Metric II 5

[vpl]

The original post is getting a little hoary -- not to mention hard to read.

So this is an opportunity to continue the debate in a nice, new post where people may actually read your input because they don't have to wade through 100's of other posts to do so.

Patricia Lougheed

Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.

 

[mabn]

I assume you mean 100's of imperial threads.... equalling roughly 115 metric threads.

 

[JamesCG]

Sorry I didn't notice this thread so I posted in the old one.

James Goodstadt

 

[aspearin1]

As a chemical engineer focussing on natural sciences, much of my schooling trained me for metric system. But then getting into industry and having to deal with some mechanical engineering and designing fixtures, the English system started to take over. I work with a company that measures distance in inches and mass in grams. Though I'm comfortable with the English system, it only makes sense to go metric, despite the arrogance of our ways.

ChemE, M.E. EIT
"The only constant in life is change." -Bruce Lee

 

[Tobalcane]

Why is it that when we weigh something in metric it is in kilograms? But they really mean Newtons. And in standard when somebody asks for the mass we tell them in pound force, but not pound mass. I think before the scientific/engineering community tries to settle on a unit convention, the public has to understand what the units really mean.

Go Mechanical Engineering
Tobalcane

 

[GSC]

Tobalcane >

When we weight something in metric we weight according to Isaac Newton's Second Law of Motion. The acceleration of an object is proportional to the force exerted on it divided by the mass. This is how force is normally defined, by the formula usually stated as F = k·m·a. (The units can be chosen so that k = 1 and the formula then becomes F = m·a in that system of units.) So force is measured in Newtons, while mass is measured in Kilograms.

Gravitational force (one kind of weight) is what makes it difficult to lift objects up, and mass is what makes it difficult to move objects sideways (complicated by friction).

If we think further, then a balance measures mass and not force. However, the spring scales and load cells measure force (Robert Hooke expressed his Law that the distance a spring stretches is proportional to the force exerted on it).

The magnitudes of the measurements of mass and force (weight here) may be the same, within the limits of the precision of the measurement, at some places on earth if the mass is measured in pounds mass and the force is measured in pounds force, for example. But the magnitudes are never the same on Earth if the mass is in kilograms and the force in newtons, or the mass in pounds and the force in poundals!

The pound mass is the older definition of the pound. It is also the primary definition of the pound. Before the redefinition of the pounds as fractions of a kilogram, they were defined as the mass of independently maintained artifacts. 1 pound avoirdupois as 0.453 592 37 kg (US).

The modern practice is to use pounds for the mass units. If the force units of the same name are used, they should be identified as such (pounds force).

GSC

 

[friartuck]

I have been using both metric and 'old money' for a long long time. I am conversant with both and I help my kids with their homework...which of course in in some form of metric. As an engineer, we learn mm, m and kG etc. and keep a constancy. The 'Industry' also uses pretty much the same units, however, I cannot for the life of me understand why my kids bring home questions involving what I consider to be non-standard 'metric'. They use cm, decilitres, etc.

In addition, my son has just started work with a refrigeration company and he comes home telling me that 'today Dad, I installed a 3 ton AC unit using 3/8 pipe and the brackets were 3 feet wide. The refrigerant gas fill was 200 grammes and the plantroom he put the AC plant in was 30 feet in the air and measured about 20 feet by 5metres. He also tested the system to something like 250PSI.

I Give up.

What is the world coming to.

Someone help me before I go mad.

Friar Tuck of Sherwood

 

[HgTX]

"I cannot for the life of me understand why my kids bring home questions involving what I consider to be non-standard 'metric'."

Because a system that requires three orders of magnitude between unit increments is not practical.

Hg

 

[ChrisConley]

I was trained in metric for most of my life including university. I started working in the HVAC industry and quickly had to learn what the hell a Btu was, what 110 deg F is and that no one sells 25mm pipe.

Most of the formulas I use are imperial, and most of my design is done in imperial units. Having said that, all of the work I produce is released in metric.

The set of plans I design in imperial, convert to metric is then converted back to imperial by the various contractors and suppliers that use the plans. We actually release a table in our specifications that states what we mean when we say 300mm x 300mm duct.

It makes me laugh... but maybe my daughter (who is only one) will one day get to work only in one set of units.

