Outdoor model train scales

In the earlier post on gauge and scale I mentioned that the "large", outdoor scales range in size from 1:20.3 to 1:32. While these may seem like random numbers, there is a very logical reason behind them, dating back to the early history of model trains.

Some of the earliest model trains in the late 1800s were made by Märklin in Germany. They built three sizes of trains and named them "1", "2", and "3" gauge. All three were on the large size, reflecting the technology at the time. "1" gauge is 45 mm between the rails, about 1.77 inches.

When Lionel started making electric toy trains in the early 1900s in the U.S. they decided to name their gauge "0", pronounced "zero", because it was somewhat smaller than "1" gauge. However, people reading "0" (zero) thought it was the letter "oh", and so "O" has forever been the name of 1:48 scale. The smaller O scale trains quickly surpassed the larger 1 gauge trains in popularity because they took up less space. While "1" gauge trains continued to be produced in smaller quanitities, "2" and "3" stopped being produced.

Later in the 1930s Märklin came out with an even smaller scale, 1:87, and named it "half-oh", or "HO" for short (even though it was quite a bit bigger than half of 1:48). HO quickly leaped ahead of O in popularity, as many other manufacturers followed Märklin's lead. "1" became an almost forgotten gauge.

Fast forward to the late 1960s when a family named Lehman in Germany decided to build electric trains that could run outdoors. They chose "1" gauge track and named their new company LGB for Lehman Gross Bahn -- which translates literally to "Lehman Large Trains". For their initial line of trains they chose to model European prototypes that used a 1 meter narrow gauge. A 45 mm gauge track, when used to model a meter gauge prototype, yields a scale of 1:22.5. This soon became known informally as "G" scale. However, "G" was never officially recognized as a scale, and today people often mistakenly use the term "G" for any train running on "1" gauge track.

LGB trains were a hit, first in Europe and then in the states. In the 1970s LGB introduced more trains, including models of standard gauge European trains and 3-foot narrow gauge U.S. trains. LGB was vague about the scale of these new models, in part so that the cars from one size prototype wouldn't look out of place in the same train with others, and this resulted in a lot of confusion. (Today some modelers feel that LGB's failure to provide accurate scale info with their models ultimately contributed to their sales decline and their recent bankruptcy.)

In the 1990s and 2000s many other manufacturers entered the large scale train market and fortunately almost all of them provided specific scale info. For "1" gauge models based on a 3-foot U.S. narrow gauge prototype the scale of 1:20.3 is correct. The NMRA has recognized this as "F" scale . For "1" gauge models based on standard gauge the correct scale is 1:32, which is now recognized as "H" scale. It's easy to remember these letters because F-G-H are all "1" gauge scales, based on 3 ft gauge, 1 meter gauge, and standard gauge prototypes respectively.

Unfortunately, before H scale was established Aristocraft introduced a line of "1" gauge products based on standard gauge prototypes in 1:29 scale. As such the trains were somewhat larger than they should be given the wheelbase of the trains. Aristocraft chose 1:29 apparently because this allowed the LGB narrow gauge boxcars to look correctly proportioned next to Aristocraft product. USA Trains copied this practice, and their product line became very popular due to their lower prices and US prototypes, so other manufacturers followed their lead. Today large scale modelers now have to be aware that some standard gauge product is 1:29 scale and some is 1:32, and to try not to mix them because they will look funny together if you do.

Just to complete the confusion, a lot of the non-train models that are available for adding scenery to your outdoor layout are 1:24 scale, which kinda-sorta works with some of the other scales if you don't look too closely, or if you separate the 1:24 models from the trains visually.

One other point to note is that although all the "1" gauge trains will run on the same track, there are still separate lines of F, G, and H scale track. That's because while the rail gauge is the same, tie sizes vary greatly between scales.

Now, having said all of the above its worth noting that Garden railroaders tend to be a lot more relaxed than indoor modelers about prototypical accuracy. Many happily run trains of mixed scales. Others may run all their narrow gauge trains one day and all their standard gauge the next. And despite such sacreligious behavior they amazingly still get their layouts featured in Garden Railway magazine! :)

For my outdoor layout I have chosen a U.S. 3 foot narrow gauge prototype, so my scale is F (1:20.3). Actually, to be precise, my scale is Fn3, reflecting the 3 foot narrow gauge. However, the "n3" is usually not mentioned since virtually everyone in F scale is doing narrow gauge.

Gauge vs. Scale

In model train conversations it's common to hear the terms "gauge" and "scale" used interchangeably, as in "HO gauge" as a synonym for "HO scale". This is especially true for model railroading newcomers. While this causes no harm, as everyone understands what is being said, the two terms have different meanings:

Scale -- The size of the model relative to the prototype.

Gauge -- The distance between the two rails.

For example, N scale is 1:160, which means it is 160th the size of the prototype. If a prototype freight car is 80 feet long, in N scale it would be 160th of that, or 1/2 of a foot long.

In terms of gauge, prototype standard gauge is 4 ft 8.5 in between the rails, which translates to 9 mm between the rails in N scale. ("N" was chosen for the name of 1:160 scale because of the Nine mm rail gauge. )

So, if you say something is HO gauge what you are saying is that it is 1:87 (HO) scale and standard gauge. Similarly, the term "HOn3" means a model that is 1:87 scale, but representing a prototype narrow gauge of 3 feet. The "n3" of "HOn3" means: "narrow gauge, 3 feet". There is also an Nn3 -- 1:160 scale and a narrow gauge of 3 feet. Another popular example of modeling narrow gauge is On2.5 gauge -- which is O scale (1:48), narrow gauge of 2.5 feet.

The National Model Railroad Association (NMRA) has their own web page on scale and gauge which covers this topic in detail, including a list of scales common for indoor model railroads.

Although many model railroad scales have been established they clearly do not enjoy equal popularity. The most popular scale by far is HO, with N a distant (but growing) second, and the other scales further behind. TT scale (1:120) is virtually dead, killed off by the introduction of N in the 1960s. OO scale (1:76.2) is very popular -- perhaps the most popular -- in Britain but is almost unheard of elsewhere.

The NMRA web page I linked to does not, for some reason, list the "large" scales, from F (1:20.3) to H (1:32). These scales are commonly referred to as "outdoor" or "garden" railway scales because, although you can run them indoors, they are mostly used outdoors.