Hey everyone,
This started out with trying to figure out how to rig a single cardan joint and a double cardan joint in blender. Once that was done I wanted to model one of each, the way they are typically designed in real life.
You can see them animated here.
If you want to rig one yourself, here’s the python code for the driver:
atan(tan(axle)/cos(angle))
Where:
axle -> driving shaft rotation angle
angle -> angle between shafts
result of the driver -> driven shaft rotation angle
This is just too cool!
Excellent job! 
simple and powerful! I would like see your animation - full animation. Are you planning to do something into this way?
Good luck
The animation is beautiful
Wow, that animation is mesmerizing.
It’s really amazing! Could you write small tutorial how to rig it properly?
Here’s a rigged single joint and double joint. Select the objects to see the drivers/constraints.
cardan_single.blend (564 KB)cardan_double.blend (592 KB)
Wow cool! thanks for sharing the files. Like you did with the mini tank. I can learn from this again!
Woah! By moment I thought it was exactly solution for my problem
I have a solution for BGE based on rigging. But still I have problem with double cardan system. It doesn’t work properly. Anybody want take a look? And another problem - my cardian system can rotate only about 25 degrees in y and x axis.
Ps. You can control cardan joint by draggin : empty-object"target #1" in view mode, or wasd in BGE.
Edit: awesome, I find out exactly what I needed. And I post the last effect of my play with bones, and your model.
This is multiple cardan system, joined by empty objects. I will try improve it a little, for robots. Anyway, your ideas helps me a lot. thank you 
cardan sys - rigged.blend (1.16 MB)cartanpede.blend (747 KB)
here’s a formal solution
Wow nice tutorial, thanks!
