How to Use Circular Pattern

cheyenne_greatorex

I am trying to model a vented brake disc.  I completed the basic design and got the point where I wanted to fillet the intersection between the ribs and the inside surface of the rotor disc.  Filleting one is easy, but I want to fillet the rest automatically.  I thought that I would be able to use circular pattern to propagate the fillet to each rib, but the tool just reports an error.  I also tried using the tool on the faces, but that didn't work either.

Is what I want possible or am I just going about it the wrong way?

I tried another solution.  Instead of creating the ribs using a circular pattern, I used an extrude to cut a whole in the brake disc.  I filleted that hole and I was able to use circular pattern to replicate the hole and its fillets all the way around.  The problem with this design is that the ribs aren't rectangular, they're trapezoidal, because the extrude creates the void between the ribs rather than the ribs themselves.

I tried a variation on my second solution, I chamfered the extruded hole.  This got me pretty close, but I had to guess at the angle needed to make the chamfer so that the ribs would be rectangular.  I made an additional sketch to help me try to figure out the exact angle, but it didn't turn out right and the ribs are still a little wider at the bottom than at the top.

I've learned a lot, but have more to go, and any help or insight would be greatly appreciated.  I feel like either this is a hard problem to solve, or I'm missing an obviously easy way to go about it.

Here's the model in question...

https://cad.onshape.com/documents/e97d7a489fb5bd5e60fc78d8

cheyenne_greatorex

After trying several different approaches, I have got it.  I had to extrude the space between the ribs from the side.  I defined the negative space based on a sketch where I laid out the ribs as spokes.  That allowed me to make sure the ribs are rectangular and the negative space is trapezoidal.  By varying the angles, rather than distances, I an change the size of the ribs and the spaces, and then when I use the circular pattern, I just divide 360 by the size of one rib and one space to get the number of copies.