This ideal massless joint provides a gear constraint between
frames frame_a and frame_b. The axes of rotation
of frame_a and frame_b may be arbitrary.
Reference
Schweiger, Christian ;
Otter, Martin:
Modelling
3D Mechanical Effects of 1-dim. Powertrains. In: Proceedings of the 3rd International
Modelica Conference. Linköping : The Modelica Association and Linköping University,
November 3-4, 2003, pp. 149-158