Me Kinematics of Machinery 2 Ma

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ME1232 Kinematics of Machinery

Two Mark Questions & Answers

S4 Mechanical Engineering


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KINEMATICS OF MACHINES (ME 1232)

UNIT-1

SIMPLE MECHANISM.

TWO MARKS :-

Define 1)Kinematic Link 2)Kinematic pair 3)Kinematic chain 4)Kleins equation for

joints 5)Degree of freedom of mechanism.6)Kutzbachs relation 7)Grashoffs law8)Inversion of mechanism 9)Mechanical advantage of mechanism 10)Transmission

angle?

1)Kinematic linkIt is a resistive body which go to make a part of a machine having relative

motion between them.

2)Kinematic pair.When two links are in contact with each other it is known as a pair.If the pair

makes constrain motion it is known as kinematic pair.3)Kinematic chain.

When a number of links connected in space make relative motion of any point ona link with respect to any other point on the other link follow a definite law it is known as

kinematic chain.

4)Kleins equation for joints.

h-Higher pair jointl-Number of links

j-Lower pair joint

5)Degree of freedom. Of mechanism.

It is defined as the minimum number of input parameters which must beindependently controlled inorder to bring the mechanism into a useful engineering

purpose.

6)Kutzbachs relation.

n-Degree of freedom.

l-Number of links.

h-Higher pair joint

j-Lower pair joint.7)Grashoffs law.

Sum of shortest link length and sum of longest link length is not greater than the

sum of remaining link length.8)Inversion of mechanism.

The method of obtaining different mechanism by fixing different links in a

kinematic chain is known as inversion of mechanism.9)Mechanical advantage of mechanism.


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It is defined as the ratio of output torque to the input torque also defined as the

ratio of load to effort.10)Transmission angle.

The acute angle between follower and coupler is known as transmission angle.

11)Toggle position.

If the driver and coupler lie in the same straight line at this point mechanicaladvantage is maximum.Under this condition the mechanism is known as toggle position.

12)List out few types of rocking mechanism?

Pendulam motion is called rocking mechanism.1.Quick return motion mechanism.

2.Crank and rocker mechanism.

3.Cam and follower mechanism.13)Define pantograph?

It is device which is used to reproduce a displacement exactly in a enlarged

scale.14)Name the application of crank and slotted lever quick return motion mechanism?

1.Shamping machines.2.Siotting mechanism.

3.Rotary internal combustion engine.15)Define structure?

It is an assemblage of a number of resistant bodies having no relative motion between

themand meant for carrying loads having straining action.16)What is simple mechanism?

A mechanism with four link is known as simple mechanism.

17)Define mechanism?When one of the link of a kinematic chain is fixed,the chain is known as a mechanism.

18)Define equivalent mechanism?

The mechanism, that obtained has the same number of the degree of freedom,as the

original mechanism called equivalent mechanism.19)Define single slider crank chain mechanism?

A single slider crank chain is a modification of the basic four bar chain. It consist of

one sliding pair and three turning pair.20)Define double slider crank chain mechanism?

A kinematic chain which consist of two turning pair and two sliding pair is

known as double slider crank mechanism.

16 MARKS : -

1) Explain (A)Classification of kinematic link?

(B) 1)Indexing mechanism 2)Snap action mechanism 3)Motion

adjustment mechanism 4)Scott Russel mechanism.

(A)Classification of kinematic link

(a)Classification based on relative motion between links.1)Sliding pair.


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In a sliding pair minimum number of degree of freedom is only one.

2)Turning pair.

In a turning pair also degree of freedom is one.when two links are connected such

that one link revolves around another link it forms a turning pair.

3)Cylindrical pair.

In a cylindrical pair degree of freedom is two.If one link turns and slides along

another link it forms a cylindrical pair.

4)Rolling pair.

In a rolling pair degree of freedom is two.The object moves both linearly andangularly.

5)Spherical pair.In a spherical pair degree of freedom is three.It can both move left and right,up and

down,and rotate along the same point.

(b)Based on nature of contact.1)Lower pair.

If contact between two links is surface contact also having degree of freedom one,

then the pair is known as lower pair.Example: Sliding pair.

2)Higher pair.

If contact between two links is either point contact or line contact then the pair isknown as higher pair.

Example: Point contact-Rolling pair.

Line contact-Cylindrical pair.

3)Mechanical pair.(a)Open pair.

In this pair everything is open to the admosphere.

(b)Closed pair.In this pair everything is closed from the admosphere.

(B)Indexing mechanism.

This type of mechanism is used in automatic lathes etc.

Assume one revolution of the driver.In 360 degrees,270 degrees makes locking of

follower. Remaining 90 degrees is used to make rotation of the follower.

2)Snap action mechanism.

It is used in calling bells, bicycle bells etc.

3)Motion adjustment mechanism.

The mechanism used to adjust or modify any one of the links in a mechanism is

known as motion adjustment mechanism. Differential screw used in bench vice, pipe


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wrench, Lathe chuck and screw jack are some of the examples of motion adjustment

mechanism.

4)Scott Russel mechanism.

This is one of the mechanism to produce straight line motion mechanism.The mechanism

in which the straight line is copied from a existing straight line constrain is known asScott Russel mechanism.

