“Lieutenant Grace Hopper codes problems onto punch tape for feeding into a new calculating machine invented by Commander Howard H. Aiken, USNR. The calculator will be presented to Harvard University by IBM Corporation, for use by the US Navy for the duration of the war. The machine is a revolutionary new electrical device of major importance to the war effort. It will explore vast fields in pure mathematics and in all sciences, previously barred by excessively intricate and time-consuming calculations. Two years of research were required to develop the basic theory behind the giant calculator. Six years of design and construction and testing were necessary to transform Commander Aiken's original conception into the completed machine at the engineering laboratory of IBM in Endicott, N.Y.” Aug. 4, 1944
“Rear Admiral Grace M. Hopper salutes crew members as she comes aboard the U.S.S. Constitution in Boston's Charlestown section for her retirement ceremony. Hopper, the U.S. Navy's oldest commissioned officer on active duty, retired after serving over 40 years in a Navy uniform. The 188-year-old U.S.S. Constitution is the oldest still commissioned warship afloat in the world.” Aug. 14, 1986
VOLKER LANDWEHRThe first proposal for the meter was the described pendulum in about 1668. But the French Academy of Science decided to choose the form of the earth as a base in 1791
Because, as I said, they didn't want to use the old 'second' because of the wacky switch to decimal time. Mercifully that wasn't foisted on the West, or that ridiculous decimal calendar scheme, either.
The meter was the one ten-millionth part of the longitudinal length North-Pole to Equator through Paris.
Measured incorrectly, in a direction that involves the oblateness of the Earth's shape (in a way that an equatorial circumferential measurement wouldn't ... but then it wouldn't pass through Paris...)
They built prototype meter bars that were used as definition. Sometime the realization set in that aging might change the prototype meter and duplicating might be faulty. So a definition was looked for which described the length of the prototype meter bar with firm physical characteristics...
And that is why the 'universal' (artifact-free) definition from 1960 to 1983 was a frequency of krypton-86 light ... ending in a decimal fraction of a wavelength! It was the length of the historical platimum-iridium artifact at BIPM that was, and is, the determinant of 'how long a meter is'.
And the real problem is, once the base of the system is no longer a legitimate universal physical constant, there is no use claiming it is 'logical' because it is merely divisible by the number of dactyl appendages on the inventors -- which is OK, but the decimal-inch system used by American machinists does this perfectly effectively, much more compellingly than, say, measuring the wheelbase of large steam locomotives in millimeters (of which silliness much more anon).
The meter is too long; the millimeter too short, the degree C too coarse without a decimal, the unit of pressure almost hopeless ... the scheme takes little interest in human-scale units. Sure, there is the decimeter ... but that's deprecated under SI (which is different from cgs or mks measurements).
Now, if you're raised to know no better, you can of course get used to inconvenient units. I'm sure there are plenty of people who are used to European tolerancing conventions, which I find ridiculously overcomplicated for the practical use people need to use a tolerancing system for. I'm not going to complain too vociferously about using a centigrade system founded in phase changes of water because it needs decimals to describe the range of human temperatures adequately: I in fact find decimal adjustment of the comfort zone on a Fahrenheit thermostat useful for adjustments around 'room temperature' (say. 68 to 72 degrees or so) just as I do for fever-thermometer gradations in that system. But to require a decimal notation to discriminate wider effective ranges of temperature, and to have the range of body temperature in an arbitrary range of the chosen unit, is not so bright if the system is to be as useful to humans as something like the Modulor was meant to be.
The fact that the 'time' involved does not fit into the groups-of-three SI framework applied to time in seconds, and would hence be deprecated, is a mere intellectual bagatelle Could you please elaborate?
Gladly. SI at some point adopted the convention that any unit that is not a multiple of three away from the base unit 'shouldn't be used', with decimals forward and backward (and presumably significant figures whether actually 'significant' in the mathematical sense or not to match) in the coefficient being used to make the transition. This is why the measurements of long objects like locomotives are found denominated in mm, instead of something more sensible like cm or dm -- and why the official support for cgs, the system that chemists and other scientists called the 'metric system' for so long, is a kind of double-think for the SI people.
