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2 MarksVSA School of Engineering-Salem.

Department of Mechanical Engineering

KINEMATICS OF MACHINERY

Unit 1

1. Define degrees of freedom.

It is defined as the numer of input parameters !hich must e controlled

independentl" in order to ring the de#ice into a particular position.$he degrees of freedom of a mechanism %n& is gi#en "

n ' (%L-)&-2*-h

L ' +umer of links* ' +umer of *oints

h ' +umer of higher pairs.

2. What is meant by spatial mechanism?

Spatial mechanism ha#e special geometric characteristics in that all re#olute a,es

are parallel and perpendicular to the plane of motion and all prism a,es lie in the plane ofmotion.

3. Classify the constrained motion.

$here are three t"pes.

)& ompletel" constrained motion %eg. Suare ar mo#ing in a suare hole&

2& In completel" constrained motion % eg. ircular shaft in a hole&

(& Successfull" constrained motion %eg. Piston and c"linder&

4. What is meant by nmber synthesis?

E,pressing moilit" or degree of freedom of a mechanism in terms of the numerof links and the numer of pair connections of a gi#en t"pe is kno!n as numer

s"nthesis.

!. What are the some important in"ersions of for chain mechanism?

)& rank-rocker mechanism.

2& rank-crank mechanism.

(& /ocker-rocker mechanism.

#. What is toggle position?

It is the position of a mechanism at !hich the mechanical ad#antage is infiniteand the sine of angle et!een the coupler and dri#ing link is 0ero.

$. What is pantograph?

Pantograph is a de#ice !hich is used to reproduce a displacement e,actl" in an

enlarged or reduced scale. It is used in dra!ing offices1 for duplicating the dra!ings1

maps1 plans1 etc. It !orks on the principle of ar chain mechanism.

P/EPA/ED 34 5S.67E PA$/I8 9+A+A/A6

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%. What are the applications of single slider cran& mechanism?)& /otar" or 9rome engines.

2& rank and slotted le#er mechanism.

(& 7scillating c"linder engine.& 3ull engine

;&

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1$. What is meant by motion ad/stment mechanism?

$he mechanism used to ad*ust or modif" the motion of the link are kno!n asmotion ad*ustment mechanism. Motion ad*ustment is otained " !edges1 le#ers and

rack and pinion.

1%. Whether a cycle chain is &inematic chain or not?

A c"cle chain is a comination of se#eral links !ith turning pair.

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Unit 2

1. What is &inematic analysis?

$he o*ecti#e of the kinematics anal"sis is to determine the kinematic uantities

such as displacements1 #elocities and accelerations of the elements in a mechanism.

2. What is displacement?It is defined as the distance mo#ed " a od" !ith respect to a certain fi,ed point.

3. What is "ector?

A #ector is a straight line of a certain length possessing a starting point and a

terminal point at !hich it carries an arro! head.

4. Write do-n the different types of motion.

)& /ectilinear motion.2& ur#ilinear motion.

(& ircular motion.

!. What is 0ectilinear motion?

In this motion1 the particles of a od" mo#e in straight parallel paths. Such a

motion is also kno!n as $ranslator" motion or straight line motion.

#. What is Cr"ilinear motion?

In this motion1 the particles of a od" mo#e along parallel circular arcs or cur#ed

paths.

$. What is Circlar motion?

@hen all the particles of a od" tra#el in concentric circles then the motion is said

to e circular motion.

%. What is the difference bet-een "elocity and speed

Velocit" is defined as the rate of change of displacement of a od" !ith respect tothe time.

Speed is defined as the rate of change of linear displacement of a od" !ith

respect to the time.


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'. What are the different methods are sed for finding the "elocity?

)& 9raphical method.2& Anal"tical method.

1*. Write the different types of graphical method.

)& /elati#e #elocit" method.

2& Instantaneous centre method.

11. What is configration diagram?

It is a skeleton or a line diagram !hich represents a machine or a mechanism. $o

stud" the #elocit" and acceleration of an" mechanisms1 first !e ha#e to dra! the

configuration diagram. It is also kno!n as space diagram.

12. What is acceleration?

$he rate of change of #elocit" !ith respect to time is kno!n as acceleration.

13. What is deceleration?

$he negati#e acceleration is kno!n as deceleration or retardation.

