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November 2003

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Subject:
From:
"Ingemar Hernefjord (KC/EMW)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 6 Nov 2003 08:59:18 +0100
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text/plain
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text/plain (234 lines)
Talking rocket scientists, heard about one snail (1 snail)? I have seen it sometimes, thought it was a joke, but it is not!

slinch is a unit of mass invented by the U.S. National Aeronautics and Space Administration (NASA). The unit is part of a system based on the pound of force and the inch. One slinch is the mass accelerated at one inch per second per second by a force of one pound; thus the slinch equals exactly 12 slugs or about 386.088 pounds (175.1268 kilograms). The word is a contraction of slug-inch. In the U.S. military aircraft industry, this unit is sometimes called a mug. It has also been called a snail.

As acceleration seems to be so important for many cardrivers, I don't understand why they have missed a snailometer!

Ingemar


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Kasprzak, Bill (sys)
USX
Sent: den 5 november 2003 18:33
To: [log in to unmask]
Subject: Re: [TN] OFF-TOPIC: Engineering Specs :-)


Brian,

With all due respect,

If it was simple, anyone could do it. That's why these units of measurement
were adopted in the first place. It requires us rocket scientists to keep
everything in order. How else would anyone know the correct distance for the
cricket pitch between the wickets.

Since we've battered around the English units, can anyone tell the story of
the origin of the meter and the liter? How about time? 60 minutes, 60
seconds and 24 hours seems pretty silly too.

It would be nice for all of us to speak one language too. In the meantime
we'll just keep on moving along.

Bill Kasprzak
Moog Inc, Electronics Process Engineering


-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Wednesday, November 05, 2003 10:14 AM
To: [log in to unmask]
Subject: Re: [TN] OFF-TOPIC: Engineering Specs :-)


Of course, this makes the metric system look stupid. It makes much more
sense to have 12 inches = 1 foot; 3 feet = 1 yard; 5.5 yards = 1 rod, pole
or perch; 4 rods, poles or perches = 1 chain (the length of a cricket pitch
between the wickets); 10 chains = 1 furlong; 8 furlongs = 1 statute mile. In
summary, 1 mile = 8 furlongs = 80 chains = 320 rods, poles or perches = 1760
yards = 5280 feet = 63360 inches. It is this simplicity that dictates why
printed circuits are largely dimensioned in imperial measures, rather than
the complex metric system. Similarly, imperial weights, volumes, areas etc.
are equally simple.

Brian

Ingemar Hernefjord (KC/EMW) wrote:
> The history of length and weight is funny to read
>
> examples pasted from english history article:
>
> The foot was declared one-third yard and the inch one thirty-sixth.
> King Edward II in 1324 recognising the Iron Ulna was not universally
> used declared "3 barleycorns, round and dry make an inch"
>
>
> Going as far back in time as Noah's ark, the lack of a universally
> understood unit of measurement was not a serious drawback. Most
> measuring was done by one craftsman completing one job at a time,
> rather than assembling a number of articles piecemeal to be put
> together later. It didn't make much difference how accurate the
> measuring sticks were or even how long they were. The cubit of Noah's
> time was the length of a man's forearm or the distance from the tip of
> the elbow to the end of his middle finger.
>
> For the United Kingdom, the basic English unit of length was the yard
> of three feet, or the fathom of six. Half a yard was the 18-inch
> cubit, and half a cubit was called a span, which was the distance
> across the hand from the tip of the thumb to the tip of the little
> finger when the fingers were spread out as far as possible. A hand was
> half a span. During the thirteenth century King Edward I decreed the
> 'Iron Ulna' after the bone of the forearm to become the main unit of
> measurement, which later became the 'yard'. He ordered a permanent
> measuring stick made of iron to serve as a master standard yardstick
> for his entire kingdom. King Edward realised that constancy and
> permanence were the key to any standard. The foot was declared
> one-third yard and the inch one thirty-sixth.
>
>
> Regards
>
> Ingemar Hernefjord
> Ericsson Microwave Systems
>
>
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Brian Ellis
> Sent: den 4 november 2003 17:24
> To: [log in to unmask]
> Subject: [TN] OFF-TOPIC: Engineering Specs :-)
>
>
> Origins of engineering specs
>
>   Subject:  Origins of engineering specs and government
>   decisions. Ever wonder where engineering specifications come from?
>
>   The US standard railroad gauge (distance between the rails) is 4 feet,
>   8.5 inches, an exceedingly odd number. Why was that gauge used?
>   Because that's the way they built them in England, and the English
>   built the first US railroads.
>
>   Why did the English build them like that?
>
>   Because the first rail lines were built by the people who built the
>   pre-railroad tramways, and that is the gauge they used.
>
>   Why did they use that particular gauge then?
>
>   Because the people who built the tramways used the same jigs and tools
>   that they used for building wagons, which used the same 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 the old, long distance roads in England, because that's the
>   spacing of the wheel ruts in the granite sets.
>
>   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 everyone else had to
>   match for fear of destroying their wagon wheels. Since the chariots
>   were made for (or by) Imperial Rome, they all had the same wheel
> spacing.
>
>   The United States standard railroad gauge of 4 feet, 8.5 inches is
>   derived from the specification for an Imperial Roman war chariot.
>
>   Specifications and Bureaucracies live forever.
>
>   The Imperial Roman war chariots were made just wide enough to
>   accommodate the back ends of two war-horses.
>
>   Now let's cut to the present...
>
>   The Space Shuttle, sitting on its launch pad, has two booster rockets
>   attached to the sides of the main fuel tank. These are solid rocket
>   boosters, or SRBs. A company builds SRBs at its factory in Utah. The
>   engineers who designed the SRBs wanted 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 has to run through a tunnel in the
>   mountains.
>
>   The SRBs had to fit through that tunnel, which 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 arguably the world's most
>   advanced transportation system was determined two thousand years ago
>   by a horse's ass.
>
>   Which is pretty much how most government decisions are made.
>
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