A project we did in team for an engineering class of machine elements. This is a planetary gearbox to drive an openable stadium roof.
This gearbox is composed of 4 planetary stages wich brings the the ratio to 215:1.
The output torque wich it was design for is about 10000 lbs*ft @ 2 RPM
It ain't fully engineered, there's a lot of guesswork and rules of the thumb in the design.
But every shafts, bearings, gears, keyways and splines have been engineered.