I just finished this piece, it’s titled “Up Draft”. After fooling around with several “flapping” mechanisms I settled on this configuration. Here’s a quick test before I put everything in place:

There was a bit of adjusting and fitting before everything came together. One neat feature, there’s a bit of spring action on the arm coming from the center post. This was intended to solve a problem where there was a bit too much push and pull. The result adds some nice additional movement.