Enrollment No: _______________________

Exam Seat No:_______________________

C.U.SHAH UNIVERSITY Winter Examination-2015 Subject Name: Kinematics and Dynamics of Machines Subject Code: 4TE03KDM1

Branch: B.Tech (Automobile)

Semester: 3 Date: 05/12/2015 Time: 2:30 To 5:30 Marks: 70 Instructions: (1) Use of Programmable calculator & any other electronic instrument is prohibited. (2) Instructions written on main answer book are strictly to be obeyed. (3) Draw neat diagrams and figures (if necessary) at right places. (4) Assume suitable data if needed. Q-1 a)

b)

c)

d)

e)

f)

g)

h)

Attempt the following questions: Which of the following is an inversion of double slider crank chain? (a) Coupling rod of a locomotive (b) Pendulum pump (c) Elliptical trammels (d) Oscillating cylinder engine The mechanism forms a structure, when the number of degrees of freedom (n) is equal to (a) 0 (b) 1 (c) 2 (d) – 1 According to Aronhold Kennedy’s theorem, if three bodies move relatively to each other, their instantaneous centres will lie on a (a) straight line (b) parabolic curve (c) ellipse (d) none of these In a pantograph, all the pairs are (a) turning pairs (b) sliding pairs (c) spherical pairs (d) self-closed pairs When the crank is at the inner dead centre, in a horizontal reciprocating steam engine, then the velocity of the piston will be (a) zero (b) minimum (c) maximum (d) non of these The centrifugal tension in belts (a) increases power transmitted (b) decreases power transmitted (c) have no effect on the power transmitted (d) increases power transmitted up to a certain speed and then decreases The velocity ratio of two pulleys connected by an open belt or crossed belt is (a) directly proportional to their diameters (b) inversely proportional to their diameters (c) directly proportional to the square of their diameters (d) inversely proportional to the square of their diameters The type of gears used to connect two non-parallel non-intersecting shafts are (a) spur gears (b) helical gears (c) spiral gears (d) none of these Page 1 || 4

(14)

If the module of a gear be m, the number of teeth T and pitch circle diameter D, then (a) m = D/T (b) D = T/m (c) m = D/2T (d) none of these j) The size of a cam depends upon (a) base circle (b) pitch circle (c) prime circle (d) pitch curve k) Offset is provided to a cam follower mechanism to (a) minimize the side thrust (b) accelerate (c) avoid jerk (d) none of these l) The rotor of a ship rotates in clockwise direction when viewed from the stern and the ship takes a left turn. The effect of the gyroscopic couple acting on it will be (a) to raise the bow and stern (b) to lower the bow and stern (c) to raise the bow and lower the stern (d) to lower the bow and raise the stern m) When there is a reduction in amplitude over every cycle of vibration, then the body is said to have (a) free vibration (b) forced vibration (c) damped vibration (d) none of these n) For dynamic balancing of a shaft, (a) the net dynamic force acting on the shaft is equal to zero (b) the net couple due to dynamic forces acting on the shaft is equal to zero (c) both (a) and (b) (d) none of the above i)

Attempt any four questions from Q-2 to Q-8 Q-2 (a) (b) (c)

Q-3 (a) (b) (c)

Q-4 (a)

Attempt all questions Explain types of Instantaneous Centres for mechanism. Distinguish Completely constrained, Incompletely constrained and Successfully constrained motion with neat sketch. PQRS is a four bar chain with link PS fixed. The lengths of the links are PQ = 62.5 mm; QR = 175 mm; RS = 112.5 mm; and PS = 200 mm. The crank PQ rotates at 10 rad/s clockwise. Draw the velocity and acceleration diagram when angle QPS = 60° and Q and R lie on the same side of PS. Find the angular velocity and angular acceleration of links QR and RS. Attempt all questions Explain Hart straight line motion mechanism with the help of neat sketch. Draw sketches of any two inversions of double slider crank mechanism and State their applications. The crank and connecting rod of a reciprocating engine are 200 mm and 700 mm respectively. The crank is rotating in clockwise direction at 120 rad/s. Find with the help of Klein’s construction: 1. Velocity and acceleration of the piston, 2. Velocity and acceleration of the midpoint of the connecting rod, and 3. Angular velocity and angular acceleration of the connecting rod, at the instant when the crank is at 30° to I.D.C. (inner dead centre). Attempt all questions Derive an expression for the minimum number of teeth required on a pinion in Page 2 || 4

(3) (4) (7)

(3) (4) (7)

(7)

(b)

Q-5 (a) (b)

Q-6 (a) (b)

(c)

Q-7 (a)

order to avoid interference in an involute gear. A cam, with a minimum radius of 25 mm, rotating clockwise at a uniform speed is to be designed to give a roller follower, at the end of a valve rod, motion described below : 1. To raise the valve through 50 mm during 120° rotation of the cam ; 2. To keep the valve fully raised through next 30°; 3. To lower the valve during next 60°; and 4. To keep the valve closed during rest of the revolution i.e. 150° ; The diameter of the roller is 20 mm and the diameter of the cam shaft is 25 mm. Draw the profile of the cam when the line of stroke of the valve rod passes through the axis of the cam shaft. The displacement of the valve, while being raised and lowered, is to take place with simple harmonic motion. Attempt all questions Classify the various types of follower according to surface contact and motion of the follower with neat sketch. In an epicyclic gear train, an arm carries two gears A and B having 36 and 45 teeth respectively. If the arm rotates at 150 r.p.m. in the anticlockwise direction about the centre of the gear A which is fixed, determine the speed of gear B. If the gear A instead of being fixed makes 300 r.p.m. in the clockwise direction, what will be the speed of gear B?

Attempt all questions Discuss relative merits and demerits of belt drive over chain drive. The power is transmitted from a pulley 1 m diameter running at 200 r.p.m. to a pulley 2.25 m diameter by means of a belt. Find the speed lost by the driven pulley as a result of creep, if the stress on the tight and slack side of the belt is 1.4 MPa and 0.5 MPa respectively. The Young’s modulus for the material of the belt is 100 MPa. Define vibrations. Explain different types of vibrations with neat sketches and applications.

Attempt all questions With neat schematic diagrams discuss the effect of gyroscopic couple on a naval Page 3 || 4

(7)

(7) (7)

(3) (4)

(7)

(7)

(b)

Q-8 (a) (b)

ship during steering, pitching, and rolling. Four masses m1, m2, m3 and m4 are 200 kg, 300 kg, 240 kg and 260 kg respectively. The corresponding radii of rotation are 0.2 m, 0.15 m, 0.25 m and 0.3 m respectively and the angles between successive masses are 45°, 75° and 135°. Find the position and magnitude of the balance mass required, if its radius of rotation is 0.2 m. Attempt all questions Define the terms “Static balancing” and “Dynamic balancing”. State the necessary conditions to achieve them. An aeroplane makes a half circle of 100m radius, towards left when flying at 400 km/hr. The engine and propeller of plane weights 500 kg and has a radius of gyration of 30 cm. the engine rotates at 3000 r.p.m. anticlockwise, when viewed from front end. Find the gyroscopic couple and its effect on aeroplane.

Page 4 || 4

(7)

(7) (7)