Edwards air show B-1 speed record attempt

"phil hunt" wrote in message
. ..
On Fri, 24 Oct 2003 00:08:31 -0000, Jim Battista wrote:

Not you that's stupid, the system. It's broken at a basic level --
you should never have to remember anything, which requires 1 to 1 to
1 conversions.

It would certainly be possible to have the baisc unit of length 10
cm, the unit of volume that length cubed, and thre unit of mass that
volume of water.

Why not just admit that SI is just another arbitrarily bounded measurement
system and get over the eurocentic ego trip?

Tarver Engineering wrote:

"Gene Nygaard" wrote in message


snip


Aircraft already have units of measure. Why use different units? Why is
anyone working in NASA Operations that does not know aircraft units?

What you write is a non-sequitur.


You also underestimate the effects of systematic miseducation. The
mere existence of a conversion factor from pounds to kilograms on a
calculator isn't going to undo the fact that some favorite teacher has
drummed into someone's head the notion that pounds are always units of
force and not units of mass, so you can't really convert between
pounds and kilograms. In fact, in today's screwed up world, there are
a number of textbooks which tell you just exactly that.


Why change from the units of aerospace to some other arbitrary set of units
in the first palce? In my 20 20 hindsight I can say for a fact that
attempting to apply si units to aerospace has come at the cost of confusion
and we are very fortunate to have avoided toumbstones.


In fact, the calculator is the end of any need to change to si
units, as si is a slide rule reality.

Any time you make a conversion, at least other than by factors that
are exact powers of 10, you lose something.


Perhaps, but not enough to matter from an engineering, of operational
standpoint.


Any time there is a need to make conversions, it is an opportunity for
all sorts of other errors, including misentry of the numbers into the
calculator, transposition of digits in copying the result, or
whatever.


In that case, why stray from what already works and play silly SI games?



snip
As much as I dislike feet and inches, I have to agree with you there,
John. Don't you Americans have a saying: "If it ain't broken, don't fix
it!"?
The question of course is whether it's broken :-)
I would tend to think that as long as you're aware that there is a
potential for problems (like the US vs. imperial gallon thing) there
really shouldn't be any.
Still, I'm glad at least scientists tend to use the same system
world-wide (although in my lab the non metric dimensions of equipment
bought in the US still causes occasional difficulties.)

Regards,
Ralph Savelsberg

"Ralph Savelsberg" wrote in message
...

snip
As much as I dislike feet and inches, I have to agree with you there,
John. Don't you Americans have a saying: "If it ain't broken, don't fix
it!"?

Just look at what medling with the units of aerospace has done. Add pounds
and check the aircraft's weight, how simple can it be? Mass flow rate makes
thrust and that is pounds of fuel.

The question of course is whether it's broken :-)
I would tend to think that as long as you're aware that there is a
potential for problems (like the US vs. imperial gallon thing) there
really shouldn't be any.

Why would you buy fuel by volume in a high reliability sysetm driven by
weight? (mass)

Still, I'm glad at least scientists tend to use the same system
world-wide (although in my lab the non metric dimensions of equipment
bought in the US still causes occasional difficulties.)

I do like the metric system for wavelength type math, but engineering
problems are best done in a "measurement and reference system" consistent
with an easy solution. If the customer needs a different measurement and
reference system, it is usually trivial to remap the results. In the cases
discussed here, the measurement and reference system led directly to
unexpected results.

In article ,
wrote:

On Fri, 24 Oct 2003 06:12:29 -0400, Peter Kemp
peter_n_kempathotmaildotcom@ wrote:

On or about Thu, 23 Oct 2003 21:24:18 -0700,
(Harry Andreas) allegedly uttered:

In article , Peter Kemp
peter_n_kempathotmaildotcom@ wrote:

Especially living in the US as I currently do, it drives me nuts to
work in mm, inches and U just to get a single box to fit a rack.

Whoever thought of U as a unit of measurement really needs to suffer
in a major way. The sooner racks become standardised on a metric
measurement, the happier I'll be.

Hate to break it to you, but the U is a metric spec.

1U = 44.45mm = 1.75 inches. It may be definable in terms of mm, but
since it generally applies to 19 inch racks (ugh) I consider it an
imperial measure.

Roll on the replacement by V = 50mm :-) in the 500mm rack (500 mm wide
AND deep).

Oh, and Gene, a U is a unit used to measure the height of equipment in
"standard" 19inch racks of equipments, be they computers, radios, or
any other technical equipment.

Of course, even standard 19 inch racks are not standard, they come in
lots of non-standard depths - which can be a real arse when you fly
somewhere for an installation to discover the rack is particularly
shallow and now you can't close the door :-)

Is that really half of the width of a 3½ inch diskette? That standard
size is 90.0 mm, not 88.9 mm.

