ME35, KINEMATICS OF MACHINERY

DEPARTMENT OF MECHANICAL ENGINEERING

THE RAJAS ENGINEERING COLLEGE

VADAKKANGULAM- 627 116

MODEL EXAMINATION- NOV 2010

ME35, KINEMATICS OF MACHINERY

Year/Semester : II/III                                                             Time : 9.30 to 12.30am

Branch: MECHANICAL ENGG.                                          Date : 12.11.10

Maximum Marks : 100

Part – A

Answer all the Questions                                                      10 X 2 = 20

                                   

1. What is Grashoff’s law?
2. Define degree of freedom and give the DOF for a shaft in a circular hole.
3. Explain the coriolis component of acceleration.
4. Define rubbing velocity.
5. State the expressions for maximum velocity and acceleration of a follower moves with cycloidal motion.
6. Define pitch point in context with cam.
7. State law of gearing.
8. Define interference in gears.
9. Define the term coefficient of friction.
10. Explain briefly the significance of friction in braking.

Part – B

                                                                                   

Answer all the Questions                                                      5 X 16 = 80

11. a i) Explain the inversions of four bar chain with neat sketches.

   ii) Explain with neat sketches the following:

            Offset slider mechanism

            An indexing mechanism

            OR

b i) Explain the inversions of single slider crank chains

   ii) Explain mechanical advantage and transmission angle in 4 bar mechanisms.

12. a) The crank of a slider crank mechanism is 15 cm and the connecting rod is 60 cm long. The crank makes 300 rpm in the clockwise direction. When it has turned 45⁰ from inner dead centre position, determine

i)                    Velocity of slider

ii)                  Angular velocity of connecting rod

iii)                Linear velocity at the midpoint of connecting rod.

OR

           

             b) In a four bar mechanism, the crank QA rotates at 36 rad/s. The lengths of the

                 links AB = 200 mm; BC = 400 mm; CD = 450 mm and AD = 60 mm.

                 AD is the fixed link. At  the instant when AB is at right angle to AD,

                 determine the velocity of

i)                    the midpoint of the link

ii)                  a point on link CD, 100 mm from the pin connecting the CD and AD

13. a) From the following data draw the profile of a cam in which the follower moves

          with SHM during ascent while it moves with uniformly accelerated and

          decelerated motion during descent.

                   Least radius of the cam = 50 mm

                   Angle of ascent = 48⁰

                   Angle of dwell = 42⁰

                         Angle of descent = 60⁰

                         Lift  of the follower = 40 mm

                         Diameter of the roller = 30 mm

                         If the cam rotates at 360 rpm anticlockwise find the maximum velocity

                and acceleration of the follower during ascent and descent.

OR

             b) Draw the profile of disc cam to give uniform acceleration and retardation outstroke of 25 mm to a knife edge follower during first half of revolution. Return of cam also takes place with uniform motion during remaining half of cam revolution. Assume minimum radius of cam as 25mm.

        14) a) i) An epi cyclic gear train is shown below. How many revolution does the arm makes,

                         1) When A makes one revolution in clockwise and D makes half a revolution in the opposite sense.

                         2) When A makes one revolution in clockwise and D remains stationary.

The number of teeth in gears A and D are 40 & 90 respectively.

     ii)  What is reverted gear train? Explain the arrangement of various gears in a reverted gear train and express the characteristic equations used to define their operations.

                                                            OR

   b) i) State and prove law of gearing?

       ii) A pair of involute spur gears with 16^o pressure angle and pitch of module 6mm is in mesh. The number of teeth in pinion is 16 and its rotational speed is 240 rpm. The gear ratio is 1.75. In order to avoid the interference, determine

1)      addenda on pinion and wheel

2)      length of path of contact

3)      maximum velocity of sliding on either side of pitch point.

15) a) The pitch of 50mm mean diameter threaded screw of a screw jack is 12.5 mm. The coefficient of friction between the screw and the nut is 0.13. Determine the torque required on the screw to raise the load of 25KN, assuming the load to rotate with the screw. Determine the ratio of the torque required to raise the load to the torque required to lower the load and also the efficiency of the screw jack.   

                                                            OR

b) A single plate cutch, both sides are effective, is to be designed from an automobile vehicle whose engine is rated to give 100 kW at 2400 rpm and maximum torque 500 N.m. The outer diameter of the friction plate is 25% more than the inner diameter. The intensity of pressure between the plates is not to exceed 0.07 N/mm². The co-efficient of friction may be assumed equal to0.3. Calculate the dimensions of the friction plate.