Fwd: Railroad gauges and horses' behinds (fwd)
Rudolph C Troike
rtroike at U.ARIZONA.EDU
Fri Mar 16 19:05:38 UTC 2001
This sounds like an updated bit of folklore (we do deal with folk-things
in the ADS), but it would be funnier if the specification for Roman
chariots were documented. You do see the ruts in stone roads all over the
former Empire, even in Syria.
---------- Forwarded message ----------
Date: Fri, 16 Mar 2001 09:40:53 -0700
From: Elaine Lim <etl at u.arizona.edu>
To: Rudy <rtroike at u.arizona.edu>
Subject: Fwd: Railroad gauges and horses' behinds
Does the expression, "We've always done it that way!" ring any bells?
The US standard railroad gauge (distance between the rails) is 4 feet,
8.5 inches. That is an exceedingly odd number.
Why was that gauge used? Because that is the way they built them in
England, and English expatriates built the US railroads.
Why did the English build them like that?
Because the first rail lines were built by the same people who built the
pre railroad tramways, and that is 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 the same wheel spacing.
Why did the wagons have that particular odd wheel spacing? Well, if
they tried to use any other spacing, the wagon wheels would break on
some of the old, long distance roads in England, because that's the
spacing of the wheel ruts. So who built those old rutted roads?
Imperial Rome built the first long distance roads in Europe (and
England) for their legions. The roads have been used ever since.
And the ruts in the roads? Roman war chariots formed the initial ruts,
which everyone else had to match for fear of destroying their wagon
wheels. Since the chariots were made for (or by) Imperial Rome, they
all had the same wheel spacing.
The United States standard railroad gauge of 4 feet, 8.5 inches is
derived from the original specification for an Imperial Roman war
Specifications and bureaucracies live forever. So the next time you are
handed a specification and wonder what horses ass came up with it, you
may be exactly right. This is because the Imperial Roman war chariots
were made just wide enough to accommodate the back ends of two
Now, the twist to the story... There is an interesting extension to the
story about railroad gauges and horses' behinds.
When we see a Space Shuttle sitting on its launch pad, there are two big
booster rockets attached to the sides of the main tank. These are solid
rocket boosters, or SRBs. "Thiokol" makes the SRBs at their factory at
Utah. The engineers who designed the SRBs might have preferred to make
them a bit fatter, but the SRBs had to be shipped by train from the
factory to the launch site. The railroad line from the factory happens to
run through a tunnel in the mountains. The SRBs had to fit through that
tunnel. The tunnel is slightly wider than the railroad track, and the
railroad track is about as wide as two horses' behinds. So, a major
design feature of what is arguably the world's most advanced
transportation system was determined over two thousand years ago by the
width of a horse's ass.
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