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My experience in the attic where my min / max thermometer indicates a range of between 5 and 40 C, is that if the sleeper base is not securely fastened, it is more likely to move that the rail in the joiners. This is why I am in the very slow process of relaying everything.

David
 

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QUOTE So there is consensus... ?

I cannot recall any other attic dwellers endorsing my experience, so I would be reluctant to say there was a consensus just yet. If we don't hear too many other comments in the next day or so, I could set up a poll specifically to see what ideas can be flushed out of the woodwork, so to speak.

Looking at the problem analytically, with a 40 or 50 degree temperature range, metal rail, especially nickel silver if I remember correctly from past discussions on the Forum, is going to change in length. When push comes to shove, the weakest link is the one which is going to give. In the case of track there are three joints to consider, starting from the bottom:-
  1. Baseboard to track base
  2. Track base to rail
  3. Rail end to rail end

What we really don't want is the track base to rail being the one to give. I can remember at least one post in the past which recounted the tale of a layout where the track had been secured to the base so firmly without any gaps between the rails that the rail lifted from the sleepers destroying the whole thing. So, like so many things in life, it's about getting the balance right. We want the sleepers to stay where they were put and the rail to expand lengthways in the sleepers.

This leads to a conflict between the need to allow the rail to move easily within a rail joiner, so the rail joiner should be loose, and the need for the rail joiner to be tight to ensure continuity of power. I resolve this conflict by powering each rail with its own wire soldered to the underside and connected to the power bus underneath. This allows the rail joiners to be pure "alignment" devices.

Further thought on this subject soon brings the realisation that the baseboards need to be stable as well. A search on "baseboard construction" will reveal rather a large number of discussions on the subject which I think did come to a consensus of "6 to 12 mm plywood primed with emulsion", at least that's what I remember.

David
 
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