Building the Octagon Pt.32 Burning bridges.

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Not happy with the timber cross and outboard stays. Poor resistance to torque. It also rocks too readily if the feet are not fixed down. So now I have made the Obs. floor, pier aperture larger by removing a couple of floorboards. I am trying to see how large a regular pyramid I can squeeze into a manageable aperture with the feet right out near the walls.

The 4x4 posts are presently too long for this which forces them too far apart at the top. If I shorten the posts I can no longer use them sunk into concrete in the big pipe if I decide to follow that route. I'll just have to do a mock-up on the ground and measure that instead.

I decided to have one more go at a simple, pyramidal pier  using the 4x4s. As can be seen in the image alongside. I had to saw the posts to 4m in length to be able to fit them together at the top. They are pushed out at the bottom as close to the ground floor, perimeter joists as possible. I removed some temporary floor boards to allow the pyramid to dictate its own needs. It took a lot of lifting and poking the heavy 4x4s through small gaps before there was proper clearance for pier isolation from the building. 

I dropped a plumbline from the top of the pyramid to ensure it was centered over the big pipe. My thinking is that the wider the four legs are spaced the less they will obstruct the ground floor. In fact there is no real point on making the pyramid full height to support the mounting. A secondary pier could easily have been added to the top of the pyramid.

The legs of the pyramid want to slide relative to one another, at the top, so bracing and/or plywood cladding will be required to stiffen the structure into a solid geometric form. Cladding will also make the pier top, as seen in the observatory, rather more 'decorative' than a gathering of sawn 4x4s.

I used up the small reserve of self-compacting sand & gravel to fill in the concrete pipe and flatten the floor. Once that was done I'd have to make a conscious decision to uncover it again. So that rids me of a number of options to worry about. Having a flat floor, at last, provided the opportunity to rotate the ladder by 90°. I shall climb into the observatory through the pyramid, under the mounting, without hindrance and with a free choice over ladder inclination.

My camera seems to suffer from mild, barrel distortion. Nothing I try makes everything look parallel.

Click on any image for an enlargement. 

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