[no_mind_golfer]

Jeff.
Thanks for the links. Not universal joint though. It looks like synchronized shaft rotation with uncocking action through gears. Wish I could have similar arrangement on my wrists.

I concur....

http://www.golflabs.com/Images/tse_4.jpg

I talked to Paul Wilson of Swing Machine Golf who has seen up close (and met the designer of) Iron Byron and he says it too has gears to close the club face 90deg in the downswing. They did because its part of the deceleration mechanism (shafts were breaking post impact without gears controlling the decel) and because Bryon Nelson did it. He said they all do (swing machines) so I guess *(and it looks like in the video it must)* pingman does as well.

I see no reason why the club face would open/close on its own as a result of interial forces.