Roll No. ......................"'total No. of Questions: 09] [Total No. of Pages: 04

B.Tech. (Se.m. -4th)if

THEORY OF MACHINES -II

SUBJECT CODE: ME -204

Paper ID : [A0809][Note: Please fill subject code and paper ID on OMR)

Time: 03 Hours

Instruction to.Candidates:

1) Section - A is Compulsory.

2) Attempt any Four questions from Section - B.3) Attempt any Two questions from Section - C.

Q1)

Maximum Marks: 60. .

Section -A

(10x2=20)

a).

Define rubbing velocity at a pin joint.

b) In what ways mechanism differ from a machine?

c) What is meant by instantaneous centre 'of rotation?

d) Define nonnal pitch and axial pitch relating to helical gears.

e) Explain the gyroscopic effect on sea going vessels.

f) Explain the tenns 'fluctuation of energy' and 'fluctuation of speed' asapplied to fly wheels.

g)

h)

Explain the tenns 'static balancing' and 'dynamic balancing'.

Explain the tenn 'Synthesis of Mechanism' .

i) Explain the tenn 'Couple Curves'.

j) Desc~ibe the classification of synthesis problem.

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Section -B ~(4 x 5 = 20)

Q2) In a Whitworth quick return motion mechanism, as shown in fig., the distancebetween the fixed centers is 50 mm and the length of the driving crank is .

75 mm. The length of the slotted lever is 150 mm and the length of theconnecting rod is 135 mm. Find the ratio of the time of cutting stroke to thetime of return stroke and also the effective stroke.

p

Q3) In a link work, as shown in figure, the crankAB rotates about A at a uniformspeed of 150 r.p.m. The lever DC oscillates about the fixed point D, beingconnected to AB by the connecting linkBC. The block F moves, in horizontal, .

guides being given by the link EF, when the crqnk AB is at 30°. Thedimensions of the various links are:AB = 150 mm; BC = 450 mm; CE = 300 mm;and EF = 350 mm.Find, for the given configuration,. .

(a) Velocity of slider F,(b) Angular velocity of DC, and(c) Rubbing speed at pin C which is 50 mm is diameter.

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Q4) During forward stroke of the piston of the double acting steam engine, theturning moment has the maximum value of2000 N-m when the crank makesan angle of 80°with the inner dead centre. The turning moment diagram forthe engine may be assumed for simplicity to be represented by two triangles. ,If the crank makes 100 r.p.m. and the radius of gyration of the flywheel is1.75m, find the coefficient of flection of energy and the flywheel to keep the

~sp-eedwithin :to.75% of the mean speed. Also determine the crank angle atwhich the speed has its minimum and maximum values.

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Q{ The cranks and connecting rods of a 4-cylinder in-line engine running at1800 r.p.m. are 60 mm and 240 mm each respectively and the cylinders are

~ .spaced 150 mm apart. If the cylinders are numbered 1to 4 in sequence from -one end, the cranks appear at intervals of 90° in an end view in the order1-4-2-3.The reciprocating mass cdrresponding to each cylinder is 1.5 kg.

Determine:

(a)

(b)

Unbalanced primary and secondary forces, if any, and

Unbalanced primary and secondary couples with reference to gentralplane of the engine.

Q6) A racing car weighs 20kN. It/has a wheel base of2 m, track width 1m andheight ofC.G. 300 mm above the ground level and lies midway between thefront and rear axle. The engine flywheel t:otates at 3000 r.p.m. clockwisewhen viewed from the front. The moment of inertia of the flywheel is4 K.g-m2and moment of inertia of each wheel is 3 kg-m2.Find the reactionsbetween the wheels and the ground wht?nthe car takes a curve of 15m radiustowards right at 30 kniIhr, taking into consideration the gyroscopic and thecentrifugal effects. Each wheel radius is400 mm.

Section - C

(2 x 10 =20)

Q7) The mechanism of a wrapping machine, as shown in fig. has the followingdimensions:

° A= 100mm'AC= 700mm"BC=200 mm'a C=200mm" a E=400mm"I ' , '3 '2 '°2D = 200 mm and BD = 150 rpm

~

The crank alA rotates at a uniform speed of 100 rad/s. Find the velocity ofthe point E of the bell crank lever by instantaneous centre method.

E

\1

\c

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Q8) A pair of 20° full depth involute spur gears having 30 and 50 teeth respectively. 4of module 4 mm are In mesh. The smaller gear rotates at 1000 r.p.m.Determine: .. . ,.

(a) Sliding velocities at engagement and at disengagement of pair of ateeth, and

(b) Contact ratio.

Q9) In an epicycle gear train, as shown in fig. the wheel C is keyed to the shaft Band wheel F is keyed to Shaft A. The Wheels D and E rotate together on apin fixed to the arm G. The number of teeth on wheels C, D, E and Fare 35,65,32 and 68 respedively. .DE

G . -B A

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