Magic or Physics? Does the rattleback defy conservation of momentum?

The rattleback exhibits very interesting rotational dynamics due to its mass distribution which has implications on its product of inertia.

Read more about it: https://en.wikipedia.org/wiki/Rattleback

These prints need to be sanded well to work. I have used a nail buffer to smooth the part until the layer lines are invisible and it shines. If you print them larger or add more mass to them they work better. Print with 100% infill.

Here is a video of a couple of mine. https://www.youtube.com/watch?v=J8-X5AMy96Y&feature=youtu.be