Playground
Here's a subject ripe with possibilities—not to mention potential hokiness. I include it mostly because I'd actually built a scale, functional swing set that had no readily apparent means of operation. However, it got lost in one of my many moves. So, we have a swing set, merry-go-round and seesaws. Did I miss anything?
The mechanisms required are dirt simple: cranks for the swings and seesaw, and a straight up low-RPM motor for the merry-go-round. I'll expand this page at some point in the future.
Bu the way, the swing set inspired the hammock.