This is a prototype of my most recent water engine based on expanding fibers in a long leaf pine cone. A bit underwelming untill you build one and watch it cycle over and over. Then you get all thse ideas for making it go faster or pull more weight, wind a clock, etc.
The petals from a pine cone most be removed from the cone & kept intact. Then they are glued with superglue or any waterproof glue so that the 90 degrees of movement (from wet to dry) is doubled to 180, unless 90 degrees is acceptable. I have jpgs of a prototype I hope to post.
I was working on using this action for a humidity indicator, but when I saw that it can dip itself in water and the rise out to dry, I went with the water engine!