[PBH]

Some relations of surface speed and RPM.

Approximation -> Let's say that a point "P" in the middle of the the shoulders are the center of
all rotation.

Use "RPM" as the basic RPM of the pivot.

Left shoulder (surface) speed = (2 * radius1 * pi * RPM)*60, radius1 = P->left shoulder, unit = m/s.
Hand (surface) speed = (2 * radius2 * pi * RPM)*60 + hand overtaking speed, radius2 = P->hands, unit = m/s.
Clubhead (surface) speed = (2 * radius3 * pi * RPM)*60 + hand overtaking speed + clubhead overtaking speed,
radius3 = P->clubhead, unit = m/s.

Note: radius1 is constant, radius2 increases sligthly in downswing, radius3 increases more.

Another way to see it(but less usefull) would be that left shoulder, hands and clubhead have different RPMs.