@FreeCAD I've been busy in #FreeCAD making design after design for a DIY remotely operable variable capacitors with an eye to designing something that is easy and reasonably inexpensive for anyone to make. I think I'm getting close to something I'm satisfied with. Most people don't need this, but it's actually pretty useful in #HamRadio. Hams tend to scrounge for large variable capacitors and then bend their designs to fit whatever they can turn up; this is parametric so a ham can choose desired parameters, get some PCBs printed, buy some common parts, 3d print a few others, and have a working butterfly capacitor.

The trickiest part will probably be the workflow from FreeCAD design into #KiCAD to create the gerbers to send off to make the PCBs. That will take some manual work for anyone who wants to change the design parameters, beyond just changing some numbers in a VarSet.

This is about 120mm on a side. It uses printed PCBs for the fixed capacitor plates, PTFE film for the dielectric, and laser-cut copper for the rotors. A 3d-printed 60-tooth GT2 pulley for the effector (don't want metal there; it will change the behavior of the capacitor!) and a 16-tooth pulley on a nema17 pancake stepper to drive it. I haven't modeled the belt, but that's kind of the trivial part to imagine, I hope!