Railroad Info
Model RR Scales
World RR Gauges
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Photograph by Bernd Billmayer, © 1999
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Curves: “G” Scale equivalents: Railroad curves are actually a bit complex - not just a simple radius. They are measured in degrees of curvature per 100 ft. To simplify this, a very sharp curve for a 3 ft. narrow gauge railroad is 30 degrees. The equivalent curve in a “G” Scale layout is about a 7 ft. radius. Most modern railroads like to keep the curves to less than 2 degrees. To reduce the high degree of wear, many curves have automatic grease units built into the rail to help reduce friction.

Gauge: The distance between two rails. Standard gauge is
4’ 8 1/2”, narrow gauge is anything less, with 36” being a common narrow gauge. Numerous gauges exist throughout the world anywhere from 7' 1/4” to 72”.

Grade: The slope of a railroad on a hill, measured in the vertical rise (ft) per 100 horizontal feet. 3% grade = 3’ rise every 100’ - this is extremely steep for a train. Generally, railroads like to stay under a 1.5% grade. The maximum in the U.S. is about 5% - not on a mainline.

Model Rail Materials: Many materials are used for model railroad rails. Brass, stainless steel and aluminum are generally used for the large scale trains, nickel silver for smaller scale (HO, N, Z), steel and zinc plated for many “O” (Lionel type). Nickel silver has excellent qualities for wear resistance and electrical conductivity compared to brass, which is softer and oxidizes (“rusts”) creating poor electrical conductivity. Some large scale locomotives use metal “shoes” to make electrical contact with the rails and tends to clean and reduce the oxidation. Many commercial track cleaners are available and work well to keep the rails clean.

Prototype: The full sized object that a model is designed from.

Rail Weight: How a rail is classified. Rail weight is measured in pounds per yard. Most mainline rail is 136 lbs. per yard. Maximum is about 155 lbs. The weight, date, and location where the rail was manufactured is stamped on the side of the rail.

Ratio: The numeric values comparing model size to full size in any units. 1:22.5 means that 1” on the model equals 22.5” on the full sized object or 1mm on model equals 22.5mm on full sized object.

Ruling Grade: The maximum grade on a railroad. This is usually a short distance, but the steepest part on the entire line.

Scale: The proportion of a model size to the full sized object. This can be noted as a fraction (3/16”), ratio (1:22.5), or a letter (HO scale). Often confused with Gauge in model railroads -- it is not the same as gauge.

Super Elevation: The difference in height from one rail to the other, measured in inches. It is used on curves to allow for higher speeds.

Whyte Classification System: This is the standard method to classify all steam locomotives. It is based upon their wheel configuration. An “0-4-0” is a small locomotive with no front pilot wheels, 4 large drive wheels (2 on each side), and no trailing wheels. This does not include the tender in most cases. A large locomotive would be a 2-8-4, and the largest is a 4-8-8-4. It does not take into account the gauge of the locomotive, only the wheel arrangement.

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