The crowning jewel in the nonsense, for me, is the conversion from grays to sieverts, involving as it does a factor of 100 that is not supposed to be supported. There are facile explanations for this, but none that really get around the cognitive dissonance. Now, note the relevance to the context of using a light-second as the definition of a length; SI either requires meters or mm for that length (and the current BIPM definition, I think, may actually have it in km; I'd need a pencil and paper and see defined units for that facile divisor number, but the magnitude seems right). Neither of those does what IslandMan's light-nanosecond does (with a wholly coherent SI rule-of-three division!) or what an attoparsec does, which is a human-scale unit of measurement that is actually at some human scale.
I understand that there are currently seven basic SI dimensions that can not be deviated [note: I think the English word you want here is "derived"]by [from] multiplication of other SI-dimensions: meter, kilogram, second, ampere, kelvin, mole, candela.[/quote]
I think that is right, but I see no particular difficulty in fixing "accepted" values for these as the community has done (however, the way SI originally tried to do this with the second was something of a comical disaster, reminiscent of the Bangalore software development in YahooGroups "/neo/"). In my opinion there is great sense in defining chemical quantities in gram-molecular weight as this can be done to any necessary precision and no one is expecting these to be human-relatable magnitude, or fixing a unit of technical light measurement that as defined does not have to be used to compare or gauge direct human experience.
Discussions of human haptic incompetence in gauging the magnitude of numbers represented by large exponents is well established. As has human difficulty in relegating important discrimination of quantities to the decimal part of their numerical base-10 representation.
Personally, I'd like to see the number system itself revised to hexadecimal, but I don't expect that to get much more traction than 18th-century decimal time.
I'm not going to complain too vociferously about using a centigrade system founded in phase changes of water because it needs decimals to describe the range of human temperatures adequately: I in fact find decimal adjustment of the comfort zone on a Fahrenheit thermostat useful for adjustments around 'room temperature' (say. 68 to 72 degrees or so) just as I do for fever-thermometer gradations in that system. But to require a decimal notation to discriminate wider effective ranges of temperature, and to have the range of body temperature in an arbitrary range of the chosen unit, is not so bright if the system is to be as useful to humans as something like the Modulor was meant to be.
I've always wondered about what was so special about having 100 divisions between the "freezing" point of water and the temperature of water when the vapor pressure that can't be expressed as a simple round number in any unit except "atmospheres" (well maybe torr). Getting an accurate calculation of heat energy involves looking up a table of some sort for any combination of units.
My vote for unit of temperature would be electron-volts, but that gets very messy in relationship to human comfort...
The crowning jewel in the nonsense, for me, is the conversion from grays to sieverts, involving as it does a factor of 100 that is not supposed to be supported. There are facile explanations for this, but none that really get around the cognitive dissonance.
Roentgens/RADs to Grays? 1 Sv = 100 REM - I always convert Sv to REM as my memory of significant dose milestones is in REM or mREM.
Not octal??? I was a fan of the big Cray designed CDC machines....
A brief but nonetheless excellent essay on many of these points:
- PDN.
@RME: I just wanted to clarify the historical order of the events around the meter without any judgement. But perhaps I just misunderstood your post.
The topic seems very emotional to you. So I just comment some -in my point of view - discrepancies.
You do not like the meter because of its definition but you like inch and yard?
The inch started as three barley corn in a row in the UK and is now defined as part of the meter same as yard and feet.
You seem to prefer units based on phisical constant but prefer degree Fahrenheit over degree Celsius. In both systems you need decimals to describe the human body temperature. 96°F are too low and 100°F is feaver.
I think we all prefer what we grew up with. One system is not necessarily better than the other. For me as an engineer the system must be workable and that the SI system was.
BTW thanks for the word derive.
It nice to see all those alternatives. But the definitions were necessary at a time when these constants weren't know. Before the introduction of the meter there were different length unit in almost each principality.Regards, Volker
erikemNot octal??? I was a fan of the big Cray designed CDC machines....
Odd number of binary digits. And shorter/more digits required than decimal. Why cut off two fingers to accord with obsolete computer conventions?
