... normally quoted for commercial model turnouts. It can be significantly different from the other radii where the V-crossing type is not curviform. It has little use or meaning in prototype track design. In each case above it is important to specify whether the dimension quoted is to the track centre-line or to the outer rail of the curve. Modellers usually mean the track centre-line, but the calculations are made in the outer rail, so it's necessary to remember to subtract half the track gauge from the result. 2_250848_170000000.png The Internal Geometric radius to the track centre-line (r) is calculated as: R= G/(1 -COS(K )) r= R- G/2 Where G is the track gauge, and K is the crossing angle. Templot uses RAM unit crossing angles, so K can be calculated as K= ARCTAN(1 /N) where N is the unit crossing angle. Remember that this is not the actual radius in the turnout, except in the case of a gaunt turnout ...