14. What is meant by coincident points?

@hen a point on one link is sliding along another rotating link1 then the point is

kno!n as coincident point.

1!. What is centrode?

$he locus of all instantaneous centre is kno!n as centrode.

1#. What is space centrode?

$he locus of the instantaneous centre in space during a definite motion of theod" is called the space centrode.

1$. What is ody centrode?

$he locus of all instantaneous centre relati#e to the od" itself is called the od"centrode.

1%. What is nstantaneos a)is?

A line dra!n through an instantaneous centre and perpendicular to the plane ofmotion is called instantaneous a,is.

1'. What is a)ode?

$he locus of Instantaneous a,is is kno!n as a,ode.

2*. Write do-n the different types of nstantaneos centres.


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)& ?i,ed Instantaneous centres.

2& Permanent Instantaneous centres.(& +either fi,ed nor permanent Instantaneous centres.

21. Define ennedys theorem.

$he 8enned">s theorem states that if three odies mo#e relati#el" to each other1

the" ha#e three instantaneous centres and lie on a straight line.

22. What are properties of instantaneos centre?

)& A rigid link rotates instantaneousl" relati#e to another link at the instantaneous

centre for the configurations of the mechanism.2& $he t!o rigid links ha#e no linear #elocit" relati#e to each other at the

instantaneous centre. At this point the t!o rigid links ha#e the same linear #elocit"

relati#e to the rigid link.

23. What is anglar "elocity ratio theorem?

$he angular #elocit" ratio theorem states that the angular #elocit" ratio of an" t!oodies in planar relati#e to a third od" is in#ersel" proportional to the segments into

!hich the common instantaneous centre cuts the line of centres.

24. +)plain any t-o methods of redcing interference in gears.

). $he height of the teeth ma" e reduced.

2. $he pressure angle ma" e increased.

(. $he face of gear tooth ma" e relie#ed.

2!. What is the effects of centrifgal tension in belt dri"es?

). entrifugal tension !ill increase the tension on oth tight and slack sides.2. entrifugal tension has no effect on the po!er transmitted " the elt dri#e.


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Unit 31. What is a cam?

A cam is a rotating machine element !hich gi#es reciprocating or oscillating

motion to another element kno!n as follo!er.

2. (i"e some e)amples of cam.

)& /adial or disc cams.

2& "lindrical or arrel cams.(& End or face cams.

& @edge cams.

3. Define tangent cam.

@hen the flanks of the cam are straight and tangential to the ase circle and nose

circle the cam is kno!n as tangent cam.

4. What ate the different motions of the follo-er?

)& Bniform motion.

2& Simple harmonic motion.(& Bniform acceleration and retardation.

& "cloidal motion.

!. 5o- can high srface stress in flat faced follo-er be minimi6ed?

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$. Define d-ell period?

$he periodduring !hich the follo!er remains at rest is called d!ell period.

%. +)plain offset follo-er.

@hen the motion of the follo!er is along an a,is a!a" from the a,is of the camcentre1 it is called offset follo!er.

'. Define trace point.

It is a reference point on the follo!er and is used to generate the pitch cur#e. Incase of knife edge follo!er the knife edge represents the trace point and the pitch cur#e

corresponds to the cam profile.

1*. Define pressre angle -ith respect to cams.

It is the angle et!een the direction of the follo!er motion and a normal to thepitch cur#e. $his angle is #er" important in designing a cam profile. If the pressure angle

is too large1 a reciprocating follo!er !ill *am in its earings.

)). Define lift or stroke in cam.It is the ma,imum tra#el of the follo!er from its lo!est position to the topmost

position.

12. Define nderctting in cam. 5o- it occrs?

$he cam profile must e continuous cur#e !ithout an" loop. If the cur#ature of

the pitch cur#e is too sharp1 then the part of the cam shape !ould e lost and thereafter

the intended cam motion !ould not e achie#ed. Such a cam is said to e undercut.Bndercutting occurs in the cam ecause of attempting to achie#e too great a

follo!er lift !ith #er" small cam rotation !ith a smaller cam.

13. What do yo &no- abot nomogram?

In nomogram1 " kno!ing the #alues of total lift of the follo!er and the cam

rotation angle for each segment of the displacement diagram1 !e can read directl" the

ma,imum pressure angle occurring in the segment for a particular choice of prime curcleradius.

