MarbleElevator - Spiral Staircase

This is a demonstrator for my new marble elevator.
See it in action: https://www.youtube.com/playlist?list=PLzWcdLH8XcMcDHO28YEF-xlPWmG5SjJiw

This lift needs to fit into the eye of an existing spiral staircase. The opening is only 49mm in diameter, and the design should be another spiral staircase, on which the marbles climb upwards.

Earlier attempts using plywood did not work. I had to cut very thin parts and they were not robust. This design uses 1.5mm kraftplex material and works just