SI units in science (Re: Estes' latest ad)

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James Wentworth

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Nov 24, 1998, 3:00:00 AM11/24/98
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Rob Edmonds <RobEd...@aol.com>

<< I'm not knocking Bill, as he covers all areas of science & technology and
he is a stickler for the
use of SI units. >>

>Why do you want to ruin kids with those SI units? SI units discourage the
>development of a sense of proprtion. Numbers like 1/4, 1/2, 2, 3 ,4 and 6
>have a real, intrinsic meaning to them that is important to the development
>of design skills in the child's mind. A number like ".317" has no intrinsic
>meaning, it only stimulates the symbolic side of their minds (in that they
>can recognize a "three", a "one" and a "seven". Perhaps the concept
>that the "point" means that the number is less than one rather than
>greater than one has a tiny bit of intrinsic appeal). If all you want
>is a bunch of scientists, OK, but if you want engineers, your not going
>to produce them with units divisible by a meaningless number like ten.
>There are plenty of useful benefits to dividing things into two's,
>three's an four's, but very few to >dividing them in five.
>RE

Rob, I would have agreed with you about this as late as five years ago.
Like every other American pupil, I was taught the US Customary units and
the metric system (Systeme International d'Unites, also known as SI). SI
is an inherently superior system (USC is *not* a system, but a collection
of units) because the units are inter-related. The fundamental SI units are
related by factors of 1 000, not 10 (millimeter, meter, kilometer,
etc.). Units such as the centimeter, which do not follow this
progression, are not used for engineering or scientific purposes. The
centimeter is used for everyday purposes, and because it is derived from
the SI units it is very easy to convert back and forth between
centimeters, millimeters and meters (just mentally move the decimal point).

Wernher von Braun and his team used SI units for all of their
calculations and converted only the final results to USC units, for the
consumption of their American colleagues. Wernher von Braun loathed
inch-pound units and stated so on several occasions.

SI is the metrological language of science, and I applaud Bill Nye for
using it exclusively on his program. Anyone who wishes to understand the
sciences, even at the layman's level, should be acquainted with SI.

America is far more metricated than most citizens realize. Many products
which are labelled in USC units (3.5" floppy diskettes, for example) are
actually made to SI specifications. Forty-three of the state departments
of transportation have converted to SI, and all federal government
buildings are built to SI specifications. All federal government
procurements are to SI standards (including NASA and the armed
services). Next year the federal tax forms will be printed on A4 (the
international standard size) paper.

Like it or not, we live in a metric world.


Jason
--
James J. Wentworth
d005...@dc.seflin.org


The Silent Observer

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Nov 24, 1998, 3:00:00 AM11/24/98
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James Wentworth wrote:
>
> Next year the federal tax forms will be printed on A4 (the
> international standard size) paper.

Irrelevant to me -- I don't expect to file another paper return in the
foreseeable future. In 1998, for my tax year 1997 return, I paid a
whopping $4.95 to file electronically, after downloading and using
software supplied for free by the filing provider. I had my refund in
hand less than two weeks after uploading the return. I don't intend to
ever go back...

--
WARNING!! This area has been designated an official DOPE FREE ZONE!!

If you're going to be a dope, please do it somewhere else!

Donald Qualls, aka The Silent Observer NAR # 70141-SR Insured
Rocket Pages http://members.aol.com/silntobsvr/launches.htm

Opinions expressed are my own -- take them for what they're worth
and don't expect them to be perfect.

Phil Bulmer

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Nov 24, 1998, 3:00:00 AM11/24/98
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> America is far more metricated than most citizens realize. Many products

> which are labelled in USC units (3.5" floppy diskettes, for example) are
> actually made to SI specifications. Forty-three of the state departments

> of transportation have converted to SI, and all federal government
> buildings are built to SI specifications. All federal government
> procurements are to SI standards (including NASA and the armed

> services). Next year the federal tax forms will be printed on A4 (the
> international standard size) paper.
>

> Like it or not, we live in a metric world.
>
>
>
>
> Jason
> --
> James J. Wentworth
> d005...@dc.seflin.org
>
>

This is a most interesting thread. It is one of the few instances where the
US is 'following' the UK. Being a child of the late sixties (I missed the
Apollo 11 landing by a week -bummer) I grew up being fully conversant with
both imperial and new 'European' metric units. Inches are fine units of
measurement, they are nice manageable chunks but fractions of an inch are a
real swine. If you look at a scale drawing of a rocket (as I do frequently)
then what the heck is say 10.3"? The figure after the decimal is in base 10
as are 1,000ths of inches. What a cock up! Try drawing a line 10.3" against
a rule, you can't do it! Adding fractions together is not a lot of fun
either!
As for children in school, well I teach 11 to 18 year olds here in the UK
and they don't have any problem with metric. Give them fractions of inches
to both measure and add up and you will see glazed expressions within 30
seconds.

When I was a lad we had pounds, shillings and pence. Nothing was in base 10
and there were 244 pence to the pound. A number of German spies who landed
in the UK during the war were caught out because they didn't understand the
money and would hand over 'pounds' when they were charged an amount in
'shillings' (asking to buy a bottle of cider to take away in a pub on an
east coast beach whilst wearing a suit with the lower 6" (150mm) dripping
wet was another good way of getting caught).

Forget patriotism, we went to metric and it is the best thing we ever did.
If you build scale models then I bet the ones built from metric plans
rather than imperial are just that little bit more accurate in the very
fine detail.


Phil

(My opinions only, if you don't like them divide by 25.4)


MindSpring User

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Nov 24, 1998, 3:00:00 AM11/24/98
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It's tough to really knock SI units since they are based entirely on the
planet earth and it's properties: The meter (metre?) is based on the
circumferance of the earth. The liter (litre?) is based on a volume of
water using the centimeter, at 4 degrees C (one cubic centimeter of water =
1 gram). And so forth. Very sensible, very easy to repeat.

HOWEVER! Two bones of contention.

Firstly, as noted elsewhere, base ten does not lend itself to easy division
by oddball numbers. If I have twelve inches I can easily end up with a
whole number when dividing into 2, 3, 4, or 6, and easy-to-handle
half-inches when 5 or 8 happen. Divide a centimeter by three and you get a
radical. Ouch.

Secondly, and this one really grates me, the kilogram is a measure of MASS
not WEIGHT, and yet we record weight in grams! A kilo of material is still
a kilo, as mass remains constant, even when in zero-g and apparently
weightless. The proper unit to use when measuring the force applied by a
mass due to gravity is Newtons. Man, this detail bugs me, it only serves to
confuse people about the distinction between weight and mass. And yet bacon
is sold by the kilo.

Just my $0.02. Sorry for the lack of rocket content. I'll shut up now.

MindSpring User

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Nov 24, 1998, 3:00:00 AM11/24/98
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MindSpring User wrote in message <73ef2c$pfa$1...@samsara0.mindspring.com>...

>and easy-to-handle
>half-inches when 5 or 8 happen.
^^^^

Pre-coffee brain burp. Sorry. NOW I'll shut up.

Robert J. Kelley

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Nov 24, 1998, 3:00:00 AM11/24/98
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"MindSpring User" <don...@mindspring.com> writes:

>It's tough to really knock SI units since they are based entirely on the
>planet earth and it's properties: The meter (metre?) is based on the
>circumferance of the earth. The liter (litre?) is based on a volume of
>water using the centimeter, at 4 degrees C (one cubic centimeter of water =
>1 gram). And so forth. Very sensible, very easy to repeat.

There are some really wonderful consequences of this.

>HOWEVER! Two bones of contention.

