Modeling Information
The prototype does curve easements and super-elevation to improve performance, especially on the
mainline where equipment is moving at speed. On a railroad model layout where compressed curve
radius are well below what’s typical on prototype mainlines, easements are especially helpful by improving performance on curves, not to mention improving the looks of lengthy equipment entering a model curves.
Paul Mallory, in his Trackwork Handbook, identified a simplified way of creating easements. It was based on a 9 inch spiral into a 24 inch radius curve. His technique essentially was:
1. Identify the centerline of the tangent track.
2. Identify the radius of the curve.
3. on the easement template identify the curve radius offset distance from the centerline of the tangent track.
4. Identify the new radius location and draw the curve.
5. Use the easement template to join the centerline of the tangent track to the curve. (Those locations he called the point of tangency and the point of curvature.
The WWSL
The WWSL's operational profile (in terms of train speed, etc) has no prototype engineering requirement for easements on its right of way. Easements will not improve performance at speed because the WWSL is a low speed operation. An easement might help equipment look better and run better on curves but most of the WWSL equipment is 40 and 50 foot rolling stock. I have decided however to include modest easements in my plans.
Using the Mallory easement process I found that the offset from the tangent for a 24 inch radius curve was 9/ 64 of an inch. That wasnt much of an easement and was a hassle trying to lay out on the benchwork. Instead I decided for the WWSL vers. 3.0 I would simplify things by using Ribbon Rail curves as part of my track laying process. For 24 inch radius curves I will use a 5 inch section of 26 inch radius template on each end of the curve, on 26 inch radius curves I will use a 5 inch section of 28 inch radius template on each end of the curve.
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