EXPERIMENT NO.10

                                            Expt. No.10

10.0  Questions for confirmation of learning

1. The process of providing the second mass in order to counteract the effect of the centrifugal force of the first mass is called balancing of rotating masses.

2. a) To reduce vibrations and bending of the shafts. b) To minimize noise production.

c) To provide max. efficiency. d) To prevent wear and tear.

3. a) Neglect. b) Attention. c) Poor knowledge. d) Wrong calculations.

4. Unbalanced                                                                      

11.0  Conclusion :

            1. increase.      2. directly.      

3. Causes:   a) parts are not properly balanced  b) setting up of dynamic forces

                   d) Increase in loads e) stresses in various members.

    Necessity: To prevent from bending of shafts and vibrations.

12.0  Questions:

1. Whenever a certain masses is attached to a rotating shaft, it exerts some centrifugal force, whose effect is to bend the shaft and to produce vibrations in it.  In order to prevent the effect of centrifugal force, another mass is attached to the opposite side of the shaft, at such a position so as to balance the effect of the centrifugal force of the first mass.

2.  It is very essential that all the rotating and reciprocating parts should be completely balanced. If these parts are not properly balanced, the dynamic forces are set up. These forces not only increase the load on bearing and stresses in various members, but also produce uneven and even dangerous vibrations. So it is important to balance the system.

3. When the center of mass does not lie on the axis, an unbalance is produced. This is the principle reason of unbalance of a revolving rotor.

6. The center of the masses of the system must lie on the axis of rotation. This is the condition of static balancing.

7. The algebraic sum of the moments about any point in the plane must be zero. This condition and the condition for static balancing together give dynamic balancing.

9. In a rotating system the immediate indication of unbalance is vibration.

11. a) Center of mass does not coincide with axis of rotation. b) Unbalanced centrifugal                                 forces.

12. When there is a reduction in amplitude over every cycle of vibration, then it is called as damping of vibrations.