Unit Wise 16 Mark Questions

8/10/2019 Unit Wise 16 Mark Questions

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6 MARK QUESTIONS

UNITWISE

UNIT I. BASICS OF MECHANISMS

1.1. (a) Sketch a slider crank chain and its various inversions stating

actual machines which they are used in practice.

Or

(b) Draw the sketch of a mechanism in which a point traces an exact

straight line. The mechanism must of only revolute pairs prove that the

point traces an exact straight line motion.

1.2. (a) Sketch and explain briefly the following mechanisms:

(i) Quick-return motion mechanism of a shaping machine

(ii) Oscillating cylinder engine mechanism

(iii) Ratchet mechanism

(iv) Indexing mechanism.

Or

(b) Sketch and explain any four inversions of a double-slider crank

chain. Mention also the application of each inversion.

1.3. (a) Explain the inversions of double slider crank chain with a neat

sketch.

Or

(b) (i) In a crank and slotted lever quick return mechanism , the distance

between the fixed centres is 150 mm and the driving crank is 75 mm


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long. Determine the ratio of time taken to the cutting stroke to the return

stroke.

(ii) With a neat sketch explain the any one of the straight line

generating mechanisms.

1.4. (a) Determine the mobility of all mechanism shown in figure 1,2

and 3.

Figure l

Figure 2


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Figure 3

Or

(b) Sketch and explain all the inversions of double slider crank chain

mechanism.

1.5. (a) State Grashoffs law and explain the inversion of single Slider

crank chain with example.

Or

(b) Explain the following:

(i) Indexing mechanisms

(ii) Reversing Mechanism

(iii) Straight line Mechanism.

1.6. (a) Explain in detail with neat sketches, all the four inversions of a

single-slider crank chain.

Or

(b) (i) The distance between two parallel shafts is 18 mm and they are

connected by an Oldham's coupling. The driving shaft revolves at 160


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rpm. What will be the maximum speed of sliding of the tongue of the

intermediate piece along its groove?

(ii) Explain the following with a neat sketch:

(1) Elliptical trammel

(2) Scotch yoke mechanism

1.7. (a) Perform the kinematic analysis of the following Exact Straight

Line motion mechanisms.

(i) Peaucellier Mechanism

(ii) Hart's Mechanism.

Or

(b) (i) In a whitworth quick return mechanism, driving crank is 120 mm

long. The distance between the fixed center is 240 mm. The line of

stroke of ram passes through the center of rotation of slotted lever,

whose free end is connected to the ram by a connecting link.

Determine the ratio of time of cutting to time of return.

(ii) Explain any two inversion of a double slider crank mechanism

1.8. (a)

(i) Explain the inversions of four bar chain, with neat sketches.

(ii) Explain with neat sketches the following:

Offset slider mechanism

An Indexing mechanism.

Or

(b) (i) Explain the inversions of single slider crank chains, with neat

sketches.

(ii) Explain mechanical advantage and transmission angle related to

four-bar mechanisms


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UNIT II. KINEMATIC ANALYSIS

2.1. (a) Figure 12(a) shows the mechanism of a radial valve gear. The

crank OA turns uniformly at 150 revolution per minute and is pinned at

A to rod AB. The point C in the rod is guided in the circular path with D

as centre and DC as radius. The dimensions of various links are:

OA = 150 mm; AB = 550 mm; AC = 450 mm; DC = 500 mm;

BE = 350 mm. Determine velocity and acceleration of the ram E for the

given position of the mechanism.

Figure 12(a)

Or

(b) In a Whitworth quick return motion, as shown in Figure 12(b). OA is

a crank rotating at 30 revolutions per minute in a clockwise direction.

The dimensions of various links are: OA = 150 mm; OC = 10 mm;

CD = 125 mm; and DR = 500 mm.

Determine the acceleration of the sliding block R and the angular

accelerating of the slotted lever CA.


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Figure 12(b)

2.2. (a) ABCD is a four bar mechanism with the link AD fixed. The

lengths of the links are: AB = 60 mm, BC = 175 mm, CD = 110 mm

and DA = 200 mm.