14. 5o- can yo pre"ent nderctting in cam?

)& 3" decreasing the follo!er lift.2& 3" increasing cam rotation angle.

(& 3" increasing the cam si0e.

1!. What do yo &no- abot gra"ity cam?

In this t"pe1 the rise of the cam is achie#ed " the rising surface of the cam and

the return " the force of gra#it" or due to the !eight of the cam.


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1#. Write the different types of follo-er.)& 8nife edge follo!er

2& /oller follo!er

(& Mushroom or flat faced follo!er& Spherical faced or cur#ed shoe follo!er.

1$. What is cam profile?

$he surface of cam !hich comes into contact !ith follo!er1 is kno!n as camprofile.

1%. What is base circle?

It is the smallest circle that can e dra!n to the cam profile. $he radius of the ase

circle is called the least radius of the cam.

1'. What is trace point?

It is a reference point on the follo!er to trace the cam profile. In case of a knife

edge follo!er1 the knife edge itself is a tracing point and in roller follo!er1 the centre ofthe roller is the tracing point.

2*. What is pitch cr"e?

$he locus or path of the tracing point is kno!n as the pitch cur#e. ?or the purpose

of la"ing out the cam profiles1 it is assumed that the cam is fi,ed and the follo!er rotates

around it.

21. What is prime circle?

$he smallest circle dra!n tangent to the pitch cur#e is kno!n as prime circle.

22. What is pressre angle?

It is the angle et!een the direction of the follo!er motion and a normal to the

pitch cur#e. $his angle is #er" important in cam design as it represents steepness of thecam profile.

23. What is pitch point?

It is the point on the pitch cur#e at !hich the pressure angle is ma,imum.

24. What is pitch circle?

It is the circle passing through the pitch point and concentric !ith the ase circle.

2!. What is cam angle?

It is the angle of rotation of the cam for a definite displacement of the follo!er.


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Unit 4

1. What is an angle of obli7ity in gear?

It is the angle et!een the common normal to t!o gear teeth at the point ofcontact and the common tangent at the pitch point. It is also called as pressure angle.

2. What is be"el gearing? 8ention its types.@hen the non-parallel or intersecting ut coplanar shafts connected " gears1 the"

are called e#el gears and the arrangement is e#el gearing.

$"pes.

)& Ske! e#el gearing2& Spiral gearing.

3. What is meant by arc of approach?

It is the portion of the path of contact from the eginning of the engagement to the

pitch point.

4. What is meant by arc of recess?It is the position of the path of contact from pitch point to the end of the

engagement to the pitch point.

!. What is meant by ,rc of contact?

It is the path traced " a point on the pitch circle from the eginning to the end of

engagement of a pair of teeth.


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#. 9tate la- of gearing.

$he la! of gearing states that for otaining a constant #elocit" ratio1 at an" instantof teeth the common normal at each point of contact should al!a"s pass through a pitch

point1 situated on the line *oining the centre of rotation of the pair of mating gears.

$. Define normal and a)ial pitch in helical gears.

+ormal pitch is the distance et!een similar faces of ad*acent teeth1 along a heli,

on the pitch c"linder normal to the teeth.

A,ial pitch is the distance measured parallel to the a,is et!een similar faces of aad*acent teeth.

%. What are the methods to a"oid interference?

). $he height of the teeth ma" e reduced.

2. $he pressure angle ma" e increased.

(. $he radial flank of the pinion ma" e cut ack.

'. What is the ad"antage -hen arc of recess is e7al to arc of approach in a meshing

gears?

@hen arc of recess eual to arc of approach1 the !ork !asted " friction is

minimum and efficienc" of dri#e is ma,imum.

1*. What do yo &no- abot tmbler gear?

$umler gears are those !hich are used in lathes for re#ersing the direction of

rotation of dri#en gears.

11. Define contact ratio.

It is the ratio of the length of arc of contact to the circular pitch is kno!n as

contact ratio. $he #alue gi#es the numer of pairs of teeth in contact.

12. Where -ill the interference occr in an in"olte pinion and gear are in mesh

ha"ing same si6e of addendm?

$here !ill e an interference et!een the tip of pinion and flank of gear.

13. Define interference.

$he phenomenon !hen the tip of tooth undercuts the roots on its mating gear is

kno!n as interference.

