Take a look at the following simple example robot arm:
I want to know the torque required on that bottom motor to rotate the arm. Since it's not exactly rotating directly against gravity like the other joints I'm not sure how to analyze. Assume we know the mass of every part of the robot arm and the distances to the base.
For reference, I am planning on securing my base rotation motor's shaft through a ball bearing rotary table to the rest of the arm. I'm considering the torque required on that motor to properly pick the right component and make sure I get enough speed as well. So understanding how to analyze the forces would really help!