>Firstly, as noted elsewhere, base ten does not lend itself to easy division
>by oddball numbers. If I have twelve inches I can easily end up with a
>whole number when dividing into 2, 3, 4, or 6, and easy-to-handle
>half-inches when 5 or 8 happen. Divide a centimeter by three and you get a
>radical. Ouch.

I agree, ouch. Deal with it. It seems to me that Imperial units were
developed on the basis of dividing quantities in half, which is a useful
way to divide things, and an easy division to verify.

>Secondly, and this one really grates me, the kilogram is a measure of
>MASS not WEIGHT, and yet we record weight in grams!

Nobody actually records weight, weight is irrelevant. Any decent scale
actually measures mass, not weight. The distinction in terrestrial
applications isn't that great though. Your bathroom scale probably
wouldn't work well on the moon because it's a spring scale and it
actually measures weight. Your doctor's scale probably would, because
it measures mass.

>A kilo of material is still a kilo, as mass remains constant, even when
>in zero-g and apparently weightless.

True.

>The proper unit to use when measuring the force applied by a mass due to
>gravity is Newtons.

True.

>Man, this detail bugs me, it only serves to confuse people about the
>distinction between weight and mass.

You are one of the confused people, and I know why. It's not your fault.
Your confusion stems from common usage of the verb "to weigh". What it
actually means when you weigh something is that you're measuring its mass.
People wouldn't get confused if it were more common to use the verb "to
mass", as in, "I'm going to mass this bacon". Presto, confusion allayed.

My physics and chemistry teacher always used the verb "to mass".

>And yet bacon is sold by the kilo.

Bacon is sold by mass, not by weight.

This has everything to do with rockets: substitute AP for bacon....


MindSpring User

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Nov 24, 1998, 3:00:00 AM11/24/98
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>>Secondly, and this one really grates me, the kilogram is a measure of
>>MASS not WEIGHT, and yet we record weight in grams!
>
>Nobody actually records weight, weight is irrelevant.

Lord knows I've tried to tell my wife that...

>Any decent scale actually measures mass, not weight.

<snip>


>You are one of the confused people, and I know why. It's not your fault.
>Your confusion stems from common usage of the verb "to weigh". What it
>actually means when you weigh something is that you're measuring its mass.
>People wouldn't get confused if it were more common to use the verb "to
>mass", as in, "I'm going to mass this bacon". Presto, confusion allayed.
>
>My physics and chemistry teacher always used the verb "to mass".


Whoa, gimme a second, I need to rearrange my thinking. There, that's got
it. I had never considered that a nice beam scale would indeed cancel out
local gravity. Oy. Good one. Beam scale, good. Spring scale, bad.
Thanks, I love it!

>Bacon is sold by mass, not by weight.

...some settling of contents may occur during shipping...

The Silent Observer

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Nov 24, 1998, 3:00:00 AM11/24/98
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MindSpring User wrote:
>
> Whoa, gimme a second, I need to rearrange my thinking. There, that's got
> it. I had never considered that a nice beam scale would indeed cancel out
> local gravity. Oy. Good one. Beam scale, good. Spring scale, bad.
> Thanks, I love it!

Well, spring scales have their place, too. Since they directly measure
*force* (thanks to Hooke's Law), a well calibrated form of spring scale
(such as a cantilevered mass with strain gages on the beam), with the
bob mass precalibrated against a beam balance in a known acceleration
field (such as that at the surface of the earth) can be used as an
accelerometer. Say, there might even be a rocketry product in that...
B)

In addition, a spring scale (of one sort or another) is exactly what you
want when you're (for instance) measuring the breaking strength of a
piece of line or bungee for use as a shock cord, or when testing the
thrust curve of a rocket motor, or even when applying torque to a bolt
to ensure it's tight, but not too tight (though in that case the spring
scale has to measure force at a calibrated distance from the axis).

And don't forget that a beam balance won't work in microgravity -- what
we used to call "free fall" or "zero G" conditions. For the Skylab
missions, NASA came up with a way to mass astronauts in microgravity:
they put them in a widget that shook them back and forth and used (get
this) spring scales (in this case, in form of strain gages on calibrated
beams) to measure the force needed to accelerate the astronaut at a
measured rate. So, if you're in orbit, "beam balance, bad, spring scale
(with shaker widget) good!"

R. J. Talley

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Nov 24, 1998, 3:00:00 AM11/24/98
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I teach also, (11TH GRADE) and I'm a former Weather Tech. with the USAF. I
love SI units when doing calculations and measuring is muuuuuuuuuuuuuuuuuuch
easier. However, I hate anything French, wish most European continentals
would go away and never be heard from again, and love to wave my "we kicked
everybody's ass during the world wars flag" . So in short, for teaching
purposes and for utilitarian reasons, I support the metric system and think
we should make it our first priority in schools. But, for purely romantic
and nationalistic/americentric reasons, I like good old pounds, inches and
feet. By the by, has anyone gone above 100 rods with an Estes kit yet?

Reece
NAR 69594


R. J. Talley

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Nov 24, 1998, 3:00:00 AM11/24/98
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Oh Lord, please don't let the Canooks get going on what language means. The
English speaking ones are tolerable at best eh? But those Frenchies, geez
Luise, they don't know in from out nor left from right. But some of them,
just one or two mind you, can sing pretty good.


Gene Nygaard

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Nov 25, 1998, 3:00:00 AM11/25/98
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In article <365B0633...@ix.netcom.com>,

The Silent Observer <sil...@ix.netcom.com> wrote:

> And don't forget that a beam balance won't work in microgravity -- what
> we used to call "free fall" or "zero G" conditions. For the Skylab
> missions, NASA came up with a way to mass astronauts in microgravity:
> they put them in a widget that shook them back and forth and used (get
> this) spring scales (in this case, in form of strain gages on calibrated
> beams) to measure the force needed to accelerate the astronaut at a
> measured rate. So, if you're in orbit, "beam balance, bad, spring scale
> (with shaker widget) good!"

Actually, the device they use is a spring, but not a spring scale. It
measures mass by timing the oscillations of the spring after it is set in
motion; a spring scale measures force by measuring the distance the spring is
extended.

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/

-----------== Posted via Deja News, The Discussion Network ==----------
http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own

Gene Nygaard

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Nov 25, 1998, 3:00:00 AM11/25/98
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In article <73ef2c$pfa$1...@samsara0.mindspring.com>,
"MindSpring User" <don...@mindspring.com> wrote:

>
> HOWEVER! Two bones of contention.
>

...


>
> Secondly, and this one really grates me, the kilogram is a measure of MASS

> not WEIGHT, and yet we record weight in grams! A kilo of material is still


> a kilo, as mass remains constant, even when in zero-g and apparently

> weightless. The proper unit to use when measuring the force applied by a
> mass due to gravity is Newtons. Man, this detail bugs me, it only serves to
> confuse people about the distinction between weight and mass. And yet bacon


> is sold by the kilo.

A kilogram is a unit of mass, right. But that in no way means that it is not
a unit of weight.

The problem is that weight is an ambiguous word. It means mass more often
than it means one particular kind of force in the jargon of archery, or a
different kind of force in the jargon of physics.

Of course, bacon is sold by the kilogram. (Note that kilo should not be used
as a shorthand version of this unit; kilo- is a prefix which can be attached
to many different units. Use the spelled-out word, or in technical works the
international symbol kg which is recognized in all languages is preferred.)
That's because the net weight in the grocery store is "weight" is its
original meaning, the quantity measured by a gravitational balance which is
mass. To express this weight in newtons would be incorrect.

Consider this from NIST, National Institute of Standards and Technology, the
United States national standards agency (successor to the National Bureau of
Standards:

In commercial and everyday use, and especially in common
parlance, weight is usually used as a synonym for mass.
Thus the SI unit of the quantity weight used in this
sense is the kilogram (kg) and the verb "to weigh" means
"to determine the mass of" or "to have a mass of".

