I have started modelling Felix in OpenSCAD. OpenSCAD is the bees-knees – if you don’t like to move your hands from the keyboard.
OpenSCAD is an Open Source tool to create solid 3D CAD objects. You can create quite complex objects ready to be 3D printed. But this is not a interactive modeller, you describe your model in text.
Last year I discovered OpenSCAD, and for the kind of stuff I currently model (mostly mechanical contraptions) it is perfect. I have been a Vim user for many years and by setting OpenSCAD to automatically reload and compile (from the Design Menu), I can describe all my geometry in Vim with solid syntax highlighting and (for me) a very natural workflow.
So I begin by modelling the TowerPro servo and the two types of servo horns I plan to use with Felix.
You can follow the development (and download the CAD files) from my GitHub repository.