Why is the standard US railway guage 4' 8.5" ?

[Spr.Earl]

The US standard railroad gauge (distance between the rails) is 4'
8.5". That is an exceedingly odd number.

Why was that gauge used?

It is because that was the way railways were built in England, and
British expatriates built the US railroads.

So why did the English build them like that?

This is because the first rail lines were constructed by the same
people who built the pre-railroad horse drawn 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.

Okay! Why did the wagons have that particular odd width between the
wheels?

Well, if they tried to use any other spacing, the wagon wheels would
not match the ruts on the old, long distance highways.

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 became the standard
rut. Otherwise your wagon would not fit and would break. And, long before
the EU, it was the same standard for the whole of Europe.

The USA standard railroad gauge of 4' 8.5" is derived from the
original specifications for an Imperial Roman war chariot.

And why pray did the Imperial Roman war chariots come up with this
standard size. Easy. So that two Imperial Roman horses could fit into the
shafts of an Imperial Roman war chariot (or the back end of two war horses
if you prefer).

Now the twist to the story...

When you 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 in a factory in Utah.
The engineers who designed the SRBs would 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.
The SRBs had to fit through that tunnel. The tunnel is slightly wider than
the railroad track, and the railroad track, as you now know, is about as
wide as two horses' behinds.

So, a major Space Shuttle 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 bum.

 

[Michael OLeary]

A nice story, but it doesn't explain why so many different gauges have been used worldwide:

Railroad Gauge Width - http://parovoz.com/spravka/gauges-e.html

Also, some relevent comments here:

A history of track gauge
How 4 feet, 8-1/2 inches became the standard
by George W. Hilton
http://www.trains.com/Content/Dynamic/Articles/000/000/003/011gsqfq.asp

At the outset, the choice of 4 feet 8-1/2 appeared arbitrary. The tramways of the Newcastle area had a variety of other gauges, wider and narrower, any of which Stephenson might have chosen.

.......

The survival of this gauge for road vehicles in Western Europe, including Britain, resulted in its being carried over onto early railways. An oral tradition says it was established at two strides of a Roman soldier by Julius Caesar to standardize ruts for his war chariots, but this has no documentary evidence and is not generally accepted. As English railway historian Charles E. Lee wrote, it probably represents the optimal size of a road vehicle relative to the indivisible size of a horse. Anything less would have underutilized the horse, and anything greater would have put excessive strain on the animal. The gauge has been carried over into automotive transport, also.

In railroading, the optimal gauge with respect to a horse is irrelevant. Rather, the relevant indivisibility is that of a human being. Any technological process has to be adapted to the fact that human beings generally come only in one size, from 5 feet, 0 inches to 6 feet, 6 inches. Certainly, the gauge of 4 feet, 8-1/2, inches was not grossly inappropriate. It allowed passenger cars that seated two people in comfort on each side of an aisle wide enough for people to pass. Freight cars were large enough to accommodate the size of packages that people could carry in and stack. The equipment had a moderate degree of overhang.

 

[Spr.Earl]

Could it be that narrow gauge was and is for high steep mountains i.e. Switzerland,Chili,Peru,Bolivia,India etc. because it was more suitable for the terrain for construction reason's at the time?
Who know's what problem's the Engineer faced at the time?
Could these problem's have dictated the gauge?
Me think's yes.
But a neat bit of trivia though,yes?

 

[Armymatters]

Railway gauge's have ruined some perfectly good designs for the military before... take the Churchill tank. The tank had to be designed around the standard British railway gauge, and as a result, the design suffered. They had trouble fitting in bigger armament when it became clear that the original gun was insufficient for tank killing. The Churchill, even though it was classified as a heavy tank for the age, had a relatively pathetic gun; in the later models, a 75mm gun, the same found on the original Sherman. If the tank was a bit more wider, it probally would have taken a larger turret that could accomodate a larger gun, besides the 95mm howitzer or a 280mm Spigot motar.

 

[Spr.Earl]

I did not think that a trivial thing as as a railroad could set off a argument.
I posted just for general knowledge.