I have yet to lay any of the 2nd track of my planned double track sections, some of which go around some curves which readers here will probably regard as quite tight. My layout is N scale. My actual innermost track (already laid) has a radius of 315mm on the tightest curves.
I've mainly been designing and building to the European NEM standards because they're more comprehensive and comprehensible compared to the NMRA standrds, and also because I'm keener on European and Japanese prototypes than USAian ones.
But I think I have found what seems to be an error in the NEM specifications for the radial distance between two curved tracks. And as a result I don't know what the correct figure is for the minimum spacing.
The most obvious place to start is NEM103 `Umgrenzung des lichten Raumes bei Gleisfhrung im Bogen' (`Dimensions of the structure gauge for curved track')
But NEM112 `Gleisabstaende' (`Track spacing')
These discrepancies are quite substantial. What, if anything, am I missing ? Surely the track spacing should be derived from the dynamic envelope in exactly the same manner as the structure gauge.
I looked at the NMRA specs too. S-7 `Clearances'
This brings me on to another question. The last time I bought a loco I found it quite difficult to find out its minimum requirements for track geometry. Is there some conventional way of finding this out without asking the retailer ?