Perpendicular Slotted Ellipses

These are interesting because as they roll, the center of mass remains a constant height above the table! This means they roll smoothly, and have no desired resting position (unless material is >2mm thick)

From the excellent book "How Round Is Your Circle".
Blog posts:
[wgprojects - perpendicular-rolling-ellipses](http://wgprojects.blogspot.com/2014/07/perpendicular-rolling-ellipses.html)
[wgprojects - perpendicular-rolling-ellipses-2](http://wgprojects.blogspot.com/2014/07/perpendicul