My Platform
The Ground Board
The part that sits on feet resting on the ground is the Ground Board. One fundamental principle (from Dobson's work) is that you want three feet resting on the ground, and mounted close to the support bearings for the platform, for stability and rigidity.
I first saw this design idea for the support bearings in the work of Reed, seen at the Yahoo eqplatforms group. Using "ball transfer" bearings to support the axial load simplifies construction. At most, my insight was that the two bearings on the South end can be mounted together on a single support, thus reducing the number of alignment points.
The North axial load bearings are also ball transfers, and another idea from Brian Reed is to drill the support mounting holes oversize and use a fender washer to mount the support and bearings with adjustability.
The same approach was used for the motors. I chose to use two motors, connected electrically in parallel, so that there is drive on each end of the North sector. A planned improvement is to mount the drive rollers on shafts supported by bearings on each end, with a flexible coupling to the motor shaft. This will remove radial loads from the motor bearings and improve their life.