rub rub rub
Good. I still had fun. There is even a gentleman who helps me, and who made me a nice drawing: We see our Pioupiou, its propeller, and ball bearings. (You can also see other tricks there, like too much leverage between the bearing and the propeller. But since I don't know how to draw so well, I keep this image there.) Anyway. There is in particular the pivot of the propeller. This is THE critical point…