Beercan Iris Experiment
There's nothing like a quick experiment to see what the constraints on the problem are. Beyold, the quick and dirty (actually quite smelly) beercan iris.
I just cut the pieces by eye from an old beer can, so they're fairly thin aluminium sheet. I didn't optimize the shape in any way and, for this purpose, I didn't need to deal with a fancy closing mechanism - fingers work fine.
Anyway, hope that helps you. Certainly helped me understand the problem a bit better.
- It does close completely (I didn't think it would). Or as near as makes no difference.
- Whatever you make the petals out of, it had better be flexible. The petals have a noticeable S-shaped bend when the iris is fully closed and the upper cover is on. If they were more rigid it would not close completely.
- My iris would have a problem opening up again - the pivot pins (read "wire brads") stick up just enough that the petals catch on them as they open. Perhaps the petals should have been wider at the outside end, so they didn't clear the pivot pin of the next petal when fully closed?