2) In a crank and slotted lever quick return motion mechanism,the length of the fixedlink is 300mm and that of the crank is 150mm.Determine the maximum angle the slotted

lever will make the fixed link.Also determine the ratio of the time of cutting and return

stroke.If the length of slotted bar is 700mm, What would be the length of thestroke,assuming that the line of stroke passes through the positions of the free end of the

slotted lever?

Given data:AB=300mm=0.3m

AE=150mm=0.15mBP1=700mm=0.7m

Inclination of the slotted bar with fixed link:

LetABE=inclination of the slotted bar withthe vertical axis.

sinABE=sin(900-/2)

=AE/AB

=0.15/0.3=0.5

ABE=(90-/2)=300

Time ratio of cutting stroke to the return stroke:

We know that,

(900-/2)=30

=1200

Time for cutting stroke=

Time for return stroke=

=3600-120

0

1200

Answer=2

Length of stroke=p1p2

=2(BP1)sin(900-/2)

=2*0.7sin(900-600)

L=450mm.

3) Explain the different types of quick return motion mechanism?

Quick return motion are of two types.They are,

1)Crank and slotted lever quick return motion mechanism.2)Whitworth quick return motion mechanism


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Crank and slotted lever quick return motion mechanism.

In this mechanism,the link AC forming the turning pair is fixed.The driving crank CB

revolves with uniform angular speed about the fixed center C.A sliding block attached to

the crank pin at B slides along the slotted bar AP and thus causes AP to oscillate about

the pivorted point A.A short link PR transmits the motion from AP to ram which carriesthe tool and reciprocates along the line of stroke R1R2.In the extreme positions,AP1 and

AP2 are tangential to the circle and the cutting tool is at the end of the stroke.The forward

or cutting stroke occurs when the crank rotates from the position CB1 to CB2 in theclockwise direction.The return stroke occurs when the crank rotates from the position

CB2 to CB1 in the clockwise direction.Since the crank has uniform angular

speed,thereforeTime of cutting stroke

Time of return stroke =

Since the tool travels a distance of R1R2 during cutting and return ,therefore

length of stroke =R1R2=P1P2=2AP

Whitworth quick return motion mechanism.

In this mechanism,the link CD forming the turning pair is fixed.The driving crank CArotates at a uniform angular speed.The slider attached to the crank pin at A slides along

the slotted bar PA which oscillates at a pivoted point D.The connecting rod PR carries the

ram at R to which a cutting tool is fixed.The motion of the tool is constrained along theline RD produced along a line passing through D and perpendicular to CD.When the

driving crank CA moves from the position CA1 to CA2 through an angle in the

clockwise direction,the tool moves from left to right through a distance 2PD.Now when

the driving crank moves from the position CA1 to CA2 through an angle in theclockwise direction,the tool moves back from right to left hand end.Since CA rotates at

uniform angular velocity therefore time taken for return stroke is less than time taken for

cutting stroke.then ratio between time taken for cutting and return stroke is,

Time of cutting stroke

Time of return stroke

Explain 1)Elliptical trammels 2)Skotch yoke mechanism 3)Offset mechanism 4)Ratchet

mechanism 5)Escapement mechanism?

1)Elliptical trammels.It is one of the inversion of double slider crank chain mechanism.It is an

instrument used to draw ellipse.This inversion is obtained by fixing the slotted bar.Link 4

has two straight grooves cut in it, at right angle to each other.the link 1 and 3,are knownas sliders and forms sliding pair with link4.the link AB is a bar which forms turning pair

with link 1 and 3.When the links 1 and 3 slide along their respective grooves,such as P

traces out a ellipse on the surface of link 4.


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b) Ternary Joint

(i) If three are connected to the same junction, then is known ternary

joint

(ii) One ternary joint is equivalent to two binary joints.Illustration:

In the fig:

No of binary joints = A+B+C

= 3

Number of Ternary joints = C+E

Equivalent binary joints = 2+2

= 4

Hence total number of binary joints = 3 + 4 = 7

Based on Klines Equation

L = 2/3 (J+2)

6 = 2/3 (9)

6=6

Hence is a Kinematic Chain.

D

Link(4) Link (3)

E Link (5) C

Link (6) Link (2)

A Link (1) B


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c) Quaternary JointIf four links are connected to the same joint then it is a Quaternary joint.

One quaternary joint = Three binary joints

In the figure Number of binary joint C = 1

Number of ternary joints = A + B + E + F

Equivalent binary joints = 8

Number of quaternary joints = D, G

Equivalent binary joints = 6,

Total Number of Equivalent binary joints

J = 15

Based on Klines equation

L = 2/3 (I+2)

11 = 2/3 (17)

L.H.S. R.H.S

Link (11)

Link 5

Link 3

Link 4

Link 1

Link (2Link (8

Link 7

LinkLink 10

Link (6

A B

D

C

E

F

G


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Hence it is not a kinematics chain

In the figure if the link (DG) is deleted then it would be a kinematic chain.

The chain is represented as

5) Inversion of four Bar Kinematic Chain

The inversions of four bar kinematic chain are as follows

a) Beam Engine:

i) This is also known as crank and lever mechanism.

Link (1) Frame

Link (2) Crank

Link (3) Connecting rod

Link (4) lever arrangement

Link (5) Piston

ii) In this mechanism one link oscillated while the other rotates about fixed

link.

iii) It is used to convert the rotary motion into reciprocating motion.

