This is from the NMRA S-7 Clearances. It states that “NMRA Type II Gages used the Old Time dimensions for Narrow Gauge gages.“. With that in mind since I model in On30, I thought to create gages for O scale – Old Time/On3, Classic and Modern since the NMRA so nicely provided the needed dimensions, On30, On2 and On18 not so much.
Since I have a Prusa I3 MK3 FDM printer I can actually print the gages if I want and share the STL files so others can do the same.
Note: This is just me making my own guesses – since this is a WordPress website people can suggest different ideas and argue against my suggestions/conclusions. To that end I am creating sub-pages for each of the gages. Old Time/On3, Classic and Modern are taken directly from the NMRA page. On30, On2 and On18 will be “calculated/Guesstamated”.