I saw a picture of marble machine years ago and I finally got around to trying to make my own. I seriously had doubts about getting it working; so I didn’t want to invest money in nice wood. Therefore, besides the dowels, everything you see was made from a scrap 2×4.
As expected, it was a challenge to get mechanism worked out. I had to remake the cup and adjust the pivot point but I eventually got it working as shown in video.
Build Instructions: https://www.instructables.com/id/Wooden-Marble-Roller-Machine/
In Action: https://youtu.be/sel0w0gXGQk