Piston

Fixed frame (link (1))

Crank

Link (2)

Connecting rod

Link(3)


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b) Coupling Rod of Locomotive Engine Wheel

i) This is also known as Double Crank mechanism. Since both cranks rotate about

the points in the fixed link.

ii) It consists of four links

iii) The opposite links are equal in length,

iv) Links (1) and (3) work as two cranks

v) This motion is also known as rotary rotary converter.

c) Watts Indicator Mechanism:

i) This mechanism was invented by Watt for his steam Engine to guide the

position rod.

ii) It is also known as simple indicator.

iii) It is also known as double lever mechanism

iv) Links BC and DEF work as levers whose displacement is directly

proportional to steam or gas pressure.

A

C

B

D

B1

D1

E1

F1

F

E

C1

Piston

CylinderGas

Pressure

Link (4)

Lever 1 ac (link (4))

Lever 2 DFE (link(3))

AB Connecting rod (lin

(3))

Link (1)

A

D

B

C

Link (4)Crank (1)

Crank (2)Link (3)


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iii) Inversion of Basic Single Slider Crank Chain

Single Slider Crank Chain

a) Pendulum Of Bull Engine

i) This mechanism is obtained by fixing link (4)

ii) The crank (Link (2)) rotates while link (3) Oscillates about a pin pivoted

to the fixed link (4) at A end link (1) reciprocates

iii) This is used to supply feed water to boiler pans.

Connecting rod ( link (3))

Crank (link (2))

Piston ( link (4))

Cylinder (link (1))

Piston Piston rod Link (1)

(Slider)

Link (4)

Guide way

s

Link (2) Crank

Fly wheel

B

O

A


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b) Oscillating Cylinder Engine

1) This is used to convert reciprocally motion into rotary motion.

2) Link (3) is fixed link (3) rotates, the link (1) reciprocates, link (4)

Oscillates about a pin pivoted to the link (A)

c) Internal Rotary Combustion Engine.

(i) In the engine, the slider is replaced by a piston and link (1) by a cylinder

pivoted at O.

(ii) Odd numbers of cylinder are symmetrically placed at regular interval in same

plane.

(iii) The Crank is fixed and common to all cylinders.

(iv) The reciprocating motion is converted into rotary motion.

Link (4)

Piston

Cylinder

(link (1))

Link (3) Connecting rod

Link (2)

Crank

B

A

O


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MODULE 2

INSTANTANEOUS CENTRE, VELOCITY & ACCELARATION DIAGRAMS

TWO MARKS :-

1.What are the components of acceleration?

i Radial component of accelerationii Tangential component of acceleration

2.Write an expression for find number of instantaneous centers in a mechanism?

N=n(n-1)/2,n-no of links3.What is expression for Cariolis componenet of acceleration?

aBC=2r

Where =Angular velocity of OA

V=Linear velocity of B

4.What are the expression for radial and tangential component of acceleration?i Radial component

arOB=OB*OB

ii Tangential component

arOB=OB*OB

Where OB=Angular velocity of link OB

OB=Angular acceleration of link OB

OB=Length of link OB.

5.How can we represent the direction of linear velocity of any point on a link withrespect to another point on the same line?

The direction is perpendicular to the line joining the points.

6.Define instantaneous center axis?Instantaneous axis is a line drawn through an instantaneous center

and perpendicular to the plane of motion.

7.What are the names of instantaneous center?i. Virtual center.

ii. Centro.

iii. Rotopole.

8.How can we apply instantaneous center method to determine velocity?Consider three points A,B,C on a rigid link.I being instantaneous

Center.Let VA,VB,VC be the points A,B&C.

Then we have

VA/IA=VB/IB=VC/IC


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9.What is the objective of Kinematic analysis?

The objective of Kinematic analysis is to determine the Kinematic

quantities such as displacement,velocity and acceleration of the element in amechanism.

10.Write any two rules to locate Instantaneous center?

a) When two links are connected by a pin joint the instantaneouscenter lies on the center of the pin.

b) When two links have a sliding contact,the instantaneous center

lies at infinity in a direction perpendicular to the path of motionof slide.

16 MARKS :-

1) .PQRS is a four bar chain with link PS fixed the length of the links

PQ=62.5mm,QR=175mm,RS=112.5mm,PS=200mm.If the crank

PQ rotates at 10 rad/sec clockwise direction.Draw the velocity and

acceleration diagram when angle QPS=60 0and Q and R lie on thesame side of PS.Find the angular velocity and angular acceleration

of links QR and RS.

Space diagram: Scale

1cm=30mm


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Velocity diagram: Scale

1cm=0.1m/s

WPQ=10 rad/secVQP=VQ=0.0625*10

=0.625m/s

WQR=0.36/0.175=2rad/s

WRS=0.43/0.1125=3.8rad/s

acceleration diagram: Scale1cm=1m/s2

arPQ=V2

Q/QP=0.6252/0.0625

=6.25m/sarRS=V

2/RS=0.432/0.1125=1.644m/s2

arQR=V2QR/QR=.362/0.175=0.74m/s2

Angular acceleration of QR,QR=atQR/QR

=3.6/0.175

=20.57rad/sec2

Angular acceleration of RS,RS=atRS/RS

=5.3/0.1125=47.1rad/sec2

RESULT:

i Angular velocity of QR=2rad/sec

ii Angular velocity of RS=3.8rad/sec

iii Angular acceleration of QR=20.57rad/sec2iv Angular acceleration of RS=47.1rad/sec2

2.The crank of a slider crank mechanism rotates clockwise at a constantspeed of 300r.p.m.The crank is 150mm and the connecting rod is 600mm

long.Determine

i Linear velocity and acceleration of the midpoint of theconnecting rod.

ii Angular velocity and Angular accelerationof the connecting

rod,at a crank angle of 450

from inner dead center position.

