Needed an avatar. This is my first submission, and I'm more programmer than artist, so go easy.
Overall, I'm happy with my first spin effect. There are things I like and things I don't like, but at this point I'd have to start a new piece to fix the CoM errors.
Here are some WIPs, at 4x zoom: WIP1 WIP2
To animate, I started with a single fully-shaded frame. Then I duplicated and flipped it horizontally, and tried to extract 3d information from the two. I added a block colored frame in between, and then went frame-by-frame. Added shading, fixed a few issues, and called it done.