# The Importance Of Unbalance

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Unbalance is the most influential reasons of vibration on a rigid rotor. When designing high speed rotors and precise rotors, it is a important factor to be considered in the design. The way which used in the experiment is add the unbalance mass on the rotor, then, make whole system be balanced. The report has contained two tables which show the results collected from the experiment. It has included four diagrams, two tables and discussion section for results.

Theory
Rigid Rotor: Working speed is lower than the lowest-order critical speed of the rotor is called rigid rotor.
Static balance: It is a balancing which included determining primary force into the current plane. Then, added a suitable mass in the position of the plane
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Specific unbalance: □(→┬e=(m□(→┬r ))/M)

Figure 2.1: The detail drawing of the theory of the static balance. For the static unbalance rotor, no matter how many eccentric mass, just needed to keep single-plane balance.

Dynamic balance The mass of static unbalance rotor could not be considered it is distributed perpendicular to its axis of rotation in the same plane. When the rotor rotating, due to the centrifugal force caused by each eccentric mass are not on the same plane, thus, the formation of the inertia couple, the rotor is still unbalance. This process of balancing called dynamic unbalance. Mechanical condition of dynamic balance: Both of the sum of the vectors of each eccentric mass 's inertial force and the moments of them are zero.
∑▒F1=0 , ∑▒M1=0

Figure 2.2: The detail drawing of the theory of the dynamic balance.
Unbalance mass on each support pivot due to unbalance : (mrω^2 l)/L. where "l" is the distance between two balance mass, "ω" means the angular velocity, "m" is the mass of unbalance mass and "L" means the total