28.08.2021 Double checking the numbers.

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Saturday afternoon: Continuing dark overcast and breezy at 60F. 

Still not in the mood to be making more sawdust.
So I physically checked all the diameters again:

The dome is 4.30m in diameter.
The base ring is 15cm wide. Twice 15cm = 30cm.
The distance between the inside edges of the base ring is 4m.
The centres of the base ring lie on a 4.15m Ø circle.
The building's 14 points also lie on a circle of 4.15m Ø.
Which is only 75mm from the dome wall.
80-90mm from the dome wall for the roller track is probably safer.
The rollers need to be moved inwards, away from the dome wall, for clearance.
This slightly increases the cantilevering of the upward loads on the base ring.

The dome skirt clearance from the rollers is critical during the dome lowering into place on top of the 4m high building. Is it reasonable to expect placement of such a bulky object to within a few millimetres? 

The slightest breeze could move the dome in any direction. Even with a remote control handset the crane driver is going to be some distance below and away from the dome/building. Unless they stand in the building itself to closely monitor the lowering? Would this be considered safe working practice? Despite the advantages of much greater precision. If this were a machine or structural steelwork the load would normally require fixing bolts. Which is far higher precision than I need. Unless they use crowbars are used to move the load slightly?

What can I do to make the lowering an easier and safer task? The dome skirt will have to fit over the building and/or the rollers. The rollers are bright white and the dome dark green. No problem with contrast. The sheer weight of the dome makes certain options all but impossible. One damaged roller could make the lift impossible to complete.

If I removed all the rollers I would have to lift the dome over 20cm/8" in stages to refit them all. This is not a job for crowbars levering against the building timbers! There is no room for jacks. No obvious way to lift the dome safely with a chain hoist from within. I will just have to rely on an experienced crane driver managing the lift safely.

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