[dlam]

Drew,
What is the left shoulder hinge pin?

If that includes the scapula, ribs and humerus joint as one hinge I would agree.
You mention the primary assembly unit working at one RPM.But it has to match with the PIVOT RPM. There is no use swinging the arms if it's not in synch with the body.
The "connection" in a physical sense to the PIVOT is through the left scapula and ribcage.


Bernt,
Agree that clubhead is moving at a different rate than than shoulder, different from the wrist and different from the pivot.
RPM is speed and a measurement of tempo not rhythm. Rhythm as you correctly describe is the pattern each part of the machine's rpm's blending together.