Re: [SI-LIST] :PCB Bd thkness'

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From: David Instone (david_instone@uk.xyratex.com)
Date: Wed Mar 08 2000 - 08:21:22 PST


OK I can resist no longer! see below
Killoy Richard-P29744 wrote:
...snip....
> built by English expatriates. Why did the English people 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.
...snip...
> Okay! Why did the wagons use
> that odd wheel spacing? Well, if they tried to use any other spacing,
> the wagons would break on some of the old long distance roads, because
> that's the spacing of the old wheel ruts.
An interesting theory, but The early wagon ways were simply wooden
boards laid end to end in two lines. When these were pulled by a rope
from a stationary engine at one enf of a line. they had to do something
to stop the wagons coming off. So they put vertical boards on the
OUTSIDE edges of the running boards. The distance between these boards?
5 feet, a nice round number. Now when they came to put in switches it
doesn't work if the rails are flanged so they flanged the wheels on the
inside and keeping the same wheel spacing and a tad for running
clearance gives you 4 ft 8.5 inches over the flanges.

Going back to the first point, if Brunel had had his way we would have
had 7 ft spacing. The Great Western (of England) built their lines on
this rail gauge.

> So who built these old
> rutted roads? The first long distance roads in Europe were built by
> Imperial Rome for the benefit of their legions. The roads have been
> used ever since.
> And the ruts? The initial ruts, which everyone else had to match for
> fear of destroying their wagons, were first made by Roman war
> chariots. Since the chariots were made for or by Imperial Rome, they
> were alike in the matter of wheel spacing. Thus, we have the answer to
> the original questions. The United States standard railroad gauge of 4
> feet, 8.5 inches derived from the original specification for an
> Imperial Roman army war chariot. Specs and bureaucracies live forever.
> So, the next time you're handed a specification and wonder what
> horse's ass came up with it, you may be exactly right. As it turns
> out, the Imperial Roman chariots were made to be just wide enough to
> accommodate the back ends of two war horses.
>
> There's a very interesting extension of the railroad gauge story and
> horses' behinds. When we see a Space Shuttle sitting on the launch
> pad, there are two big booster rockets attached to the sides of the
> main fuel tank, well known as the solid rocket boosters, or SRBs. The
> SRBs are made by Thiokol at a 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 to the factory runs through a tunnel in the
> mountains. The SRBs had to fit through that tunnel.
> The tunnel is only slightly wider than a railroad track and the
> railroad track is about as wide as two horses' behinds.

Another misunderstood feature of railways is that there are two gauges.
Rail Gauge and Loading Gauge. The former refers only to width between
the rails. The later to the maximum dimensions, both width and
height,of the wagons, locos etc. In the UK we use a smaller Loading
gauge than in the US although we use the Rail gauge. You can stack two
containers on one wagon, we can only do one. Our passenger coaches are
much narrower. So our tunnels are smaller than yours and much nearer
the two horses backside dimension.

So if we had built the shuttle it might conceivably have needed 4
boosters!

> So as it
> stands, a major design feature of what is arguably the world's most
> advanced transportation and rocket system, conceivably was determined
> by the width of a horse's backside, or two.
> As an astronaut, how would you like to be saddled with that?
>
> ------------

-- 
Regards

Dave Instone. Compliance Engineer Test Systems, MP24/22 Xyratex, Langstone Rd., Havant, Hampshire, P09 1SA, UK. Tel: +44 (0)23-92-496862 (direct line) Fax: +44 (0)23-92-496014 http://www.xyratex.com Tel: +44 (0)23-92-486363

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