12.2.2 Constraint and Load Choices

The entire set of constraint functions provided by Mech is quite redundant. Almost any geometric constraint can be duplicated by some other constraint or combination of constraints. However, the algebraic expressions generated by functionally identical constraints can be quite different. It is important to use the simplest possible representation of a mechanism joint to reduce the size of the model.
The one time when a more complicated constraint set should be considered is when it is possible to remove a body from a model by replacing the entire body with a compound constraint. The OrthoRevolute4 and ParaRevolute4 constraints in Modeler3D are good candidates for replacing entire bodies in a model, as is the RelativeDistance1 constraint that is commonly used to replace a connecting rod. It is often possible to eliminate multiple bodies, even interlinked bodies, with a correctly chosen compound constraint.
A body cannot be eliminated from a mechanism when the inertia of the body is relevant to the analysis. But even this has an exception: the gyroscopic forces associated with a body that is spinning rapidly about an axis of symmetry can be duplicated by a GyroMoment forcing function, thus eliminating the body itself from the model.