Have I commented before that I'm a huge fan of conceptual art? Here's one from 2014! a HUGE Concept drone for DHL package delivery.
In order to modeling every single mechanical part or detail, first you have to imagine it, studied it, and applied in a logical way to get a convincing result, proportions are important too, it's quite similar to drawing
I'm still struggling and learning these concepts, soon I'm going to share my lastest 3D models