Engineering Specifications

From: jim, julie, and cal smylie (smylie@pnx.com)
Date: Mon Mar 13 2000 - 20:13:28 PST


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This is off topic, but I think everyone needs a laugh now and then. Got
this from a friend and, yes, we are both engineers.

The US standard railroad gauge (width between the two 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 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 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? 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? Roman
war chariots first 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 were all alike in the matter of
wheel spacing. The United States 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 _______ came
up with it, you may be exactly right, because
the Imperial Roman war chariots were made just wide enough to
accommodate the back ends of two war horses. Thus, we have the answer to
the original question.

Now the twist to the story..............

There's 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 fuel
tank. These are solid rocket boosters, or SRBs. The SRBs are made by
Thiokol at their factory in 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 had 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, the 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 _______!



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