A simple method to measure friction torque M generated in revolution joint of the grey inner ring and the orange outer one. The grey ring is fixed on the blue shaft, the orange ring is fixed on the green hand assembly.
M = PLsinα
P: weight of the pink weight
L: distance from the pink weight to the rotation axis
α: angle shown by the green hand
Force applied to the revolution joint is the weight of the hand assembly including the pink weight.
The hand assembly (without the pink weight) must be adjusted with the violet nuts to be in static balance.