21.06.2022 Pier improvements?

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 Tuesday 21st June. Longest Day. Summer Solstice.

 I have been giving some thought to the very tall [4m] telescope pier. 

 The pier must be moved by 65cm to the SW. To bring it central in the larger building. What could I do to improve the pier while I can?

 The obvious negative was the need to cut a hole [dog kennel door] in the western side of the cladding near the top. This was to allow me to climb the stepladder INSIDE the pier. In order to reach the observatory floor. No plywood could be used lower down because of the large stepladder. So the open side was a potential weakness.

 The pier is pyramidal and consists of four, full length 4x4s. It rests on buried carport anchors. Which are spaced at the maximum footprint. To remain inside the original 3m/10' diameter building. These footings are tapered, precast concrete blocks. They have heavy steel brackets on threaded rods on top. These attach to the bottom of the pier's four legs. Which allows fine height adjustment.

 Once clad in thick plywood, the pier was very stiff. It showed great resistance to twisting [torsion] at the top. I tested this repeatedly over time. By applying a long, steel pipe as a lever near the top.  

 Of course I was careful to ensure the pier was isolated from the observatory structure. Only near the ground did the pier footings approach those of the building. No transmission of vibration was noted between the pier and the building. I jumped up and down on the observatory floor. With a highly magnified view of the sun on the large computer monitor. No movement was ever detected. 

 I shan't expand the pier dimensions despite the new building having a larger footprint. 4.3m : 3m. I will need to dig up the pier footings and move them SW. Or I could just leave them in place and buy and bury four new footings in their new positions. They are quite inexpensive and are sunk to ground level. So will never become a nuisance. 

 Can I arrange the stepladder to completely avoid the pier? This would allow the pier to be fully clad with plywood from top to bottom. Providing a theoretical improvement in stiffness. Possibly less prone to the timber legs warping? If there ever was any. 

 Maintaining alignment, of the massive mounting on top, has never proved to be a problem. I used high magnification and imaging software to check regularly by drift alignment. 

 This drawing gives some idea of the difference in scale between 4.3m Ø and 3m Ø. The 3m square, forming the feet of the existing pier, has been moved [red] to the centre of the larger building. Leaving lots of room for the stepladder. 

 The diagonal stepladder arrangement [red] is very difficult to achieve without cutting large numbers of floor joists. A west:east arrangement [blue] is much easier.

 The more central stepladder [E] in blue, is ideal in some ways, but not others. I would have to walk through the underside of the pier. To reach the bottom of the stepladder. Requiring that two cladding surfaces are cutaway at ground floor level for reasonable access. 

 The lower position [S] in blue, would avoid the need for reducing the cladding. Though the door might prove a problem, if it hits the stepladder. [More stepladder treads are shown here than in practice.]

 I never wanted the stepladder to be external to the observatory. This would provide a clear observatory floor. Though at the expense of greatly reduced security. Not to mention exposure to winter weather. Snow and ice on the aluminium treads could be lethal. 

 Imagine arriving at the top of the stepladder. Then having to open a secure external door 4m above the ground. While carrying the usual items. This could be dangerous and unpleasant in cold or windy conditions.  Far better to have a secure door at ground level. The be safely sheltered inside. While carrying the laptop case and cameras up the steep stepladder. 

 The choice of the stepladder rising from east to west caused some problems. Particularly when imaging the sun early in the morning. I have to stretch out over the big opening in the floor to reach the camera on the tail end of the telescope. A bit silly!

 A stepladder rising from west to east and moved bodily to the south makes sense. This would place the hole in the floor where I rarely need to stand. There are tall trees to the west. Making aiming the telescopes that way completely pointless. So I don't need to be behind the telescopes.

 I gave up the heavy, counterbalanced trapdoor after a while. This was due to bulky storage downstairs precisely where the weights needed to drop. Though I could have fixed pipes to house the weights. To avoid them resting on the stored items. 

 Once the larger observatory is cleared of such bulky storage I can reconsider using the trapdoor. A much lighter trapdoor would make good sense. I used larch, terrace boards and they are thick and solid! They perfectly matched the observatory floor but the trapdoor was foolishly heavy! A plywood sandwich over polystyrene might work better. 

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