Theory of Machines - 1 - May 2014
Mechanical Engineering (Semester 4)
TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.
1(a) What do you mean by initial tension in belt drive?(5 marks)
1(b) With the help of a simple four bar mechanism explain the types of instantaneous centres.(5 marks)
1(c) Explain the term pressure angle with respect to a clam mechanism.What are the methods to control it?(5 marks)
1(d) Explain the type of constrained motions.(5 marks)
1(e) With the help of neatsketch explain Grasshopper's mechanism.(5 marks)
2(a) A cam with a minimum radius of 25mm is be designed for a knife edge follower with the following data:
to rise the follower through 35mm during 60° rotation of the cam.
dwell for the next 40° of the cam rotation
descending of the follower during the next 90° of the cam rotation.
dwell during the rest of the cam rotation.
If the ascending and decending of the cam is with SHM and UARM respectively.Draw the displacement,velocity,acceleration and jerk diagram if the cam rotates at 150rpm.(14 marks) 2(b) The universal coupling is used to connect two shaft toghether.The input shaft rotates at a uniform speed of 1200 rpm.Find the greatest permissible angle between the shaft axes so the the total fluctuation of seed may not exceed 200rpm .Also find the maximum speed of driven shaft.(6 marks) 3(a) The mechanism of a wrapping machine as shown in the figure has the following dimensions: O1A=100mm;AC=700mm;BC=200mm;O3C=200mm;O2E=400mm;O2=200mm and BD =150mm.The crank O1A rotates at a uniform speed of 100 rad/s.Find the velocity of the point E of the bell crank lever by: Instantaneous center method Relative velocity method. (14 marks) 3(b) Find the degree of freedom for the following mechanism as shown in the figure (6 marks) 4(a) The centre to centre distance between the two sprockets of a chain is 600mm.The chain drive is used to reduce the speed from 180 rpm to 90 rpm.The driving sprocket has 18teeth and a pitch circle of 480mm.Determine the number of teeth on the driven sprocket ,pitch and length of the chain.(7 marks) 4(b) Two 20° involute spur gear mesh externally and give a velocity ratio of 3.Module is 3mm and the number of pair of teeth in contact.(7 marks) 4(c) Derive the equation for centrifugal tension with respect to belt drive.What is its effect on power transmission?(6 marks) 5(a) A cord is wrapped around a solid cylinder of radius 'r' and mass 'm' The cylinder is released from rest.Determine the velocity of its centre of mass after it has moved down a distance 'h'(7 marks) 5(b) With the help of a neat sketch explain law of gearing.(7 marks) 5(c) What do you mean by Coriolis components of acceleration? Draw its different direction.(6 marks) 6(a) Differentiate between the following:
Belt drive and chain drive(5 marks) 6(b) Involute and cycloidal gear tooth profile.(5 marks) 6(c) Ackerman and Davis steering gear mechanism.(5 marks) 6(d) Machine and structure.(5 marks)