Start
General Info on the BMPCC
Pitfalls
Planning your Setup
Lenses & Adapters
Power & Batteries
Audio
Recording Media
Camera Support
Monitors & EVF
Postproduction
DIY Stuff
Help
Since FreeCAD has an involute gear function, it's very easy to design a FF Gear ring with it, here is a quick screencast on how to do it:
FF Gear in FreeCAD
And here the Forum Thread which explains it in more detail:
http://forum.freecadweb.org/viewtopic.php?f=3&t=7505