The presentation details about types of rigid rotors and flexible rotors used in mechanical systems and experimental method of balancing these rotors to avoid mechanical vibrations.

1. PREPARED BY
RAHUL KSHIRSAGAR

2. OVERVIEW
 Difference between Rigid Rotor and Flexible Rotor.
 Rigid Rotor balancing using cradle balancing machine.
 Graphical method for calculating correction of mass and
its position.
 Flexible Rotor balancing using influence coefficient
method.

3. DIFFERENCE BETWEEN RIGID
ROTOR AND FLEXIBLE ROTOR
 Rigid Rotor:-As long the rotor does not experience any
deformations while operating at the critical speed, the
rotor is known as rigid rotor
 Flexible rotor:- While running at critical speed, if the rotor
bends and the bend centre line whirls around and set up
additional centrifugal forces then the rotor is called as
flexible rotor.

4. Rigid Rotor balancing using cradle
balancing machine.

5. Procedure is followed by based on following four
observations
 without addition of trial mass to the rotor
 with a trial mass at θ = 00
 with a trial mass at θ = 1800
 with same trial mass at θ = ±900
Where θ is measured from reference plane

6. Graphical method for calculating correction of mass
required to be placed and its position for system
balancing.
 OA vector is the amplitude
measured without trial mass
 OB vector is the amplitude
measured in the trial run by adding
a trial mass at 0˚
 AB vector represents the effect of
the trial mass
 OC vector measured in the trial
run at 180˚
 Thus, AB vector = AC vector with
phase difference of 180˚

8. BALANCING OF FLEXIBLE ROTOR USING
INFLUENCE COEFFICIENT METHOD

9. A ROTOR SYSTEM WITH MEASUREMENT
LOCATIONS AND BALANCING PLANES

10.  Let p number of balancing planes where p>2
 q number of measuring planes and these are q=2 at the
bearing planes
 let unbalance in each plane U = me

11.  Therefore the response can be related with influence
coefficient and unbalance as

13.  By knowing the influence coefficient, from
equation (1),we can obtain residual unbalance as
follows

14.  Influence coefficient is obtained
experimentally as follows by adding a trial
mass at plane 1.