**If you are not part of the solution, then you are part of the precipitate.**

 

[BigH]

I use both. I like both. If I start a project in one unit, I hate changing to the other, viz., English, then SI. My one problem with SI is that standard units are not used throughout the world. mm is favoured yet in many countries, they use cm. kN/m2 or kPa is favoured, yet you will see N/mm2 used or t/m2. Then, you are scrambling to see if N/mm2 = MPa or what.

 

[DrillerNic]

I'm just about to bring a Norwegian drill rig onto a UK Platform. They use SI units and the UK and the project, uses the dog's breakfast that is 'Oilfield Units'.

We have converted all the instrumentation into oilfield units, the only concern that we have is that a Norwegian driller, when told that the mud is 10.4 pounds per gallon in, but 9.8 pounds per gallon out, won't know instantly that that is BAD, as he'll still be working out in his head "9.8ppg that's equal to let me see...about 1.18. 1.18!!! oh Shiiii...."

 

[makeup]

during my apprenticeship we had to be fully conversant with both imperial and metric forms. Machines are either one or the other and therefore drawings had to be converted to make life easy. This was the job of the machinist. It was so common that you could do most in yur head, mm to .001"

 

[unc]

I posted the following in the original Metric thread before I noticed this newer thread so here it is again.

I have read nearly all these posts and have noticed many pros and cons for both metric and Imperial/Customary systems of measures. It would seem to me that neither system is ideal in all situations and for a number a reasons. The Imperial system (and its many similar European counterparts) used multiple named units based roughly on either body parts or what were items of common knowledge such as grains. The obvious disadvantage was the complete irregularilty of the different magnitudes (e.g. 12 inches in a foot, 16 ounces in pound, 1760 yards in a mile and so on. This of course made for extreme difficulty in computation of multiples and subdivisions and an even bigger problem in working with compound units.

The advantages of most of these units was the relevance to day to day usage, and their basis in the case of length to body parts and the relative ease of remembering and recording values of usually one or two digits with only infrequent forays into three digit values or more. Another great advantage of many of these units was their exact divisibility into halves, quarters and significantly, thirds.

The French scientific establishment attempted to bring order to this chaos and introduce the metric system. A brilliant idea, but grossly flawed in its choice of number base. Although the Hindu-Arabic number system had been in use in Europe to differining degrees for about 600 hundred years, it did not come into general use until about the 16th century and then of course only by the educated and merchant classes. When did universal education begin in Europe and so when did literacy and numeracy become widespreaed? Thus, had the French used a base 12 number system at the time Napoleon introduced the metric system it would not have been a major task. As it was, the system was opposed by the French populace, was then rescinded and only reintroduced in the 1820s when it was also introduced in the school system.

So, if we had a system of weights and measures based on a duodecimal number system, we would have all the advantages of the current metric system plus the added advantages of simpler calculation. Not only that but the system could still retain its scientifically based suffixes for engineering and scientific uses, but could also retain many of the familiar common unit names for day to day commerce. In fact, even with the metric system today, there is a growing trend to assign common names to many metric measures. In the early 1900s Germany redefined the pound (Pfund) to be exactly 500 grams and Germans today still order cheese and cut meats by the "Pfund" or "halb Pfund". Metric glasses of beer in Holland are ordered in "Pintjas". I am sure there are many more examples and would welcome contributions to the list.

So, to summerize, lets have a worldwide metric system but lets make it a duodecimal one.
All that is needed to bring it about is for American industry to find a significant economic advantage it may give over their competitors and it would be on its way.

PS There is nothing special about base 10. In base 12, (in which 12 decimal is written as 10), multiplication and division by 12 (10) would work exactly the same, add a zero or move the point one place left correspondingly. Oh and of cours, 1/2 would be 0.6, 1/4 would be 0.3 and 1/3 would be 0.4, exactly!!!

PPS. Note that in the world in which we live, our three dimensional space is better suited to packasging items in dozens. Twelve items can be packed as 1 x 12, 2 x 6, 3 x 4 and even 2 x 2 x 3. Ten can only be packed 1 x 10 or 2 x 5. As a result of this, during the second world war a\group of clerks in the Army Transport Service found the erconomies of using duodecimal arithmetic so great in figring cubages of packing cases for goods to be sent to war after reading an article by an Amercan, F. Emerson Andrews.