Examples: the child's weight is 23 kg
the briefcase weighs 6 kg
Net wt. 227 g


NIST Special Publication 811 (1995 ed.), _Guide for the Use of the
International System of Units (SI)_ by Barry N. Taylor

Or similarly from The National Standard of Canada, CAN/CSA-Z234.1-89 Canadian
Metric Practice Guide, January 1989:

5.7.3 Considerable confusion exists in the use of the term "weight."
In commercial and everyday use, the term "weight" nearly always means
mass. In science and technology, "weight" has primarily meant a force
due to gravity. In scientific and technical work, the term "weight"
should be replaced by the term "mass" or "force," depending on the
application.

5.7.4 The use of the verb "to weigh" meaning "to determine the mass
of," e.g., "I weighed this object and determined its mass to be 5 kg,"
is correct.

Gene Nygaard
http://ourworld.compuserve.com/homepages/weight.htm
| There is another type of measure that is also very
| ancient and that is the measure of mass. . . .
| As time passed, each nation and region developed
| its own standard masses against which unknown masses
| could be compared. The chief such unit is called
| pound in English, from a Latin word meaning "a weight."
| Isaac Asimov
| Realm of Measure,l960

Gene Nygaard

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Nov 25, 1998, 3:00:00 AM11/25/98
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Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/weight.htm

James Wentworth

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Nov 25, 1998, 3:00:00 AM11/25/98
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R. J. Talley (om...@earthlink.net) wrote:
: However, I hate anything French, wish most European continentals

: would go away and never be heard from again, and love to wave my "we kicked
: everybody's ass during the world wars flag" . So in short, for teaching

If not for the French and other European Continentals (Poles and
Hessians) who helped the 13 colonies during the revolution, we would
probably still be a part of the British Commonwealth today.

: purposes and for utilitarian reasons, I support the metric system and think


: we should make it our first priority in schools. But, for purely romantic
: and nationalistic/americentric reasons, I like good old pounds, inches and
: feet. By the by, has anyone gone above 100 rods with an Estes kit yet?

The metric system is as American as apple pie. Thomas Jefferson,
Benjamin Franklin and John Quincy Adams all strongly endorsed the US
adoption of the metric system, and they had input with the French Academy
of Sciences when the standards for the system were being discussed.
Alexander Graham Bell and Thomas Edison also urged the US to adopt the
metric system (Bell testified before Congress on this subject). Bell,
Edison, Maxwell (a BRITISH scientist, no less) and other American and
European scientists were instrumental in developing the cgs
(centimeter-gram-second) system, a forerunner of today's SI metric system.
All electrical units are metric, and this was established by several
International Electrical Congresses. The US Congress made the metric
system legal for commerce and trade in 1866, and the United States was
one of the signatory nations to the 1875 Treaty of the Meter.

Being a descendant of rather recent British immigrants to the US, I have
no ill feelings towards the United Kingdom. The fact remains, however,
that it is the "US" customary units that are foreign, not the metric
system. If that isn't enough to persuade you, consider this: The Germans
have had an historical dislike for France and things French that rivals the
Anglo-British rivalry, yet Germany enthusiastically embraced the metric
system.

Vamidpowr

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Nov 25, 1998, 3:00:00 AM11/25/98
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>From: "Phil Bulmer"

>Inches are fine units of
>measurement, they are nice manageable chunks but fractions of an inch are a
real swine.

<Snip>


>Try drawing a line 10.3" against
>a rule, you can't do it!

That depends on your tools. Metric is great, but even so I still design all my
kits using the inch standard, because (being an American over 40) that's how I
think.

The trick is to use an engineer's ruler. Instead of being divided into 16ths,
32nds, etc., this triangular ruler is divided into 10ths, 20ths, etc., up to
60ths of an inch. It also makes scale conversions a snap. Most business
supply stores, many pharmacies, some supermarkets and all college book stores
carry them (at least over here--You may have some difficulty finding them in
the UK). No modeler should be without one.

Chuck Barndt
The Launch Pad
http://www.the-launch-pad.com

Bob Stephenson

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Nov 25, 1998, 3:00:00 AM11/25/98
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MindSpring User wrote in message <73ef2c$pfa$1...@samsara0.mindspring.com>...

Snip

>HOWEVER! Two bones of contention.
>

>Firstly, as noted elsewhere, base ten does not lend itself to easy division
>by oddball numbers. If I have twelve inches I can easily end up with a
>whole number when dividing into 2, 3, 4, or 6, and easy-to-handle
>half-inches when 5 or 8 happen. Divide a centimeter by three and you get a
>radical. Ouch.
>


Okay, I'll bite - what is one fifth of a foot in inches ? How about one
seventh of a yard ? Sorry, but IMHO this argument won't hold rocket fuel
unless you have decifractiphobia (a fear of decimal fractions :^)

>Secondly, and this one really grates me, the kilogram is a measure of MASS
>not WEIGHT,

kerrect...

>and yet we record weight in grams!

not quite right, grams are still only a measure of mass ! Weight is an
imprecise term that refers to the force of gravity on a body and is measured
in Newtons... however the distinction between the two is 'beyond' the
understanding of many people (no flame intended). Hence the common
misconception that 'weight' is measured in grams (or kilograms or tonnes
etc).

Part of the basis of the SI system is the philosophy of using appropriate
units for appropriate applications - I don't think you will find the
astronomic unit (AU) in the SI system but I'm sure it won't go away just
because of that. I could be wrong but I also don't think that the parsec is
SI either (and probably a whole host of other measurements to boot).

<Big cheesy grin>
One thing though, if you guys in the US of A liked Imperial measurements so
much why did you come up with the US gallon ? There must be a good story
there somewhere, anyone out there care to explain ?
</Big cheesy grin>

Cheers

Bob Stephenson
bste...@netspeed.com.au
Canberra, AUSTRALIA

Feel free to visit my model rocketry homepage
http://www.netpseed.com.au/bstephen/NCRHome.htm

"I therefore think I am (but I could be wrong)"


MindSpring User

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Nov 25, 1998, 3:00:00 AM11/25/98
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><Big cheesy grin>
>One thing though, if you guys in the US of A liked Imperial measurements so
>much why did you come up with the US gallon ? There must be a good story
>there somewhere, anyone out there care to explain ?
></Big cheesy grin>

You made me curious. Here's what I found. It's YOUR fault! We here in the
US were minding our own business, and then boom, you guys across the puddle
up and changed things on us! Hmmph, you can bet I'll be telling that story
to the guy at the gas pump as I fill the tank on my Triumph motorcycle with
it's four (imperial) gallon tank! Makes me wonder, though. For the decade
I've owned this bike I've measured out the oil for the forks in US pints.
Uhoh.

Any way, the story is at

http://members.aol.com/jackproot/met/spvolas.html

and it says:

In England, the Winchester standards were used since the 15th Century. They
were slowly modified, as usual : at the
beginning of the 18th Century, we had a wine gallon containing 231 cubic
inches, an ale gallon of 282 cubic inches and even a
corn ("Winchester") gallon. The bushel was defined at a time as "any round
measure with a plain and even bottom, being 18.5
inches wide throughout and 8 inches deep" (hence its official US definition
: 2150.42 cu.in.)
The Weights and Measures Act of 1824 defined an Imperial British Gallon to
replace all others : it was to contain 10 pounds
of pure water at 62°F (inspired by the decimal system ?) (= 4.5459631
liters).

At the same time in the US, the old wine gallon (also called Queen Anne's
gallon) just discarded in England became the new
official US Gallon (= 3.785411784 liter).

