Not a bad build, rather simple design. Functionality needs a lot of work. The small gear at the top of the tower for rotation of the arm is poorly supported and therefore doesn't engage most of the time. The trolly that should move back and forth across the arm is operated by one motor that pulls two strings in opposite directions. On my model the strings kept getting slack and knotting up. Base is rather small and not as stable as I would like.
Summary: Not bad as a display piece but not very fun to operate.