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SP8: Coup Perdu Clock

This clock has a Coup Perdu escapement and an electric rewind. Coup Perdu is French for "lost beat" allowing a half second pendulum swing to show full second movement on the dial. The Coup Perdu escapement has 60 large ticks per minute from a 9.8" pendulum. An optional deadbeat escapement produces 120 small ticks per minute for slightly quieter operation.


A small electric motor rewinds the clock every few minutes for continuous operation. I estimate around 6 months of battery life using two AA batteries. 

The overall size is around 10.5" (265mm) wide by 13.4" (340mm) tall and 6.1" (155mm) deep. All parts can be printed on a Prusa Mini or any machine with at least a 175x175mm print area. 

The total print time is just under 90 hours and just over a kg of PLA filament. The images posted on this page were printed with MatterHackers blue raspberry Quantum PLA. It is my new favorite color for clock gears.

The clock can be built as either a desktop or wall mounted clock.

The design is posted to MyMiniFactory

A video of the clock is shown below.


The clock is provided with a traditional Roman numeral dial and simple numbers. 



The electronics in this clock are cheap and easily available. The rewind mechanism uses a small N20 motor with a 1000:1 gear ratio.


The motor is enabled by a small lever arm that tips when the weight shell drops past the trigger point. A magnet makes contact with a small reed switch to turn on the motor. 

The motor shuts off when the weight shell lifts for the lever arm to tip away from the reed switch.

Here is a close up of the trigger mechanism.



The clock shown here is printed using MatterHackers blue raspberry Quantum PLA. The filament strands consist of two different colors fused side by side. The resulting gears change colors as they rotate. 

The filament is a bit pricey, but well worth it. All the gears in this clock take about 0.3kg of filament.

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