(not so) Secret Codes

In past posts I've mentioned Code 80 and Code 55 track. In model railroading, "Code xx" simply means the height of the rail above the top of the ties (a.k.a. "sleepers" in the British Commonwealth) in thousandths of an inch. For example: Code 80 track has 0.080" high rails.

"Why should I care about rail height?", you may ask. And many model railroaders happily build their layouts without ever worrying about rail height. However, it's just one more aspect of realism that a modeler may or may not be concerned about.

The problem is that most model train track has rails that are ridiculously big, and although most people don't notice at first glance, if you are looking at a detailed model of a railroad scene the oversize rail can often ruin the illusion.

In the prototype (a.k.a. "real life"), modern rails in the U.S. tend to all share the same flat-bottomed profile, as shown at the link. However, rail sizes can vary greatly. By convention, the rail size metric used is "pounds per yard" of rail. At one extreme, the early DRG narrow gauge lines used 30 lb. rail -- which is about 3 1/8" in height. At the other extreme the Pennsylvania Railroad (PRR) once used 155 lb rail for their main lines -- the heaviest rail in common use, and about 8" in height. Modern class 1 (the busiest main lines) rail tends to be in the 100-132 lb range (6-7 1/8" high), although some heavier rail (140 lb) is starting to be used. It's typical for a railroad to mix rail sizes -- sidings, spurs, branches and yards often have smaller rail -- often 80-90 lb or less.

How does that compare to the model? Well, in N (1:160) scale Code 80 was long the N scale standard, and is still the most commonly used rail. Code 80 is equivalent to over 13" high rail -- about double the size of a modern main line. Code 55 is now the preferred rail for N scalers more interested in the details, but even that translates to 8.8" rail height -- bigger even than the PRR. Code 40 track is available for those that want absolute accuracy, as code 40 is equivalent to about 6.4" high track (roughly 110 lbs/yard), but if you use code 40 you have to hand build your own switches. Some modelers choose code 55 for the main lines and code 40 for spurs and sidings.

How much difference does it make? Well, compare a photo of a prototype locomotive to its N scale equivalent sitting on code 80 track and you'll notice the difference right away -- of course, that's probably because you'll be looking for it. In practice, most people don't notice, especially if you "weather" your track by painting a rust color on the sides of the rails and do a good job with the ties and ballast. I have heard from one N-trak modeler who often takes his N-trak modules to conventions and he reports that no one noticed (or at least no one commented) when he converted to code 55 from code 80. However, he gets lots of comments when he makes other changes to the details.

Still, I am using code 55 on my main layout, in large part because code 55 track products look a lot better overall, not just the rail height, than do the code 60, 70 and 80 N scale products.

For the record, the reason N scale track manufacturers initially chose code 80 was operations reliability. As with all model train scales, oversize rail and wheel flanges were chosen to minimize derailments. Today, modern plastic and metal manufacturing techniques are much more precise than they were in the past, so we can acheive even better operational reliability without the oversized rails and flanges. Even so, there are potential operational issues with certain brands of N scale code 55 track, and I'll cover that in a later post on track brands.

For those interested in more details on rail heights and sizes in the prototype and in the model scales, here is a good site.

For those interested in very high accuracy model railroading, what is commonly called "fine scale" modeling, the Proto 87 site is worth a visit. The term "Proto 87" simply means trying to precisely and accurately model the prototype in HO (1:87) scale. In addition to getting the rail size right, they also try to model exact replicas of (for example) switches and wheel flanges. This type of modeling is not for everyone, as there is a lot of extra effort required. But its a lot of fun to look at the results of a successful Proto87 modeler.