Space diagram: Scale

1cm=75mm


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Velocity diagram: Scale

1cm=1m/sNAB=300r.p.m

WAB=2**300/60=31.41rad/secVAB=VB=AB*WAB

=0.15*31.41=4.7m/s

Acceleration diagram: Scale

1cm=50m/sec2

arBA=aB=V

2BA/BA

=4.72/0.15

=147.27m/sec2Linear Velocity,Vd=4m/s

Linear acceleration,ad=117.5m/s

Angular velocity,WBC=VBC/BC

=3.5/0.6=5.83rad/sec

2

Angular acceleration,BC=atBC/BC

=102.5/0.6=170.8rad/sec2

RESULT:

i Linear velocity=4m/s

ii Linear acceleration=117.5m/s2

iii Angular Velocity=5.83rad/sec2

iv Angular acceleration=170.8rad

/sec

2

3.An engine mechanism is shown in the following figure the crank CB=100mm

and the connecting rod BA=300mm with a center of gravity G 100mm from

point B in the position shown the crank shaft has a speed of 75 rad/sec and

an angular acceleration 0f 1200 rad/sec2.Findi Velocity of G and angular Velocity of AB

ii Acceleration of G and angular aceeleration of AB

Space diagram: Scale1cm=50mm

Velocity diagram: Scale1cm=2m/s

WCB=75rad/secVBC=VB=CB*WCB

=0.1*75

=7.5 m/s


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MODULE -3

KINAMATICS OF CAMS

TWO MARKS :-

1.What is cam ?

Cam is a rotating mechanical member used for transmitting desired motion to a

follower by direct contact

2.Classification of cam?

(i) according to cam shape(ii) according to follower movement

(iii) according to manner of constraint of the follower

3.Classify cam based on a shape ?(i) wedge cam

(ii) radial cams

(iii) spiral cams(iv) drum cams

(v) spherical cams

4.classification of follower ?

(i) According to follower shape

(ii)according to motion of follower

5.What is roller follower?

In place of a knife edge roller is provided at the contacting end of the follower

6.Spherical follower ?

In the contacting end of the follower is of spherical shape .

7.Angle of ascend ?

The angle of rotation of the cam from the position when the follower begins to rise

till it reaches its highest points . it is dHQRWHGE\

8. Angle of descend?The angle through which the cam rotates during the time the follower returns to the

LQLWLDOSRVLWLRQ,WLVGHQRWHGE\ U

9.Angle of dwell?

It is the angle through which the cam rotates while the follower remains stationary at

the highest or the lowest .


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10. Angle of action ?

The total angle moved by the cam during its rotation between the beginning of riseand the end of return of the follower

11.What is radial or disc cams?

In radial cams the follower reciprocates or oscillates in a direction perpendicular to thecam axis . The cams are all radial rams. In actual practice, radial cams are widely used

due to their simplicity and compactness.

12.What is dwell?

The zero displacement or the absence of motion of the follower during the motion of the

cam is called dwell.

13. What is classification of followers according to follower shape?

(i) Knife edge follower(ii) Roller follower

(iii) Mushroom or flat faced follower and(iv) Spherical faced or curved shoe follower

14.What is classification of follower according to the motion of the follower?

(i) Reciprocating or translating follower

(ii) Oscillating or rotating follower

15.What is classification of followers according to the path of motion ?

(i) Radial follower and(ii) Offset follower

16.What are the motion of the follower ?

The follower can have any of the following four types of motions

(i) Uniform velocity(ii) Simple harmonic motion

(iii) uniform acceleration and retardation

(iv) cycloidal motion.

17.What is the application of cam?

Closing and opening of inlet and exit value operating in IC engine .

18.What are the necessary elements of a cam mechanism?

(i) Cam-The driving member is known as the cam

(ii) Follower-The driven member is known as the follower.(iii) Frame-It supports the cam and guider the follower.

19.What is translating angle?The wedge is replaced by a flat plate with a groove . The plate cam moves back and

forth imparting a translatory motion to the follower. Thus these cams are also known as

translating cams.


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20.Write the formula for maximum velocity?

Vo (max) = 2 V

R

Vr (max)= V

R

16 MARKS :-BRIEF ANSWERS

(1) A cam rotating clockwise at a uniform speed of 1000 r.p.m Is required to

give a roller follower the motion defined below :1.Follower to move outwards through 50mm during 120 of cam rotation

2. Follower to dwell for next 60 of cam rotation

3. Follower to return to its standing position during next 90 of cam rotation

4. Follower to dwell for the next of the cam rotationThe minimum radius of the cam is 50 mm and the diameter of roller is

comm. . The line of stroke of the follower is offset by 20mm from the

axis of the cam shaft . If the displacement of the follower takes placewith uniform and equal acceleration and retardation of both the outward

and return stoke draw profile of the cam and find the maximum velocity

and acceleration during outstroke and return stroke.(16)

Displacement diagram(8)

Draw a rectangular block of length 18cm breath 50cm

Divided the block for forward dwell of return strokeDivide forward and return stroke to equal halves.

