.....regarding gravity powered devices , has ...two parts :
-bad news for "inventing":no need to imagine new mechanisms
-good news for "reinventing" : we can apply variable leverage to so many existing mechanisms.
Let's take a look at a very old mechanism (1785) :
http://kmoddl.library.cornell.edu/model.php?m=13 (http://kmoddl.library.cornell.edu/model.php?m=13)
If we add two "heavy-points"/masses we can play it ,as a self-moving seesaw-pendulum (swinging mass+rotating mass).
It's not the same game with new cards , but a new game with old cards...
Al_ex
.....if we replay an old,unsuccessful test of a wheel:
https://www.youtube.com/watch?v=Rgp6gcSaF2Y
in a simplified manner , as a lever (two opposite arms...1:06-1:56 only!) :
https://www.youtube.com/watch?v=FQ02MjqBk7s
so to take advantage of the main dynamics property of our gravitational field...
Al_ex