14. What yo meant by non standard gear teeth?

$he gear teeth otained " modif"ing the standard proportions of gear teeth

parameters is kno!n as non standard gear teeth.

1!. Define cycloidel tooth profile and in"olte tooth profile.


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A c"cloid is the cur#e traced " a point on the circumference of a circle !hich

rolls !ithout slipping on a fi,ed straight line.In#olute profile is defined as the locus of a point on a straight line !hich rolls

!ithout slipping on the circumference of a circle.

1#. Define ac&lash.

It is the difference et!een the tooth space and the tooth thickness along the pitch

circle.

3acklash ' $ooth space C $ooth thickness.

1$. What is gear train?

$!o or more gears re made to mesh !ith each other to transmit po!er from oneshaft to another. Such a comination is called a gear train.

1%. What are the types of gear trains?

). Simple gear train.

2. ompound gear train.

(. /e#erted gear train.. Epic"clic gear train.

1'. Write "elocity ratio in compond train of -heels?

Speed of last follo!er- Product of teeth on dri#es.Speed of first dri#er- Product of teeth on follo!ers.

2*. Define simple gear train.

@hen there is onl" one gear on each shaft1 it is called as simple gear train.

21. What is meant compond gear train?

@hen there are more than one gear on shaft1 it is called a compound gear train.

22. What is the ad"antage of a compond gear train o"er a simple gear train?

$he 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 otained !ith small

gears.

23. What is re"erted gear train?

@hen the a,es of the first and last !heels are co-a,ial the train is kno!n asre#erted gear train.

24. What are the e)ternally applied tor7es sed to &eep the gear train in

e7ilibrim?


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). Impart torue on the dri#ing memer.

2. /esisting or holding torue on the dri#en memer.(.

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?riction is the important factor in engineering and ph"sical applications such as

elt and ropes1 *is1 clutches and rakes1 so it is the necessar" one.If the friction e,ceeds certain #alue it !ill cause heat1 damage and !ear !hen

applied. So it is called necessar" e#il.

14. What are the belt materials?

). Leather.

2. otton or faric.

(. /uer.. 3alata.

;. +"lon.

1!. +)plain "elocity ratio.

It is defined as the ratio et!een #elocit" of the dri#er and follo!er or dri#en.

1#. 9tate the la- of belting.

La! of elting states that the centre line of the elt as it approaches the pulle"

must lie in a plane perpendicular to the a,is of the pulle" or must lie in the plane of thepulle"1 other!ise1 the elt !ill runoff the pulle".

1$. What is slip?

$he relati#e motion et!een elt and pulle" due to insufficient friction is calledslip.

1%. What is creep?

$he phenomenon of sudden contraction and e,pansions of elt !hen it passes

from slack side to tight side is called as creep.

1'. What is centrifgal effect on belts?

During operation1 as the elt passes o#er a pulle" the centrifugal effect due to itsself !eight to lift the elt from the pulle" surface. $his reduces the normal reaction and

hence the frictional resistance.

2*. What is the cross belt sed instead of open belt?

). ross elt is used !here the direction of rotation of dri#en pulle" is opposite to

dri#ing pulle".2. @here !e need more po!er transmission there !e can use cross elt dri#e.

21. What is -ipping?


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If the centre distance et!een t!o pulle"s are too long then the elt egins to

#irate in a direction perpendicular to the direction of motion of elt. $his phenomenon iscalled !ipping. It can e a#oided " idler pulle"s.

22. Why lbrication redces friction?

In practical all the mating surfaces are ha#ing roughness !ith it. It causes friction.

If the surfaces are smooth then friction is #er" less. Lurication smoothens the mating

surface " introducing oil film et!een it. $he fluids are ha#ing high smoothness than

solids and thus lurication reduces friction.

23. What yo meant by cro-ning in plley?

$he process of increasing the frictional resistance on the pulle" surface is kno!nas cro!ning. It is done in order to a#oid slipping of the elt.

24. What is bra&e?

3rake is a de#ice " means of !hich motion of a od" is retarded for slo!ing

do!n or to ring it to rest !hich !orks on the principle of frictional force1 it acts against

the dri#ing force.

2!. +)plain self energi6ing.

@hen moments of efforts applied on the reak drum and frictional force are in the

same direction1 the reaking torue ecomes ma,imum. In such a case the rake is saidto e partiall" self actuating or self energi0ing.


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