kom 2 marks q&a.docx

8/9/2019 KOM 2 MARKS Q&A.docx

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ME 3104 - Kinematics of Machinery

BHARATHIYAR COE!E O" E#!I#EERI#! A#$ TECH#OO!Y

KARAIKA-%0&%0&

$E'ARTME#T O" MECHA#ICA E#!I#EERI#!

Bharathiyar College of Engineering and Technology, Mechanical Department


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ME 3104

KI#EMATIC( O" MACHI#ERY

T)O MARK *+E(TIO#( )ITH A#()ER(

ACA$EMIC YEAR ,014 - ,01



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're.are/ By

Mr ' AYAK+MAR2 MTech

Mr#'AHA#IE2 MTech



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+#IT 1

'art A 56estions7



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1. What is Kinematics?Kinematics is the study of motion position, !elocity, acceleration". # ma$or goal of %nderstanding &inematics is to de!elop the a'ility to design a system that (ill satisfy)pecified motion re*uirements. This (ill 'e the emphasis of this class.

+. What is Kinetics?Kinetics is the study of effect of forces on mo!ing 'odies. ood &inematic design

should produce good &inetics.

-. Define in&.



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# lin& is defined as a mem'er or a com'ination of mem'ers of a mechanism

connecting other mem'ers and ha!ing relati!e motion 'et(een them. The lin& may

consist of one or more resistant 'odies. # lin& may 'e called as &inematic lin& or

element. Eg/ 0eciprocating steam engine.

. Define Kinematic 2air.Kinematic pair is a $oint of t(o lin&s ha!ing relati!e motion 'et(een them. The types

of &inematic pair are classified according to 3ature of contact lo(er pair, higher pair"

3ature of mechanical contact Closed pair, unclosed pair"



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3ature of relati!e motion )liding pair, turning pair, rolling pair, scre( pair,

spherical pair"

4. Define Kinematic ChainWhen the &inematic pairs are coupled in such a (ay that the last lin& is $oined to the

first lin& to transmit definite motion it is called a &inematic chain.Eg/ The cran& shaft of an engine forms a &inematic pair (ith the 'earings (hich are

fi5ed in a pair, the connecting rod (ith the cran& forms a second &inematic pair, the

piston (ith the connecting rod forms a third pair and the piston (ith the cylinder



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forms the fourth pair. The total com'ination of these lin&s is a &inematic chain. Eg/

a(n mo(er.

6. Define Degrees of 7reedom.8t is defined as the num'er of input parameters (hich must 'e independently

controlled in order to 'ring the mechanism in to useful engineering purposes.8t is also defined as the num'er of independent relati!e motions, 'oth translational

and rotational, a pair can ha!e.



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9. Define 2antograph.2antograph is used to copy the cur!es in reduced or enlarged scales. :ence this

mechanism finds its use in copying de!ices such as engra!ing or profiling machines.

;. What is meant 'y spatial mechanism?)patial mechanism ha!e a geometric characteristics in that all re!olute a5es are

parallel and perpendicular to the plane of motion and all prism lie in the plane of

motion.



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11. What are the important applications of a single slider cran& mechanism?1. 0otary or nome engine.+. Cran& and slotted le!er mechanism.-. scillating cylinder engine.

. Bull engine and4. :and pump.

1+. i!e some e5amples for &inematic pairs.1. Cran& and connecting rod,+. Connecting rod and piston rod, and



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-. 2iston and engine cylinder.

1-. What is meant 'y transmission angle?

8n a four 'ar chain mechanism, the angle 'et(een the coupler and the follo(er

dri!en" lin& is called as the transmission angle.

1. What are the applications of in!ersion of dou'le slider cran& chain mechanism?



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8t consists of t(o sliding pairs and t(o turning pairs. There are three important

in!ersions of dou'le slider cran& chain. 1" Elliptical trammel. +" )cotch yo&e

mechanism. -" ldham@s coupling. i!e some e5amples for &inematic pairs.

14. Write do(n the rashof@s la( for a four 'ar mechanism?

rashof@s la( states that the sum of the shortest and longest lin&s cannot 'e greater

than the sum of the remaining t(o lin&s lengths, if there is to 'e continuous relati!e

motion 'et(een t(o mem'ers.



