Just an update in comments, to make terminology more consistent
If an item is added as a generic ChPhysicsItem into a ChSystem, maybe it needs to load forces. This was not possible in previous ChSystem (it worked for ChBody and regular ChLink-derived stuff, though). Now it is more general.
New class: ChShaftsTorqueConverter.
This is an important tool for simulation of drivelines in vehicle models. It connects two 1D items of ChShaft type, using a model of torque converter.
A third ChShaft is used to represent the connection to the truss, because the difference between input and output torque is applied to a stator connected to the vehicle truss.