15.01.2022 Top rail-channel struts.

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Saturday 15th 29F. Another cool but sunny day is promised.

 I need stabilizers for the top guide rail/channel. Though I haven't really thought about the problem until now. The drawer slides were doing all the work. Until I took one off and discovered that shutter was no longer stable.

The image gives a very rough idea of what is needed. I have drawn in struts to show the general proportions. [Not remotely to scale!]  The top rail-channel is too short. The struts would be upright as seen from this angle.

BTW: The gently sloping ladder has a large and heavy paving slab lying at the base to stop it sliding away. The pipe insulation quickly proved to have enough friction to fully stabilize the ladder. The pipe insulation also protects the dome against cosmetic damage. 

I always adjust the ladder and paving slab to avoid all rocking before adding the pipe insulation. This arrangement has proved very safe in use. Without a single worrying moment. Access to the top of the dome through the top of the slit is via a sturdy [Japanese] tripod stepladder. Though this obviously requires the shutters are open. Which is not always the case.

 The guide rail-channel has to remain level under widely varying and dynamic loads.  Resistance against twisting and longitudinal movement is vital. Which means triangulation is required. The support struts need to lean inwards from the dome's segment joint. Which is outboard and below. Where there are plenty of existing M12 bolts to choose from as secure fixings. I do not want to make fresh holes in the dome if I can help it. Even though I use rubber tap washers to weather proof each bolt.

Strips of aluminium would need to be thick enough to resist bending. Making the end bends then becomes a problem. Heat treatment? A flat, triangular plate with tabs might work. Tubing must be flattened at the ends and then bent. Though the 12mm bolts place minimum dimensions on the flat sections. 

I automatically think in terms of aluminium because it is easily worked. Not to mention corrosion free without further treatment. I am not a fan of rusting steel and try to avoid it. 

Which leaves stainless steel. A stiff, hard material. Which is difficult to drill and saw with used tools. It easily work hardens if the active cutting edge becomes dull and starts rubbing. I would need ready-made strips of suitable dimensions. Sawing from flat sheet is a complete non-starter.

 Is there anything "off the shelf" which might become useful struts with only a little imagination? I had better do some measuring first. The dome was covered in rime frost "fur."

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