In other words, was Harry Andreas telling you that this standard size
isn't really 1.75 mm = 44.45 mm, but rather 45 mm = 1 98/127 in or
about 1.77 in? That's what it sounds like to me, but I don't know if
that is the case or not.

I almost don't want to go here, but... a 2 x 4 piece of lumber is really
only 1.75 x 3.75, and I've seen some that are only 1.5 x 3.5

--
Harry Andreas
Engineering raconteur

On Fri, 24 Oct 2003 10:42:31 +0200, Andreas Parsch wrote:

Jim Battista wrote:


Not you that's stupid, the system. It's broken at a basic level --
you should never have to remember anything, which requires 1 to 1 to
1 conversions. Meters lead to liters lead to grams lead to calories
and newtons, all based rigidly off a better-defined meter.


I agree that there are some "anomalies" in the SI, like e.g. the basic
(as in "used when deriving other SI units") unit of mass is
"kilogram", while all other basic units are non-prefixed. Still,
1-to-1 conversion factors between units (called "coherent units" IIRC)
are the basic idea behind SI, and are very common - e.g. you need a
force of 1 N to accelerate a mass of 1 kg by 1 m/s^2.

Anyway, if you say SI is "broken at a basic level" because of the
inconsistency involving kilogram/gram/liter/cubic-meter, what do you
call the US/Imperial system? "Utterly and fundamentally broken by
design" ;-) ??

Andreas

Actually, the unit of mass is the gram.

Al Minyard

On Fri, 24 Oct 2003 15:41:25 GMT, Gene Nygaard wrote:

You also underestimate the effects of systematic miseducation. The
mere existence of a conversion factor from pounds to kilograms on a
calculator isn't going to undo the fact that some favorite teacher has
drummed into someone's head the notion that pounds are always units of
force and not units of mass, so you can't really convert between
pounds and kilograms. In fact, in today's screwed up world, there are
a number of textbooks which tell you just exactly that.

If everyone standardised on SI units, and used kg whenever they
meant mass, and N whenever they meant force, there would be no
misunderstandings.

Same with the Gimli glider. Why in the world were U.S. gallons ever
involved in that improbable, couldn't-be-written-as fiction string of
errors, when you had a Canadian airline on a domestic flight? It's a
lot easier to mix up gallons and gallons than it is to mix up gallons
and litres.

Indeed.

--
"It's easier to find people online who openly support the KKK than
people who openly support the RIAA" -- comment on Wikipedia
(Email: , but first subtract 275 and reverse
the last two letters).

In article ,
Ralph Savelsberg wrote:

As much as I dislike feet and inches, I have to agree with you there,
John. Don't you Americans have a saying: "If it ain't broken, don't fix
it!"?

In the area of US measurements it should be: "If we can't fix it, pretend
that it isn't broken".

The question of course is whether it's broken :-)

It is.

--
Göran Larsson http://www.mitt-eget.com/

"phil hunt" wrote in message
. ..
On Fri, 24 Oct 2003 15:41:25 GMT, Gene Nygaard
wrote:

You also underestimate the effects of systematic miseducation. The
mere existence of a conversion factor from pounds to kilograms on a
calculator isn't going to undo the fact that some favorite teacher has
drummed into someone's head the notion that pounds are always units of
force and not units of mass, so you can't really convert between
pounds and kilograms. In fact, in today's screwed up world, there are
a number of textbooks which tell you just exactly that.

If everyone standardised on SI units, and used kg whenever they
meant mass, and N whenever they meant force, there would be no
misunderstandings.

If we left things alone, instead of being globalist egotistical loons, these
problems would not occur.

"Tarver Engineering" wrote...

Aircraft buy fuel by weight,

Nope. The aircraft don't do any buying at all. Aircraft may display fuel loads
in pounds or kilograms, but that is after the aircraft system converts a tank
level (i.e., quantity or volume) to a weight via density-sensing probes or other
means.

Jet fuel is dispensed and sold by the gallon in the US and by the liter in most
other countries. Airline companies buy fuel by the gallon, and Pilots and
Flight Engineers use calculators, slide rules, and pencil & paper to convert
those liters or gallons to pounds or kilograms for use in load verification and
flight planning.

Alan Minyard wrote:

Actually, the unit of mass is the gram.

Of course the gram is a unit of mass, but it's not _the_ unit (depends
on the definition of "_the_" ;-) ). All I said is that the kilogram is
used in SI to derive units, and not the gram (as in 1 N = 1 kg m / s^2).

Andreas