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+#IT-,

'art A 56estions7

1. What are the important concepts in !elocity analysis?1. The a'solute !elocity of any point on a mechanism is the !elocity of that point (ith

reference to ground.



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. :o( to represent the direction of linear !elocity of any point on a lin& (ith respect to

another point on the same lin&?The direction of linear !elocity of any point on a lin& (ith respect to another point on

the same lin& is perpendicular to the line $oining the points.

4. Define Kennedy@s theorem.The Kennedy@s theorem states that if three 'odies mo!e relati!ely to each other, they

ha!e three instantaneous centers and lie on a straight line.



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6. Define displacement.8t may 'e defined as the distance mo!ed 'y a 'ody (ith respect to a fi5ed certain

fi5ed point. When there is no displacement in a 'ody it is said to 'e at rest and (hen

it is 'eing displaced, it is said to 'e in motion.

9. What are the types of motions?1. 0ectilinear motion.+. Cur!ilinear motion.-. Circular motion.

;. What are the methods for determining the !elocity of a 'ody?



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8mportant methods for determining the !elocity of a 'ody are/1. raphical method/ i" 0elati!e !elocity method

ii" 8nstantaneous centre method+. #nalytical method.


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1=. Define speed.)peed may 'e defined as the rate of change of linear displacement of a 'ody (ith

respect to the time. )ince the speed is irrespecti!e of its direction, therefore it is a

scalar *uantity.

11. What is deceleration?The negati!e acceleration is also &no(n as deceleration or retardation.

1+. Define #cceleration.The rate of change of !elocity (ith respect to time is &no(n as acceleration.



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1-. Define coincident points.When a point on one lin& is sliding along another rotating lin&, then the point is &no(n

as coincident point.

1. Define centrode.

The locus of all instantaneous centre@s i.e., 81, 8+," is &no(n as centrode.

14. Define #5ode.The locus of all instantaneous a5is is &no(n as a5ode.

16. Define Body centrode.



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The locus of all instantaneous centre relati!e to the 'ody itself is called the 'ody

centrode.

+#IT -3

1. What is synthesis?



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points at (hich the generated and desired function agree are &no(n as

precision points or accuracy points.. What is che'yche! spacing?

The 'est spacing of the precision points, for first trial is called che'yche!

spacing4. Write the freudenstein@s e*uation and its significance.

The freudenstein@s e*uation is cos"F&1cos &+cos G&-



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+#IT-4

'art A 56estions7

1. What is cam? # cam is a rotating machine element (hich gi!es reciprocating or" oscillating motion

to another element &no(n as follo(er



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+. Define tangent cam?When the flan&s of the cam are straight and tangential to the 'ase circle and nose

circle, the cam is &no(n as tangent cam.

-. Distinguish radial and cylindrical cams.

0adial cam Cylindrical cam

8n this cam, the follo(er reciprocates or" oscillates in a direction

perpendicular to the a5is.

8n this the follo(er reciprocates or" oscillates in a direction parallel to

the cam a5is.



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. What are the different motions of the follo(er? i" %niform motion, ii" )imple harmonic motion, iii" %niform acceleration and retardation, and i!" Cycloidal motion.

4. Compare 0oller and mushroom follo(er of a cam.

).3o 0oller 7ollo(er Mushroom 7ollo(er



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1. 0oller follo(ers are e5tensi!ely used (here more space is

a!aila'le.

The mushroom follo(ers are generally used (here space is limited.

+. 8t is used in stationary gas engines, oil engines and aircraft !al!es

in engines.

8t is used in cams (hich operate the !al!es in automo'ile engines.

6. E5plain offset follo(er.When the motion of the follo(er is along an a5is a(ay from the a5is of the cam

centre, it is called offset follo(er.



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9. Define trace point in the study of cams. 8t is a reference point on the follo(er and is used to generate the pitch cur!e. 8n case

of &nife edge follo(er the &nife edge represents the trace point and the pitch cur!e

corresponds to the cam profile. 8n a roller follo(er the centre of the roller represents

the trace point.

;. Define pressure angle (ith respect to cams.



