I designed this Chaotic Pendulum a few years ago but just realized did not publish. Most Chaotic Pendula are made of metal to give it a lot of inertia. Plastic has a low density, so this was designed to use 3/8 hardware to give it mass. You can "balance" it by adding nuts and bolts to get the desired action. bearings are just standard roller blade/ fidget spinner bearings. The mounting rod is just a 3/8 lag bolt with head cut off. Used washers to space as needed.

Video:https://www.youtube.com/watch?v=Gk7ZSwaoEp8