Join the diagonal of the forward and return stroke block and mark the

mid pointsThen divide the c4ntre line in to six equal parts

the remain four and in to with divide in and that corresponding points are

markedJoin all the points

Offset type;(8)Draw a circle of radius of 50mm and a roller of diameter of 10mm on

the centreNow draw another circle join center of the roller

Join them tangentially and then transfer the points from the

displacement diameter to here .Take the degree for forward dwell and out stroke and divide the form

and latter to six equal parts.


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Draw a roller at each points and joining its ends gives the cam profile.

(2)Draw the profile of the cam when the roller follower moves with cycloid

motion during outstroke and return stroke as given below:

(i) Out stroke with max displacement of 31.4mm during 180 of cam

rotation.(ii) Return stroke for the next 150of cam rotations.

(iii) Dwell for the remaining 30 of cam rotation min radius of the cam is

15mm and roller diameter of follower is 10mm . draw the profile for(iv) (a) Radial type (b)offset type(16)

Displacement diagram (4)

Draw a rectangular block of length 18cm breath 50cmDivided the block for forward dwell of return stroke

Divide forward and return stroke to equal halves.

Join the diagonal of the forward and return stroke block and mark themid points

Draw a circle of radius 4.99 mm from the end of forward stroke andstarting of return stroke and join opposite angles parallel to the block .

From the middle of the upper and lower of block parallel to the middleline .

Plot the points and join them.

Radial type:(6)

Draw the circle radius of 30mm and roller diameter 20mm

Now draw another circle join center of the rollerTake the degree for forward dwell and out stroke and divide the form

and latter to six equal parts.

Join them tangentially and then transfer the points from the displacement

Join them to the centre of the circle trans for the points from thedisplacement diagram

Draw a roller at each points and joining its ends gives the cam profile.

Offset type(6):

Draw the circle radius of 30mm roller and 20mm

Now draw another circle join center of the roller

Offset 10mm.Join them tangentially and then transfer the points from the displacement

diameter to here .

Take the degree for forward dwell and out stroke and divide the form

and latter to six equal parts.Draw a roller at each points and joining its ends gives the cam profile.

(3)A cam rotating clock wise at uniform speed pf 1000r.p.m is required to givea knife edge follower the motion defined below

(a)follower to move outward through 2.5m during 120 of cam rotation

(b)follower to dwell for next 60 of cam rotation(c) follower to set up to its starting position during next 90 of cam rotation


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(d)follower to dwell for the next of the rotation

The minimum radius of the cam is 50mm an the line of stroke of the followeris axial . If the displacement of the follower takes place with uniform and equal

acceleration and retardation on both outward and return stroke dean

the cam profile.(16)

Displacement diagram : (7)

Draw a rectangular block of length 18cmand breath of 25cm.

Divided the block for forward dwell of return strokeDivide forward and return stroke to equal halves.

Join the diagonal of the forward and return stroke block and mark the

mid pointsThen divide the c4ntre line in to six equal parts

the remain four and in to with divide in and that corresponding points are

markedJoin all the points

Cam profile (axial /radial )(9)Draw the circle of radius 50mm

Now draw the another circle from centre of the rollerJoin them axially and transfer the lengths from the displacement diagram.

Take the degree for forward dwell and out stroke and divide the form and

latter to six equal parts.Draw a roller at each points and joining its ends gives the cam profile.

Join the all points.

(4)A cam profile is to give the following motion to a knife edge follower

(i)out stroke during 60 of cam rotation.

Dwell for the next 30 of am rotation.

Return stroke dieing next60 of cam rotation .Dwell for the remaining 210 of cam rotation.

The stroke of follower is 40mm and the minimum radius of the cam is 50mm. The

follower moves with uniform velocity during both the outstroke and return stroke . Drawthe profile of the outstroke and return stroke. Drawn the profile of the cam when

(a)The axis of the follower passes through the axis of the cm shaft

(b)Axis of the follower id offset by 20mm right hand side from axis of thecam shaft . (16)

Displacement diagram (7)

Draw a rectangular block of length 18cmand breath of 40mm.

Divided the block for forward dwell of return stroke

Divide forward and return stroke to equal halves.Join the start and end of the forward and return stroke.

Radial type cam profile:(9)

Draw the circle of radius 50mm .


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Take the degree for forward dwell and out stroke and divide the form and

latter to six equal parts.Draw a roller at each points and joining its ends gives the cam profile.

Join the all points.

5.For the following data draw the profile of a cam with a flat faced follower line of

motion which passes through the cam centre.

Least radius of the cam = 30mmAngle of asce4nt an descent each = 72

Angle of dwell in lifted position =30

Follower lift =27.5mmThe out ward stroke takes place with s.h.m and the inward strokes with uniform

acceleration and retardation . If the uniform speed of rotation of the cam is 3000r.p.m

What will be the maximum velocity and acceleration during out ward and inward strokeof the follower?(16)

Displacement diagram(7)

Draw a rectangular block of length 18cmand breath of 25cm.

