Shuttle Design Criteria: Width of Horse's Ass

This is a fun anecdote, unfortunitely, it's untrue...

From http://www.scsra.org/library/milspec-debunk.html

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

Forwarded-by: Keith Bostic bostic@...
Forwarded-by: Steve Dekorte 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
wall@...
Carnegie Mellon University
http://www.contrib.andrew.cmu.edu/~wall

> When we see a space shuttle sitting on the launch pad, there are
two
> big booster rockets attached to the sides of the main fuel tank.
> These are the solid rocket boosters, or SRB's. The SRB's are made by
> Thiokol at a factory in Utah. The engineers who designed the SRB's
> might have preferred to make them a bit fatter, but the SRB's had
to
> be shipped by train from the factory to the launch site.
>
> The railroad line to the factory runs through a tunnel in the
> mountains. The SRB's had to fit through that tunnel. The tunnel is
> slightly wider than a railroad track,and the US standard railroad
> gauge (the distance between the rails) is 4 feet, 8.5 inches.
That's
> an exceedingly odd number.
>
> Why was that gauge used? Because that's the way they built them in
> England, and the US railroads were built by English expatriates.
> Why did the English people build them like that? Because the first
> rail lines were built by the same people who built the pre-railroad
> tramways, and that's the gauge they used.
>
> Why did "they" use that gauge then? Because the people who built the
> tramways used the same jigs and tools that they used for building
> wagons, which used that wheel spacing.
>
> Okay! Why did the wagons use that odd wheel spacing? Well, if they
> tried to use any other spacing, the wagons would break on some of
> the old, long distance roads, because that's the spacing of the old
> wheel ruts.
>
> So who built these old rutted roads? The first long distance roads
in
> Europe were built by Imperial Rome for the benefit of their
legions.
> The roads have been used ever since.
>
> And the ruts? The initial ruts, which everyone else had to match
for
> fear of destroying their wagons, were first made by Roman war
> chariots. Since the chariots were made for or by Imperial Rome they
> were all alike in the matter of wheel spacing, thus, we have the
> answer to the original question.
>
> The United States standard railroad gauge of 4 feet, 8.5 inches
> derives from the original specification for an Imperial Roman army
> war chariot. Specs and bureaucracies live forever. So, the next
time