Dual Brachistochrone curve

thingiverse

Here is a Brachistochrone curve where two marbles race down it from different starting points and meet at the bottom simultaneously. The curved tracks keep the marbles on course, staying in the middle path as they roll down. Getting the orientation right is crucial when printing this design. The grains should be aligned with the direction of each marble's path to minimize resistance along the way. Printing in a different orientation will add extra steps - sanding will be needed to smooth out the surface. I haven't printed this yet, but I'm confident that the gentle curves won't require any supports during printing.