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8t is the angle 'et(een the direction of the follo(er motion and a normal to the pitch

cur!e. This angle is !ery important in designing a cam profile. 8f the pressure angle is

too large, a reciprocating follo(er (ill $am in its 'earings.


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The cam profile must 'e continuous cur!e (ithout any loop. 8f the cur!ature of the

pitch cur!e is too sharp, then the part of the cam shape (ould 'e lost and thereafter

the intended cam motion (ould not 'e achie!ed. )uch a cam is said to 'e undercut.%ndercutting occurs in the cam 'ecause of attempting to achie!e too great a follo(er

lift (ith !ery small cam rotation (ith a smaller cam.

11. What do you &no( a'out 3omogram?8n 3omogram, 'y &no(ing the !alues of total lift of the follo(er " and the cam

rotation angle H" for each segment of the displacement diagram, (e can read



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directly the ma5imum pressure angle occurring n the segment for a particular choice

of prime circle radius 0=".

1+.What are the classifications of cam 'ased on the follo(er mo!ement?1" 0ise0eturn0ise 000" cams,

+" D(ell0ise0eturnD(ell D00D" cams,-" D(ell0iseD(ell0eturnD(ell D0D0D" cams," D(ell0iseD(ell D0D" cams.



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1-. What are the different types of cams?1. Wedge or" flat cams+. 0adial or" Disc cams-. )piral cams. Cylindrical or" Barrel or" Drum Cams

4. Con$ugate cams6. lo'oidal cams9. )pherical cams

1.What do you &no( a'out gra!ity cam?



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8n this type, the rise of the cam is achie!ed 'y the rising surface of the cam and the

return 'y the force of gra!ity of die to the (eight of the cam.

14. Define Trace point.8t is a reference point on the follo(er to trace the cam profile. 8n case of a &nife edge

follo(er, the &nife edge itself is a tracing point and in roller follo(er, the centre of the

roller is the tracing point.

16. Define pressure angle.



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8t is the angle 'et(een the direction of the follo(er motion and a normal to the pitch

cur!e. This is !ery important in cam design as it represents steepness of the cam

profile. 8f the pressure angle is too large, a reciprocating follo(er (ill $am in its

'earings.

19. Define 2rime circle.The smallest circle dra(n tangent to the pitch cur!e is &no(n as the prime circle.

1;. Define #ngle of #scent.



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The angle of rotation of cam from the position (hen the follo(er 'egins to rise till it

reaches its highest position is &no(n as angle of ascent. 8t is also &no(n as out

stro&e and is denoted 'y =.

1


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acceleration and retardation, the !alues (ill 'e >ero at the centre and ma5imum at

the ends of diameter.

+=. What are the different shapes of high speed cams?1. Circular #rc cam (ith flat faced follo(er

+. Tangent cam (ith reciprocating roller follo(er

+1. Define cam angle.8t is the angle of rotation of the cam for a definite displacement of the follo(er.

++. What are the classifications of follo(er 'ased on the follo(er mo!ement?



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i" 0eciprocating or" translating follo(er.ii" scillating or" rotating follo(er.

+-. Define 2itch cur!e.The locus of the tracing point is &no(n as the pitch cur!e. 7or the purpose of laying

out the cam profiles, it is assumed that the cam is fi5ed and the follo(er rotates

around it.

+. What are the classifications of the follo(er 'ased on the path of motion of the

follo(er?



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a" 0adial follo(er.'" ffset follo(er.

+4. What are the classifications of cam 'ase on the constraint of the follo(er?a" 2reloaded spring cams.'" 2ositi!e dri!e cams.c" ra!ity cams.



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+#IT

'art A 56estions7



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1. )tate la( of earing.

The la( of gearing states that for o'taining a constant !elocity ratio, at any instant of

teeth the common normal at each point of contact should al(ays pass through a

pitch point, situated on the line $oining the centre of rotation of the pair of matinggears.

+. Define normal and a5ial pitch in helical gears.



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3ormal pitch is the distance 'et(een similar face of ad$acent teeth, along a heli5 on

the pitch cylinder normal to the teeth.

#5ial pitch is the distance measured parallel to the a5is 'et(een similar faces of a

ad$acent teeth.

