Enantiomorphic Rattleback/Celtic

Per Wikipedia: A rattleback is a semi-ellipsoidal top which will rotate on its axis in a preferred direction. If spun in the opposite direction, it becomes unstable, "rattles" to a stop and reverses its spin to the preferred direction. The model can be scaled up or down, but it doesn't work as well scaled smaller in my testing. Larger the better is what I found. I have included 2 versions of the model that spin in opposite directions. The surface that you spin the rattleback on will affect how well it changes direction. I found it seems to work best on a UHMW plastic cutting board. I have seen other models where the designer suggests sanding the curved surface. I have not tried that, but I imagine it would help. The model is split into various parts to ease adjusting colors and the weight distribution of the model by changing the infill percentages. Half the fun is playing with the size and weight distribution to see what works best!