  A detailed analysis of three pendular motion models is presented. Inertial
effects, self-oscillation, and memory, together with non-constant moment of
inertia, hysteresis and negative damping are shown to be required for the
comprehensive description of the free pendulum oscillatory regime. The effects
of very high initial amplitudes, friction in the roller bearing axle, drag, and
pendulum geometry are also analysed and discussed. The model that consists of a
fractional differential equation provides both the best explanation of, and the
best fits to, experimental high resolution and long-time data gathered from
standard action-camera videos.
