Big Bear Observatory

Making the dome

(click on the pictures to view!)

The dome is 4m in diameter and the skeleton is made from 25x25mm*1.5mm square steel tubing. It was available in 4m lenght and the first thing was to bend it to proper curvature. Made a simple bending tool (3 rolls, middle one adjustable) from scrap parts. And then some muscle!
The base ring is made from 30x30*1.5mm material and was about max size for manual bending. The base has two rounds of it for an effective 60x30 welded frame. The curvature was measured with a simple tool (visible on the floor & in my hand). The welding was mostly done with MIG equipment - its easy to learn and use (I had some pro help from work colleagues to get started).
Nowadays I would let the machines do the work and also make the base ring from much heavier material. Actually IŽll propably upgrade the current construction with a new base ring for better circularity and level.

covered with 0.5mm galvanized steel hand riveted together. Some 3000 rivets...

As You can see I made the dome before I had the building.
The storage building in the background stands where the observatory is now.
The dome project took actually two years - in the first summer I made the frame and on the second it was covered.

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Juhani Kyyrö
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