-. What is the ma5imum efficiency in (orm and (orm gear?

Ima5 F 1sinJ1GsinJ



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. What are the ad!antages and limitations of gear dri!e? Write any t(o.

A/8anta9es7

1. )ince there is no slip, so e5act !elocity ratio is o'tained.

+. 8t is more efficient and effecti!e means of po(er transmission.

imitations7



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1. Manufacture of gear is complicated.

+. The error in cutting teeth may cause !i'ration and noise during operation.

4. Define interference.

The phenomenon (hen the tip of tooth undercuts the roots on its mating gear is

&no(n as interference.



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6. Define cycloidal tooth profile and in!olute tooth profile.

# cycloid is the cur!e traced 'y a point on the circumference of a circle (hich rolls

(ithout slipping on a fi5ed straight line.

8n!olute profile is defined as the locus of a point on a straight line (hich rolls (ithout

slipping on the circumference of a circle.



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9. Define circular pitch and diametral pitch in spur gears.

Circular pitch pc" / 8t is the distance measured along the circumference of the pitch

circle from a point on one teeth to the corresponding point on the ad$acent tooth.

pcFLDT

Diametral pitch pD" / 8t is the ratio of num'er of teeth to the pitch circle diameter.

'$:T;$:


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;. Define Bac&slash.

8t is the difference 'et(een the tooth space and the tooth thic&ness along the pitch

circle.

Bac=s>ash : Tooth s.ace ? Tooth thic=ness


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T(o or more gears re made to mesh (ith each other to transmit po(er from one shaft

to another. )uch a com'ination is called a gear train or train of (heels.

1=. Write !elocity ratio in compound train of (heels?

)peed of last follo(er 2roduct of teeth on dri!ers

)peed of first dri!er 2roduct of teeth on follo(ers.

11. Define simple gear train.



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When there is only one gear on each shaft, it is &no(n as simple gear train.

1+. What is re!erted gear train?

When the a5es of the first and last (heels are coa5ial, the train is &no(n as re!erted

gear train.

1-. Where the epicyclic gear trains are used?



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The epicyclic gear trains are used in the 'ac& gear of lathe, differential gears of the

automo'iles, pulley 'loc&s, (rist (atches, etc.

1. Write do(n the difference 'et(een in!olute and cycloidal tooth profile.

).3o 8n!olute Tooth 2rofile Cycloidal Tooth 2rofile

1. Aariation in centre distance does not affect the !elocity ratio. The centre distance should not !ary.



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+. 2ressure angle remains constant throughout the teeth. 2ressure angle !aries. 8 t is >ero at the pitch point and ma5imum at

the start and end of engagement.

-. 8nterference occurs. 3o interference occurs.

. Wea&er teeth. )tronger teeth.

14. Define Contact 0atio.

8t is the ratio of the length of arc contact to the circular pitch is &no(n as contact ratio.

The !alue gi!es the num'er of pairs of teeth in contact.



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1. The height of the teeth may 'e reduced.+. The pressure angle may 'e increased.-. The radial flan& of the pinion may 'e cut 'ac& undercutting".

1


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Tum'ler gears are those (hich are used in lathes for re!ersing the direction of

rotation of dri!en gears.

+1. What you meant 'y nonstandard gear teeth?The gear tooth o'tained 'y modifying the standard proportions of gear teeth

parameters is &no(n as non standard gear teeth.

++. What is meant 'y compound gear train?When there are more than one gear on shaft, it is called a compound gear train.

+-. What is the ad!antage of a compound gear train o!er a simple gear train?



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The ad!antage of a compound gear train o!er a simple gear train is that a much

larger speed reduction from the first shaft to the last shaft can 'e o'tained (ith small

gears.

+. )tate the methods to find the !elocity ratio of epicyclic gear train.T(o methods are/1" Ta'ulation method.+" #lge'raic method.

+4. What is the e5ternally applied tor*ues used to &eep the gear train in e*uili'rium?1" 8mpart tor*ue on the dri!ing mem'er.



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+" 0esisting or holding tor*ue on the dri!en mem'er.-" :olding or 'ra&ing tor*ue on the fi5ed mem'er.


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