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I'm doing some research for a story I'm writing which revolves around a train as the setting. The story is fantasy but I'd still like to ground elements in reality enough to make them believable. Since I know almost nothing about trains, and you do, I was hoping to pick your brains a bit on the topic. I chose this section of the forum because most of my current questions have to do with rail lines for the most part.

In trying to research the topic I did not find any references to trains that used more than 2 support rails (there are of course subways that have a third rail for power). Is there any fundamental reason for this or is it more a matter of economics (with additional rails increasing the cost per mile of a line)?

For the story I'm looking at having rather huge train cars, probably on the order of 20 feet wide. I was imagining these running on 4 rails with 6 foot gaps so the overall gauge between the outermost would be 18 feet. The point of the 4 rails would be to spread the weight a bit more and potentially to prevent derailment if one rail was damaged in a localized area.

Because of the size of the cars I'm imagining them mounted on several (probably 4) articulated trucks to allow for a bit better turning. In addition since I imagine that having a single engine pull many of these enormous cars would put unacceptable stresses on the couplings, each car has a small engine to help with the load in addition to the big engine at front (and possibly a smaller engine behind).

Does that explanation sound at all plausible or are you currently in facepalm mode?


Guy with the green hat
I'd say facepalm mode, or at least close to it.:D

While the story is debated, the common rumor of how railroad lines came to the standard gauge of 4 feet, 8 & 1/2 inches, is that Roman chariots were built to be pulled by two horses. The chariots left wheel ruts in the Roman roads, which meant that anyone else who wanted to move wagons on those roads had to build their wagons to that same gauge, lest they end up destroying their wagon wheels from a rough ride. Some of those Roman roads ran through Britain, where the first steam locomotives were built. Some of the first railcars were old wagons, and so the rails had to be laid to that same gauge. The railroad evolved throughout the years, but the standard gauge stayed the same.

Now, for the number of rails. A railroad uses a track for vehicles in which the rail both supports and guides the vehicles. Most systems use a two rail setup. A few used one rail (monorail).

There are two types of railcar that I can think of that used more than two rails. The first one is the "transfer table",

Transfer tables are large platforms mounted on wheels that roll on rails. They were often used for moving other railcars. The one in the picture has standard gauge railway track on the platform. A standard gauge railcar would be rolled onto the transfer table, go for a ride down the transfer table track, and be shunted off the table onto one of several tracks in a car shop. Alternatively, transfer tables could also be used at boat launch facilities. Instead of carrying normal railcars, they would carry special cars used for launching boats into and retrieving boats from the water.

However, transfer tables usually operate alone. They are not made into trains. Also, they do not run very fast at all, as they are merely shunting equipment around.

The other one is this old rail gun:

It runs on four rails and looks like it would take one locomotive on each track to move the thing, judging by the two sets of couplings and buffers.

Your train idea does leave me with a few questions. Why is the train so big? Why go for width rather than length? A huge width means the right-of-way is going to use a lot more real estate than necessary. I imagine curves for the train track would be a problem. Also, having an engine on every car is going to be a maintenance nightmare, not to mention trying to keep fuel tanks full, etc.


first- thank you for the reply.

The story involves an alternative history setting and takes place in a steampunk-ish setting, so I don't mind diverging from historical norms. My concern is more about physical constraints.

In part the train is large because it's essentially an armored convoy through very dangerous territory, and partially because it's a common trope of steampunk to have things that are (absurdly) large given the available construction materials. Each car will have essentially three levels, the bottom holding the engines used to provide a little extra push as well as crew bunks and support areas like kitchens, The middle has passenger and cargo areas, and the top has defensive emplacements. It's almost more comparable in terms of scale to a land version of an ocean liner.

Right of way is essentially moot as the setting is much more sparsely inhabited than real world earth. Cool Railgun pic, btw!



BLE Hogger
Welcome Jason,

Being a 4th Gen railroader working on my 35th year of service as well as an avid reader, I'm nowhere near needing to support my face in my palms. I tend to lean towards history & historical fiction myself these days.

You've selected a genre that not only allows, but by definition, expects you to deal with familiar things in unfamiliar ways. Your train idea doesn't necessarily need to be grounded in actual logical physics and engineering, it functions as designed by you solely because the author(you) says it does. You're privileged to go any direction you want with it and your specific audience expects it.

Have fun!


I can certainly wave away inconsistencies with a cry of "artistic license" but i'd like to craft the setting well enough to at least not make those familiar with the topic groan in disgust, if you get my meaning. I'd like to try and be faithful and only take liberties where the story really needs it, if possible.


By way of a more specific query, can anyone point me to a good resource on why train rails are shaped the way they are? I'm thinking here of the "I" cross section. I've looked around at wikipedia and the like but not found any good resource on why they are shaped that way and how exactly they fit to the trains wheels.


Sith Lord
Google Image search "rail wheel section interface"

Pretty much everything is 'slanty' and on straight track runs, it's more or less self aligning
This seems interesting enough... except it's "Tire" and not "Tyre" bahh...

>>it's essentially an armored convoy through very dangerous territory
Problem with large armored trains in the bad guys territory... a $20 sledge hammer/crowbar/or wrench to the tracks can kinda bring the whole works to a screeching halt... or just use a small bit of explosives :D


nice link, it does explain quite a bit.

The enemy in this case isn't particularly intelligent or technologically developed. More like animals.


New Member
The enemy in this case isn't particularly intelligent or technologically developed. More like animals.

Oh, I get it... the threat is management.

Well Jason, now you need to look at it from a whole new perspective...
4 rails would be like the glass half full, versus, the glass half empty syndrome...

The threat from the enemy is that they will try to tell you , you have twice as much glass ( rails ) as what you need.

You sound like a switched on type of bloke...
Go with your ideas mate, sounds good.

Look forward to it.
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Jon Bentz

New Member
Hitler was flirting with the idea of Super Trains before WWII. He didn't like conventional railways and commissioned a study on how they could be 'improved'. What they came up with was a four rail extra wide gauge not unlike the idea described at the start of this thread. It was to be a completely new network of lines - in some ways a parallel to the Autobahn. Here are some links:

The last one has some illustrations of motive power - totally crazy! Trains on steroids! is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to - An online railroad bookstore featuring a curated selection of new and used railroad books. Railroad pictorials, railroad history, steam locomotives, passenger trains, modern railroading. Hundreds of titles available, most at discount prices! We also have a video and children's book section. - An online model railroad bookstore featuring a curated selection of new and used books. Layout design, track plans, scenery and structure building, wiring, DCC, Tinplate, Toy Trains, Price Guides and more.

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