Jimbo Franz

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Nov 25, 1998, 3:00:00 AM11/25/98
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Vamidpowr wrote:
>
> The trick is to use an engineer's ruler. Instead of being divided into 16ths,
> 32nds, etc., this triangular ruler is divided into 10ths, 20ths, etc., up to
> 60ths of an inch. It also makes scale conversions a snap. Most business
> supply stores, many pharmacies, some supermarkets and all college book stores
> carry them.

-- They're called scales, because they scale things from big to little.
They are not rulers.


--Jimbo Franz--

www.USRockets.com

Perspective is everything

Mario Perdue

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Nov 25, 1998, 3:00:00 AM11/25/98
to
On Wed, 25 Nov 1998 23:12:28 -0800, Jimbo Franz <in...@usrockets.com>
wrote:

>Vamidpowr wrote:
>>
>> The trick is to use an engineer's ruler. Instead of being divided into 16ths,
>> 32nds, etc., this triangular ruler is divided into 10ths, 20ths, etc., up to
>> 60ths of an inch. It also makes scale conversions a snap. Most business
>> supply stores, many pharmacies, some supermarkets and all college book stores
>> carry them.
>
>-- They're called scales, because they scale things from big to little.
>They are not rulers.
>

No, they're called scales because one definition of "scale" is "a
series of marks used for measuring." Another definition is "an
instrument, as a ruler, that bears such marks." As it happens, an
Engineer's or Architect's Scale is a set of rulers that make it easy
to draw things according to a fixed proportion (also known as scale.)

Mario
NAR #22012

"X-ray-Delta-One, this is Mission Control, two-one-five-six, transmission concluded."

Michael Brown

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Nov 26, 1998, 3:00:00 AM11/26/98
to
Bob Stephenson wrote:
>
> >and yet we record weight in grams!
>
> not quite right, grams are still only a measure of mass ! Weight is an
> imprecise term that refers to the force of gravity on a body and is measured
> in Newtons... however the distinction between the two is 'beyond' the
> understanding of many people (no flame intended). Hence the common
> misconception that 'weight' is measured in grams (or kilograms or tonnes
> etc).

In US Customary Units, mass and force are numerically
the same, which is not the case in SI. There is a
conversion constant, g_c, that converts lb_m ft/s^2
into lb_f.

Force [=] lb_f (pounds-force)
Mass [=] lb_m (pounds-mass)
g_c = 32.2 (lb_m*ft/s^2)/lb_f
g = acceleration due to gravity
g/g_c = 1 lb_f/lb_m (at sea level)

F*g_c = m*g
F = m * g/g_c

In the vernacular, the subcripts for force and
mass are dropped, leaving lb (pound) for both
mass and weight. As you have already noted, most
people don't know the difference.


-Mike

R. J. Talley

unread,
Nov 26, 1998, 3:00:00 AM11/26/98
to
Oh I knew I'd catch flack for my remarks. As a history teacher with a
graduate degree in American History I know all the stuff about where and
when the US got involved with the metric system, it's good to see others do
too. I'm also very much aware to what degree and why, several European
countries added to our revolution. So, my anti-Europe remarks are just so
much hyperbole. Whip me with a wet meter stick!

Reece


Jimbo Franz

unread,
Nov 26, 1998, 3:00:00 AM11/26/98
to
Mario Perdue wrote:
>
> On Wed, 25 Nov 1998 23:12:28 -0800, Jimbo Franz <in...@usrockets.com>
> wrote:
>
> >-- They're called scales, because they scale things from big to little.
> >They are not rulers.
> >
>
> No, they're called scales because one definition of "scale" is "a
> series of marks used for measuring." Another definition is "an
> instrument, as a ruler, that bears such marks." As it happens, an
> Engineer's or Architect's Scale is a set of rulers that make it easy
> to draw things according to a fixed proportion (also known as scale.)

-- That fixed proportion is what make it a scale. It is never a ruler, a
ruler is for measuring at 1:1 scale only. ;<)

Steve Olson

unread,
Nov 26, 1998, 3:00:00 AM11/26/98
to

Jimbo Franz wrote in message <365D7F3A...@usrockets.com>...

>....a ruler is for measuring at 1:1 scale only. ;<)

A ruler is the titular leader of a country (°¿°)


Gene Nygaard

unread,
Nov 27, 1998, 3:00:00 AM11/27/98
to
In article <365bd...@203.37.54.9>,
"Bob Stephenson" <bte...@netspeed.com.au> wrote:

>
> <Big cheesy grin>
> One thing though, if you guys in the US of A liked Imperial measurements so
> much why did you come up with the US gallon ? There must be a good story
> there somewhere, anyone out there care to explain ?
> </Big cheesy grin>
>

> Cheers
>
> Bob Stephenson
> bste...@netspeed.com.au
> Canberra, AUSTRALIA


It's quite simple. We didn't change! It is you who were still associated
with Britain in the 1820s who changed to a completely new, "imperial" gallon.
We in the United States stuck with much older units; Queen Anne's wine
gallon for liquids--she had a prodigious capacity for the stuff ;-) We stuck
with other old English units, the Winchester gallon (seldom used by that
names any more, just quarts and pints or fractions of a bushel or peck) and
bushel for dry commodities.

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/internat.htm

Bob Stephenson

unread,
Nov 27, 1998, 3:00:00 AM11/27/98
to

MindSpring User wrote in message <73ij4r$dg8$1...@camel0.mindspring.com>...

>><Big cheesy grin>
>>One thing though, if you guys in the US of A liked Imperial measurements
so
>>much why did you come up with the US gallon ? There must be a good story
>>there somewhere, anyone out there care to explain ?
>></Big cheesy grin>
>
>You made me curious. Here's what I found. It's YOUR fault! We here in
the
>US were minding our own business, and then boom, you guys across the puddle
>up and changed things on us! Hmmph, you can bet I'll be telling that story
>to the guy at the gas pump as I fill the tank on my Triumph motorcycle with
>it's four (imperial) gallon tank! Makes me wonder, though. For the decade
>I've owned this bike I've measured out the oil for the forks in US pints.
>Uhoh.
>
Ringtaketataketa ... (sound of chainsaw pruning post)

Great stuff ! I tell the guys that I work with regularly that I read rmr
for all the interesting things I learn (well, apart from all the POL and
FLAME rubbish that is). This just goes to confirm my opinion of the group -
good one MindSpring, I stand a little the wiser for your efforts :^).

Just one question though, why do you refer to the Pacific Ocean as the
puddle ? Ohhhh, you have us confused with our English cousins ! You know
it's really quite easy to tell us apart - aside from the way we mangle the
language that is. We're the ones with plenty of wide open space and sunny,
calm weather suitable for rocket flying :^)) (at least I hope so this
Summer).

Cheers

Bob Stephenson
bste...@netspeed.com.au
Canberra, AUSTRALIA

Feel free to visit my model rocketry homepage

dracomi...@my-dejanews.com

unread,
Nov 27, 1998, 3:00:00 AM11/27/98
to
It always makes me chuckle a little when I see a foreign jet aircraft in a
reference manual with its engines rated in "kilograms of thrust"!?! They're
just taking SI an making the same mistakes with it that the EE system makes.

On a related topic, to speak of the specific impulse of a rocket motor in
"seconds" is confusing and incorrect. In US units, it is measured in
lbf-seconds/lbm, at which time people cross out both "pounds" and say
"seconds" but lbf and lbm are not equivalent. I much prefer Isp measured in
Newton-seconds/kilogram as it was intended. How many Newton-seconds will you
get from each kilogram of propellant? Pretty obvious if I just said the Isp
of the propellant was 2100 Newton-seconds per kilogram. If I expressed the
Isp in seconds, what does *that* tell you?

