What would be a reasonable minimum thickness for the timbers?
Which bullhead flexible track are you aiming to match?
The two common sizes use the technical terms "thick" and "thin".
1. "Thin" is the original design aiming to match traditional rivetted ply with a sleeper thickness of 1/32" (0.8mm). That applies to SMP Scaleway, Ratio EMtrack bases, C&L original (thin), and now also DCC Concepts.
The height to rail top is 0.8mm sleepers + 0.6mm chair base + 1.9mm code 75 rail = 3.3mm overall.
The 0.6mm chair base is of course the essential feature which provides the daylight under the rail above the ballast, in contradistinction to most flat-bottom track.
SMP Scaleway may be a bit thinner to match their soldered copper-clad pointwork kits:
3/64" SRBP copper laminate (1.2mm) + 1.9mm rail = 3.1mm overall.
Ratio EMtrack bases had 1.0mm sleepers but with only 0.4mm chair base, so the end result was the same.
2. "Thick" matches the new Peco bullhead and the C&L/Exactoscale (thick) bases, originally matching 1/16" (1.6mm) plywood:
1.6mm sleeper + 0.6mm chair base + 1.9mm code 75 rail = 4.1mm overall
which also matches Peco code 75 flat-bottom to rail top.
There are pros and cons. The "thin" is prone to curling and gauge variations if not carefully stuck down, but generally regarded as easier to ballast. Lots of layouts have used it successfully.
The "thick" is generally more robust, stable and accurate, but more difficult to ballast (Peco foam inlay anyone?
If you decide on turnout bases in multiple sections you don't really have much choice. It would have to be the thick version, if allowing for a sub-base.
Say a sheet of 40 thou (1.0mm) plasticard as the sub-base, with 0.6mm timber sections stuck onto it (with what, he asks?)
Or maybe 30 thou (0.8mm) plasticard or 1/32" plywood sub-base, with 0.8mm timber sections stuck onto it.
I can see the Peco bullhead rapidly dominating the market. As they do.
Over to you.
p.s. If doing this commercially you should obviously ignore my figures and check actual products yourself.
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