

The best explanation: A MINIMUM of TWO COMPRESSION rings are required because of the high-pressure difference between the combustion chamber and the crankcase at the beginning of the power stroke. This difference MAY be as high as 70 atmospheres.

Correct option is (b) 10-20

The explanation is: Total seal of USA MANUFACTURES a gapless rings which though costlier, is claimed to reduce gas leakage by 10 to 20 percent when compared to a conventional RING. The ring gaps are different types depending on their cheapness.

Correct choice is (c) Silicon and manganese

The explanation: The material that is generally USED for the PISTON ring is fine-grained ALLOY cast iron CONTAINING silicon and manganese. It has good heat and wear-resisting qualities. There are two types of iron alloy in use they are gray cast iron and ductile iron.

Right option is (c) 0.07-0.12

The EXPLANATION: The end gap for the top COMPRESSION ring is controlled from 0.07 to 0.12 millimeters PER 25 mm of bore size. The second end gap should be 0.12-0.25mm wider than the top ring gap to prevent the gas buildup.

The correct choice is (a) MACHINING the narrow grooves

For explanation: The advantages of having a REDUCED ring width are better resistance to scuffing, better resistance to ring flutter, problems on ring inertia are reduced, lower PISTON HEIGHT, and CONSEQUENTLY lower engine height and the disadvantage is machining the narrow grooves I’m the piston accurately is quite difficult.

Right ANSWER is (d) Both blow bye and scuffing

Best explanation: The amount of end gap has to be determined cautiously. Excessive end gap WOULD result in blow-by and scuffing of the ring. On the other hand,the lesser the CLEARANCE would cause the ring ends to BUTT at high temperature resulting in non-uniform PRESSURE.

Right choice is (b) Composite rail scraper ring

Explanation: The composite rail scraper ring is highly useful for worn-out cylinders having OVALITY or taper in the bores. Several steel rails are chrome PLATED and have rounded ends provide a SMOOTH SCRAPING action reducing wear of CYLINDER wall.

The correct choice is (a) Proper protecting lubrication film

Easy explanation: The main cause for scuffing is overheatedengine, lack of lubrication, insufficient clearance. An overheated engine WHEREIN there is no proper cooling system and LEAKAGE of COOLANT. When a protective LUBRICATING oil film is provided no scuffing TAKES place.

Right choice is (a) Thermal set

For explanation I would say: The thermal set is DEFINED ad the percentage gap collapses when the ring closed to nominal cylinder diameter for 6 hours at 350 degrees centigrade. The value thermal set for U1 is 12.5 it depends on the MATERIAL used and the METHOD used for casting.

Correct OPTION is (a) Ring expander

Easy explanation: The primary purpose of a ring expander it to make up for the CYLINDER WEAR which happens after some time. This cylinder wear has to avoided or else it MAY lead to many wear like scuffing, rapid wear, and ring BREAKAGE as well.

Right choice is (b) EASY passage for the heat to flow from crown to CYLINDER

To EXPLAIN I would say: The PISTON ring should seal for the high-pressure gases from the combustion CHAMBER, should provide easy passage for heat flow from the piston to the crown,should maintain sufficient lubricating oil on cylinder walls throughout and should not help is detonation.

The correct answer is (a) Tin

The best I can explain: PISTON is generally COATED with tin plating to reduce the POSSIBILITY of scoring. This even helps the piston in increased the service life of the engine piston. Tin PLATED surface treatment is ANTIOXIDANT and tarnish resistant.

Right option is (c) Compression height

Best explanation: The distance between the axis of the PISTON PIN and the top of the piston crown is called compression height and determines the compression RATIO for a given engine. THUS for the same engine, a piston with lesser compression height would give a lesser compression ratio and vice VERSA.

Correct choice is (d) Spark PLUG misfire

To elaborate: Piston scuffing occurs due to excessive HEAT the piston expands and becomes tight in the cylinder. The main REASONS for this are insufficient lubrication of cylinder walls, overloading the engine, detonation. WHEREAS spark plug misfire does not affect.

The correct ANSWER is (d) DETONATION

The best I can EXPLAIN: BURNT PISTON is chiefly on account of detonation or preignition. The burning due to detonation is generally at a point farthest from the spark plug where the hot end gases rapidly release their energy.

Correct choice is (d) Increase the size of the piston skirt

To elaborate: The methods of reducing piston slap are the use of a vertical or T-slots, TAPER piston, cam ground piston, use of special ALLOYS, wire wound PISTONS, autothermic piston, bimetallic piston and offset piston whereas an increase in the piston skirt does not affect.

Correct OPTION is (d) Gravity die casting

For explanation I would say: Pistons are either cast or forged. Castings are made by gravity die-cast PROCESS USING 5-piece inner dies, a two-piece outer and usually ahead chill which can form anycast valve pockets and bowls. Core pins are used to form PINHOLES.

Right CHOICE is (a) Steel

To explain: In a wire wound piston a band of steel wire under initial tension is put between the piston pin and the oil control ring, THUS restricting the expansion of the skirt which is of SLIP TYPE or cam ground type. The main REASON to wire-wound is to avoid piston slap.

Right choice is (a) Silicon

Easiest explanation: The material added to the piston to avoid piston slap is silicon. The other ADVANTAGE of adding silicon is the piston becomes harder and thus less liable to SCUFFING and wear. HOWEVER, higher silicon CONTENT can also make the alloy brittle which leads to piston developing cracks if the detonation or pre-ignition OCCURS.

Right choice is (d) R=(swept volume+CLEARANCE volume)/clearance volume

Easy explanation: The COMPRESSION RATIO indicates the extent to which the charge in the engine is compressed. This is CALCULATED as the ratio of the volume above the PISTON at B.D.C to the volume above the piston at T.D.C.R=(swept volume+clearance volume)/clearance volume.

The correct answer is (d) Aluminum and steel

Easiest explanation: The bi-metal piston is MADE from both steel and aluminum. The skirt is formed by steel and the aluminum ALLOY cast inside of FORMS piston head and piston pin bosses. As the coefficient of thermal expansion for steel is quite small, the piston will not expand and HENCE smaller cold clearance can be maintained.

The correct answer is (b) DEFLECTOR

Easiest explanation: In a two-stroke engine a deflector is provided on the PISTON to increase the compression ratio and even in the SCAVENGING process by scavenging out the exhaust gases through the outlet port with the help of the fresh charge TRANSFERRED via the transfer port.

Correct answer is (c) 3

Easiest explanation: In a hybrid liner it is claimed that a 3mm wall thickness between cylinder BORES is sufficient on pressure-die CAST blocks, which me and REDUCED space between adjacent cylinders and hence IMPROVEMENT in overall engine packaging by OEMs.

Right option is (d) Running clearance

Explanation: Scuffing near the sealing RING area leads to localized hardening of the ring, very HIGH pressure is EXERTED against the cylinder liner RESULTING in its DISTORTION so that running clearance is deceased and the scuffing occurs near the affected area.