The Belt feature as of Creo 3.0 M090 does not calculate belt tension cause by applied torque, and therefore does not contribute to the reaction force of either of the belt connections. This leads to incorrect reaction measures.
An example would be a bicycle chain, which can be modeled as a belt with high stiffness. When torque is applied to the drive sprocket/pulley, it produces tension in the chain/belt which produces both a torque and a radial reaction force in the driven sprocket/pulley. It would be great if this reaction force was computed, but currently it is simply ignored.
In these screenshots you can see a ramp torque being applied to one pulley, while the other pulley is constrained with a servo motor at constant speed. The measured belt tension, however, is constant. This is wrong, as tension should be increasing as torque is increased.
If anyone knows how to make this measurement work, please let me know.