 

[epoisses]

The French did not invent the base 10, it was already used by the Romans. There's nothing so wrong with it that one would want to undertake the giant operation of switching to base 12. Given how complicated it would be to switch from driving on the left to driving on the right (or vice-versa depending on your point of view), switching to base 12 would be equivalent to driving upside down!

I think there would definitely be an economical advantage for companies to switch to metric (base 10), maybe even a bigger advantage than when every country switched to one single currency.

 

[unc]

in reply to epoisses.

Where did I say the French invented base 10? All I said was that they made the mistake of using base 10 when they introduced the metric system. They could just as easily taken a harder look at the decimal system and extended it to a duodecimal system with the addition of two more symbols and from there developed the metric system based on that number base. Note that the name metric does NOT imply a decimal base as the Greek word from which it derives means roughly "to measure".

As for the Romans, they did not use a true decimal system as they had symbols for 1 and 5 and all their multiples, that is for integers. For fractions, the Romans used a system of names for fractions in TWELFTHS and many submultiples of these. Why, because it makes more sense to be able to work in a system that allows for exact halves, qaurters AND thirds, something our decimal system does not do nor most other bases suggested as alternatives (binary, octal or hexadecimal.

If using a system of weights and measures that had the most often used measures subdivided into 12ths was so bad, why did it last for so long? History should tell you that if something does not suit the uses for which it is intended, it will tend to fall out of use. But the old 12 base stayed with us in our lengths and weights for hundreds if not one or two thousands of years despite the use of a decimal based number system, and of course are still here today in clocks and compasses.

Note that I am not saying such a system would be easy to implement, but rather it would be a better system.

As for the ease of switching from base 10 to base 12, what is your justification for saying it would be like changing to driving "upside down". Have you done any pilot studies? Have you performed a case study? Have you collected any evidence to support this assertion?

Apart from that, I think you are being very dismissive of people's abilities to effect such a change. After all, the British switched from a system of 12 pennies to the shilling, 20 shillings to the pound (all done while using a decimal number system) to a pure decimal system. And if I'm not mistaken, one nation was able to send men to the moon and bring them back again using systems developed under the US Customary system of measures (with the help I suppose of one or two engineers). I don't think you give people enough credit.

Furthermore, if as was done by the French under Napoleon the system was taught in schools, then in one generation you would have a duodecimally cognizant population. It is only we who have been taught one system that would have difficulty in "unlearning" our decimal times table. As for changing existing systems throughout the world, we now have a positive advantage to assist in that process, something called I think "computers".

Penultimatley, your thought that there would be an "economical advantage for companies to switch to metric (base 10)" would be better than a multitude of different systems is not in question, but that does not invalidate the argument that the use of a base twelve system of numbering and a coherent system of weights and measures based on that number system would be even better than the base 10 system, now erroneously called the metric system. Any number base could be used and still be called a "metric" system.

To conclude, making comments on your beliefs in the suitability of one system versus another is perfectly valid, but they are just that, your unsubstantiated beliefs. When you have completed a full investigation of the pros and cons of different number bases I would be happy to hear your results. And if you are about to ask have I done such a study then the answer is "YES". It would still be a valuable input to see the results of similar investigations by others if they care to provide them as it would serve to point out any flaws, false assumptions or erroneous conclusions in my own work.

 

[HgTX]

unc, I was trying to find an interpretation of your posts that doesn't lead me to the conclusion that you're nuts, but I'm not managing to do so. I must be misunderstanding something here...

Are you advocating shifting to an entirely base-12 number system? "10" would mean twelve, etc.?

Or a system in which each prefix level means 12 of the previous? So 1 dam would be 12 m, and 1 dm would be 1/12 m?

Surely you aren't advocating changing the entire number system, or implying that failure to do so was merely a Napoleonic oversight. That system had been in place by then for the better part of a millenium. Choice of number system is hardly on the same level as the relatively trivial matter of which units to use to label said numbers.

But that only leaves the possibility that what you're advocating is the mess of combining a duodecimal unit system with a decimal number system. The whole point of the "metric" system was to have a system of units that were easy to relate to each other--you convert one to another simply by moving the decimal place around.

I must be missing something.

