A good reaction?

When performing a motion study, there are obviously a number of moving parts all connected with each other, pushing and pulling in response to the driving forces set up.

Reaction forces and moments are frequently plotted at joints but it can often be difficult to work out if they make sense when only presented with a graph.

A more visual clue to understanding what is going on is the Reaction Force Vector.

When you create a reaction force plot as normal, you are asked to pick the joint in question (say Concentric2 below). However whilst you are in the same selection window, if you also pick the face of one of the connected parts a new option appears (as if by magic) at the bottom.

The option to ‘Show vector in the graphics window’ appears and picking this displays the vector for the reaction force or moment.

This vector can be used to get an appreciation of how the forces act in your model and updates dynamically when the model is re-run or re-played. Quite useful when trying to understand how all the joints carry the load in a model, and another sanity check when you Import Motion Loads to a stress study.