3D-Printed Grandfather Clock Doubles as a Modern Art Piece

As you know from your middle school science classes, a perpetual motion machine is impossible. But you can make a machine run for a very long time if it is efficient enough. A swinging pendulum will keep swinging for quite a while, which is why they were commonly used to drive clocks before reliable electric motors came along. The swinging of the pendulum is nice and regular, so it can drive the clock's mechanism. This maker applied that concept to a 3D-printed grandfather clock that doubles as a modern art piece.

This project started with The Arnfield Gravity Escapement designed by JBV Creative. This is a 3D-printable, pendulum-driven escapement mechanism. Like many similar mechanisms, it uses a weight attached to a cord wound around a spool to rotate the input gear, while the swinging pendulum actuates the ratchet at regular intervals. The Arnfield Gravity Escapement can only run for a few minutes before it needs to be wound again. But the subject of this article can run for around 100 minutes per winding, or indefinitely if mains power is available.

A few upgrades made the extended runtime possible. The most obvious is the long weight cord (actually a ball chain), with two weights. Because those can drop further, they can keep the mechanism running longer. An additional gear drive also makes every inch of drop turn the mechanism further, similar to how a single revolution of a bicycle's chain rings will rotate the wheel more than that. An extra-long pendulum has a two-second swing to actuate the ratchet.

Even with those improvements, this mechanism would need rewinding every hour and half or so. That's pretty inconvenient, so this clock got a motor for automatic rewinding. When the weight drops to the bottom, it trips a limit switch monitored by an ESP32 development board. The ESP32 then activates the electric motor to pull the weight back up to the top.

As an interesting quirk, the mechanism doesn't drive clock hands at all—there is no analog clock face. Instead, the ESP32 detects each swing of the pendulum using a Hall effect sensor and magnet. When the ESP32 first turns on, it pulls the time using NTP (Network Time Protocol). But after that, it keeps time by monitoring the pendulum swing. It then shows the current time on a standard four-digit seven-segment display, just like a digital clock.