The crank AB rotates at 100 rpm constant clockwise and the angleBAD = 60. At this instant.

(i) Draw the velocity diagram with suitable scale.

(ii) Find the velocity of the point C.

(iii) Find the magnitude and direction of the angular velocity of the link

BC.

(iv)Draw the acceleration diagram with suitable scale.

(v) Find the acceleration of the point C.

Or

(b) Derive necessary expressions for the velocity and acceleration of the

piston of a reciprocating engine. Assuming a set of data, illustrate the,

Calculation of velocity and acceleration.


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2.3. (a) In a toggle mechanism, as shown in the fig (1), D is constrained

to move on a horizontal path. The dimensions of the various links are:

AB = 200 mm, BC = 300 mm, OC = 150 mm and BD = 450 mm. The

crank OC is rotating in a counter clockwise direction at a speed of 180

rpm, increasing at the rate of 50 rad/s2. Determine for given

configuration,

(i) Velocity and acceleration of the slider D and

(ii) Angular velocity and angular acceleration of BD.

Or

(b) The dimensions and configuration of the four bar mechanism, shown

in fig.

P1A= 300 mm; P2B=360 mm; AB=360 mm and P1P2 = 600 mm. The

angle AP1P2 = 60. The crank P1A has a constant angular velocity of 10

rad/s in clockwise direction. Determine the angular velocities and

angular accelerations of P2B and AB and the velocity and acceleration of

the joint B.


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2.4. (a) The dimensions and configurations of the four bar mechanism,shown in figure 4. Are as follows: P1A = 30 cm; P2B = 36 cm;

AB = 36cm; P1P2=60 cm. The angle AP1P2=60. The crank P1A has an

angular velocity of 10 rad/Sec and an angular acceleration of 30

radlsec2, both clockwise. Determine the angular velocities and angular

accelerations of P2B and AB and the velocity and acceleration of the

joint B.

Fig4.

Or

(b) Synthesize a 4-bar linkage to generate the function y=x1.5

for the

interval 1 X 4. The input Crank is to start from a= 30 and have a


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range of 90o. Take three accuracy pints. Calculate the input and output

angles at the accuracy points.

2.5. (a) In the toggle mechanism as shown in fig, the slider D is

constrained to move on a horizontal path. The crank OA is rotating in

the counterclockwise direction at a speed of 180 r.p.m. The dimensions

of various links are as follows:

OA = 180mm; CB = 240 mm; AB = 360 mm and BD = 540 mm. for the

given configuration. Find:

(i) Velocity of slider

(i) Angular velocity of links AB, CB and BD

(iii) Velocities of rubbing on the pins of diameter 30mm at A and D.

Or

(b) PQRS is a four bar chain with the link PS fixed. The lengths of the

links are PQ = 62.5 mm; QR = 175 mm; RS = 112.5 mm and PS =200mm. The crank PQ rotates at 10 rad/s clockwise. Draw the velocity

and acceleration diagram when angle QPS = 60 and Q and R lie on the

same side of PS. Find the angular velocity and angular acceleration of

links QR and RS.


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2.6. (a) The following data refer to the dimensions of the links of a four-

bar mechanism: AB =50 mm; BC = 66 mm; CD= 56 mm and AD (fixed

link) = 100 mm. At the instant when L. DAB = 60, the link AB has an

angular velocity of 10.5 rad/s in the counter clockwise direction.

Determine the velocity of point C, velocity of point E on the link BC

while BE = 40 mm and the angular velocities of the links BC and

CD. Also sketch the mechanism and indicate the data.

Or

(b) Refer Fig. 12(b), showing the configuration of a slider-crank

mechanism and determine the acceleration at B & E and the angular

acceleration of the link AB. The crank rotates at 20 rad/sCounter clockwise

Fig. 12(b)

2.7. (a) A reciprocating engine mechanism shown in the figure had crank100 mm long rotates in clockwise direction with an angular velocity of

75 rad/sec and an angular acceleration of 1200 rad/sec2. The connecting

rod is 300 mm long and its center of gravity (G) is 100 mm from the

crank end. Determine Velocity and acceleration of G and Angular

velocity and angular acceleration of Connecting rod.


