# Calculated Reaction Forces

I am looking at a hinge joint (elbow), and I understand that there are
5 constraints out of a possible 6 degrees of freedom to allow for
flexion/extension movement. When running an analysis and then looking
at the resulting AnyBody chart, (Jnts - Elbow - Constraints - Reaction

• F), how am I to interpret the F[0]-F[4]? I’m running a 2-D problem
very similar to the dumbbell example in the tutorials, and am
interested in the Fx, Fy, and Mz in the elbow. Am I looking in the
completely wrong area of the model to find these values?

Hi Sarah,

Sorry about the late reply. We are usually quicker, but it is the
vacation season, and pretty much the rest of us are headed out for
the ISB conference in Cleveland.

The first three reaction forces (numbers 0, 1 and 2) in a
revolute joint are the forces, and the remaining two (numbers 3 and 4)
are the moment reactions. These reactions, I believe, are in the
global coordinate system, which might not be what you are looking for
when you deal with a moving model.

In which coordinate system are you interested in finding these
reactions?

You can gain more control of the output by creating an object of type
AnyForceMomentMeasure. Please have a look at the reference manual for
a full explanation and come back here if you do not understand it.

Best regards
AnyBody Support

— In anyscript@yahoogroups.com, “Sarah R. Sullivan” <sarsulli@e…>
wrote:
> I am looking at a hinge joint (elbow), and I understand that there
are
> 5 constraints out of a possible 6 degrees of freedom to allow for
> flexion/extension movement. When running an analysis and then
looking
> at the resulting AnyBody chart, (Jnts - Elbow - Constraints -
Reaction
> - F), how am I to interpret the F[0]-F[4]? I’m running a 2-D
problem
> very similar to the dumbbell example in the tutorials, and am
> interested in the Fx, Fy, and Mz in the elbow. Am I looking in the
> completely wrong area of the model to find these values?