So recently I've gotten interested in track laying and spiral easements and what not for 1:1 railroads. I was also looking at the maximum curvature specifications and general track laying guidelines. I read somewhere that the minimum radius for mainline interchange service in the US is 410 feet. So it got me thinking about what the minimum is for some of the bigger modern diesel engines is like an SD80/SD90/SD70ACU or an AC6000CW.
So I read in the Conrail historical archives that the maximum curvature for a single unit is 27.4 degrees. I was sure what curvature meant in this regard - so I looked it up and according to Wikipedia the formula for converting from a chord length to radius is:
r = C / (2 * sin(Dc/2)) Assuming in this case the cord length is the distance between the bolsters (54' 2") that works out to a radius of 114 feet. Using the standard 100 foot chord length for surveying right-of-way in the US, this comes out to 211 feet.
Working backwards to 1/4" scale, that equates to a radius of 28.5 and 52.75 respectively, or roughly O57 and O106. So it seems our models maybe aren't all that far off from the prototype, or I'm using the wrong formula to convert the degree of curvature to real world radius.
Does anyone know where I went wrong?
