Prototype Information
On the prototype, curves are banked, or superelevated, to allow faster speeds through the curve and to reduce lateral forces, which could overturn the train. (Think NASCAR racing and the high banked curves.)
At the scale speeds of model railroads, superelevation is not required; however, many modelers use superelevation because it greatly adds to the realistic appearance of a train rounding a curve.
A superelevated curve cannot be directly connected to tangent track—superelevation must be gradually increased from zero to full elevation. On highways, superelevation is run in on the tangent adjacent to the curve; however, this method is not suitable for railroads, because in the absence of counter-balancing lateral forces, the train may overturn to the inside of the curve.
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.
There was a web site (that I've forgetten where) that analyized the superelevation of all the curves in the ATSF Pasadena Subdivision in 1988 between MP 84 and MP 139. Some of this was 90 MPH territory. The results suggest that modelers often overdo superelevation.
|
Superelevation |
Frequency |
HO Equivalent |
|
None |
5 |
-- |
|
½” to 1” |
15 |
0.0115” |
|
1½” to 2” |
15 |
0.0230” |
|
2½” to 3” |
10 |
0.0344” (~1/32”) |
|
3½” to 4” |
6 |
0.0459” |
|
4½” to 5” |
3 |
0.0574” |
|
5½” to 6” |
0 |
0.0689” (~1/16”) |
Pic xxx superelevation
Modeling Information
If you plan to superelevate your curves, there are a few things to keep in mind: It's the outer rail that's raised, not the inner rail that's dropped. The best way to accomplish this is to shim under the outer rail when the track is installed. Don’t try to build superelevation into the roadbed since it’s nearly impossible to do so successfully. Remember that while prototypical superelevation may be as much as 5-6”, it is most often much less than that.
The transition from level to superelevated track must be very gradual. Superelevation introduces a twist into trackwork that will result in derailments of stiffer or longer equipment if the transition isn’t long and gradual. Model trackwork experts typically recommend a transition equal to twice the length of the longest cars that will be operated. For HO, that’s about two feet entering the superelevated track and two feet exiting the superelevated track.
The WWSL
Operationally, the WWSL does not have a requirement for superelevating track. I am only going to superelevate one curve - the main line on the Chehelis River section, to satisfy an Achievement Program requirement.
There are two ways to model superelevated trac. The first technique is to use varying thickness' of stripwood under the outside rail to to achieve the superelevation plane. The stripwood is then sanded to to the final superelevation plane. The second technique is to use multiple layers of masking tape. The tape is very thin, does not need to be sanded to shape like stripwood.
I am planning to superelevate the curve using multiple layers of masking tape.
Project Process
To be developed
Resource
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