Cheers,
Joe

Robert J. Kelley

unread,
Nov 27, 1998, 3:00:00 AM11/27/98
to
dracomi...@my-dejanews.com writes:

> On a related topic, to speak of the specific impulse of a rocket motor in
>"seconds" is confusing and incorrect. In US units, it is measured in
>lbf-seconds/lbm, at which time people cross out both "pounds" and say
>"seconds" but lbf and lbm are not equivalent. I much prefer Isp measured in
>Newton-seconds/kilogram as it was intended. How many Newton-seconds will you
>get from each kilogram of propellant? Pretty obvious if I just said the Isp
>of the propellant was 2100 Newton-seconds per kilogram. If I expressed the
>Isp in seconds, what does *that* tell you?

It's interesting, but Isp in seconds means something intuitive to me.
that a hypothetical rocket could exert thrust commensurate with its weight
for a given number of seconds; it could exert a force equal to the force of
gravity on itself. Isn't that slightly more meaningful (on earth) than
ns/kg? Maybe just a little?

All this aside, I'd just plain be happier if rocketry used SI units, if for
nothing more than a vehicle to integrate SI-awareness into the rest of my
life.

Robert Kelley
TRA #6399 L2
Portland, OR

RobEdmonds

unread,
Nov 28, 1998, 3:00:00 AM11/28/98
to
<<Okay, I'll bite - what is one fifth of a foot in inches ? How about one
seventh of a yard ?>>

That's the point. One fith and one seventh are proportions that are basically
useless for design purposes. 2, 3 and 4 are useful. I spend hours sitting
here trying to figure out how to separate 12 or 24-inch pieces of wood into a
whole bunch of pieces that will fit together in various laminations and
symmetrical assemblies. This depends entirely on there being simple, regular
proportions at all levels in the design process. There just isn't time to pull
out a calculator every time I move a line or make a decision. I have to be
able to know instantly that, for example, I can fill 3/8 of an inch with either
two 3/16" sheets or three 1/4" sheets. You just can't do that if you have a
buch of stuff made in 5 and 2 and a bunch of long strings of digits to
interpret every time you want to compare something. There is rarely ever a
reason to divide something by 5, yet the metric system bends over backwards to
let you do it at the expense of all the other potential dividends. It's fine
for science or academics, but if you're actually out there trying to design
somebody a kit with it, the metric system just doesn't make any sense.
RE

Gene Nygaard

unread,
Nov 28, 1998, 3:00:00 AM11/28/98
to
In article <73nb6a$ruj$1...@nnrp1.dejanews.com>,

dracomi...@my-dejanews.com wrote:
> It always makes me chuckle a little when I see a foreign jet aircraft in a
> reference manual with its engines rated in "kilograms of thrust"!?! They're
> just taking SI an making the same mistakes with it that the EE system makes.

Nobody's taking SI and making the same mistakes here. What they are using is
kilograms force which were considered acceptable before the introduction of
the International System of Units in 1960. It is not acceptable in SI.

Sometimes the problem is that they are converting from pounds, and the proper
conversion factors for pounds force to newtons are not well enough
publicized. A lot of people, and especially rocket scientists, seem
blissfully unaware that pounds are used to measure two different quantities.
In that case, I'd say that the problem lies with the use of the English
customary units, not with the metric units.

>
> On a related topic, to speak of the specific impulse of a rocket motor in
> "seconds" is confusing and incorrect. In US units, it is measured in
> lbf-seconds/lbm, at which time people cross out both "pounds" and say
> "seconds" but lbf and lbm are not equivalent. I much prefer Isp measured in
> Newton-seconds/kilogram as it was intended. How many Newton-seconds will you
> get from each kilogram of propellant? Pretty obvious if I just said the Isp
> of the propellant was 2100 Newton-seconds per kilogram. If I expressed the
> Isp in seconds, what does *that* tell you?
>

> Cheers,
> Joe

I agree with you there (except, of course, newtons should not be spelled with
a capital letter in English).

Gene Nygaard
http://ourworld.compuserve.com/homepages/Gene_Nygaard/

The Silent Observer

unread,
Nov 28, 1998, 3:00:00 AM11/28/98
to
dracomi...@my-dejanews.com wrote:
>
> If I expressed the
> Isp in seconds, what does *that* tell you?

Well, as it happens, if you multiply by G (whether you use 32.2 ft/s^2
or 9.81 m/s^2, doesn't matter) it will give you the effective exhaust
velocity, which is a pretty useful thing to know in some
circumstances...

Mark Fields

unread,
Nov 28, 1998, 3:00:00 AM11/28/98
to
RobEdmonds wrote:

> <<Okay, I'll bite - what is one fifth of a foot in inches ? How about one
> seventh of a yard ?>>
>
> That's the point. One fith and one seventh are proportions that are basically
> useless for design purposes. 2, 3 and 4 are useful. I spend hours sitting
> here trying to figure out how to separate 12 or 24-inch pieces of wood into a
> whole bunch of pieces that will fit together in various laminations and
> symmetrical assemblies. This depends entirely on there being simple, regular
> proportions at all levels in the design process. There just isn't time to pull
> out a calculator every time I move a line or make a decision.

> I have to be
> able to know instantly that, for example, I can fill 3/8 of an inch with either
> two 3/16" sheets or three 1/4" sheets.

I think perhaps it would be "two 3/16" sheets" or "three 1/8" sheets"????

Jimbo Franz

unread,
Nov 28, 1998, 3:00:00 AM11/28/98
to
RobEdmonds wrote:
>
> <<Okay, I'll bite - what is one fifth of a foot in inches ? How about one
> seventh of a yard ?>>
>
> That's the point. One fith and one seventh are proportions that are basically
> useless for design purposes. 2, 3 and 4 are useful. I spend hours sitting
> here trying to figure out how to separate 12 or 24-inch pieces of wood into a
> whole bunch of pieces that will fit together in various laminations and
> symmetrical assemblies. This depends entirely on there being simple, regular
> proportions at all levels in the design process. There just isn't time to pull
> out a calculator every time I move a line or make a decision. I have to be
> able to know instantly that, for example, I can fill 3/8 of an inch with either
> two 3/16" sheets or three 1/4" sheets. You just can't do that if you have a

> buch of stuff made in 5 and 2 and a bunch of long strings of digits to
> interpret every time you want to compare something. There is rarely ever a
> reason to divide something by 5, yet the metric system bends over backwards to
> let you do it at the expense of all the other potential dividends. It's fine
> for science or academics, but if you're actually out there trying to design
> somebody a kit with it, the metric system just doesn't make any sense.
> RE

-- Because you chose to work in inches doesn't mean another system
doesn't make sense. If you purchased ply in metric thickness, metric
would make sense. I can fill 9mm with three 3mm or one 6mm and one 3mm
sheets. How much more simple and regular can proportions get than
tenths, hundredths, tens, hundreds, etc.?

Bob Stephenson

unread,
Nov 29, 1998, 3:00:00 AM11/29/98
to

MindSpring User wrote in message <73o79m$o02$1...@camel18.mindspring.com>...
Snip...
>

>Ooooh, you're an Ausie! Sorry 'bout that. And that means summer is just
>around the bend for you, while I sit here above the equator checking my
>furnace and sharpening my snow shovel. I'm so jealous of you right now
that
>I'm gonna say that this whole gallon thing is STILL your fault. So there.
>
>Actually, I hope you have a wonderful, safe, and high flying summer.
>
>Have fun.
>
Yeah, I'm one of the Colonial club... and yes, we are heading into summer
right now :^) My only problem is that the wind is being unkind at the
moment.

