(color online) Experimented setup of “Boer resonant instrument for forced vibration”,^[35] a fine iron bar with a matching nut is added to a Pohl’s torsion pendulum, and a double-well potential structure is introduced by a torsion pendulum apparatus through adding weights to the copper rotating wheel of Pohl’s torsion pendulum basis. Extremely rich experiment results can be explored in the torsion pendulum experiment, including rich patterns of periodic and chaotic motions and diverse bifurcations between these patterns, by varying a single experimental parameter, the frequency of the driving force, only.