As per Victor Wowk / Crawford, the trial mass added to the rotor must create a force equivalent to 10% of the rotor weight, which means It should be
-
large enough to produce a measurable vibration change of 30% and/or phase change of 30 degree.
-
small enough to avoid overstressing the rotor or introducing excessive vibration.
You may use the calculator below to approximately estimate the trial mass that could be placed in the rotor during a balancing activity.