Kythera is a simple spur gear editor for the Macintosh.

With Kythera you can quickly design complex gear trains, and visualize their motion on the screen. You can also quickly export your gears in DXF format, STL, or as PDF templates, and Kythera will also generate OpenSCAD files for frames to hold your gears that you can quickly modify to your own purpose.

Kythera also has a number of powerful tools, including tools for reshaping a chain of gears to fit a particular linear dimension, and for quickly constructing custom motion works, which allow you to design custom clocks with a custom rate of motion separating two arms of your clock.

Kythera also includes a gear calculator which allows you to find fractions which approximate certain decimal values–helping you make quick work designing gear trains for approximating other celestial movements, such as the phase of the moon.

We intend Kythera to be a starting point for designing complex gear trains which you can either then print directly on your 3D printer, or import into a 3D CAD editor (such as OpenSCAD) for building more complex mechanisms, such as gear trains for your robotic projects.

Kythera v1.0 is available now on the Apple App Store.

From the author.

My interest in Kythera started with a desire to build an Orrery, by designing a system of gears which approximated the motion of the planets in the solar system. I couldn’t find any good solutions for performing the complex mathematical operations required to figure out the proper gear ratios and placing the gears in a 3D mechanism, so I started in 2016 building Kythera, to aid in the design of an Orrery with custom ratios closely matching data from NASA.

Of course I’m still a ways away from assembling my Orrery, but Kythera has become robust enough that hopefully you will also find it useful.


Besides extensive in-app help, we have a number of tutorials to help you make the most of Kythera, and we have published a number of articles at The Hacking Den.

Bugs? Suggestions? Complaints?

Please contact us with your comments!