Hi colouredpages, the thing with making a wheel (or anything round) , using the Array Modifier is, that you need to model details curved and get the math right; when you are using Object Offset on the Array Modifier you’d need to rotate the Object (probably an Empty) 360/10=36°,
Now, I am not a teacher, but you might want to look at this: https://blog.cgcookie.com/forums/topic/slight-problem-with-adding-a-bevel-to-some-parts-of-the-shell-edges/
The main thing I’d want you to take away from this is to use the Simple Deform > Bend Modifier and not the Array when it comes to wheels.
