This is a different take on my "noisemaker.” After working with several vehicle models with integral turning wheels it occurred to me that I should be able to design something similar to the toy in http://www.thingiverse.com/thing:388748 but using the cone/bearing concept such that I could print the entire thing in one unit. What do you know, it worked! My son likes the “key” handle on this one: He shows it to people and tells them to wind it up so that it will spin. “Keep winding… keep winding… .” As I'm finding with many items that rely on close tolerances, best to set Slic3r for "external perimeters first." Also, if you really want to be able to spin it 'round and 'round instead of emulating my kid's practical joke, you might want to add some mass to the end opposite the key.