Prototype Information
The prototype does curve easements and super-elevation to improve performance, especially on the
mainline where equipment is moving at speed.
Prototype railroads use
spiral easement curves on high-speed main lines to provide a constant
superelevation run in along the length of the spiral. Spiral easements
also provide a gradual increase to full lateral acceleration, resulting
in a smoother ride for passengers and freight.
Walter Mason Camp, Notes on Track, google books Chapter V discusses easements on curves. He describes six different easement curves used by railroads in the early 1900's: The Cubic Parabola, The Tapering Curve, The Torrey Easement Curve, The Searles Spiral Curve, The Railroad Spiral Curve, The Holbrook Spiral Curve.
Each of the easement curve engineering had a couple of pages of algebraic calculations. The Holbrook Spiral Curve had 4 pages of calculations. My brain hurt!
Modeling Information
Railroad Modelers have several techniques for laying out and modeling curve easements.
- Do nothing! Your railroad model may not require prototype easements on its curves.
- Pseudo curve easements using Ribbon Rail or Fast Track Sweepsticks in gradually increasing radius' and lengths for curved track..
- Mallory generic modeling template.
- Rattan
- Prototype engineering calculations
See 4.2.4.5 Easements for Curves for additional information and my simplification.
Reference
Walter Mason Camp, Notes on Track, Google books Chapter V.
The John Galt Line Railroad Company Spiral Easement Curve Calculator
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