If you visit the Copenhagen City Hall, you’ll see an ornate mechanical clock. By itself, this is unremarkable, of course. There are plenty of ornate clocks in city halls around the world ...

The clock uses an idler wheel to move the hour ring so it doesn’t need a separate hour hand. After he built his first design, [wyojustin] realized he could add a planetary gear that could move ...

Making a mechanical Lego clock that keeps time for a billion years ... The escapement wheel moves one tooth per second, and multiple gear trains transmit motion to display everything from days ...