Good Engineering Lasts Forever.
The U.S. 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's the way they built them in England, and the U.S. railroads were built by English expatriates.
Why did the English build them that way?
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
Because the people who built the tramways used the same jigs and tools that they used
for building wagons, which used that wheel spacing.
So why did the wagons have that particular odd 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 was the spacing of the wheel ruts.
So who built those old rutted roads?
The first long distance
roads in Europe (and England) were built by Imperial Rome for
their legions. The roads have been used ever since.
And the ruts in the roads?
The ruts in the roads, which
everyone had to match for fear of destroying their wagon wheels, were first
formed by Roman war chariots. Since the chariots were made for (or by) Imperial
Rome, they were all alike in the matter of wheel spacing.
The U.S. standard railroad gauge of 4 feet-8.5 inches derives from the original specification for an Imperial Roman war chariot.
Specifications and bureaucracies live forever.
So the next time you are
handed a specification and wonder what horse's behind came up
with it, you may be exactly right, because the Imperial Roman war chariots were made just
wide enough to accommodate the back end/side by side oftwo war horses.
Thus we have the answer to the original question.
Now for the twist to the story.
When we see a space shuttle sitting on it's launching pad, there are two booster rockets attached to the side of the main fuel tank. These are solid rocket boosters, or SRB's.
The SRB's are made by
Thiokol at their 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 from the
factory had to run through a tunnel in the mountains. The tunnel is slightly
wider than the railroad track, and the railroad track is about as wide as two
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 back side.
Don't you just love engineering?
Back to Index