And the systems that go to longer word boundaries (32-bit, 64-bit, etc.) begin to be a bit Sumerian in the number of special characters required.
Quite a bit of the thinking was expressed better than I could do it back in the time of introduction of 16-bit processors.
Electron-volts is a wee tad mis-scaled for human temperature ranges, but this could be accommodated as simply as the metric/SI system does human-scale pressure changes: denominate a multiples unit as the general range of measurements and 'standardize' on the decimal conventions that zero in on it. If it is consistent, easy to memorize, and provides decent approximation to the scale of fine gradation in everyday contexts, you have a contender.
Of course, Celsius and Fahrenheit are relatively equally unsuited for scientific use because they are relative; the 'correct' units are degrees Kelvin and Rankine respectively. And here the 'centigrade' unit width makes things a bit better, because everything at human range and relative precision is large, but less large than degrees R, and requiring a decimal is no more or less of an issue given that magnitude.
The IxD of some of the European derived units is not quite thought through. Take for instance the 'unit' of specific fuel consumption per distance run. In the English system, this looks at the desired unit (the distance the vehicle runs) divided by the fuel used, and the result properly gets larger for better end result. The Germans emphasize the fuel consumed, which looks sensible if you are going directly to fuel cost for known runs, but then spoil both the sense and the SI consistency by defining the "mileage" in terms of 100km, which requires a division to get an answer that means more than a guide number, produces numbers with significance in decimal places. Yes, it's consistent in getting smaller with lower consumption, but the numbers get smaller and give you no instinctive grasp of how far you can go on the fuel you have unless you are very, very familiar weith discriminting small decimal numbers.
VOLKER LANDWEHRYou do not like the meter because of its definition but you like inch and yard?
Now you are putting words in my mouth to say something just the opposite of what I was discussing. Are you by some chance a climate scientist?
What we were discussing was human-scale units; more specifically the amusing use of very large quantities combined with very small quantities that happen to produce a human-relevant metric.
Many of my European friends try to trot out that tired old "whose inch do you use" without recognizing it is European inches and national prides that were the root of the problem in the first place. An international convention that standardized on a legitimate human-scale metric, like an "inch" at 2.5 "cm" could easily resolve all that petty stupidity at a stroke.
Because the problem ... and it is a problem ... is that the meter is too long to be a practical measure of human scale, just as the yard is -- and no, I don't favor 'yards' over 'meters' except incidentally, as a whole-number multiple of a foot. Meanwhile, 'as it happens' the length of an average human thumb is not a multiple of 10 ... let alone a multiple of 1000 ... of a human foot.
I have always liked a couple of intermediate units like the span and the cubit, the former, incidentally, corresponding rather well to the decimeter (which, as noted, the European foolish-consistency-lovers try to deprecate out of existence) and the latter coming reasonably close to a half-meter.
Proof of the fundamental confusion, if you want to trot out all those wack inches, is that the fundamental unit notation in the metric system is contradictory. It ought to be defined in terms of fundamental units, so let's look at meter-kilogram-sec... oh, wait, that's a derived unit. So we use the scientific convention which uses grams to solve that problem, centimeter-gram... oh wait, that still doesn't work, and I hear cries from the general direction of Bienne that the derived unit of length is supposed to be 'withering away'. Consistency demands meter-gram-second, which is just as "consnstent" and "internationally defined" as your arguments try to be saying, but the results of calculations would have the very worst lose-one-decimal-place-with-all-the-shifting-and-your-lander-hits-Mars-too-hard lack of instinctive proportion that I was actually discussing as being a problem with the meter.
The reason I dislike the 'meter', to make it a bit clearer, is that it pretends to be a logically-derived number when most of its history plainly indicates it is essentially pseudoscientific in any "natural" derivation from human measurements made for human purposes. And then we get people who try to claim that just because its system is base-10-consistent, it is necessarily better even for human-scale measurements - the latter extension being where I have the problem with the validity of the 'you were holding it wrong' style of argument.
Thankfully there's significant figures that can come to the rescue.
