Horse, Rail and Rocket
Created | Updated Jan 28, 2002
The United States Standard Railroad Gauge, (the distance between the rails,) is 4 feet, 8½ inches. Here is the reason for such an unlikely and unrounded number:
4 feet, 8½ inches was the rail gauge that had been used previously in Britain and Ireland, and British expatriate engineers imported much of America's original rail "hardware, including track and engines. The first British railway lines had been designed and built by the same engineers who had built the pre-railroad tramways, so that was the gauge with which they stuck.
Tramways used that same gauge because the tramway builders had used the same construction jigs and tools that
had previously been used to manufacture horse carriages, and so shared the same wheel spacing.
The horse carriages had that particular wheel spacing because, had they tried to use any other spacing, the carriage wheels would have been broken on some of the old, long distance roads in Britain; they ran best in the same spacing as the worn wheel ruts. The old rutted roads were built by Imperial Rome, and have been used, maintained and improved ever since.
Roman war chariots formed the initial ruts. Since the chariots were made for, and by, Imperial Rome, they all had the same wheel spacing. The United States Standard Railroad Gauge of 4 feet, 8½ inches is derived from the original specification for an Imperial Roman war chariot, i.e the width of two Roman horses' backsides!
To update the story relating railroad gauges and horses' behinds; when the Space Shuttle sits on its launch pad, there are two large booster rockets attached to the sides of the main tank. These are solid rocket boosters, (or SRBs). A sub-contracting company makes the SRB units at their factory in Utah. The engineers who designed the SRBs might have preferred manufacturing them to a different size, but the SRBs had to be shipped by rail from the factory to the launch site. The railroad line from the factory runs 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 probably the world's greatest transport machine was influenced more than two thousand years ago by the width of a horse's behind!
4 feet, 8½ inches was the rail gauge that had been used previously in Britain and Ireland, and British expatriate engineers imported much of America's original rail "hardware, including track and engines. The first British railway lines had been designed and built by the same engineers who had built the pre-railroad tramways, so that was the gauge with which they stuck.
Tramways used that same gauge because the tramway builders had used the same construction jigs and tools that
had previously been used to manufacture horse carriages, and so shared the same wheel spacing.
The horse carriages had that particular wheel spacing because, had they tried to use any other spacing, the carriage wheels would have been broken on some of the old, long distance roads in Britain; they ran best in the same spacing as the worn wheel ruts. The old rutted roads were built by Imperial Rome, and have been used, maintained and improved ever since.
Roman war chariots formed the initial ruts. Since the chariots were made for, and by, Imperial Rome, they all had the same wheel spacing. The United States Standard Railroad Gauge of 4 feet, 8½ inches is derived from the original specification for an Imperial Roman war chariot, i.e the width of two Roman horses' backsides!
To update the story relating railroad gauges and horses' behinds; when the Space Shuttle sits on its launch pad, there are two large booster rockets attached to the sides of the main tank. These are solid rocket boosters, (or SRBs). A sub-contracting company makes the SRB units at their factory in Utah. The engineers who designed the SRBs might have preferred manufacturing them to a different size, but the SRBs had to be shipped by rail from the factory to the launch site. The railroad line from the factory runs 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 probably the world's greatest transport machine was influenced more than two thousand years ago by the width of a horse's behind!
