Recently, this topic was brought up in the MRH Forum. I was surprised to learn that the layout drawing software The 3rd PlanIT follows transition curves. Times are changing.
Now that the overall picture of “the bent stick method” is clear, I tried to explain it in My Model Railroad Dictionary.
[The bent stick method] is one of the methods for setting transition curves in a layout, and the curve is drawn using the bending of a square stick. MOROP’s NEM113 (pdf file: figure cited) is recommended.
It is thought to have originated from the “flat spline” used by draftsmen to draw smooth curves before CAD (Wikipedia).
In the United States, it was popularized by the NMRA Data Sheet D3c.1 published in 1952 (MR Forum) and “Track Planning for Realistic Operation” by John Armstrong published in 1963 (MRH Forum).
NMRA Data Sheet D3c.1 published in 1952 (MR Forum)
“Track Planning for Realistic Operation” by John Armstrong published in 1963 (MRH Forum)
Looking at the arrangement of these restraining pins, it can be inferred that they did not understand that the deflection of a cantilever is expressed as a cubic function and is an approximation of a clothoid curve. This seems to have led to the errors in the article in the June 2010 issue of MR magazine and the explanation on Trains.com (Trains.com, May 23, 2017).