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Or

(b) Derive the expression for determining the angular position of the

coupler link and the output link of a four bar mechanism

UNIT- III. KINEMATICS OF CAMS

3.1. (a) The following particulars relate to a symmetrical circular cam

operating a flat faced follower :Least radius = 16 mm, nose radius = 3.2 mm, distance between cam

shaft centre and nose centre = 25 mm, angle of action of cam = 150 ,

and cam shaft speed = 600 revolution per minute. Assuming that there is

no dwell between ascent or descent, determine the lift of the valve, the

flank radius and the acceleration and retardation of the follower at a

point where circular nose merges into circular flank.

Or

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

cycloidal motion as given below:

(i) Outstroke with maximum displacement of 44mm during 180 of

cam rotation.


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

(iii) Dwell for the remaining 30 of cam rotation.

The minimum radius of the cam is 20 mm and the diameter of the roller

is 10 mm. The axis of the roller follower passes through the cam shaft

axis

3.2. (a) The line of action of a roller follower is offset by 12 mm to the

right of the axis of the cam shaft axis. Draw the displacement diagram

and the profile of the cam for the following requirements:

(i) Follower to move outward through 30 mm during 100 degrees

of cam rotation.

(ii) Follower to dwell for 20 degrees of cam rotation.(iii) Follower to return to initial position during 90 degrees of cam

rotation.

(iv) Follower to dwell for the remaining period of cam rotation.

The minimum radius of the cam is 35 mm. The radius of the roller is 20

mm. The outward and return strokes take place with Simple Harmonic

motion.

Or

(b) The following data refers to a 'Circular-arc cam' working with a flat

faced reciprocating follower.

Minimum radius of cam= 30 mm, total angle of cam action= 120,

radius of circular arc = 80 mm, and nose radius = 10 mm.

Find:(i) The distance of the centre of the nose circle from the cam axis.

(ii) The angle through which the cam turns when the point of

contact moves from the junction of minimum radius arc and circular arc

to the junction of nose arc and circular arc,


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(iii) Velocity and acceleration of the follower when the cam has

turned through an angle of 20 from the beginning point of lift. The

angular velocity of the cam is 10 rad/s.

3.3. (a) Draw the cam profile of a cam to raise a valve with SHM

through 50 mm in 120 of cam rotation keep it fully raised through 30

of cam rotation and to lower it with harmonic motion in 60 of cam

rotation.

The valve remains closed during the rest of the revolution. The diameter

of the roller is 20 mm and the minimum radius of the cam is 25 mm. The

diameter of the cam shaft is 25 mm. The axis of the valve rod passes

through the axis of the cam shaft. If the cam rotates at uniform speed of

100 rpm, determine the maximum velocity and acceleration of a valveduring rising and lowering.

Or

(b) Draw a cam profile to drive an oscillating roller follower to the

displacement for the specifications below.

(i) Follower to move outwards through an angular displacement of

15 during the first 120 of cam rotation.(ii) The follower to return to its initial position during next 120 of

cam rotation.

(iii) The follower to dwell during the next 120 of cam rotation.

The distance between the pivot centre and roller centre = 125 mm. The

distance between pivot centre and cam axis = 135 mm. Minimum radius

of the cam = 50 mm; radius of roller = 10 mm. Out stroke and return

stroke takes place with Simple Harmonic Motion.

3.4. (a) A cam drives a flat reciprocating follower, the motion defined

below :

(i) Follower to move outwards through 25 mm during 120 of cam

rotation with SHM.

(ii) Follower to move dwell for next 30 of cam rotation.


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(iii) Follower to return to its starting position during next 120 of

cam rotation with SHM.

(iv) Follower to dwell for the next goo of the cam rotation.

The minimum radius of the cam is 40 mm. Draw the profile of the cam.