Hg

 

[epoisses]

unc, I am glad you found your base 12 religion and I won't continue to attempt to disturb your SUBSTANTIATED beliefs. When you will have convinced the world of your superior system, please don't forget to keep us posted!
*LOL*

 

[makeup]

You,ve all been reading to many books. What's wrong with what we have, I mean what could not be done in " I worked with imperial measurement for 20 years and never had a reject.

 

[unc]

HgTX

Apologies for my inadequate explanation but to describe the proposal in a short post is perhaps unfair to readers. However I shall try to end your frustration.

"Are you advocating shifting to an entirely base-12 number system? "10" would mean twelve, etc.?"
Yes I am. There is nothing strange about this. *I'm sure you have had experience of hexadecimal numbering where letters A to F are used to represent values 10 to 15 decimal and 16 decimal is represented as 10, meaning one group of 16 plus zero units. In this system 20 would be decimal 32 and so on. 100 in hexadecimal is 16 x 16 decimal or 256.

In a base 12 system of course 10 would be 12 decimal, 20 would be 24 decimal and 100 would be 144 12 x 12 or 144 decimal.

In each of these positional notation systems each succesive position is the next succesive power of the base. Because base 10 has only 10 digit symbols (0 - 9). A base 12 system would require two new digit symbols to represent values of 10 and 11 decimal.

OK, so having defined the digits and retained both the positional notation of the decimal sytem, what does base 12 do for us? Well to begin, multiplication by 12 in this system would work exactly the same as multiplication by 10 in base 10, you just add zero. Likewise, dividing by 12 (written as 10 in base 12) just means moving the point one position to the left. This functionality is the same for all base systems, multiply or divide by the base and you just move the point right or left.

Ok, so why bother when we already have that in our decimal system. Well that comes back to the question of why people continued to use twelves for millenia despite using a deciaml number system. Why, because it was very useful. You can take a half of 12 (6) or a quarter of 12 (3), but even better you can take a third of 12 (4) without any fractional parts or repeating digits. So in base 12, 1/2 = 0.6, 1/4 = 0.3 and 1/3 = 0.4. This is just one simple example of the advantages of base 12.

Now, if we assume the implementation of a base 12 number system, then all weights and measures should also use the same system. Thus the basic measure for length would be subdivided into 12 parts, and each of these subdivided in 12 parts and so on. Likewise multiples of each measure would be 12 times the preceding value. Of course, these would all be written as 1, 10, 100, 1000 ... and fractional values 0.1, 0.01, 0.001 ...

Now about the "Napoleonic oversight", it was one of the progenitors of the metric system that in retrospect made a comment that in hindsight that the system would have been better based on 12. Yes the decimal system was in use for hundreds of years and is believed to have ecolved because we as humans have two hands with five digits each. But I think we have all gone beyond the stage of counting on our fingers.

Finally, your question of whether I am advocating the combination of a decimal and duodecimal system is not what I am suggesting. I am saying leave the decimal system behind and use a pure duodecimal system throughout.

If my explanation still leaves you confused then that is possibly a deficiency in my presentation. You can however find many excellent references to various number systems including duodecimal on the web.

 

[unc]

makeup

I,m not saying the old measures weren't good, just that they can be improved beyond what even the metric system provides.

A set of measures with a consistent increase in magnitude (as in the metric system) but with advantages not found in the decimal based metric system. Division by 2, 4 and 3 without irrational numbers as results in the case of division by three, statement of values with fewer digits than the decimal system both for integers and fractional values, greater regularity in the multiplication table, and significant improvements in visual identification of factors and divisibility.

Further benefits include finer graduations in fractional values and the retention of easily recognized names for commonly used measures, and the consequent ability to specify measurements using single or double digits for most commonly required day to day usage.

PS As an example, not necessarily part of the proposed system but what we should expect, I quote an adverstisement from my local chemist (Drug Store for our cousins across the pond) for photo prints from digital media.

151 x 102mm (6" x 4")
photos price each
1 - 19 49p
20 - 49 39p
50 or more 29p


203 x 151mm (8" x 6")
photos price each
1 - 19 £1.19
20 - 49 99p
50 or more 79p

I know which form of measures I prefer to quote (and remember). I dread the day when the Imperial measures are removed entirely.