justintime66

Yes Peco TT points turn 11.25 degrees.

I am planning to build a TT:120 layout in the attic and having settled on a general plan I am pondering what double track centres to use in the curves. Minimum radius in current plan is 550mm with transition curves in most places. I will be using Peco track. Medium radius points give a "natural" double track centre of 35.5mm (at least as far as SCARM library goes). Critical Rolling stock will be A4, pullman / BR Mk 1 coaches and HST with MK 3 coaches. Intention is that HST is only modern train, so at least I don't need to be driven by clash between two sets of Mk.3 coaches. I am currently using geometry to calculate theoretical separations between rolling stock at my planned radii. I'll confirm some of my maths with test tracks when A4, pullmans & peco track arrive this week. But unfortunately the crucial piece in the jigsaw (Mk.3 coach) is not due for release until summer 2024 (strange given Class 43 locos available this autumn according to Hornby).The Peco track geometry would give a gap between parallel running stock of 11.5mm on straights. So practical question what should minimum gap be for planning purposes (giving a descent margin for build & running tolerances and bearing in mind I won't be able to test with Mk.3 when laying track / building some of bridges). I have considered setting double track spacing in curves so that the 11.5mm gap between critical case stock in curves is maintained. However, that would increase track separation more than necessary and the gap of 11.5mm would only be visible when both HST & pullman trains were running. I note that Hornby's new trackwork has 43mm centres (same as Tillig I think). So 43mm may be the safe answer. But tracks do look a bit too far apart when I put my current limited rolling stock Vent van, brake van & petrol tanker) on 43mm separated tracks.