Sketch with Steve
Introduction to runway models
Learning how to use a track gauge was one of the first jobs I took on as a model railroader.
You may have seen one hanging next to the cash register at your local DIY store. Maybe in the days of point-and-click trail planning software, you thought it was a step backwards, a waste of time. And while it’s true that software is much more accurate, it can have a frustrating and steep learning curve. There is nothing better than paper and pencil for creating new ideas and seeing what might be possible in your space.
A trail planning template, like the green HO scale in the photo above, helps you turn your sketchy ideas into a buildable trail plan. The dimensions of traceable track components, such as turnouts and crossovers, are generic and do not match the geometry of any particular manufacturer’s components. But the shapes are precise, helping you decide whether your shoelace will work or your garden ladder will accommodate three or four turnouts. And although the model curves are designed to match the shape of the section track components (each curve segment is 30 degrees), even if you plan to use flextrack, following the model curves may allow you to stay honest in a way freehand sketches never could.
For example, to join two straight lines, extend both track axes until they intersect, then position the stencil so that the curve you want to use just touches the two lines without intersecting (the geometry calls that a tangent). Then just draw the curve between the two tangent points. You can do the same with a compass, but with a template it is much easier.
To make a smooth, crease-free transition from a curve to a straight line, mark the center point of the curve, then use a ruler to draw a radius from there to the tangent point where the straight line will begin. Then use a square to draw the tangent track at a right angle to the radius. Or, if the corner of your model is not rounded like mine, just use the edge of the model.
To place a gentle curve at the end of a straight track, do the reverse. Draw a guideline at right angles to the straight line, starting from the desired point of tangency, then place the center point of your curve along that guideline.
If you are using long rolling stock, such as intermodal flat cars or modern passenger transport equipment, you may want to make the entry of your curves more gradual with an easement. Just incorporate a wider radius section to start your curve. So that the transition does not bend, make sure that the center point of both curves is along the same straight line, at right angles to the tangent where the curves meet.
Limitations of tracking models
Learning to use a runway model also means knowing its limits. When designing complex tracks like crossings or yard ladders, you may find that the generic turnouts and crossings in the model are not precise enough to know for sure if things will work as intended. This is when you make photocopies of your track components and glue them together to test the fit, or bite the bullet and buy that track planning software. But track planning software has only been around for a little over 30 years, and some of the greatest model trains in history were designed by people like John Armstrong using only paper, pencil and their trusty track model.