Marble Clock is a 3D printed rolling ball clock that tells the time by the location of marbles/balls. It consists of 3 main rails, where,
The 5-minute rail with 1-minute intervals The 15-minute rail with 15-minute intervals The 12-hour rail with 1-hour intervalsadd up and tell the time.
Outline
In the first step, I will give you a little bit of history of rolling ball clocks and ball clocks in general. Next, I will explain the Idea behind this project. Then I will give you an insight into the design process of this clock, so you’ll be able to design your own clock. I’ll give you a 3d print guide so you can easily print the required pieces and arrange them. After giving you a step by step assembly guide and show you how to sync your clock, I’ll end the instructable with a troubleshooting guide. So, if you encounter any problems during your build you can solve them easily.
The purpose of this instructable is not just to give you a cookbook. I’ll show you the way I built this project and provide you with open-ended questions, so you can add your own ideas, and take this project even further. Many parts I’ve designed are not connected. This way you can change the design to your own liking and then glue them together.
I strongly encourage you to share your build when it’s done!
Let’s get started.”

Link