@Jim Guthrie
Hi Jim,
In the Peco launch video it was briefly mentioned that they were using the MOROP NEM TT:120 standards.
I can find only one MOROP standard showing dimensions for 12mm gauge:
https://www.morop.org/images/NEM_register/NEM_E/nem110_en_2009_20111116.pdf
which shows a flangeway of 0.9mm min , 1.0mm max and check gauge 11.0mm min.
In Templot I currently have the flangeway at 0.85mm. I must have got that from somewhere 25 years ago when I first compiled the list, but I can't remember where. I will change it to 1.0mm.
Are you planning a TT-120 layout?
From Wikipedia:
"Commercial support for British outline TT:120 was introduced in June 2022. It has a scale of 2.54mm to the foot or one tenth of an inch to the foot and uses 12mm gauge track, just like the TT scale used both in the USA and continental Europe. The new scale was announced in June 2022 by the UK manufacturere
PECO. The company launched its new TT:120 scale 12mm gauge code 55 track and UK prototype accessories. Writing in the Peco Publications & Publicity magazine,
Railway Modeller, editor Craig Tiley stated,
'To explain: rather than perpetuating the hybrid combination of 3mm:1ft scale and 12mm gauge track that was adopted by Tri-ang for its TT range during the 1950s and '60s, Peco has instead chosen the accurate scale and gauge combination of 2.54mm:1ft on 12mm track. This equates to a ratio of 1:120 (hence the term TT:120) which represents a brand new scale for commercial items in British outline.
On the same date UK-based manufacturer Gaugemaster announced plans to introduce a new range of products for TT:120 scale, which could include
Class 66 locomotives, subject to demand.
cheers,
Martin.