IF you open the attached model.

It is basic rotational inertia - no gravity, or other effects

Select a Gearbox - ratio of 3

Then Select Kollmorgen motor and while it runs through them, MD crashes.

Quite a lot of associated bugs actually, which I have hopefully now corrected.  This code as it is new needs extensive checking.  Howver I will pout this code up on the internet as it is alrady way better that the old code.