RMENow you are putting words in my mouth to say something just the opposite of what I was discussing. Are you by some chance a climate scientist? Big Smile
Perhaps I misunderstood you. Thats quite easy in foreign language. But among others you said: "The meter is too long; the millimeter too short, the degree C too coarse without a decimal, the unit of pressure almost hopeless ... the scheme takes little interest in human-scale units. Sure, there is the decimeter ... but that's deprecated under SI (which is different from cgs or mks measurements)."
I didn't intend to put words in your mouth.
I'm a civil engineer (structural design) having worke my whole professional life with [mm] (steel structures) and[m] (concrete structures). I can't follow the above cited thoughts. I can't understand the reason and use of human-scale measurements.
RMEAn international convention that standardized on a legitimate human-scale metric, like an "inch" at 2.5 "cm" could easily resolve all that petty stupidity at a stroke.
But what for. The meter could easily be the standard too.
RMEThe reason I dislike the 'meter', to make it a bit clearer, is that it pretends to be a logically-derived number when most of its history plainly indicates it is essentially pseudoscientific in any "natural" derivation from human measurements made for human purposes.
I'm sure you know that the definitions of kilogram and second are similar arbitrarily. As is inch.
Reading my post I think I really don't understand your intentions.Regards, Volker
VOLKER LANDWEHR I can't understand the reason and use of human-scale measurements.
I rest my case.
"The metric system is the tool of the devil! My car gets forty rods to the hogshead and that's the way I likes it!"
-Abe Simpson
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.
I'm surprised the cubit hasn't come up (or did I miss it?)
Or the "stone."
BTW - 40 rods per hogshead is pretty abysmal mileage.... My truck gets about 670,000 rods per hogshead...
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
zugmann "The metric system is the tool of the devil! My car gets forty rods to the hogshead and that's the way I likes it!"-Abe Simpson
"The metric system is the tool of the devil! My car gets forty rods to the hogshead and that's the way I likes it!"-Abe Simpson
It is the devil's work. Having it introduced into everyday life of those familiar with the English system creates mind-boggling havoc. The airplanes I worked on for a living are still called out in English units of measurments. Can't say the same for cars. Methinks it was a plot on the part of tool manufacturers.
Norm
tree68I'm surprised the cubit hasn't come up (or did I miss it?)
You didn't see it. I doubt you missed it. [note: where is the smiley for 'rimshot'?]
One of the most 'useful' canonical definitions of a cubit is 18", or 1.5 feet. That is remarkably close to 500cm, or 0.5meter. So if, say, approximating distance with a forearm, someone in the field might choose this for estimating in whole units in either system. It's about the longest effective dimension of human scale that can be used to measure distance (the fathom, or distance on Leo's Infinite Man between outstretched fingertips) being longer but difficult to apply consistently or without a helper/spotter...)
It has a conceptual defect in that it isn't an even multiple of 2.5 (the 'standard inch' representation in nominal cm) which can be fixed by standardizing a cubit around that ... say 20" for a more precise half-meter.
Or the "stone."[/quote]
Don't ask me to defend it. Any more than I'd defend English pre-decimal currency, even where there are reasons for it (wasn't the silver groat the unit that was supposed to make cab-fare more convenient in the 1830s?) as tradition is a miserable substitute for engineering convenience. I note we have recently touched on that most ridiculous of the English units, the 'hundredweight', in conjunction with where 'doing the ton' came from; it takes a puissant empire, indeed, to make a unit like that commonly-used.
mudchicken Thankfully there's significant figures that can come to the rescue.
People should understand the difference between 0's as "placeholders" and real values. E.g., 20, 20., 20.0, and 20.00 can have 4 different meanings, respectively: +/- 1/2 interval of 5 ft. for the first, and likewise +/- 0.5 ft., 0.05 ft., and 0.005 ft. for the others, respectively.