Divided the block for forward dwell of return stroke

Divide forward and return stroke to equal halves.Join the diagonal of forward stroke with curved fine.

Join the diagonal of return stroke and mark mid points . Divide its centre line

in to six equal parts and join the other and four points to upper and lower endsof diagonal.

Radial type:(9)

Draw the circle of radius 50mm

Now draw the another circle from centre of the roller

Join them axially and transfer the lengths from the displacement diagram.Take the degree for forward dwell and out stroke and divide the form and

latter to six equal parts.

Draw a roller at each points and joining its ends gives the cam profile.Instead of joining the points make a perpendicular line of joints its edges.

6. Draw the radial cam and explain its terminologies? (16)

Diagram : (9)

Cam profile ;(7)

The surface of the cam it comes into contact with the followerBase circle :

The smallest circle that can be drawn to the cam profile .

Trace point :The reference point on the follower to trace the cam profile.


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Pitch curve:

The locus or path of the tracing pointPrime circle :

The smallest circle drawn tangent to the pitch curve .

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The angle between the direction of the follower motion and the normal to thepitch curve.

Pitch circle :

The circle passing through the pitch points and concentric with the base circle .Pitch point :

Point on the pitch curves at which the pressure angle is maximum .

Cam angle :Angle of rotation the am for a definite displacement of the follower

Left or stroke :

Maximum displacement of the follower from the base circle of the cam.

Note: Inside ( ) indicate marks weightage

MODULE -4

GEARS & CLUTHES

TW O MARKS :-

1.Define spur gear.

A spur gear is a cylindrical gear whose tooth traces are straight line generationof the reference cylinder. They are used to transmit rotary motion between

parallel shafts.

2. Define addendum and dedendum.

Addendum is the radial distance of a tooth from the pitch circle to the top of the

tooth.

Dedendum is the radial distance of a tooth from the pitch circle to the bottom ofthe tooth.

3.Define circular pitch.It is the distance measured on the circumference of the pitch circle from a point

of one tooth to the corresponding point on the next tooth. It is denoted by Pc

Circular pitch Pc= /DT

Where D = Diameter of pitch circle.T = Number of teeth on the wheel.


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4. Define I) path of contact. II) Length of path of contact.

Path of contact: It is the path traced by the point of contact of two teeth from thebeginning to the end of engagement.

Length of path of contact: It is the length of common normal cut- off by the

addendum circles of the wheel and pinion.

5. State the law of gearing.

Law of gearing states that, the common normal at the point of contact between a pair

of teeth must always pass through the pitch point.

6.Define conjugate action.

When the tooth profiles are so shaped so as to produce a constant angular velocity ratioduring Meshing, then the surface are said to de conjugate.

7.Define angle of approach.The angle of approach is defined as the angle through which a gear rotates from the

instant a pair of teeth comes into contact until the teeth are in contact at the pitch point.

8. List out the characteristics of in volute action.a) Arc of contact.

b) Length of path of contact.

c) Contact ratio.

9.Define contact ratio.

Contact ratio is defined as the ratio of the length of arc of contact to the circular pitchathematically.

Contact ratio = length of arc of contact

Pc

Where Pc = circular path.

10. What is the advantage of in volute gear?

The most important advantage of involutes gear is that the center distance for a pairof involute gears can be varied within limits without changing the velocity ratio.

11. What are the conditions to be satisfied for interchangeability of all gears.For interchangeability of all gears, the set must have the same circular pitch, module,

diameter pitch, pressure, angle, addendum and dedendum and tooth thickness must be

one half of the circular pitch.

12.Define gear tooth system.

A tooth system is a standard which specifies the relationship between addendum,

dedendum, working depth, tooth thickness and pressure angle to attaininterchangeability of gears of tooth numbers but of the same pressure angle and pitch

13.Define cycloid.A cycloid is the curve traced by a point on the circumference of a circle which rolls


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without slipping on a fixed straight line.

14.Define clearance.

The amount by which the dedendum of a gear exceeds the addendum of the mating

gear is called clearance.

15. When in volute interference occurs.

If the teeth are of such proportion that the beginning of contact occurs before the

interference point is met then the involute proportion of the driven gear will mate anon in volute portion of the driving gear and involute interference is said to occur.

16. What is the principle reason for employing non standard gears?a) To eliminate the undercutting.

b) To prevent interference.

c) To maintain reasonable contact ratio.

17. What are the advantages and disadvantages of gear drive.Advantages:

a) It transmits exact velocity ratio.b) It has high efficiency.

Disadvantages:

a) The manufacture of gears require special tool and equipment.b) The error in cutting teeth may cause vibrations and noise during operation.

18.Define helix angle ().It is the angle between the line drawn through one of the teeth and the center line of

the shaft on which the gear is maintained.

19.Define gear ratio.The quotient of the number of teeth on the wheel divided by the number of threads onthe worm.

20.Define gear train.

A combination of gears that is used for transmitting motion from one shaft to anothershaft is known as gear train.

E.g. spur gear, spiral gear.

21. Define velocity ratio.

Velocity ratio of a simple gear train is defined as the ratio of the angular velocity of

the first gear in the train to the angular velocity of the last gear.

22. Define epicycles gear train.

In a gear train when the axes of shafts over which the gears are mounted moverelative to a fixed axis is called epicyclic gear train.

.

