(3)
Remove rotor assembly from balancing machine and remove material from surface indicated in applicable manual as required to bring rotor assembly into balance within limits specified.
(4)
Reinstall rotor assembly in balancing machine and recheck balance. Continue balancing procedure until rotor assembly is balanced within limits specified in applicable manual.
(5)
Remove rotor assembly from balancing machine.
(6)
Spot treat material removal area with appropriate touch-up solution as specified in applicable manual.
C. Method No. 412C: General Balancing
(1)
Force Balance or Static Force Balance is a single plane balance procedure by which a mass distribution of a rigid rotor is adjusted in order to make sure that the residual static unbalance is within specified limits which needs correction in only one plane.
Material is removed or added in equal amounts from the two sides to bring the plane into balance.
(2)
Dual-Plane Balance is a procedure by which the mass distribution of a rigid rotor is adjusted in order to make sure that the residual unbalance in two arbitrary planes limits are as specified of those planes.
Material is removed or added as necessary to bring each plane into balance.
The general balancing procedure includes the following:
.
Reviewing balance procedure terms—See Step (3)
.
Determining specifications of the balancing machine that will be used—See Step (4)
.
Determining the Class of balancing to be performed—See Step (5)
.
Performing the actual balancing procedure—See Step (6)
(3)
Refer to Table 404 to familiarize yourself with balancing procedure terms.
(4)
Refer to Table 405 to identify the specifications of recommended balancing machines.
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Table 404. Balancing Terms and Explanations
Term Explanation
Amplitude Measurement of the maximum or peak value of the sine wave of voltage Measuring produced by the pickups. This maximum value represents the amount of unbalance in the work-piece.
Balancing Tolerance The maximum amount of unbalance usually expressed in ounce/inches that can remain in a part without affecting its performance in operation.
Clay-In The process of balancing where no material is removed and balance is achieved by adding modeling clay to the part or arbor.
Couple Unbalance Unbalance caused by two equal unbalances, opposite in direction and located in two separate traverse planes perpendicular to journal centerline, which cause the principle inertia axis to want to be at an angle to the journal centerline. Units are Weight X Radius X Distance (ounce inch 2). Produces motion of gyration.
Cradle A rigid, usually lightweight, support member used to join work supports to allow balancing of parts whose mass, weight distribution, geometry, or bearings interferes with the self aligning feature of the work support.
Critical Speed The speed at which a rotating body vibrates excessively. Usually the critical speed is the same as the natural frequency of the rotating assembly.
Cross Effect The change of unbalance in one plane brought about by alternating the unbalance state of the other plane.
Damping A viscous or frictional-resistance hysteresis force used to reduce the amplitude of vibration.
Equation A shortcut way of expressing a scientific law of relationship by using letters to represent the words.
Force Unbalance Unbalance that can be detected when the part is placed on level knife edges, and will cause the journal centerline to be displaced a distance from, but parallel to, the principle inertia axis. Units are Weight X Radius (ounce X inches).
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