Hi StandOff,
Thank you for your comments!
Some explanations are indeed missing.
I will add them to the game description :)
Some gears (the one in the third puzzle, and one in the fifth puzzle) have to rotate in one particuliar direction. There is a small arrow above the upper right corner of these gears to indicate that, but it's not the clearer indication there is.
I will definitely improve this if I work on an extended version of the game.
Thanks again and have a great weekend!