I spent the Winter buried in computer science study (I'm not only a bar but
also a bas (born again student ?)) and have managed to crib a little time to
build the 'Southern Cross'. She is based on the Quest 'Icarus' but all that
is left of the original is the body tube and nose cone. I have retro fitted
a 'D' motor mount with hand made stainless steel engine hook, ttw fins made
of 0.8 mm ply AND an ejection baffle system just like the old Centuri
designs. The paint job is all white with a silver nose cone and custom
colour decals.

The only thing not completed yet is the lugless launch system - I have yet
to figure out how that one is going to work. All in all this is a great
looking rocket (IMHO ;^) and should fly great if I can ever get some calm
weather to launch it.

RobEdmonds

unread,
Nov 29, 1998, 3:00:00 AM11/29/98
to
<<
I think perhaps it would be "two 3/16" sheets" or "three 1/8" sheets"????>>

See? It's so intuitive I can't even tranlate it into typing correctly.
RE

Gene Nygaard

unread,
Nov 29, 1998, 3:00:00 AM11/29/98
to
In article <365FCE4A...@ix.netcom.com>,

The Silent Observer <sil...@ix.netcom.com> wrote:
> dracomi...@my-dejanews.com wrote:
> >
> > If I expressed the
> > Isp in seconds, what does *that* tell you?
>
> Well, as it happens, if you multiply by G (whether you use 32.2 ft/s^2
> or 9.81 m/s^2, doesn't matter) it will give you the effective exhaust
> velocity, which is a pretty useful thing to know in some
> circumstances...
>

Seems to me that that is exactly the point that Joe (dracomissile22) is
making. His newton-seconds per kilogram are dimensionally equivalent to
meters per second. The conversion factor between them is 1.

That's what is useful. So why mess around with useless pseudoseconds which
are really lbf s/lbm, if you need to remember the value of small italic g
(not G, which is something different) to use them?

Mark Simpson

unread,
Nov 29, 1998, 3:00:00 AM11/29/98
to Bob Stephenson
Bob Stephenson wrote:

> I spent the Winter buried in computer science study (I'm not only a bar but
> also a bas (born again student ?)) and have managed to crib a little time to
> build the 'Southern Cross'. She is based on the Quest 'Icarus' but all that
> is left of the original is the body tube and nose cone. I have retro fitted
> a 'D' motor mount with hand made stainless steel engine hook, ttw fins made
> of 0.8 mm ply AND an ejection baffle system just like the old Centuri
> designs. The paint job is all white with a silver nose cone and custom
> colour decals.

Don't forget to get yourself a copy of Crosby, Stills and Nash's song by
the same name for background mood music. It's a classic.

Mark Simpson
NAR 71503 Level II


MindSpring User

unread,
Nov 28, 1998, 3:00:00 AM11/28/98
to

>Just one question though, why do you refer to the Pacific Ocean as the
>puddle ? Ohhhh, you have us confused with our English cousins ! You
know
>it's really quite easy to tell us apart - aside from the way we mangle the
>language that is. We're the ones with plenty of wide open space and sunny,
>calm weather suitable for rocket flying :^)) (at least I hope so this
>Summer).

Mark Johnson

unread,
Nov 30, 1998, 3:00:00 AM11/30/98
to
Gene Nygaard wrote:
>
>
> Seems to me that that is exactly the point that Joe (dracomissile22) is
> making. His newton-seconds per kilogram are dimensionally equivalent to
> meters per second. The conversion factor between them is 1.

Yup...strictly speaking, specific impulse should be expressed
in terms of characteristic exhaust velocity (abbreviated c* in
the literature, including Sutton).

The basic equation (derived, I think, by Hermann Oberth) for
velocity increase due to a rocket motor is:

v = c* x log (mass ratio)
e
where of course

mass ratio = (rocket mass + fuel mass)/rocket mass

If you don't have a calculator that does Naperian logarithms,
and you want to express the thing in terms of specific impulse,
the way I learned the equation was:

v = Isp x g x 2.303 x log(mass ratio)

This of course is in vacuum, and can equally well be stated
as 'delta v' for a rocket already in motion.
--
Mark Johnson LSI Logic Storage Systems, Inc.
M/S 18 (formerly Symbios, Inc.)
mark.j...@lsil.com 3718 N Rock Road
(316)636-8189 Wichita, KS 67226-1397

dracomi...@my-dejanews.com

unread,
Dec 1, 1998, 3:00:00 AM12/1/98
to
In article <365FCE4A...@ix.netcom.com>,
The Silent Observer <sil...@ix.netcom.com> wrote:
> dracomi...@my-dejanews.com wrote:
> >
> > If I expressed the
> > Isp in seconds, what does *that* tell you?
>
> Well, as it happens, if you multiply by G (whether you use 32.2 ft/s^2
> or 9.81 m/s^2, doesn't matter) it will give you the effective exhaust
> velocity, which is a pretty useful thing to know in some
> circumstances...
>

Exactly. Isp in N-s/kg is equal to the characteristic exhaust velocity in
m/s. When I see Isp expressed in seconds anywhere, I always multiply it by
10 in my head to get a ballpark figure for N-s/kg anyway, but why use the
incorrect nomenclature in the first place? If you like the old units, it
would be correct to express Isp in lbf-s/slug or even lbf-s/lbm, but not
"seconds."

Cheers,
Joe

Jimbo Franz

unread,
Dec 1, 1998, 3:00:00 AM12/1/98
to
RobEdmonds wrote:
>
> Show me one place in nature where a ratio that is a power of ten occurs. I can
> show you millions made from say, powers of six (honeycombs, snowflakes, packing
> cylinders closely, molecular stuctures, inscribed hexagon in a circle using the
> radius of the circle as the length of a leg, etc.). You can do the same for
> 2, 3, 4 and probably 12. You'll get nowhere with 10. It ain't even really how
> many fingers we have, those other two are really thumbs. If we were cartoon
> charaters and had eight fingers, then the metric system might be all right.
> But it would be even better to have six. Ten is just a basically useless
> number.
> RE

-- Metric was designed as an integrated system for description (size,
volume, mass, etc.) of man-made, easily scalable items. Rockets come
immediately to mind. If I were designing a flower, fractals would be the
choice for easy scaling. Pi is everywhere, would you care for a Pi based
counting system (it did have it's uses in ancient Egypt)?

What if you want to scale your design up one third?

"Let's see, 7/8 times 1.333333 is..., 7*1.3333 = 9.3333, no, that won't
work..., 8*3 = 24, 7*3 = 21*1.333 = 28, so... 28/24-24 = 1 4/24, shoot,
my ruler is in 16ths and 32nds, 4/24 = 1/6, there's the 6 I was looking
for on the snowflake project..., let's see, 1/6" is 1/72nd of a foot...,
reminds me of an airplane model I built once..., maybe I'll make that
first measurement 3/4". Yes, 1.333*3/4 = 1". We don't need no stinking
metric system!"

