The objective of this tutorial is to understand and use the:
|•||Configure Power Source dialog-box|
Gravitational Force acts vertically down, [▼] in the direction of Model's 'Global –Y-axis'. The 'Front View' [Short-Cut: F3 key] Therefore, when the force results will be important, you must start the design on the plane that represents the orientation of the actual machine. If, later you want to move a mechanism to a different plane, you must save the Model as a Library File, then select a different Plane to open the Library File.
Forces in MechDesigner