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