Kinematics of Machines - Jun 2015
Mechanical Engg. (Semester 4)
TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) With a neat sketch define the following:
i) Kinematic link
ii) Kinematic pair
iii) Kinematic chain
iv) Kinematic mechanism
v) Machine.(10 marks) 1 (b) Define inversion of a kinematic chain. With the help of a neat sketch explain inversions of single slider crank chain.(10 marks) 2 (a) With the help of a neat sketch, explain the working principle of crank and slotted lever mechanism.(10 marks) 2 (b) List various straight line generating mechanism. With the help of a neat sketch along with proof, explain how a Peaucellier mechanism generates a straight line.(10 marks) 3 PQRS is a four bar m/sm with link PS fixed as shown in Fig. Q3. The lengths of the links are; PQ=62.5 mm, OR=175 mm, RS=112.5mm, PS=200mm. The crank PQ rotates at 10 rad/s clockwise. Draw the velocity and acceleration diagrams when angles QPS=60° and Q and R lie on the same side of PS. Find angular velocity and angular acceleration of links QR and RS. (20 marks) 4 (a) Locate all the instantaneous centres of the mechanism shown in Fig Q4(a). Determine the angular velocity of link AB and velocity of slider. Crank OB rotates CW at 150 rpm.
AB= 600 mm
OB= 150 mm
i) The wheel D fixed and arm 'a' rotates at 200 RPM in the clockwise.
ii) The wheel D rotates at 20 rpm counter clockwise and the arm 'a' rotates at 200rpm clockwise. (14 marks) 8 (a) Sketch the following:
i) Disc cam with translating follower
ii) Wedge cam with translating follower.
iii) Cylindrical cam with oscillating follower.(6 marks) 8 (b) Draw the profile of a cam operating a knife edge follower having a lift of 30mm. The cam raises the follower with simple harmonic motion for 150° of the rotation followed by a period of dwell for 60°. The follower descends for the next 100° rotation of the cam with uniform velocity, again followed by a dwell period. The cam rotates at a uniform speed of 120 rpm and has a least radius of 20mm. What will be the maximum velocity and acceleration of the follower during the lift and the return?(14 marks)