This is taken and modified 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 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 is taken directly from the NMRA page. On30, and On18 will be “calculated/Guesstamated”.
“Some use HOn3 track for On18 - I did. If you run the numbers, that 9 mm (0.354 in) gauge track actually comes out to a 17 in (792 mm). Since there was a real world 18 in gauge track we simply call this On18 .. rather than On17. On18 Car Width and height In...
"Using specially manufactured 16.5 mm (0.65 in) gauge track, scaled at 7 mm to the foot (with appropriately spaced, larger Railroad Tie underneath - United States O scale rolling stock (1:48), it becomes a narrow-gauge track of 2 ft 6 in (762 mm), and is referred to as "On 2½" (or On30, as in 30 inches)." This...