Aside from the shape of the swords of the wheel (different suggestion ar there!!) there is as well the discussion with the shape and size of the upper and lower spokes. In the other models these spokes have been only symbolised to not unnessecary make the picture to complicated. Nevertheless the commentary states that the shape of the swords are like two cones of a speer comming together.
Here then the question is where do they meet ( 1) at the top of the realityscource or 2) at the middle of the spere of the protection wheel or 3, 4;..) and what diameter has the end of the cone