Calculating Tie Lengths in a Curved Switch

A curved switch consists of a diverging branch within a curve in the main line. As the branch separates from the main, the ties need to get longer to accomodate both tracks until they are far enough apart to have separate ties. In this model, the ties are perpendicularly aligned to the main rails. The radius of the diverging curve can be either larger or smaller than the radius of the main curve.

This program calculates the lengths of the ties needed to complete the switch, and the angle and number or the frog needed.

Explanation of Input Boxes

Note: All dimensional units must be the same. Inches, meters, etc. Radius of Main Line and Radius of Diverging Line There are two boxes per. One for the radius and one for an optional multiplier. The multiplier can be used to convert feet to inches, meters to centimeters, metric to english, or whatever you like. If not used, set it to 1. Normal Tie Length The length of a normal track tie. Switch ties will progressively get longer. Tie Spacing The measurement from tie to tie, not the gap between them. It is the center to center distance. The width of ties is not needed. Snap to Nearest Unit This allows you to select how much precision you need. The tie length will be rounded to the nearest unit you select here. Track Gauge This is only needed if you are using the optional frog angle and number calculator. Enter the actual gauge-face dimension. The frog angle will be calculated in degrees. The frog number is 1/2 the cotangent of 1/2 the frog angle. Both frog angle and number are rounded to .25.
Curved Switch Tie Length and Frog Calculator

 x Radius of Main Line
 x Radius of Diverging Line
  Normal Tie Length
  Tie Spacing
  Snap to nearest unit
  Track Gauge

  Frog Angle
  Frog Number

Tie Lengths Needed... (select box to solve)