Or

(b) A cam is to give the following motion to a knife-edged follower:

(i) Outstroke during 60 of cam rotation.

(ii) Dwell for the next 30 of cam rotation.

(iii) Return stroke during next 60" of cam rotation, and

(iv) Dwell for the remaining 210 of cam rotation.

The stroke of the follower is 40 mm and the minimum radius of the camis 50 mm. The follower moves with uniform velocity during both the

outstroke and return strokes. Draw the profile of the cam when the axis

of follower is off-set by 2 cm from the axis of the cam shaft.

3.5. (a) A cam is to be designed for a knife edge follower with the

following data. Cam lift = 40 mm during 90 of cam rotation with

simple harmonic motion Dwell for the next 30 During the next 60 ofcam rotation, the follower returns to its original position with simple

harmonic motion. Dwell during the remaining 180 Draw the profile of

the cam when the line of stroke is offset 20 mm from the axis of the cam

shaft. The radius of the base circle of the cam is 40mm. Determine the

maximum velocity and the acceleration of the follower during its ascent

and descent, if the cam rotates at 240 rpm.

Or

(b) Design a cam for operating the exhaust valve of an oil engine. It is

required to give uniform acceleration and retardation during opening and

closing of the valve each of which corresponds to 60 of cam rotation.

The valve must remain in the fully open position for 20 of cam rotation.


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The lift of the valve is 37.5 mm and the least radius of the cam is 40

mm. The follower is provided with a roller of radius 20 mm and its line

of stroke passes through the axis of the cam.

3.6. (a) A flat faced mushroom follower is operated by a uniformly

rotating cam. The follower is raised through a distance of 25 mm in 120

rotation of the cam, remains at rest for the next 30 and is lowered

during further 120 rotation of the cam. The raising of the follower takes

place with cycloidal motion and the lowering with uniform acceleration

and retardation. However, the uniform acceleration is 2/3rd of the

uniform retardation. The least radius of the cam is 25 mm which rotates

at 300 rpm. Draw the displacement diagram and profile of the cam.

Or

(b) The following data relate to a circular cam operating a flat faced

follower:

Least diameter = 40 mm; Lift = 12 mm; Angle of action= 160; Speed=

500 rpm. If the period of acceleration of the follower is 60% of theretardation during the lift,

Determine,

(i) The main dimensions of the cam;

(ii) The acceleration at the main points.

Also determine the maximum acceleration and deceleration during the

lift.

3.7. (a) Construct a tangent cam and mention the important

terminologies on it. Also derive the expression for displacement,

velocity and acceleration of a reciprocating roller follower when the

roller has contact with the nose.

Or


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Or

(b) Draw the profile of a cam to give following motion to a reciprocating

follower with a flat face:

(i) Follower to have a stroke of 20 mm during 120 of cam

rotation.

(ii) Follower to dwell for 30 of cam rotation.

(iii) Follower to return to its initial position during 120 of cam rotation.

(iv) Follower to dwell for remaining 90 of cam rotation.

Minimum radius of cam = 25 mm. Out stroke and return stroke of the

follower are simple harmonic

UNIT- IV. GEARS

4.1. (a) Two mating involutes spur gears of 20 pressure angle have a

gear ratio of 2. The number of teeth on the pinion of 20 and its speed is

250 revolutions per minute. The module pitch of the teeth is 12 mm. Iftheaddendum on each wheel is such that the path of approach and the

path of recess on each side are half the maximum possible length each,

Find:

(i) The addendum for pinion and gear wheel;

(ii) The length of arc contact:

(iii) The maximum velocity of sliding during approach and recess.

Assume pinion to be driver.

Or

(b) In a reverted epicyclic train shown in Figure 14(b), the arm F carries

two wheels A and D and a compound wheel B-C. The wheel A meshes

with wheel B and the wheel D meshes with wheel C. The numbers of


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teeth on wheel A, D and C are 80, 48 and 72 respectively. Find the speed

and direction of wheel D and wheel A is fixed and arm F, makes

200 revolutions per minute clockwise.

