Available diameters of tubular O and O27 track

Available diameters of tubular O and O27 track

A frequent question, especially for those who are just discovering or rediscovering vintage Lionel and Marx trains is what sizes of track are (or were) available, and how many pieces come to a circle.

Unlike other scales, Lionel marketed its track by diameter, not radius. As you undoubtedly remember from geometry class, radius is the distance from the center of the circle to the edge, while diameter is the distance from edge to edge. So a circle of O27 track is approximately 27 inches wide. O27 track stands about 7/16 of an inch tall, while higher end O gauge (also sometimes called O31) track stands about a quarter inch taller, at about 11/16 of an inch tall.

While we’re on the topic of track, here are some tips for connecting track if your new track isn’t going together as easily as it could, and some tips for screws to attach track to the table.

Here are the available sizes, in ascending order.

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Can you mix Lionel and Marx track? Yes, pretty much.

Here’s a question from the search engines: Can you mix Lionel and Marx track?

Generally speaking, yes you can. Just stick with O27 track, and you can mix Lionel, Marx, and K-Line as needed. Dad had a mixture of Lionel and Marx track in the 1950s–my theory is that someone tipped my grandfather off that you could buy a Lionel O27 starter set, expand it with cheaper Marx track, and once you had the track assembled, no one would know the difference. When we set his layout back up in the mid 1980s, we added some K-Line O27 track, because it was what we could find. I have a mixture of all three brands to this day. Read more

Non-derailing Marx switches

The Marx 1590 is the best O27 switch ever made. It’s durable, works well with all makes of trains (just put a track pin in the center rail where the switch pivots so that Lionel trains can pass), and can run off accessory power without modification.

The only downside is that it (allegedly) can’t be set to automatically switch to a position to accommodate an approaching train like a Lionel 1122, which makes it unusable in a reverse loop. That’s true if you wire them the way Marx said to wire them.

Here’s how I wire them to get that coveted feature.

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XTrkCad model railroad track software is going open source

XTrkCad, one of the many model railroad track planning programs–and the only one I know that has both Windows and Linux versions–is going open source. This also means the program is now free.

You can’t download the source code yet but you can download binaries, enter a registration code, and play with it. I’ve been doing just that.One thing I noticed right away when I started trying to use it to plan a layout using Lionel and Marx O27-profile sectional track–which it doesn’t support directly, so I had to enter the track, confusingly, using the “custom turnout” tools–is that the model railroad and toy trains people measure track differently.

A Marx or Lionel O27 curve isn’t an O27 curve in XTrkCad. It’s a curve of radius 12.5 and angle of 45 degrees.

Here are some measurements. Keep in mind this is what they’re supposed to be. Manufacturing tolerances and the effects of age sometimes cause these measurements to be off. Some of my vintage track is off by 1/8 inch or more.

O-27 12.5″
O-34 15.75″
O-42 20.25″
O-54 26.375″
O-72 35.25″

I happen to know that O27 and O34 tubular track use a 45-degree angle, and that Lionel and K-Line O42 tubular use a 30-degree angle. Unfortunately I don’t have a piece of K-Line O54 or O72 sectional tubular track to measure.

Since O42 track is supposed to be 12 sections per circle, and 180/12=15, I believe to calculate the angle measurement of O54 and O72 you can divide 180 by the number of O54 or O72 track sections in a full circle, then multiply that result by 2. The math works for the O27, O34, and O42 track sections I have, but since I don’t own any K-Line O54 or O72 track I can’t be certain.

Also, confusingly, traditional O gauge switches are straight turnouts in XTrkCad, even though one leg of them is curved. Here are the parameters I got by measuring a Lionel 1121. The measurements are close enough to represent Marx or Sakai O27 switches:

Diverging length: 8.5
Diverging angle: 45
Diverging offset: 3.75
Overall length: 8.75

And here’s what I measure on a Marx O34 switch.

Diverging length: 11.375
Diverging angle: 45
Diverging offset: 4.5
Overall length: 11.188

I believe the diverging angle would be 30 degrees on a Lionel or K-Line O42 switch, but since my vintage Marx and American Flyer locomotives won’t make it through modern O42 switches, I don’t have any of those to measure.

I’ve already used the software to draw a layout using Marx O34 track that will allow two-train operation with room on sidings for three additional trains. It’s much easier than setting up track on the floor and measuring it to see if it will fit on the table. And you can do your layout and then print an inventory to compare what you have with what you need. Not having enough track to mock up a layout isn’t a problem anymore.

On the computer some of the things I want to do don’t quite fit; if the track measurements are slightly off, the solution is to cut a section of track to move things a bit, or, if they’re off by less than a quarter inch or so, force it. O27 track has a lot of give, and, like I said, manufacturing tolerances and the effects of time can cause real-world track to not match the published standards.

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