I am still building.....
For my college project I made a example of a mini excavator undercarriage using my custom made three function driving ring.
I don't plan to build it yet,since there are some better models I would like to to first.
Here is a drive train render:
You can download a MPD file here (The file is not stepped or ordered).
If you would like to purchase my custom made driving ring for yourself then head over to my bricklink shop.