Which is one reason why I write the 'cents' portion of my checks the same as in a 'legal description' of a deed for real estate - e.g., "Twenty dollars and no one-hundredths cents" or "Forty Six and Twenty-Three one-hundredths Dollars for $46.23. (You can imagine some of the side effects to that idiosyncracy - but never has anyone refused to accept or cash a check written in that manner. MC, stop laughing when you can . . . )
Volker, I too am a civil engineer, and so would like to ask what magnitude of tolerances you apply to those dimensions ? 1 mm ~1+/ 32nd of an inch, which is generally way too fine for any outdoor application of the sort that's the subject of this thread (except for the cross-section dimensions of the steel rails and steel fasteners, etc.). Measurements truly like that will have to be specified and compensated for temperature (either scale, as long as it's consistent), or have a tolerance of - say, +/-3 mm at minimum - to have any hope of being faithfully replicated in the field.
Here in the US, the cross-slopes of sidewalks and the Americans with Disabilities Act (ADA) handicapped ramps (i.e., the the yellow or red rectangular plastic panels with the truncated cone bumps) usually cannot exceed 2% without a waiver. That's usually interpreted as 2.0% using a digital Smart Level, which means that across their typical 5 ft. width, the elevation difference cannot exceed 0.10 ft. ~ 1-1/4 inches, with a maximum + tolerance of 0.005 inch ~ 1/16 of an inch before the slope is 2.1%, which is non-conforming. Considering that the ramps and sidewalks do need do some slope for rain water to drain off them properly - say, 1% - the allowable elevation difference is reduced to 0.05 ft. As I like to say, those are tolerances for interior finish carpentry, not civil field construction, which is the point of this paragraph.
In contrast, measurements of concrete to the nearest meter (length or volume) is way too coarse unless a truly massive structure such as a dam is being built. There's an informal principle among construction field inspectors to usually - unless specified otherwise - measure for payment to 0 decimal places (for this, the nearest inch, which ~0.08 ft. ~0.1 ft. practically), calculate to 1 decimal place (for this, 0.1 cubic yard), and pay to 2 decimal places (here, 0.01 of a dollar or 1 cent).
As I've said before elsewhere, 0.01 ft. or 1/8 is a convenient and practical measurement for surveying and construction field work. Metric units are not practical: 1 mm ~1 plus/32 of an inch, which is generally much too fine and implies false precision; and 1 cm ~3/8", which is too coarse when better precision and accuracy can be achieved easily.
And calculated or measurements of characteristics such as the Tractive Effort of steam locomotives that are purported to be closer than to about the nearest 1,000 lbs. are false precision (see LeMassena's Numbers essay that I referenced above.)
And further I sayest not.
[Groans in mock pain from that pun]; then
Also belongs over on the Not So Improved Humor thread, and some kind of engineering humor collection.
Hello Paul,
we have a DIN Standard that governs the tolerances independently of the measuring units. The tolerances dependend upon the length of the measured element. For length up to 3 m the allowed tolerance is ±12 mm, 3 to 6 m: ±16mm; for 6 to 15 m: ±20 mm; 15 to 30: ±24 mm; >30 m: ±30 mm.
Steel structure tolerances are much smaller: 1 mm for length up to 2,000mm and 6 mm at 16,000 mm in steps of one mm in-between.
If there are 5 elements in a row the total length is the basis. If you have 5 elements of 6 m length each has a tolerance of ±16 mm, the tolerance of the row is ±30 mm.Steel structure tolerances are much smaller. Steel structure tolerances are much smaller. ±1 mm for length up to 2000mm and ±6 mm at 16,000 mm in steps of one mm.
Smaller tolances can be contractually agreed.
Thas has been just one example. All possible deviations are regulated.Regards, Volker
Volker -
Thanks for that explanation and examples. Those are generally entirely reasonable and practical tolerances, with the possible exception of the shorter ones for steel. Allowing only 1 mm or 1/32" for a 78-3/4" length of steel seems too small to me; I would ask to use 1/8" ~3 mm instead except in unusual circumstances.
A few years back, we had to measure / stake-out a distance on the order of 140 ft. (~43 m) - for the construction of the glass facade of a building - to a shown dimension with a precision of 1/16 inch, ~1-1/2 mm (you can see it at N 40.63378 W 75.45410 ). Some discussion with the installation subcontractor revealed that it really didn't need such accuracy, because of temperature variations and a sliding (roller) bearing, etc. What they really wanted much more certainty as to the accuracy than was usually the case - but we still had to certify to the distance. So I did, subject to the following note, as I recall it: "+/- 1/4" (~0.02 ft. or 6 mm). We were confident of that tolerance, and that note was accepted, so "end of problem" as we say. In comparision, with the steel standard you cite, for the length of 43 m the tolerance would still be only 6 mm ~1/4 inch, so both of our tolerances are essentially identical.