Figure 14(b)

4.2. (a)

(i) What is meant by interference in gears? Explain with suitable sketch.(ii) Derive an expression for the minimum number of teeth required on

the pinion meshing with gear, to avoid interference (in terms of gear

ratio and pressure angle).

(iii) Also derive an expression for the minimum number of teeth

required on the pinion meshing with a rack, to avoid interference.

Or

(b) Figure 1 shows a compound epi-cyclic train employee to run a winch

drum. Input shaft keyed to Gear 1 is driven at 40 rpm clockwise and gear

4 is fixed. Number of teeth on each gear wheel is given in figure.

Determine the speed and direction of the drum.


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Figure 1

4.3. (a) A pair of involute spur gears with 16 pressure angle and pitch

of module 6 mm is in mesh. The number of teeth on pinion is 16 and its

rotational speed is 240 rpm. When the gear ratio is 1.75, find in order

that the interference is just avoided,

(i) Addendum on the pinion and gear wheel(ii) The length of path of contact and

(iii) The maximum velocity of sliding of teeth on either side of the

pitch point.

Or

(b) In a sun and planet type epicyclic gear train, the pitch circle diameterof the annulus is to be approximately 324 mm and the module 6 mm.

When the annulus is stationary, the three armed spider makes one

revolution for every five revolutions of the sun wheel S. Determine the

number of teeth for all the wheel and exact pitch circle diameter of

annulus.


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4.4. (a) A Gear wheel with 48 teeth of involute profile meshes with

another wheel of 30 teeth. If the module is 5 mm and a standard

addendum of one module is used. Find

(i) The length of path of contact.

(ii) The length of arc of contact.

(iii) Contact ratio.

Or

(b) An epicyclic gear train consists of internal gear A, a pinion B and a

wheel C. The wheel C is concentric with A The pinion B is carried on an

arm and gears with A and number of teeth A and C are 96 and 48

respectively, determine the speeds of B and C when the gear A is fixed

4.5. (a) With a neat sketch, Explain in detail the nomenclature of the

gear.

Or

(b) An epicyclic gear train consists of a sun wheel S, a stationaryinternal gear E and three identical planet wheels P carried on a star

shaped planet carrier C. The size of different toothed wheels are such

that the planet carrier C rotates at 1/5th of the speed of the sun wheel S.

The minimum number of teeth on any wheel is 16.The driving torque on

the sun wheel is 100 N-m. Determine number of teeth on different

wheels of the train and the torque necessary to keep the internal gear

stationary.


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4.6. (a) Two gears in mesh have a module of 8 mm and a pressure angle

of 20. The larger gear has 57 while the pinion has 23 teeth. If the

addenda on pinion and gear wheel are equal to one module, find

(i) The number of pairs of teeth in contact

(ii) The angle of action of the pinion and the gear wheel

(iii) The ratio of the sliding to rolling velocity at

(1) The beginning of contact

(2) The pitch point

(3) The end of contact.

Or

(b) In an epicyclic gear train shown in Fig. 14(b), the input S has 24teeth; P and C constitute a compound planet having 30 and 18 teeth

respectively. If all the gears are of the same pitch, find the speed ratio of

the gear train. Assume A to be fixed.

Fig. 14(b)


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4.7. (a)

(i) State and prove "Law of gearing", and thus derive the expression for

"Velocity of sliding".

(ii) Prove that the maximum length of arc of contact between a pair of

gear tooth to avoid interference is (r +R) tan.

Or

(b) (i) A Simple gear train consists of three gears, each mounted on

separate shaft as shown in the figure. The shafts are parallel. The gear 1

is the driver and the gear 3 is the follower. Gear 1 is rotating clockwise

at a speed of 750 rpm. Number of teeth on gears 1, 2 and 3 are 30, 45

and 75 respectively. Determine Speed ratio of the gear train andDirection of rotation and speed of rotation of follower.

(ii) The figure shows the planetary gear arrangement that has two inputs.

Sun gear 2 rotates at 500 rpm and arm 6 rotates at 750 rpm both

clockwise, as viewed from the left. Determine the speed and direction of

rotation of gear 5. Number of teeth (T) in various gears is shown in the

figure.


