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JNTU B.Tech II THEORY OF MACHINES Previous Question Paper (May - 2019 - R13)

B.Tech | II | II-II | R13 | May - 2019

Answer PaperPaper Code: 114CJMaximum Marks: 75Time: 3 Hours

Note: This question paper contains two parts A and B.
Part A is compulsory which carries 25 marks. Answer all questions in Part A.
Part B consists of 5 Units. Answer any one full question from each unit.
Each question carries 10 marks and may have a, b, c as sub questions.
Illustrate your answers with NEAT sketches wherever necessary.

PART - A

125 marks
a
Explain briefly the working of Oscillating cylinder engine mechanism.
2 marks

Answer

In an oscillating cylinder engine mechanism, the cylinder is pivoted at a point away from the crankshaft axis. As the crank rotates, the cylinder oscillates about its pivot, eliminating the need for a connecting rod. This simplifies the mechanism by allowing the piston rod to act directly on the crank pin.

b
What will happen to the tangential and radial accelerations when a body is: (i) rotating in a circular path with uniform velocity (ii) moving on a straight path.
3 marks

Answer

(i) For uniform circular motion, the tangential acceleration is zero, while the radial (centripetal) acceleration is constant and directed toward the center. (ii) For motion on a straight path, both tangential and radial accelerations are zero, as there is no change in speed and no curvature to the path.

c
Explain the phenomenon of interference in involute gears.
2 marks

Answer

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d
What is the specific feature of Reverted gear train?
3 marks

Answer

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e
For a given velocity ratio of a flat belt drive, write the expressions for the radii of the driving and driven pulleys (i) for an open belt drive, and (ii) for a crossed belt drive.
2 marks

Answer

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f
Define the terms: ‘coefficient of fluctuation energy’ and ‘coefficient of fluctuation of speed’.
3 marks

Answer

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g
Explain the difference between the coefficient of friction and angle of friction.
2 marks

Answer

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h
Compare the use of (i) Flat belts (ii) Ropes and (iii) Chains for the transmission of power.
3 marks

Answer

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i
Explain clearly the terms ‘static balancing’ and ‘dynamic balancing’.
2 marks

Answer

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j
Show that the height of Watt governor is inversely proportional to the square of its speed.
3 marks

Answer

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PART - B

210 marks
a
A link AB of known length has its end A constrained to move vertically and the other end B constrained to move in a direction 45 to the vertical. Explain how the velocities of points C and D can be determined, where C is mid-point the of the link AB and D is a point which is at a distance x from A and at a distance y from B.
5 marks

Answer

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b
Explain how you determine the various instantaneous centers in a crossed four bar mechanism.
5 marks

Answer

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OR
3
In a slider-crank mechanism, the length of crank OA is 65 mm, and the length of connecting rod AB is 250 mm. The C.G. of the connecting rod is 6.5 mm from the crank pin, and the crank rotates anti-clockwise with uniform motion of 3000 rpm. Determine the acceleration of the wrist pin B, and the acceleration of the center of gravity of the connecting rod, when the crank makes an angle of 45 with the center line connecting O and B.
10 marks

Answer

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410 marks
a
Two equal spur gear wheels of involute teeth with 20 pressure angle have a module pitch of 3. If the number of teeth is 54, and the arc of contact is 1.75 times the circular pitch, find the addendum of the wheel.
5 marks

Answer

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b
Deduce the expressions for the Velocity ratio and Centre distance between the shaft axes of Worm and Worm Wheel.
5 marks

Answer

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OR
5
In an epicyclic gear train shown in Figure, an annular wheel ‘A’ having 54 teeth meshes with a planet wheel ‘B’ which gears with a sun wheel ‘C’. The wheels ‘A’ and ‘C’ are co-axial. The wheel ‘B’ is carried on a pin fixed on one end of the arm ‘P’ which rotates about the axes of the wheels ‘A’ and ‘C’. If ‘A’ makes 20 rpm clockwise, the arm rotates at 100 rpm ccw, and the wheel ‘C’ has 24 teeth, determine the speed and sense of rotation of the wheel ‘C’.
10 marks

Answer

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610 marks
a
Derive the Condition for transmission of Maximum Power in a belt drive, when centrifugal tension is neglected.
5 marks

Answer

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b
An engine flywheel has mass of 65 kN, and the radius of gyration is 2 m. If the maximum and minimum speeds are 120 rpm and 118 rpm respectively, find the maximum fluctuation of energy.
5 marks

Answer

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OR
7
In a turning moment diagram, the areas above and below the mean torque line taken in order are 4400, 1150, 1300, and 4550 mm2 respectively. The scales of the turning moment diagram are : Turning moment : 1mm = 100 N-m; Crank angle : 1mm = 1. Find the mass of the flywheel required to keep the speed between 297 and 303 rpm, if the radius of the gyration is 0.525m.
10 marks

Answer

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810 marks
a
Derive from first principles, the expression for the frictional moment (or torque due to friction) of a conical collar bearing, assuming uniform pressure.
5 marks

Answer

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b
Describe the construction of the (i) Roller Chain (ii) Silent Chain. How does wear affect the contact between the chain and sprocket in each case?
5 marks

Answer

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OR
9
A single plate clutch, having two active surfaces, transmits 10 kW of power, and the maximum torque developed is 120 N-m. The axial pressure is not to exceed 100 kPa. The outer diameter of the friction plate is 1.3 times the inner diameter. Determine these diameters, and the axial force exerted by the springs. Assume uniform wear and take the coefficient of friction as 0.25.
10 marks

Answer

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1010 marks
a
Explain the terms : Sensitiveness, Isochronism, Stability, and Hunting in connection with governors.
5 marks

Answer

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b
Three masses of 8 kg, 12 kg, and 15 kg attached at radial distances of 80, 100 and 60 mm respectively to a disc on a shaft are in complete balance. Find the angular positions of the masses of 12 kg and 15 kg relative to the 8 kg mass.
5 marks

Answer

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OR
1110 marks
a
What do you understand by controlling force and controlling force curves in governors? Explain with a sketch.
5 marks

Answer

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b
Draw the displacement, velocity and acceleration diagrams for a knife edge follower moving over a cam with a lift of 5 cm. Assume SHM for the motion of follower during outstroke of 130, followed by dwell period during 40 of cam rotation. Return stroke of the follower occurs with uniform acceleration and retardation, the retardation being 1.5 times the acceleration, during 120 of cam rotation, followed by dwell for the remaining period. If the speed of cam is 180 rpm, calculate the maximum velocity and acceleration of the follower during both the strokes.
5 marks

Answer

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This page contains the question paper of THEORY OF MACHINES from JNTU for B.Tech AG II II-II, May - 2019, R13.

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