If those close tolerances can be consistently achieved - and European standards are world-class quality, as many of us know - then that's great.
Hallo Paul,
+/-1 mm tolerances are for manufacturing in a workshop. I never heard of problems. I should have mentioned that the given values were element measures. For steel structures there are different erection tolerances. Regards, Volker
ChuckCobleigh mudchicken Thankfully there's significant figures that can come to the rescue. Or not. I was reminded by our sparkling, warm weather of late of my days as an undergraduate at San Diego State (College, then) when the Spring semester soon heralded the unveiling of many significant figures on campus, which coincided with many GPAs of male students plummeting. Might have done better going to a cold weather school. (Not!)
I have not been back to reply which I see has given you plenty of time to engage in meaningless blather about units of measurement which have absolutely nothing to do with coordinate syetems. Any appropriate units can be used. No one has yet told what this "Z" and "Y" are.
International standards for machine tools? Here ya go:
ANSI/ASME B89.3.4 NAS 938 ISO 841 DIN 66217 and EIA 267-C .
I had been spending at least a few seconds of blather time wondering what possible relationship machine-tool standards could possibly have to ballastless fixed-track structure. Or geodesy, for that matter.
That still hasn't been explained, coherently or otherwise. But I no longer have any interest in reviving it, or discussions of humorous exaggeration in units of measurement, or ... well, any of the diversions away from ballastless approaches to track construction.
We had Mr. Landwehr, who I suspect works directly on some of these things, about to engage MC, who has seen some American failures of the concept, over best practices in design and build. We also had some interesting discussions going about how this type of structure would handle CWR forces, what would be needed for accidents like flooding or ground settlement below the subgrade prep, and how the need for frequent control joints across one system of slab track came to be so necessary as to be called out as a feature of construction. We need to take those subjects up again.
RME Many of my European friends try to trot out that tired old "whose inch do you use" without recognizing it is European inches and national prides that were the root of the problem in the first place. An international convention that standardized on a legitimate human-scale metric, like an "inch" at 2.5 "cm" could easily resolve all that petty stupidity at a stroke.
I may be mistaken, but isn't the USGS inch slightly different than the US standard inch? (USGS 39.37in/m, standard 1in=0.0254m).
The fun thing about defining an inch to be 25.0mm would be that a foot would come out to 0.3m and then be about 0.1% longer than a light-nanosecondas opposed to 1.6% longer. OTOH, with 30 years being about a billion seconds, estimating a light year in feet is easy - about 33 quadrillion feet.
Might as well bring up a prank I pulled on my 7th grade geography teacher. One of the questions on a test was the height of a mountain (think it was Mt Cook in Kiwi land). The teacher was foolish enough not to specify which units for the answer, so I gave the answer in inches. Fortunately the teacher had a good sense of humor.
erikem RME Many of my European friends try to trot out that tired old "whose inch do you use" without recognizing it is European inches and national prides that were the root of the problem in the first place. An international convention that standardized on a legitimate human-scale metric, like an "inch" at 2.5 "cm" could easily resolve all that petty stupidity at a stroke. I may be mistaken, but isn't the USGS inch slightly different than the US standard inch? (USGS 39.37in/m, standard 1in=0.0254m). The fun thing about defining an inch to be 25.0mm would be that a foot would come out to 0.3m and then be about 0.1% longer than a light-nanosecondas opposed to 1.6% longer. OTOH, with 30 years being about a billion seconds, estimating a light year in feet is easy - about 33 quadrillion feet. Might as well bring up a prank I pulled on my 7th grade geography teacher. One of the questions on a test was the height of a mountain (think it was Mt Cook in Kiwi land). The teacher was foolish enough not to specify which units for the answer, so I gave the answer in inches. Fortunately the teacher had a good sense of humor.
