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.
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.
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
The full sized object that a model is designed from.
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.
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
The maximum grade on a railroad. This is usually a short distance, but the steepest
part on the entire line.
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.
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.