23.List out the function of differential gear used in the rear drive of an automobile.

a) To transmit motion from the engine shaft to the rear driving wheels.


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b ) To rotate the rear wheel of different speeds while the automobile is taking a turn.

24.Define bevel gears.

The gears which are used to connect shafts whose axes of rotation intersect are called

bevel gears.

25.Define limited slip differential.

The coupling unit which is sensitive to wheel speed causes most of the torque to be

directed to the slow moving wheel. This combination is called limited slipdifferential

.

16 MARKS :-

1. In a reverted gear train two shafts A and B are in the straight line and are geared

through an intermediate parallel

shaft C .the gears connecting A and C have a module of 2 and those connecting C andB have a module of 3.5.

Speed of B is less than 1/10 that of A .if two pinions have each 24 teeth ,find suitable

teeth for gears , the actual velocity ratio and corresponding distance of shaft C from

A.

Given data:

Module of gears 1, 2 = m A =2;

Module of gears 3,4 = m B =3.5;NB < 1/10 NA;

T1 = T3 =24;

To find:

1. Suitable teeth for gears.2. Actual velocity ratio, and

3. Distance between shafts C and A.

Solution1. SUITABLE TEETH FOR GEARS:

N B < 1/10 NA .

Let NB = 1/11 NA .We know that for reverted gear train

R1 + R2 = R3 + R4

Or mAT1/2 + mAT2 /2 = mB T3/2 + mBT4/2MA(T1 +T2) = MB(T3 +T4)

2(24 + T2) = 3.5(24 + T4)

T2 =18 +1.75T4

Now speed ratio, NB/NA =T1*T3 /T2*T41/11 =24*24/T2*T4T2*T4 =6336.

Sub the value of T2 ,we get

(18 +1.7574)T4 = 6336

T4 = 56


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T2 =116.

2. ACTUAL VELOCITY RATIO.

NA/NB = T2*T4/T1*T3NA/NB =11.28.

3. DISTANCE BETWEEN SHAFTS C AND A:

C = d1 + d2/2

= mA(T1 + T2 )/2= 2(116+24)/2

C=140mm.

MODULE 5

FRICTION

TWO MARKS :-

1. Define clutch.Clutch is a transmission device of an automobile which is used to engage and

disengage the power from the engine to the rest of the system.

2. What are the types of friction clutches?

Types of friction clutches are:*Disc or plate clutches.

*Cone clutches.

*Centrifugal clutches.

3. Define centrifugal clutch.

Centrifugal clutch is being increasingly used in automobile and machines

obviously it works on the principle of centrifugal force.

4. What are the types of flat drives?The types of flat drives are:

*Compound belt drive.

*Stepped or cone pulley drive.*Fast and loose pulley.

5. Define slip.

Slip is defined as the relative motion between the belt and pulley.6. Define law of belting.

Law of belting states that the centre line of the belt, as if approaches the pulley lie

in a plane perpendicular to the axis of that pulley or must lie in the plane of the pulleyotherwise the belt will run off the pulley.

7. Rope drive: Utility.The rope drives are widely used when large power is to be transmitted

continuously from one pulley to another over a considerable distance. One advantage ofrope drives is that a number of separate driver may be from the driving pulley.

8. Belt drive: Utility.

Belt drive is commonly used for transmission of power when exact velocity ratiois not required. Generally, belt drives are used to transmit power from one pulley to

another, when the two pulleys are not more than 10 meters apart.


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9. What are the types of ropes?

The types of ropes are:*Fiber ropes.

*Wire ropes.

10. Quarter turn left drive.

The quarter turn left drive is used with shafts arranged at right angles and rotatingin one definite direction.

11. Define the velocity ratio of the belt drive.

The velocity ratio of the belt drive is defined as the ratio between the velocities ofthe driver and the follower or the driven.

12. Advantages of V-belt.

*Power transmitted is more due to wedging action in the grooved pulleys.*V-belt is more compact, quite and shock absorbing.

*The V-belt drive is positive because of negligible slip between the belt and the

groove.*High velocity ratio may be obtained.

13. Disadvantages of V-belt.*It cannot be used with large center distances.

*It is not as durable as flat belt.*It is a costlier system.

14. Circular belts or ropes.

*Ropes are circular in cross section.*It is used to transmit more power.

*Distance between two pulleys is more than 8metres.

15. Belt materials.

BELT TYPES BELT MATERIALS

Flat belts Leather, canvas, cotton & rubber.V-belts Rubberized fabric & rubber.

Ropes Cotton, hemp & manila.

16. Name the types of friction.

*Static friction.

*Dynamic friction.17. Define the angle of repose.

If the angle of inclination RIWKHSODQHWRKRUL]RQWDOLVVXFKWKDWWKHERG\EHJLQ

WRPRYHGRZQWKHSODQH7KHQWKHDQJOH LVFDOOHGWKHDQJOHRIUHSRVH

18. What is meant by frictional force?

Force of friction is always acting in the direction opposite to the direction ofmotion.

19. Why self locking screws have lesser efficiency?

Self locking needs some friction on the thread surface of the screw and hence it

needs higher effort to lift a body and hence automatically the efficiency decreases.

20. What is static friction?

It is the friction experienced by a body, when at rest.

21. What is dynamic friction?


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It is the friction experienced by the body, when in motion. The dynamic friction is

also called as kinematic friction.