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such a length that the line of contact on each side of the pitch point has

half the maximum possible length. Determine the addendum height for

each gear wheel, length of the path of contact, arc of contact and contact

ratio.

UNIT-V. FRICTIONS

5.1. (a) A screw-jack has a square thread of mean diameter 6 cm and

pitch 0.8 cm. The co-efficient of friction at the screw thread is 0.09. A

load of 3 kN is to be lifted through 12 cm. Determine the torque required

and the work done in lifting the load through 12 cm. Find the efficiency

of the jack also.

Or

(b) (i) A load of 25 kN is supported by a conical pivot with angle of

cone as 120. The intensity of pressure is not to exceed 350 kN/m2. The

external radius is 2 times the internal radius. The shaft is rotating at 180

revolutions per minute and co-efficient of friction is 0.05. Find the

power absorbed in friction assuming uniform pressure.

(ii) An open belt running over two pulleys 1.5 m and 1.0 m diameters

connects two parallel shafts 4.80 m apart. The initial tension in the belt

when stationary is 3000N. If the smaller pulley is rotating at 600

revolutions per minute and the coefficient of friction between the belt

and the pulley is 0.3, determine the power transmitted taking centrifugal

tension into account. The mass of the belt is given as 0.673 kg/length.

5.2 (a)

(i) Derive an expression for the torque transmitted by a clutch, stating

clearly the assumptions made.


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(ii) A clutch is required to transmit 10 kW at 3000 rpm. It is of single

plate type, both sides being effective. The coefficient of friction is 0.25

and the axial pressure is limited to 8.5 N/ cm2

Determine the dimensions of the plate, assuming that the external

diameter is 1.4 times the inner diameter.

Or

(b) (i) Derive an expression for the centrifugal tension in rope drives. (8)

(ii) A rope pulley with 10 ropes and peripheral speed of 1500 m/min

transmits 100 kW. The angle embraced by each rope is 180, the angle

of groove is 40 and the coefficient of friction is 0.2. Find the tensions

on the tight and slack sides of the rope, allowing for centrifugal tension.The weight of each rope is 6 N per metre run.

5.3. (a) A leather belt transmit 10 kW from a motor running at 600 rpm

by an open belt drive. The diameter of the driven pulley is 350 mm and

the centre distance between the pulleys is 4 m. The speed of the driven

pulley is 180 rpm. The density of the belt material is 1.1 Mg/m3and the

maximum permissible stress in the belt material is not to exceed2.5MPa. The thickness of the belt is 12 mm and the co-efficient of

friction between the belt and pulley surface is 0.25. Determine the

necessary width of the belt.

Or

(b) (i) A band brake acts on the 3/4th of the circumference of a drum of450 mm diameter which is keyed to the shaft. The band brake provides a

braking torque of 225 N-m. One end of the band is attached to a fulcrum

pin of the lever and the other end to a pin I 00 mm from the fulcrum. If

the operating force is applied at 500 mm from the fulcrum and the co-

efficient of friction is 0.25. Determine the operating when the drum

rotates in the (a) anticlockwise direction and (ii) clockwise direction.


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(ii) A car engine has its rated output of 30 kW at 3000 rpm. The clutch

used is of single plate type, having two active surfaces. The axial

pressure is not to exceed 0.85 bar. The external diameter of the friction

plate is 1.25 times the internal diameter and the co-efficient of friction is

0.3. Determine the dimensions of the friction plate and the axial force

exerted by the springs.

5.4. (a) The pitch of 50 mm mean diameter threaded screw of a screw

jack is 12.5 mm. The coefficient of friction between the screw and the

nut is 0.13. Determine the torque required on the screw to raise the load

of 25 kN, assuming the load to rotate with the screw. Determine the ratio

of the torque required to raise the load to the torque required to lower theload and also the efficiency of the screw jack.

