B.Tech-B.Tech Mechanical Engineering Kinematics of machines (Sathyabama University, Chennai, Tamil Nadu-2012)
Monday, 19 August 2013 05:56Duraimani
(Established under section 3 of UGC Act,1956)
Course & Branch :B.E - AUTO/MECH
Title of the Paper :Kinematics of machines Max. Marks:80
Sub. Code :615301 (2006-07-08-09) Time : 3 Hours
Date :14/11/2012 Session :FN
PART - A (10 x 2 = 20)
Answer ALL the Questions
1. Differentiate Mechanism and Machine.
2. State the Grashof’s Law.
3. Define Body guidance.
4. Give the difference between structural and mechanical error.
5. Write short notes on cams and followers.
6. What is meant by active force?
7. Define the terms: 1.Diametral pitch 2.Module.
8. What are the different types of gear train?
9. Define Equilibrium speed and Mean equilibrium speed.
10. Define controlling force.
PART – B (5 x 12 = 60)
Answer All the Questions
11. What is meant by the inversion of chain? Sketch and describe the mechanisms obtained by the inversion of four bar chain.
(or)
12. A four bar mechanism has the following dimensions:
DA= 300mm; CB=AB=360mm; DC=600mm. The link DC is fixed and the angle ADC is 60o. The driving link DA rotates uniformly at a speed of 100 r.p.m clockwise and the constant driving torque has magnitude of 50 N-m. Determine the velocity of the point B and angular velocity of the driven link CB. Also find the actual mechanical advantage and the resisting torque if the efficiency of the mechanism is 70 per cent.
13. A four bar mechanism is to be designed, by using three precision points, to generate the function Y=x1.5, for the range 1≤ x ≥4.
Assuming 30o starting position and 120o finishing position for the input link and 90o starting position and 180o finishing position for the output link, find the values of x,y,θ and f corresponding to the three precision points.
(or)
14. Synthesize a slider crank mechanism so that the displacement of the slider is proportional to the square of the crank rotation in the interval 45o≤ θ≤135o.Use three precision points with Chebyshev’s spacing.
15. A cam drives a flat reciprocating follower in the following manner:
During first 120o rotation of the cam, follower moves outwards through a distance of 20 mm with simple harmonic motion. The follower dwells during next 30o of cam rotation. During next 120o of cam rotation, the follower moves inwards with simple harmonic motion. The follower dwells for the next 90o of cam rotation. The minimum radius of the cam is 25 mm. Draw the profile of the cam.
(or)
16. Each wheel of a motorcycle is of 600 mm diameter and has a moment of inertia of 1.2 kg m2. The total mass of the motorcycle and the rider is 180 kg and the combined centre of mass is 580 mm above the ground level when the motor cycle is upright. The moment of inertia of the rotating parts of the engine is 0.2 kgm2. The engine speed is 5 times the speed of the wheels and is in the same sense. Determine the angle of heel necessary when the motorcycle takes a turn of 35 m radius at a speed of 54 km/h.
17. Two gears in mesh have a module of 8mm and a pressure angle of 20o. The larger gear has 57 while the pinion has 23 teeth. If the addenda on pinion and gear wheel are equal to one module, find
(a) the number of pairs of teeth in contact.
(b) the angle of action of the pinion and the gear wheel
(c) the ratio of the sliding to rolling velocity at
(i) the beginning of contact
(ii) the pith point
(iii) the end of contact
(or)
18. An epicyclic gear train consists of sun wheel S, a stationary internal gear E and three identical planet wheels P carried on a star-shaped plant carrier C. The sizes of different toothed wheels are such that the planet carrier C rotates at 1/5th of the speed of the sun wheel S. The minimum number of teeth on any wheel is 16. The driving torque on the sun wheel is 100 N-m. Determine number of teeth on different wheels of the train and torque necessary to keep the internal gear stationary.
19. Each arm of a porter governor is 250 mm long. The upper and lower arms are pivoted to links of 40 mm and 50 mm respectively from the axis of rotation. Each ball has a mass of 5 kg and the sleeve mass is 50 kg. The force of friction on the sleeve of the mechanism is 40 N. Determine the range of speed of the governor for extreme radii of rotation of 125 mm and 150mm.
(or)
20. The radius of rotation of the balls of a Hartnell governor is 80 mm at the minimum speed of 300 r.p.m. Neglecting gravity effect, determine the speed after the sleeve has lifted by 60 mm. Also determine the initial compression of the spring and the governor effort. The particulars of the governor are given below: Length of ball arm = 150 mm: length of sleeve arm = 100 mm; mass of each ball = 4 kg; And stiffness of the spring = 25 N/mm.
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