Your patience is amazing. What you might also add is something that turning one gear set moves, such as clock hands or an iris (think old fashioned camera gear) mechanism. I grew up with Erector set kits given to me at Christmas time several years in a row by my grandfather (an architectural engineer). The joy in them was that after playing with them you ended up with (usually) a working toy that also was fun to play with. They also encouraged my imagination to make my own designs with the parts. The lasting box-of-parts toys typically had a destination reward for succeeding to put the parts together in a certain way.