B.E-B.E Aeronautical Engineering Mechanics of Machines (Sathyabama University, Chennai, Tamil Nadu-2010)
Friday, 23 August 2013 02:33Duraimani
(Established under section 3 of UGC Act,1956)
Course & Branch :B.E - AERO
Title of the Paper :Mechanics of Machines Max. Marks :80
Sub. Code :526403 Time : 3 Hours
Date :30/04/2010 Session :FN
PART - A (10 x 2 = 20)
Answer ALL the Questions
1. Define “Kinematic Chain”.
2. What do you mean by a degree of freedom?
3. What is “creep” in belts?
4. Write the function of Bearing.
5. State the law of Gearing.
6. What is meant by “Gear Trains”?
7. Define the term “balancing of rotating masses”.
8. Why are single cylinder engines not fully balanced?
9. What are the methods of isolating the vibration?
10. Define critical or whirling speed of a shaft.
PART – B (5 x 12 = 60)
Answer All the Questions
11. Write a brief note on “Crank and Slotted lever Quick return motion mechanism” with a neat sketch.
(or)
12. A 4-bar Mechanism is required such that the input and output angles are coordinated as given in the table.
| Input crank Angle |
30° |
50° |
80° |
| Output follower Angle |
0° |
30° |
60° |
13. Determine the width of a 9.75mm thick leather belt required to transmit 15KW from a motor running at 900 rpm. The diameter of the driving pulley of the motor is 300mm. The driven pulley runs at 300 rpm and the distance between the centres of two pulleys is 3 metres. The density of the leather is 1000 Kg/m3. The maximum allowable stress in the leather is 2.5MPa. The coefficient of friction between the leather and the pulley is 0.3. Assume flat, open belt drive and neglect the sag and slip of the belt.
(or)
14. Describe with a neat sketch the working of a single plate friction Clutch.
15. Two gear wheels mesh externally and are to give a velocity ratio of 3 to 1. The teeth are of involute form; module = 6mm, addendum = one module, pressure angle = 20°. The pinion rotates at 90 rpm. Determine:
(a) The number of teeth on the pinion to avoid interference on it and the corresponding number of teeth on the wheel
(b) The length of path and arc of contact
(c) The number of pairs of teeth in contact
(or)
16. A cam is to give the following motion to a knife edge follower: (a) Outstroke during 60° of cam rotation
(b) Dwell for the next 30° of cam rotation
(c) Return stroke during next 60° of cam rotation and
(d) Dwell for the remaining 210° of cam rotation.
The stroke of the follower is 40mm and the minimum radius of the cam is 50mm. The follower moves with uniform velocity during both the outstroke and return strokes. Draw the profile of the cam when the axis of the follower passes through the axis of the cam shaft.
17. Four masses A, B, C and D shown below are to be completely Balanced
| |
A |
B |
C |
D |
| Mass kg |
-- |
30 |
50 |
40 |
| Radius mm |
180 |
240 |
120 |
150 |
(a) The magnitude and the angular position of mass A
(b) The position of planes A and D
(or)
18. The cranks and connecting rods of a 4-cylinder in-line engine running at 1800 rpm are 60mm and 240mm each respectively and the cylinders are spaced 150mm apart. If the cylinders are numbered 1 to 4 in sequence from one end, the cranks appear at intervals of 90° in an end view in the order 1 – 4 – 2 – 3. The reciprocating mass corresponding to each cylinder is 1.5 kg. Determine
(a) Unbalanced primary and secondary forces, if any
(b) Unbalanced primary force and unbalanced primary couples with reference to central plane of the engine
19. In a single degree damped vibrating system, a suspended mass of 8Kg makes 30 free oscillations in 18 seconds when disturbed from its equilibrium position. The amplitude decreases to 0.25 of the initial value after 5 oscillations. Determine:
(a) the stiffness of the spring
(b) the logarithmic decrement
(c) the damping factor
(d) the damping co-efficient.
(or)
20. The two equal masses of 500 kg and radius of gyration 37.5 cm are keyed to opposite ends of a shaft 60cm long. The shaft is 7.5 cm diameter for the first 25cm and 12.5cm diameter for the next 10cm and 8.75 cm diameter for the remainder of its length. Find the natural frequency of free torsional vibration of the system and position of the node. Take modulus of rigidity as 80 MN/cm2.
| Earning: ₹ 3.65/- |