All in good fun,

Mario Perdue

unread,
Dec 1, 1998, 3:00:00 AM12/1/98
to
On Tue, 01 Dec 1998 23:03:13 -0800, Jimbo Franz <in...@usrockets.com>
wrote:

>[snip]


>
>What if you want to scale your design up one third?
>
>"Let's see, 7/8 times 1.333333 is..., 7*1.3333 = 9.3333, no, that won't
>work..., 8*3 = 24, 7*3 = 21*1.333 = 28, so... 28/24-24 = 1 4/24, shoot,
>my ruler is in 16ths and 32nds, 4/24 = 1/6, there's the 6 I was looking
>for on the snowflake project..., let's see, 1/6" is 1/72nd of a foot...,
>reminds me of an airplane model I built once..., maybe I'll make that
>first measurement 3/4". Yes, 1.333*3/4 = 1". We don't need no stinking
>metric system!"
>

>[snip]

Or you could use your 'scale,' you know... the one with the six
'rulers,' and measure it directly. :^)

RobEdmonds

unread,
Dec 2, 1998, 3:00:00 AM12/2/98
to
<<If you purchased ply in metric thickness, metric would make sense. I can fill
9mm with three 3mm or one 6mm and one 3mm
sheets.>>

That's fine until you get numbers less than one involved. Now, you could
assume that mm's are fine enough that you would only have to make integral
sizes, making that workable. But as for:

<<How much more simple and regular can proportions get than tenths, hundredths,
tens, hundreds, etc.?>>

Show me one place in nature where a ratio that is a power of ten occurs. I can

PeteAlway

unread,
Dec 2, 1998, 3:00:00 AM12/2/98
to
robed...@aol.com (RobEdmonds), Philosopher-King of Boost-Gliders wrote:

>Show me one place in nature where a ratio that is a power of ten occurs. I
can
>show you millions made from say, powers of six (honeycombs, snowflakes,
packing
>cylinders closely, molecular stuctures, inscribed hexagon in a circle using
the
>radius of the circle as the length of a leg, etc.). You can do the same for
>2, 3, 4 and probably 12. You'll get nowhere with 10. It ain't even really
how
>many fingers we have, those other two are really thumbs. If we were cartoon
>charaters and had eight fingers, then the metric system might be all right.
>But it would be even better to have six. Ten is just a basically useless
>number.

Rob, you have made an excellent case for dumping base 10. As long as nobody
hacks off any of my supernumary philanges, I could go for a switch. After all,
computers do very well in base two. And once we make the conversion in our
numbering system, fractions will be easier. None of this 8 13/32 junk. Just
1000.01101, which would be a buttload easier to read off a ruler.

But unless you are willing to dump decimal counting, decimal units make more
sense.

I wonder if the people who came up with english units were really decimal
counters. I mean counting is really just a chant of nonsense words--Wun Tou
Thri Fore Faiv Siks Sehvun Ate Nain Tehn Ulevin Tuellv (beyond that it's base
ten talking with crazy polysyllabic words like tuennisehvun and
ahunerdnsickstiate, which do not a chant make)--not unlike Eenie Meenie Miney
Moe--just remember the chant word you hit when you run out of cows or
Phillips-head rocks or whatever. So you just rember that you chant all the way
to tuellv as you place knuckles end to end to get a foot. Chant to miney when
you lay barleycorns to get a standard knuckle since Ogg's knuckles are bigger
than Kell's... Altogether a fine way of measuring when everyone counts by
chant, without bases.

So Yeah, base twelve or base 8 or base 2 would be nice if our numbering system
worked that way.

And if I can keep all my fingers.

Peter Alway


Remove a couple .com's from address to reply. Check
out the Saturn Press website for my rocketry books and posters:
http://members.aol.com/satrnpress/saturn.htm

Stefan Wimmer

unread,
Dec 2, 1998, 3:00:00 AM12/2/98
to
Rob Edmonds <RobEd...@aol.com>
>Why do you want to ruin kids with those SI units? SI units discourage the
>development of a sense of proprtion. Numbers like 1/4, 1/2, 2, 3 ,4 and 6
>have a real, intrinsic meaning to them that is important to the development
>of design skills in the child's mind. A number like ".317" has no intrinsic
>meaning, it only stimulates the symbolic side of their minds (in that they
>can recognize a "three", a "one" and a "seven". Perhaps the concept
>that the "point" means that the number is less than one rather than
>greater than one has a tiny bit of intrinsic appeal). If all you want
>is a bunch of scientists, OK, but if you want engineers, your not going
>to produce them with units divisible by a meaningless number like ten.
>There are plenty of useful benefits to dividing things into two's,
>three's an four's, but very few to >dividing them in five.
>RE


Hi Rob (et al.)

please admit that I (grown up in a SI world) find this kind of argumentation
very funny!

Having enjoyed (and still enjoying) how units interact in the SI system
without any cumbersome factors (except natural constants) I can only smile
about your argumentation - without any intend to look conceited!

The SI system is a really SYSTEMATIC array of units whereas the US/UK system
seems to me more like a collection of separately defined units (like we had in
the middleage throughout Europe too).
It is amazing how almost all formulas in rocketry are based on meters,
kilograms and seconds.

--
Stefan Wimmer Cellware Broadband
Email s...@cellware.de Rudower Chaussee 5
WWW http://www.cellware.de/ 12489 Berlin, Germany

Visit my private Homepage: Love, Electronics, Rockets, Fireworks!
http://www.geocities.com/CapeCanaveral/6368/

The Silent Observer

unread,
Dec 2, 1998, 3:00:00 AM12/2/98
to
PeteAlway wrote:
>

<snip very amusing treatment of measurments>

>
> So Yeah, base twelve or base 8 or base 2 would be nice if our numbering system
> worked that way.
>
> And if I can keep all my fingers.

Well, Peter, if we change over to binary, we can maximize the value of
counting on our fingers, not to mention forever consigning Chisanbop to
the dusty hall of hacks and work-arounds. Just think, we can teach
children how to do twos complement arithmetic in first grade, how to add
binary amounts in kindergarten, and produce a generation who find
programming in assembler as easy as many of our kids find Web research.

Of course, we'll have to get used to spending $101.1111101... for things
that used to cost $7.98. Shouldn't be any harder than converting from
English (aka US Customary) to SI (aka metric), right? B)

Andy Eng

unread,
Dec 2, 1998, 3:00:00 AM12/2/98
to
Greetings Stefan,

Just my last message for the day,

Stefan Wimmer wrote:
>
> Rob Edmonds <RobEd...@aol.com>

> >Why do you want to ruin kids with those SI units?

<ctrl-x>

> The SI system is a really SYSTEMATIC array of units whereas

Systematic, yes... Natural, no...

"Pi" is natural, so is "e", as are 1-2-3 and 3-4-5 triangles...

BTW, IMO, binary, octal & hex is anti-humane ;-)

Regards,
Andy

Jimbo Franz

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Dec 2, 1998, 3:00:00 AM12/2/98
to
Mario Perdue wrote:
>
> On Tue, 01 Dec 1998 23:03:13 -0800, Jimbo Franz <in...@usrockets.com>
> wrote:
>
> >[snip]
> >
> >What if you want to scale your design up one third?
> >
> >"Let's see, 7/8 times 1.333333 is..., 7*1.3333 = 9.3333, no, that won't
> >work..., 8*3 = 24, 7*3 = 21*1.333 = 28, so... 28/24-24 = 1 4/24, shoot,
> >my ruler is in 16ths and 32nds, 4/24 = 1/6, there's the 6 I was looking
> >for on the snowflake project..., let's see, 1/6" is 1/72nd of a foot...,
> >reminds me of an airplane model I built once..., maybe I'll make that
> >first measurement 3/4". Yes, 1.333*3/4 = 1". We don't need no stinking
> >metric system!"
> >
> >[snip]
>
> Or you could use your 'scale,' you know... the one with the six
> 'rulers,' and measure it directly. :^)

-- That's not fair: it's a base ten system and was "ruled" unacceptable
earlier. And it's for a "kit", do you require the purchase of a scale to
build the kit? "The kit is free, but the scale is gonna cost ya." ;<)

DWard

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Dec 2, 1998, 3:00:00 AM12/2/98
to
RobEdmonds wrote in message <19981202220703...@ng33.aol.com>...

