Scales & Gauges
The most popular scales in model railroading and how they relate to the real thing
|
|
Scale/gauge designation
|
Proportion to prototype
|
Track gauge
|
Approximate length of 50' boxcar
|
Minimum radius
|
Z
|
1:220
|
6.5mm
|
2 3/4"
|
5 3/4"
|
N
|
1:160
|
9.0mm
|
3 3/4"
|
7 1/2"
|
HO
|
1:87
|
16.5mm
|
7"
|
15"
|
S
|
1:64
|
7/8"
|
9 1/4"
|
22 1/2"
|
O
|
1:48
|
1 1/4"
|
12 1/2"
|
24"
|
Gn3
|
1:22.5
|
1 3/4"
|
19"
|
24" |
The proportion is expressed as a fraction of the real thing. Z scale, for instance, is 1/220 the size of real-life railroads. Track gauge is measured as the width between the inside running edge of the rails.
Narrow gauge equipment maintains the scale but runs on a smaller gauge of track, commonly found on logging and mining railroads where tight curves and low speeds were common. Standard gauge measures a scale 4'-8 1/2" apart, while 3-foot narrow gauge railroads were common in the American continent before 1900. Narrow gauge models are designated by the scale followed by a lower case "n" and then the track gauge in scale feet, such as HOn3 or Gn3.
The minimum radius refers to the tightest curve that most model equipment in that scale can handle, although that tight a curve can look unrealistic on a layout. In HO, for instance, most modelers use 18" as the minimum radius, and many go to a broader range for their mainlines.
