I have seen a number of rolling ball sculptures using a vertical screw lift. Because of the space requirements and the fact that it is kind of sexy, I decided to use that principle.
Seems simple when you look at it, but never having made on before, it became a challenge to figure out just how to approach it. Getting the spiral part to be consistent was the hardest.
After figuring out just how tall it needed to be, I set about making jig to hold the brass center rod while soldering it. A trip to the Home Depot netted me the pieces I needed to make the jig. Plumbing department first to find a brass pipe and a cast iron flange that the pipe would just slip into. Some fender washers from hardware and some brass collars I turned to fit the .25″ rod that I was using for the center post. The washers had to be turned down slightly to fit snuggly into the pipe. They will hold the rod center yet slide inside the pipe to support the bottom end of the rod as it moves up. The cast iron flange worked well as a heavy base for the jig.
Soldering was made more difficult because the heat was absorbed into the jig so it had to be concentrated close to the joint. There was a tendency to warp the center rod from the heat and still not melt the short standoff piece. There must be a easier way.
Anyway things progressed, albeit slowly, until the piece emerged from the jig. Putting it into the drive assembly for sizing came next after spending time straightening out the center shaft. In retrospect, if I do this again I will use a thick wall 1/4″ tube instead. Less heat required and less warping of the shaft.
The vertical support for the top of the spiral is from a 1/2″ square bar and 3/4″ x 1/8″ flat plate with a FR168ZZ ball bearing. This is the same bearing used for the shafts in the drive assembly. The plate is attached with 440 socket head screws. I like the looks of the socket screws and will use then as a standard through the project.
The stud and acorn nut on the top support will be used to attach an old brass National Cash Register bell for the hour strike. I think it was for the “D” drawer.
I had to be careful of the height so it didn’t hit the inside top of the dome.
Right now I have no idea how I’m going to make the hour strike happen. 
It is a bridge to cross later as there still is lots to be done to feed the balls onto the spiral.
Next step, feeding the balls into the spiral.