><<But unless you are willing to dump decimal counting, decimal units make
more
>sense.>>
>
> A fraction is true, whereas a decimal always feels like an
>approximation of something.

actually, I find it the reverse, but ya gotta limit yourself to the number
of digits that represent the actual precision of your measurements...
nothing like recording measurements to the millionth of an inch when using a
wooden yardstick :-)

>A fraction has a philosphical resonanace to it,
>whereas a decimal has, at the VERY best, some sort of woeful, bleak
>practicality.


What I don't understand is why folks SI only with decimal usage and ancient
english units with fractions? You can use fractions or decimals regardless
of your measurement system, they are independent.


-Dave "Okay, I've said my say, now I'll go back to trying to stuff a 1/2 kg
of AP into a 1.134 diameter rocket..." Ward

Jimbo Franz

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Dec 2, 1998, 3:00:00 AM12/2/98
to
RobEdmonds wrote:
>
> Fractions make you happy, they make you think of a bright sunny day and slicing
> up a pie or your birthday cake or something. A fraction is true, whereas a decimal always feels like an
> approximation of something. A fraction has a philosphical resonanace to it,

> whereas a decimal has, at the VERY best, some sort of woeful, bleak
> practicality.

-- Ah, a true believer. I will leave you to your delusions now. ;<)

RobEdmonds

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Dec 3, 1998, 3:00:00 AM12/3/98
to
<<
What if you want to scale your design up one third?

"Let's see, 7/8 times 1.333333 is..., 7*1.3333 = 9.3333, no, that won't
work..., 8*3 = 24, 7*3 = 21*1.333 = 28, so... 28/24-24 = 1 4/24, shoot,
my ruler is in 16ths and 32nds, >>

Man, you couldn't even get through the first line without putting a decimal in
there. You guys are just addicted to ten!

Incidentally, my mother gave me an architect's scale that had 24ths and 48ths
on it when I was little, and I must have used it a thousand times. No, I mean
1296 times!!
RE

RobEdmonds

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Dec 3, 1998, 3:00:00 AM12/3/98
to
<<But unless you are willing to dump decimal counting, decimal units make more
sense.>>

My bags fit a one foot piece of wood, so I never have to count higher than 12,
so the decimalness of numbers has basically no impact on me. Plus, if you had
to use fractional decimal numbers to design, I probably wouldn't do it.

Fractions make you happy, they make you think of a bright sunny day and slicing

up a pie or your birthday cake or something. Decimals make you think of the
IRS. How can you POSSIBLY use them? It's uncanny, if you watch me at the CAD,
you'll see that nowhere in any of these planes will I put in a dimension that
is not an even fraction of an inch, even if I'm typing a decimal in for
precision positioning, even when I'm setting an incidence or working with some
arbitrary part that doesn't touch anything else. There are plenty of 64th's in
those planes. A fraction is true, whereas a decimal always feels like an


approximation of something. A fraction has a philosphical resonanace to it,
whereas a decimal has, at the VERY best, some sort of woeful, bleak
practicality.

RE

By the way, what happened to the drawing and physics education thread? I never
found it again.

RobEdmonds

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Dec 3, 1998, 3:00:00 AM12/3/98
to
<<Having enjoyed (and still enjoying) how units interact in the SI system
without any cumbersome factors (except natural constants)>>

I just spent a whole article explaining that they do not do so. Ten is the
most "cumbersome factor" imaginable. It has no place anywhere in the design
world. There is no significance of any kind for the number ten in the design
world. Any measurement system based on the number ten is by definition the
barbaric poppycock of idle minds! And then:

<<It is amazing how almost all formulas in rocketry are based on meters,
kilograms and seconds.>>

They're not "based" on those in any way, the physics is completely independant
of what units we choose to quantify it with. All the rockets built in this
country were designed with English units, and flew DEMONSTRABLY better for it.
RE

I hope he doesn't hold me to that "demonstrably".


PeteAlway

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Dec 3, 1998, 3:00:00 AM12/3/98
to
robed...@aol.com (RobEdmonds) wrote:

>All the rockets built in this
>country were designed with English units, and flew DEMONSTRABLY
>better for it.

I should say here that I hold Mr. Edmonds in high esteem, as a gentleman and a
scholar who puts his money where his mouth is on some well thought-out ideas on
rocketry and education, and his design skills leave me in awe.

But this is *demonstrably* the silliest thing I've ever heard you say.

>I hope he doesn't hold me to that "demonstrably".

same here.

Peter "how many cubic inches to a pint? No fair looking it up!" Alway

Scott McCrate

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Dec 3, 1998, 3:00:00 AM12/3/98
to
1359653 Dec 1998 03:07:03 GMT

Oh, well that explains it then. Rob is an aesthete. A poet. We see sharply
designed boost gliders, he sees gently wafting balsa birds. Teach us master! You
are indeed the philosopher king of boost gliders! [Teasing, but just slightly
;0). Thanks for the awesome designs.]

Scott McCrate NAR 71680
smcc...@nospam.tui.edu
mccr...@nospam.fuse.net (remove nospam. to respond by e-mail)

doug holverson

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Dec 3, 1998, 3:00:00 AM12/3/98
to
>Oh, well that explains it then. Rob is an aesthete. A poet. We see sharply
>designed boost gliders, he sees gently wafting balsa birds. Teach us master! You
>are indeed the philosopher king of boost gliders! [Teasing, but just slightly
>;0). Thanks for the awesome designs.]
>
But way too many of them have tails! ;)

-DGH-

Mike Pearson <see .sig>

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Dec 3, 1998, 3:00:00 AM12/3/98
to
PeteAlway <pete...@aol.com.com.com> wrote:

> Peter "how many cubic inches to a pint? No fair looking it up!" Alway

American or British? Dry or liquid? <g>

--
Mike
NAR #70953 - Sr/Insured/Level-1 ~ SeaNAR - The Seattle NAR Section #568
NO Junk Email, please! Real email to: amphoto [at] blarg [dot] net.
<WARNING: Do not look into laser beam with remaining eye!>

RobEdmonds

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Dec 4, 1998, 3:00:00 AM12/4/98
to
<<actually, I find it the reverse, but ya gotta limit yourself to the number
of digits that represent the actual precision of your measurements...>>

If there are three apples and you eat two of them, you didn't eat .6667 of
them.
RE

RobEdmonds

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Dec 4, 1998, 3:00:00 AM12/4/98
to
<<What I don't understand is why folks SI only with decimal usage and ancient
english units with fractions? You can use fractions or decimals regardless
of your measurement system, they are independent.>>

Because a third of a foot is 4 inches, whereas a third of a decimeter is
something unworkable.
RE

RobEdmonds

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Dec 4, 1998, 3:00:00 AM12/4/98
to
<<-- Ah, a true believer. I will leave you to your delusions now. ;<)>>

Why is it that whether it is the English measurement system or the Macintosh
computer, the users thereof are characterized as some kind of "believers" or
"zealots". I use both of these things as a purely practical decision. There
would be too much time and effort to design these kits in the decimal system,
and there would be too much time and effort to draw them, create instructions
for them and store business information about them if I used a Windows
computer. You guys keep trying to attribute this stuff to some kind of
passionate desire, when in fact, I keep demonstrating every day that you need
English units and Macintosh computers to successfully design a series of
pleasing enjoyable kits. It is a totally practical decision. The evidence is
right here that these things benefit you in accomplishing the tasks you want to
accomplish, yet people want to dipute this as though I'm wishing on fairies or
something.
RE

RobEdmonds

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Dec 4, 1998, 3:00:00 AM12/4/98
to
<<We see sharply
>designed boost gliders, he sees gently wafting balsa birds.>>

That's actually pretty good.
RE

RobEdmonds

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Dec 4, 1998, 3:00:00 AM12/4/98