From: glen mccready To: RE: US Standard Railroad Gauge or How MilSpecs Live Forever Date: Fri, 25 Oct 1996 10:35:28 -0400

Forwarded-by: Keith Bostic <>
Forwarded-by: Steve Dekorte <>

Dan please forward this response back to everybody who got the original posting, because this particular bit of misinformation is just butt-ugly wrong.

I worked as a railroad engineering historian once upon a time, so in this rare instance I actually know what I'm talking about. This is a classic example of where a nice puffy argument gets in the inconvenient way of the real facts, which should be interesting to an engineer. There were actually many, many rail gauge specifications use in the early days. There were several dozen early railroading enterprises that started from different operating premises (such as different power ratios, gearing principles, and so forth) which tended to affect the powertrain. Obviously some of these ended up being more practical working solutions than others.

Quality of rails and the friction generated, grade, gauge, and the cost of building a bed (directly affecting gauge) were all major factors in the "alpha" phase of railroading.

For the first forty years of major railroad activity, there were divergent trends in the gauge use. These were more stark between the US and Europe, but even within the US railroads tended to be built at different gauges depending on the purpose and entity building them (the thing about English railroad engineers is just plain false, btw). For example, "trunk" or feeder lines, railroads serving mines in hilly places, and similar specialty applications -- which were originally much more economically viable than long-distance, high-capacity service-tended to be narrower gauges because of grade, and therefore powertrain, constraints. Different vendors of equipment originally supplied only a few railroads (of which there were tens of thousands by the 1880s), so for a short while interoperability wasn't a big problem. (Is this beginning to sound familiar?)

However, economies of scale kick in after a while. The obvious ones were vendors supplying parts for railroads; standardization helps mass production and therefore larger sales. Many railroads ran their own shops, but couldn't always get the capital up to build equipment for what was essentially a custom application, if you will, while trying to make money operating an enterprise. They essentially passed a point when doing it in -- shop didn't make as much economic sense. The number of things for which this applied multiplied over the years, but rails, carbeds, and trucks -- hence gauges -- were the most important early components. Then the major problem, though, (no application to Microsoft implied here, but you may take your lessons from history where you want) was interoperability. Railroads, in attempting to build more efficient networks (often prceeded by ugly business tactics in which small competitors were forced out of business after initially forming operational alliances with them, but I digress), found that the 19th century-equivalent of the gateway -- the transfer point where you had to shift freight from one gauge to another -- meant that traffic was slowed. If you could work out both a standard gauge for cars to interoperate between different railroads -- and, very very important at the time -- a business model that would allow you to ship freight from one railroad line to another without having to take the freight out of the car owned by Railroad X and put it into a car owned by Railroad Y -- you can then have an actual network as opposed to a conglomeration of vaguely interconnected subsystems. Hence standard gauge emerged as a clear concept, but one with some evolution underneath it.

Incidentally, there were some pretty freaky interim solutions tried that kind of reek of the gateway concept -- cars that had two sets of wheel trucks, cars with variable length axles that would expand or contract when changing gauges, and even the 19th-century equivalent of container cars that could be fit inside other containers. As you can guess, none of these proved practical at the time.

There was a period of settling out in which gauges got adopted as a result, after which there were three major standard gauges in use -- the current 'standard' gauge, and two narrower gauges.

So, how did this particular gauge come about? Our friend's horseshit tale of it dating back to Roman chariot widths may have occasional bits of fact, but the real answer is based on _engineering needs of the day_. The standard gauge was the widest original width you could reliably make an iron axle (pre-bessemerized steel days) that would support the then-weight of locomotives. Basic structural engineering which I won't go into in detail but which should be easy to calculate; there's a basic tradeoff between thickness, length, and number of axles in a traintruck that's related to weight bearing and stress. Of the several gauges that became more widely used in the 1840s and 1850s, what eventually became standard gauge was simply the one that was in the working tolerance ranges that was most widely used at the time.

Note also that later engineering advances -- such as reliable steel production, better power sources (diesel, electric), better car-building methods, etc. -- could not later change the gauge, because a critical mass in the mileage of track that interoperated and generated vast gobs of revenue had been reached and it would be too expensive to go back and rebuild the rail network for what were secondary, albeit superficially technical superior, reasons that may have supported a different gauge at that point. One very salient footnote to this is the final act in the process of standardization. You see, some companies claimed they built things to standard gauge, but there continued to be small differences. Occasionally these were just accidents, occasionally they were deliberate strategies used by a railroad (or sometimes even suppliers) in order to make a competitor unviable. For instance, if you wanted to kill off a little trunk line that was shipping grain from a grain elevator in Podunk, Iowa to your main line of ReallyBig Railroad corporation, you'd change the coupler that held freight cars together or the switching device that sidetracked cars, making sure your couplers worked with both systems. The trunk line would have to refit its cars to your spec or lose the business. Quite frequently, they lost the business because they wouldn't change, or spent so much money keeping up with the demands of the bigger lines that they had to sell the small lines out. Whereupon, of course, standard parts were reintroduced for the convenience of the bigger lines 8-).

There were actually several thousand important devices, ranging from switching systems to bolts and nuts, that fell into this category. In the case of standard gauge, there continued to be residual small fights about what the exact width of the distance between rails, the required width of the rails, whether rails were capped or not, whether they were spiked or welded, what the appropriate tie ratio per unit of rail was, and so forth well into the end of the 19th century. (I will spare you the history of the financial machinations that nearly bankrupted the entire country that were a parallel to the problems of getting interoperation on a technical level). The point is that the width between the rails was one factor among many that dealt with quality of the final product.

And guess what, boys and girls? It wasn't until the Interstate Commerce Commission was formed in 1887 that there emerged final order in this chaos of competing engineering standards. The ICC, for all you read about it in history books as being a price controller for tarifs, also was an umpire for allowing standardization of various bits of railroad technology as they became mature. The ICC actually did a good job of staying out of the actual engineering of things, only getting involved (at least for the first 50 years or so of its existence) with technical standards that actually affected the abilities of railroads to interoperate. While I wouldn't propose the parallel situation of, say, making the IETF a government agency (ugh), having a third party that was not commercially motivated was what actually made the gauge standard; I believe from memory the original order for standard gauge was in 1889.

So the "spec" in this case emerged from engineering practice, and it only became generally useful when the monopolistic players were forced to conform to it (the little guys never have a choice in these matters). And that is the real story.

Matt Wall
Carnegie Mellon University


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