On paper the first dome drive system looked fine, however, in reality it fell apart. As soon as I applied full power to turn the dome ring the wood bracket holding the motors just snapped. This is the mark2 design and it seems to work very well. I used an old cordless drill to power the dome and for some reason I decided to keep the chuck in place just adding weight. After removing the chuck and setting the touque up correcly the whole assembly looks much neater and works much, much better. I got rid of the old complex wood bracket and replaced with with a much simpler one, bolted directly to the top ring. The tension on the drive ring is via a simple spring fixed to the underside of the top ring. The design is so simple and worked first time, why did I not do this in the first place?
Adding a small grub screw to lock in the wheel was a real pain and to be honest took the longerst time out of building the whole assembly.