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Posted Date: 06 Dec 2008 Posted By:: pranjit kalita Member Level: Silver Points: 5 (Rs. 1)
2008 SRM University B.E Mechanical Engineering B. Tech degree examination Question paper
B.Tech DEGREE EXAMINATION,DECEMBER 2008
ME-202- KINEMATICS OF MACHINERY
Time:3 hours. Max. Marks:70
Answer ALL Questions
PART-A (10*2=20 Marks)
1. Define rubbing velocity.
2. What is meant by degrees of freedom of a mechanism?
3. State the law of static friction.
4. What is centrifugal tension in a belt?
5. What are the types of followers used in CAM?
6. What are the types of cams according to shape?
7. What are the common forms of teeth used in gears?
8. What is a simple gear train?
9. Define power of a governor.
10.Wat is the function of a governor?
PART-B (5*10=50 Marks)
11.a. In a four bar chain ABCD, AD is fixed and is 160 mm long. The crank AB is 40 mm long and rotates at 140 rpm clockwise,while the link CD=60 mm oscillates about D. BC and AD are equal length. Find the angular velocity of the link CD when angle BAD=60 degree.
b. The crank of a slider crank mechanism rotates clockwise at a constant speed of 300 rpm. The crank is 150 mm and connecting rod is 600 mm long. Determine
( i) Linear velocity and acceleration of the midpoint of the connecting rod and
(ii) Angular velocity and angular acceleration of the connecting rod at a crank angle of 45 degree from inner dead centre position.
12. a. An electric motor driven power screw moves a nut in a horizontal plane against a force of 75 KN at a speed of 300 mm/min. The screw has a single square thread of 6 mm pitch on a major diameter of 40 mm. The co-efficient of friction at the screw threads is 0.1. Estimate power of the motor.
b. An engine shaft running at 120 rpm is required to drive a machine shaft by means of a belt. The pulley on the engine shaft is of 2 m diameter and that on the machine shaft is 1 m diameter. If the belt thickness is 5 mm,determine the speed of the machine shaft when (i) there is no slip,(ii) there is a slip of 3%.
13. a. Draw the profile of the cam when the roller follower moves with cycloidal motion during outstroke and return stroke as given below :
(i) Outstroke with maximum displacement of 31.4 mm during 180 degree of cam rotation.
(ii) Return stroke for the next 150 degree of cam rotation.
(iii) Dwell for the remaining 30 degree of cam rotation.
The minimum radius of the cam is 15 mm and the roller diameter of the follower is 10 mm. The axis of the roller follower is offset by 10 mm towards right from the axis of cam shaft.
b. Draw the displacement,velocity and acceleration diagrams for a follower when it moves with uniform acceleration and retardation.Derive the expression for velocity and acceleration during outstroke and return stroke of the follower.
14. a. Two matting gears have 20 and 40 involute teeth of module 10 mm and 20 degree pressure angle. If the addendum on each wheel is such that the path of contact is maximum and interference is just avoided,determine the addendum for each gear wheel,path of contact,arc of contact and contact ratio.
b. Explain the various terminology used in gears with neat sketch.
15. a. The mass of each ball of a proell governor is 3 kg and the weight on the sleeve is 20 kg. Each arm is 220 mm long and the pivots of the upper arm and the lower arms are 20 mm from the axis. For the mid points of sleeve,the extension link of the lower arm is vertical and the radius of the path of rotation of the masses is 160 mm. The height of the governor is 180 mm. The governor speed is 150 rpm when in mid position. Determine the length of the extension link and the tension on the upper arm.
b. An aeroplane flying at 360 km/hr turns towards left and completes a quarter circle of 60 m radius. The mass of rotary engine and the propeller of the plane amounts to 450 kg with a radius of gyration of 0.3 m. The engine speed is 2000 rpm clockwise when viewed from the rear. Determine the gyroscopic couple on the aircraft and state its effect. In what way is the effect changed when the aeroplane turns towards right?
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