22. What is co-efficient of friction?

It is defined as the ratio of the limiting friction(F) to the normal reaction(R N)

EHWZHHQWKHWZRERGLHV,WLVJHQHUDOO\GHQRWHGE\

)5N.23. Define screw jack.

The screw jack is the device used to lift the heavy loads by applying a

comparatively small effort at its handle. The working principle of screw jack is similar tothat of an inclined plane.

24. Square thread vs V-thread.

*V-thread is stronger and often moves frictional to the motion than squarethreads.

*A given load may be lifted by applying lesser force by square thread as

compared to V-threads.*V-threads are capable of taking more loads as compared to square threads.

25. What is the effort required to lift a 50tonne lorry using screw jack? (

)Q = tan

= tan= 16.64

W = 50tonne

= 50*10*9.81= 490.5KN

(IIRUWUHTXLUHGWROLIWWKHORUU\3:WDQ 4

= 490.5 tan(16.69+20)= 365.59KN.

26. Open belt drive.

The open belt drive is used with shaft arranged parallel and rotating in same

direction. The tension in the lower side will be more than in the upper side belt becauseof more tension in the lower side belt, the lower side belt is known as tight side where as

the upper side is known as the slack side.

27. Open belt drive with one idler pulley.

Idler pulleys are provide to obtain high velocity ratio and when the required belt

tension cannot be obtained by other means. Idler pulley is also known as jockey pulley.


31/33

16 MARKS :-

1) Explain limiting of friction.Draw a neat sketch of a body over the surface with all the

forcesacting on it.

Consider a body of weight W is lying on a rough horizontal body B as shown infigure. In this position(a), body A is in equilibrium under the action of its own weight W,

and the normal reaction RN of B on A. now small force is applied to the body, it does not

move because of the frictional force which prevent the motion. This shows applied forceP1 is exactly balanced by the force of friction F1.

Now increase the applied force to P2 as shown in fig (1) it is still found to be in

equilibrium. This means that the force of friction has also increased to a value of F 2 = P2.

Thus every time the efforts increased the force of friction is also increases, so as tobecome exactly equal to the applied force. There is however, a limit beyond which the

force of friction cannot increase as shown in fig (d). After this, any increase in the applied

effort will not lead to any further increase in the force of friction as shown in fig (e), thusthe body A begins to move in the direction of the applied force. This maximum value of

frictional force, which comes into play, when a body just begins to slide over the surface

of the other body, is known as limiting force of friction or simply limiting friction. It maybe noted that when the applied force is less than the limiting friction, the body remains at

rest, and the friction into play is called static friction.

2. Explain with neat sketch the working of centrifugal clutch. Deduce theexpression for

the total torque transmitted.Draw the required figure.

Centrifugal clutch works on the principle of centrifugal force. The driving shaft

carries the shoes and springs. While the drivers shaft is connected to the pulley. Shoes are

mounted radially and the springs keep them away from inner rim of the pulley. When the

centrifugal force is less than the spring force, brake lining cannot make any contact withthe pulley rims.

Let


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n = no: of shoes.

m = mass of each shoe.R = inside radius of the pulley rim.

N = speed of pulley.

w = angular speed of pulley.

w1 = angular speed at which the begins.Centrifugal force on each shoe Fc = mwrSpring force exerted by each spring Fs = mw1r

Net force on the shoe =Fc-Fs

=mwr-mw1r

)ULFWLRQDOIRUFHDFWLQJRQHDFKVKRHI )c-Fs)

Frictional torque Fr = F*R

)c-Fs) R7RWDOIULFWLRQDOWRUTXHWUDQVPLWWHG7Q )c-Fs) R

= nFR.

3) Define screw jack and screw jack with square threads.

Screw jack The screw jack is the device used to lift the heavy loads by applying a

comparatively small effort at its handle. The working principle of screw jack is similar to

that of an inclined plane.

Screw jack with square threads.

Draw a figure of screw jack with its spindle having square threads.

The load to be raised or lowered is placed on the square threaded rod. It is rotated

by the application of an effort at the end of the Tommy bar (lever). The motion of nut on

the screw is analogous to sliding along an inclined plane.

Let,

W = load to be lifted.

P = horizontal force.

l = horizontal distance between the central axis of the screw and end E of the bar.

IULFWLRQDQJOHWDQ FR-efficient of friction.DQJOHRIUHSRVH

P = the pitch of the screw.

d = mean diameter of the screw.

The nut is rotated so that the screw moves against the axial load W. it is treated as

motion upwards the inclined plane. All the forces acting on the screw are considered and

the relation.

P = :VLQ

&RV :WDQ

4. Turning moment required to overcome friction in screw jack.

Torque required to overcome friction T1 = p.d/2

:WDQ G


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When the axial load is taken up by a thrust collar, then the torque required to

overcome friction at the collar T2 1 W R.Where,

1 = co efficient of friction of the collar.

R1 = outside radius.

R2 = inside radius.R = (R1+R2)/2.

7RWDOWRUTXH777:WDQ G 1 W R.

If F is the horizontal force applied tangentially, thenT = F*L = W tDQ G

In case the nut rotates in the opposite direction, i.e. the load is to be lowered, and

then the effort applied tangentially at the end of the Tommy bar is given by

T = -F*L = -:WDQ - G

Me Kinematics of Machinery 2 Ma

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