Please explain what these numbers mean. Am I right in that the number indicates how many curved sections it takes to make a circle?
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The "O" is the letter O.
The 72 indicates 72-inch diameter.
The 31 indicates 31-inch diameter.
In 3-rail O gauge, the curvatures are designated/measured by diameter. In other scales (N, HO, etc.) curvature is designated by radius.
In either instance, the number has nothing to do with the number of sections needed to make a circle (this can vary depending on the curvature, but for O31, of example, eight sections are required to make a complete circle.
Originally Posted by Allan Miller:
The "O" is the letter O.
The 72 indicates 72-inch diameter.
The 31 indicates 31-inch diameter.
In 3-rail O gauge, the curvatures are designated/measured by diameter. In other scales (N, HO, etc.) curvature is designated by radius.
In either instance, the number has nothing to do with the number of sections needed to make a circle (this can vary depending on the curvature, but for O31, of example, eight sections are required to make a complete circle.
So where are these measurments actually taken? Center-rail to center rail? Overall, i.e., from the outside of the ties to the outside of the ties on the opposite side of the circle? Does this vary from manufacturer to manufacture or from one style to another?
Does it make any difference when planning a layout?
Thanks in advance!
The diameter measurement varies by manufactuer. Lionel's tubular track is mostly outsise tie to outside tie(except O72). Fastrack is center rail, as is AtlasO. I'm not sure about Ross or Gargraves.
