Show HN: Carton Clock – A working pendulum clock made from empty drink cartons

Carton Clock is an experiment in making a functioning mechanical timepiece from discarded drink cartons. The builder set out to improve on an earlier “trash clock” by avoiding materials such as PVC and welding rods, using cartons, hot glue, paper straws, BBQ skewers, string, and metal nuts instead. Cartons’ cardboard provides structure, while their polyethylene coating offers low-friction surfaces; plastic caps can serve as mounts or gears. The first prototype showed that a carton escapement could work, but a 30-tooth wheel demanded more precision than the material allowed. A larger, simpler five-tooth design succeeded, though that clock ran for only 7.5 minutes. Browser tools developed with AI generated cutting patterns and gear designs, while 3D-printed jigs helped shape parts; neither the tools nor a supporting tripod became part of the clock itself.

The second version adds the gear trains needed to display seconds, minutes, and hours. Its escapement uses a 15-tooth wheel, and carefully proportioned gear pairs provide the required reductions, including a 60:1 drive from seconds to minutes and a 12:1 motion work linking the minute and hour hands on a shared axis. A pendulum with adjustable weights was tuned toward one swing per second, but the clock could not reliably maintain that rate: adding lower weight eventually stopped it, so the finished clock runs fast. A four-pulley arrangement lets a raised carton filled with nuts power the mechanism for a little over an hour, meeting the project’s runtime goal while exposing the limits of its improvised materials.