Smart Avionics PB-4, Руководство пользователя интерфейса

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Chapter 9. Two Plane Balancing
This manual has so far described how propellers and rotors can be balanced
by measuring the vibration in a single plane (I'm referring to the abstract
geometric surface, not the aircraft!) The accelerometer has been mounted as
close as possible to the hub of the propeller/rotor and orientated such that it
is sensing the vibration in the propeller/rotor's plane of rotation.
Single plane balancing generally works well when the diameter of the object
being balanced is much greater than its depth and also when it is attached to
the supporting shaft at exactly 90°. Aircraft propellers and gyroplane/helicopter
rotors typically satisfy those conditions and so can be balanced satisfactorily
using the single plane method. When the depth of the object being balanced
is increased relative to its diameter or if it "wobbles" on the supporting shaft,
two plane balancing is required. This chapter describes how the PB-4 can be
used to carry out two plane balancing using the two plane balancing dialog
which is accessible through the main menu.
9.1. Two plane balancing method
The two plane balancing method is really very similar to the single plane
balancing method. It involves measuring the vibration when no trial mass is
attached, measuring the vibration with trial mass attached and then calculating
a solution from those measurements. The difference is that the trial mass is
attached twice, once in each plane, and for each position of the trial mass
(not present, attached in plane 1 and attached in plane 2), vibration readings
are captured from both planes. So that means that 6 IPS/DEG values are
required to be able to calculate the two plane balance solutions that are
needed.
9.1.1. Measurement and correction planes
The planes in which the accelerometer(s) are mounted are called measurement
planes. The planes in which the trial masses and the final correction masses
are attached are called the correction planes. Typically, accelerometers are
mounted as close as possible to the bearings that support the object being
balanced.
Generally speaking, the object being balanced is either supported by bearings
at each end so that its mass is (mostly) between the bearings or it has
significant mass that overhangs one bearing. For items that are supported at
both ends, the measurement and correction planes may be close together as
is shown in the next figure.
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