https://youtu.be/2c53OtvgoRg Marblevator, Spiral Disk is my simplest Marblevator yet! Requiring only two 3D printed parts, this Marblevator runs for hours without dropping a marble. I designed the spiral disk (wheel) to run clockwise. With an 8mm ball bearing in the wheel track, as the wheel rotates clockwise, the ball bearing follows the spiraling wheel track until it reaches the end where a sloped surface ejects the ball bearing onto the base track. The ball bearing runs down the base track until it reaches the end where it waits until the wheel track start rotates into position, then falls back into the wheel track. Designed using Autodesk Fusion 360, sliced using Ultimaker Cura 4.1.0, and 3D printed in PLA on Ultimaker S5s.