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USN 10ME54

Fifth Semester B.E. Degree Examination, June/July 2014Dynamics of Machines

Time: 3 hrs. Max. Marks: 10 'Note: Answer FIVEfull questions, selecting

Y~A at least TWO questions from each part. '0'l,..... PART - A r:' tX

1 a.l'"'&xplain equilibrium with respect to two force and three force members. 0. (04 Marks)

b. 1'1(1) r: bar mechanism shown in Fig.Ql(b) is acted upon by a force P - 10.•@ N at 1200 onli . The dimensions of various links are AB = 40 mm, BC = 6, mm, CD = 50 mm,AD = 0, ,DE = 20 mm. Determine the input torque on link AB 14 tatic equilibrium.

Z + . ~ (16 Marks)

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~C(j (~.Ql(b)

a. Briefly discuss the following· «:) Q(i) D'Alembert's principle ~ (ii) Dynamicalljd ivalent system. (06 Marks)

b. The turning moment dia ~ for a four stroke e gme may be assumed for simplicity to berepresented by four i see es triangles. The areas of e triangles are suction = - 0.5cm2

,

Compression = - c. m2; Expansion = +8.1cm2 an e c aust = - 0.8cm2. 1 em' arearepresents 140 of work. Determine the mass mome :;bf1 ertia of the flywheel to keepthe fluctuati ' peed within 1% of mean speed, if the mea , ed is 400 rpm. (14 Marks).~ ~~

a. State the,,~s of dynamic friction. '(?b. Deri 'n expression for frictional torque in a flat collar bearing assuming

3 (04 Marks)iform pressure.

(06 Marks)c. (, ~ather belt is required to transmit 7.5 kW from a pulley 1.2 m in dia~tet running atr0250 rpm, the angle of contact is 1650 and u = 0.3. lfthe safe working stress fo he leather

••.\ ,J belt is 1.5 MPa and density of leather is 1000 kg/nr' and thickness of belt i~ mm,I'~" determine the width of belt taking centrifugal tension into account. (1 [ltrks)¥

"''4 a. Briefly explain the static and dynamic balancing. (04 Marlis}b. A 3.6 m long shaft carries three pulleys, two at its two ends and the third at the midpoint.

The two end pulleys have masses 79 kg and 40 kg with their radii 3 mm and 5 mm from axisof shaft respectively. The middle pulley has a mass of 50 kg with radius 8 mm. The pulleyare so keyed to the shaft that the assembly is in static balance. The shaft rotates at 300 rpmin two bearings 2.4 m apart with equal overhangs on either side. Determine(i) Relative angular positions of pulleys.(ii) Dynamic reaction on the two bearings. (16 Marks)

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(5zC'"t::o0...§

USN lOME54

Fifth Semester B.E. Degree Examination, June/July 2014Dynamics of Machines

Time: 3 hrs. Max. Marks: 100~( ~ Note: Answer FIVE full questions, selecting~I /. at least TWO questions from each part. to...0

~/ PART-A r-: ''''<,1 a.CE. plain equilibrium with respect to two force and three force members. rn (04 Marks)

b. 0"t: bar mechanism shown in Fig.Q1(b) is acted upon by a force P = 10.•6 N at 1200 onThe dimensions of various links are AB = 40 mm, BC = 6, , CD = 50 mm,

(!...rom, DE = 20 mm. Determine the input torque on link AB f~r tatic equilibrium."/6+ ~ , (16 Marks)

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2

,s-;fVC{! g.Q1(b)

a. Briefly discuss the following' ~ , Q(i) D'Alembert's principle ~ (ii) Dynamicalljcl 'valent system. (06 Marks)

b. The turning moment dia ~ for a four stroke e me may be assumed for simplicity to berepresented by four iso ce es triangles. The areas of ~ triangles are suction = - 0.5em2

;

Compression = - . 6m2; Expansion = +8.1cm2 an e < ust = - 0.8cm2

. 1 cm2 arearepresents 140 of work. Determine the mass moment,r, ertia ofthe flywheel to keepthe fluctuati peed within 1% of mean speed, if the mea ed is 400 rpm. (14 Marks).~ :;...-/

a. State thc"i\vs of dynamic friction. ~Ob. Deriw 'n expression for frictional torque in a flat collar bearing assuming.i

3 (04 Marks)iform pressure.

(06 Marks)c. eather belt is required to transmit 7.5 kW from a pulley 1.2 m in diameter running at

C~ '50 rpm, the angle of contact is 1650 and !-! = 0.3. If the safe working stress" foqe leather

•..\ belt is 1.5 MPa and density of leather is 1000 kg/rrr' and thickness of belt' i~ mm,!" determine the width of belt taking centrifugal tension into account. (10 arks)

' .•' 4 a. Briefly explain the static and dynamic balancing. (04 Marks)b. A 3.6 m long shaft carries three pulleys, two at its two ends and the third at the midpoint.

The two end pulleys have masses 79 kg and 40 kg with their radii 3 mm and 5 mm from axisof shaft respectively. The middle pulley has a mass of 50 kg with radius 8 mm. The pulleyare so keyed to the shaft that the assembly is in static balance. The shaft rotates at 300 rpmin two bearings 2.4 m apart with equal overhangs on either side. Determine(i) Relative angular positions of pulleys.(ii) Dynamic reaction on the two bearings. (16 Marks)

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lOME54

PART-B

5 a. With usual notations, explain primary and secondary unbalanced forces of reciprocatingmasses. (05 Marks)

b. A five cylinder inline engine running at 500 rpm has successive cranks at 1440 apart. Thedistance between the cylinder line is 300 mm. Piston stroke is 240 mm, length of co ectingrod is 480 mm. Examine the engine for balance of primary and secondary forces andcouples. Find the maximum value of these and position of central cran\ . hich thesemaximum values occur. The reciprocating mass for each cylinder is 150 N •~ (15 Marks)

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a. Defm tile following:(i) Sensiti ness (ii) Hunting (iii) Governer power(v) Isochro governer. (10 Marks)

b. A portor governe as all four arms 300 mm long, the ~p arms are pivoted on axis ofrotation and low a s are attached to the sleeve at d st ce 35 mm from the axis. Themass of each ball is g and the load on the sleev i 40 N. Determine the equilibriumspeed for two extreme ra .. of200 mm and 260 otation of govemer balls. (10 Marks)

6

7 a. With usual notations and dia a derive a e lression for the gyroscopic couple producedby a rotating disc. <0 (08 Marks)

b. Each road wheel of motor cycle ha ment of inertia of2 kg-mi. The rotating parts of theengine of the motor cycle, has a M. 0.2 kg-m'. The speed of the engine is 5 times thespeed of the wheel and is in the am sse. The mass of the motor cycle with rider is 200

ground lev, . The diameter of the wheel is 500 mm, themotor cycle is travelling at 1 s on a curve 0 radius. Determine(i) Gyroscopic couple, cefimfugal couple, over . ing and balancing couple in terms of

angle of heel. ~ j ~

(ii) Angle of heel. 0"::> ~ ~ (12 Marks)

A straight sided cam as both sides tangential to the base circ e a radius of 25 mm. Thetotal angle of ac ·on is 1200

, A lift of 10 mm is given to the roller 20 mm diameter, the centre ofwhich move l ng a straight line, passing through the axis of the earn, The crank shaft has aspeed of2 rpm. Determine(i) The ra ius of the nose arc.(ii) The velocity and acceleration of the roller centre when the roller in contact with the cam

at the end of one of the straight flanks adjacent to the nose and(iii) The acceleration of roller centre at peak. (20 Marks)

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