GITAM University 2007 B.E Mechanical Engineering Theory of Machines - I - Question Paper

College of Engineering
Gandhi Institute of Technology and Management, Visakhapatnam
( Affiliated to Andhra University)

B.E. (Mechanical Engineering)
3rd Year 1st Semester exams 2005-2006
(Autonomous Stream)

ME 311 Theory of Machines - I






Time: three Hours Max. Marks: 60

1. Answer ques. No. one ( Part – A) and any 4 of the remaining 7 (Part – B)
2. All parts of a ques. must be answered in 1 place, otherwise they will not be valued.
3. Figures in the right hand margin indicate marks allotted.

PART – A

1. Answer the subsequent (10x2=20)
a) Sketch and define Ackerman steering gear mechanism.
b) Explain the terms (i) Degrees of freedom of a mechanism and (ii) Inversion of a Kinematic chain.
c) How are the mechanisms classified?
d) State Kennedey’s theorem.
e) Sketch the four-bar mechanism and locate all its instantaneous centers.
f) Sketch displacement, velocity and acceleration time curves for SHM of follower.
g) What are the advantages and disadvantages of cycloidal teeth profile over Involute teeth profile?
h) What are the various methods of eliminating interference in gear wheels.
i) What is an epicyclic gear train?
j) Explain the terms resolution, accuracy and repeatability as applied to robotics.

PART – B

ans any 4 of the subsequent. If you attempt more than 4 questions, only the 1st 4 in order will be valued.

2. a) For what purpose is a pantograph used? Sketch 1 form of pantograph and show that it satisfies the needed conditions. (4)
b) A Hookes Joint is to connect 2 shaft whose axes intersect at 1500. The driving shaft rotates uniformly at 120 RPM. The driven shaft operates against a steady torque of 170 N-m and carries a flywheel whose mass is 50 Kg and radius of gyration 15Cm. What is the maximum value of the torque which must be exerted by the driving shaft. (6)
3. a) Distinguish between, complete, in complete and successful constraint of the relative motion ranging from 2 links. (4)
b) Give diagrammatic sketches of the subsequent mechanisms and state on which Kinematic chain every is based (i) ellipse trammels ii) Whitworth quick-return motion. iii) Oscillating cylinder engine and iv) Oldham shaft coupling. (6)
4. The dimensions of the different links of a pneumatic riveter shown in Fig.1 are as follows. OA = 175mm; AB = 180mm; AD = 500mm and BC = 325mm. (OAB is 1 link). obtain the velocity ratio ranging from ‘C’ and ram ‘D’ when OB is vertical. What will be the efficiency of the machine if a load of 2.5KN on the piston ‘C’ causes a thrust of 4KN at the ram ‘D’. (10)


5. A cam turning with uniform angular velocity operates a reciprocating follower through a roller 50mm diameter. The line of stroke of the follower is 25mm from the axis of the cam, the stroke of the follower is 50mm and the minimum radius of the cam is 50mm. The follower is needed to move outwards and inwards with simple harmonic motion, every stroke occupying 750 of cam rotation. During the remainder of the cam rotation the follower is to rest at the bottom of its stroke. Draw the outline of the working surface of the cam. (10)

6.
In a spiral gear drive connecting 2 shafts, the approximate centre distance is 400mm and the speed ratio = 3. The angel ranging from the 2 shafts is 500 and the normal pitch is 18mm. the spiral angle for the driving and driven wheels are equal. obtain (i) the number of teeth on every wheel (ii) Exact centre distance and (iii) efficiency of the drive, if friction angle = 60.
(10)

7. Fig.2 indicates diagrammatically a compound epicyclic gear wheels ‘A’, D and E are free to rotate independently on spindle ‘O’, while ‘B’ and ‘C’ are compound and rotate together on spindle P, on the end of arm OP. All the wheels have the teeth of identical pitch. ‘A’ has 12 teeth, ‘B’ has 30 and ‘C’ has 14 teeth cut externally. obtain the number of teeth on wheels ‘D’ and ‘E’ which are cut internally. If the wheel ‘A’ is driven clockwise at one R.P.S, while wheel ‘D’ is driven counter clockwise at five R.P.S, determine the magnitude and direction of the speeds of arm OP and wheel E. (10)


8. Write short notes on i) Homogeneous transformation matrix and ii) Direct Kinematic issue. (10)

Earning:   Approval pending.