Static and Dynamic Balancing of Rotating Mass

A Presentation prepared by me by simplifying the balancing of rotating mass.

1. Static & Dynamic Balancing of Rotating Mass Presentation By Atish Kumar Sahoo (120101mer008 )

2. Unbalance:- The condition which exists in a rotor when vibratory force or motion is imparted to its bearings as a result of centrifugal forces is called unbalance or the uneven distribution of mass about a rotor’s rotating centerline.

3. Balancing :- Balancing is defined as the process of designing (or modifying) a machine in which unbalanced forces is minimum. Balancing is the process of attempting to improve the mass distribution of a body so that it rotates in its bearings without unbalanced centrifugal forces” .

4. Mass balancing is routine for rotating machines, some reciprocating machines , and vehicles . Mass balancing is necessary for quiet operation, high speeds , long bearing life, operator comfort, controls free of malfunctioning, or a "quality" feel .

5. The objectives of balancing an engine are to ensure: 1. That the center of gravity of the system remains stationery during a complete revolution of the crank shaft and 2. That the couples involved in acceleration of the different moving parts balance each other.

6. B alancing of R otating Member :- Balancing means a process of restoring a rotor which has unbalance to a balanced state by adjusting the mass distribution of the rotor about its axis of rotation

7. Types of balancing: Static Balancing A rotating mass is said to be statically balanced if the rotating mass can rest , without turning, at any angular position in its bearings. This condition is attained when the sum of the centrifugal forces on the rotating mass due to unbalanced masses is zero in any radial direction. Or i ) Static balancing is a balance of forces due to action of gravity . ii) A body is said to be in static balance when its center of gravity is in the axis of rotation.

8. Dynamic Balancing A rotating mass is said to be dynamically balanced when it does not vibrate in its running state . To make a rotating mass dynamically balanced, it must first be statically balanced . Or i ) Dynamic balance is a balance due to the action of inertia forces . ii) A body is said to be in dynamic balance when the resultant moments or couples , which involved in the acceleration of different moving parts is equal to zero . iii) The conditions of dynamic balance are met, the conditions of static balance are also met.

9. Balancing of several masses rotating in different planes F a F b F c F d A B C D L M End view 

10. Benefits of balancing :- Increase quality of operation. Minimize vibration . Minimize audible and signal noises . Minimize structural fatigue stresses . Minimize operator annoyance and fatigue . Increase bearing life . Minimize power loss .

11. Need f or Balancing :- Rotating a rotor which has unbalance causes the following problems. The whole machine vibrates . Noise occurs due to vibration of the whole machine. Abrasion of bearings may shorten the life of the machine .