You'll need to have a very clear idea of how it's shaped, and segment the circle accordingly. (I have to admit, with all the reflections in that image, it makes it harder to imagine how it's shaped!) Basically, the areas of the rim that are lifted for the tuning rods need to all be selected and lifted together. Likewise, all other repeatable parts need to be segmented, selected and modified together to give it that "machined" symmetry.
PM me if none of that makes sense
I'll be happy to get with you (say, on Skype) and explain with a shared screen.