Or

(b) A single plate clutch, both sides are effective, is to be designed for an

automotive vehicle whose engine is rated to give 100 kW at 2400 rpm

and maximum torque 500 N-m. The outer diameter of the friction plateis 25% more than the inner diameter. The intensity of pressure between

the plates is not to exceed 0.07 N/mm2.The co-efficient of friction may

be assumed equal to 0.3. Calculate the dimensions of the friction plate.

5.5. (a) A shaft rotating at 200 r.p.m drives another shaft at 300 r.p.m

and transmits 6 KW through a belt. The belt is 100 mm wide and 10 mm

thick. The distance between the shafts is 4 m. the smaller pulley is 0.5min diameter. Calculate the stress in the belt if it is

(i) an open belt drive and (ii) a cross belt drive. Take =0.3.

Or

(b). The wheel base of the car is 3 meters and its centre of gravity is


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1.2 meters ahead the rear axle and 0.75 m above the ground level. The

coefficient of friction between the wheels and the road is 0.5. Determine

the maximum deceleration of the car when it moves on a level road. If

the braking force on all the wheels is the same and no wheel slip occurs.

5.6. (a)

(i) The following data relate to a screw jack:

Pitch of the screw thread = 8 mm

Diameter of the screw = 40 mm

Coefficient of friction between screw and nut= 0.1

Load = 20 kN

Assuming that the load rotates with the screw,

Determine(1) The ratio of torques required to raise and lower the load

(2) The efficiency of the machine.

(ii) State the law of belting and explain the application of this law in

connecting nonparallel shafts by a flat belt.

Or

(b) (i) A multi-plate disc clutch transmits 55 kW of power at 1800 rpm.

Coefficient of friction for the friction surfaces is 0 .1. Axial intensity of

pressure is not to exceed 160 kN/m2. The internal radius is 80 mm and is

0.7 times the external radius. Find the number of plates needed to

transmit the required torque.

(ii) Write briefly on friction in vehicle propulsionand braking.

5.7. (a)

(i) Prove that the torque transmitted by a cone clutch, when the intensity

of pressure is uniform is given by


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T=

{(r1

3-r23)/ (r1

2-r22)}

(ii) A power of 60kW is transmitted by a multi plate clutch at 1500 rpm.

Axial intensity of pressure is not to exceed 0.15 N/mm2. Coefficient of

friction for the friction surface is 0.15. The external radius of friction

surface is 120 mm. Also the external radius is equal to 1.25 times of

internal radius. Determine the number of plates needed to transmit the

required power, if wear is uniform.

Or

(b) (i) Prove that the maximum efficiency of screw Jack is

max=

(ii) An effort of 200 N is required to just to move a certain body up an

inclined plane of an angle 15, the force acting parallel to the plane. If

the angle of inclination of the plane is made 20o, the effort required

parallel to the plane is found to be 230N. Determine the weight of thebody and the coefficient of friction.

5.8. (a) (i) Pitch of 50 mm diameter threaded screw of a screw jack is

12.5 mm. Coefficient of friction between screw and nut is 0.10.

Determine the torque to raise a load of 25 kN rotating with the screw.

Also find the torque required to lower the load and efficiency of screw

jack. (ii) 100 kW is to be transmitted by a rope drive through a 160 cm

diameter 45 grooved pulley running at 200 rpm. Angle of overlap is

140 and coefficient of friction between pulley and rope is 0.25.

Mass of rope is 0.7 Kg/m and it can withstand a tension of 800 N.

Considering centrifugal tension, find the following:

(1) Number of ropes required


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(2) Initial tension in the rope.

Or

(b)

(i) Explain the following:

(1) Crowning of pulleys

(2) Self-locking of brakes

(3) Uses of brakes in automobiles.

(ii) A 10 kW engine develops a maximum torque of 100 N-m and is

driving a car having a single plate clutch of two active surfaces.Axial pressure is not to exceed 0.85 bar. External diameter of friction

plate is 1.25 times internal diameter. Assume uniform wear and

coefficient of friction = 0.3. Determine dimension of friction plate and

axial force exerted by the springs.

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Unit Wise 16 Mark Questions