The conditional support flange  is enabled by a boolean parameter, generally named Use Support Flange.  The usual default is false. When the value is set to true, the support flange is enabled.  This causes the component icon to change shape; a connection port appears where previously there was a small fixed reference.  Some 1-D mechanical components have a conditional support flange; a few have more than one such flange.

The following two icons show a component with the support flange disabled and enabled.

Equations

The equations of a component with a conditional support flange are in terms of the position/angle of the main flanges with respect to the support flange.  When the support flange is disabled, the support flange is internally connected to a fixed reference.  To simplify the help pages, the given equations are generally with the support flange disabled.

As an example, consider the Rotational Constant Speed component.  The pertinent component equation is .  When  is false,  is measured with respect to a fixed rotational reference, so the absolute angular velocity of the output flange is . When  is true,  is measured with respect to the support flange, which must now be connected to another rotational component.  So if the support flange has an absolute angular velocity of, say, , then the absolute angular velocity of the output flange is .

1-D Mechanical Overview