I went to SKF to learn how to design a proper bearing arrangement and share their knowledge with you all. Thank you to Roger and the team at SKF for supporting the Marble Machine :)

Download the Roller Bearing pdf here:
https://cdn.skfmediahub.skf.com/api/public/0901d196802809de/pdf_preview_medium/0901d196802809de_pdf_preview_medium.pdf#cid-121486

Download the SKF SIMPRO QUICK Simulation Software here:
https://www.skf.com/group/support/eng...

The above two tools are really powerful, hopefully they can help guide your own projects correctly.