After a long hiatus (day job duties, family activities and holiday travel), the lower rotation ring is now in place.
Thirty-four 16 mm bolts cast in concrete hold the ring in place. The ring consists of four equal segments of steel plate. The dome is secured against wind by eight C-shaped assemblies of thick steel. These contain vertical and horizontal rollers. The horizontal rollers prevent lateral movement of the rotation ring.
Before bolting, the diameter of the ring was adjusted to 350 cm, with a margin of error of only one millimeter in all directions. This high accuracy is ensures that the upper ring will rotate freely, without being squeezed by the horizontal side rollers.
The next step is to mount the upper rotation ring.