Of course we have had Mars landing space craft with the trajectory's calculated in the wrong measurement system and make a 'hard landing' from which the craft did not survive.
Never too old to have a happy childhood!
RME- Well I for one rather enjoyed your humorous and enlightened foray into the SI system. Up here in the great white north I am a hybrid existing within another hybrid. Pierre Elliot Trudeau saddled us with the metric system beginning in 1970, I think mainly to give the USA the middle finger. I was well into my 20's and grew up and educated in the Imperial System. So that's the first one. The second is that while Canada has long since converted there is still significant use of non metric units and standards in many sectors of the Canadian economy and every day use. This is due to historical ties with the United Kingdom, proximity to the United States and public opposition....nobody uses kg's for anything except packaging labelling on products, which nobody gives a hoot about,... ask any Canadian how many mL a can of coke is and you will get a blank stare despite the fact its printed right there in front of them every day. Nobody expresses their height in mm. Not doctors, not anyone. We still calculate mpg for our cars, although that one is fading. L per 100 km...what? Too many variables in play for that one. Home builders, carpenters and construction use feet and inches, period.
As for temperature we are 100% Celsius and the best I can come up with is that it really sucks, especially in the home. So both systems are in widespread general everyday use by everyone. Only exception is the "elites" who walk around thinking they are so much smarter than the rest of the Neanderthals, as in all my wooden headed addle brained fellow profs. In the Mills, mineral processing, both systems are in widespread use.
I do worry that the USA will eventually cave so please see to it that you don't. Let me guess, California, Oregon and Washington State, then no one else. That's ok.
BaltACD- I have never, and will never, ever, understand that. All those brains, all those people, all the checks, all the money ...like what? It's a bad comedy line from a terrible comedian that you can see coming.
Paul_D_North_JrWe were confident of that tolerance, and that note was accepted, so "end of problem" as we say. In comparision, with the steel standard you cite, for the length of 43 m the tolerance would still be only 6 mm ~1/4 inch, so both of our tolerances are essentially identical.
Paul, I have been lucky and found the standard in internet which is very rare.
There are too classes. The higher requrements are: L = LengthL < 30 m: 16 mm30 m > L > 250 m 0,2 x (L + 50) mm L in meterL > 250 m 0,1 x (L + 350) mm
At 43 m that would be approximately 19 mm. But stricter tolerance requirements are possible.Regards, Volker
erikemI may be mistaken, but isn't the USGS inch slightly different than the US standard inch? (USGS 39.37in/m, standard 1in=0.0254m).
I think it may be a rounding convention, not definitional in the sense of all those variant inches and toises and pouces, oh my!
The fun thing about defining an inch to be 25.0mm would be that a foot would come out to 0.3m and then be about 0.1% longer than a light-nanosecond as opposed to 1.6% longer.
Just my little bit to help Grace enlighten the kids.
Thing was that in 1876 it still might be possible to transition industrial production from 'old inches' to 'new inches', perhaps with some tolerance adjustments to make the effect "the same" where factor of safety or other fit due to the .04 was not critical. That is not as radical a shift as, say, the adjustment in the "official" American speed of sound when it turned out everyone was pulling their measurements toward an 'accepted value' that turned out to be consensual but aberrant. like some other activity concerning significant figures.
The 12" foot (and 18 or 20" 'cubit') may still cause some pain, but then again we still don't have decimal time (in America, at least, we did the decimalization logically; it's where you get the six-second increments on a cell-phone bill, or the six-minute time increments set up for my wife's cleaning business...) If you don't like feet, stick with machinist's decimal inches for a combination of haptic magnitude and high precision in one measurement ... and use some sort of despised 'new yard' to stand in for meters on longer measurements. (Note that the 2.5 conversion leaves the 'yard defect' worse instead of better, now only 0.9m, so we'd still be two cultures separated by a common metric as far as distance measurements were concerned, and the cumulative 'error' between new and old distance measures does begin to tell at surveying magnitudes...
One of the zeroth laws of science I was taught very early in life was 'always specify your units'. Had that convention been followed we would probably know somewhat more about Mars. It is as true for dane teachers as for those in nerdy fields... and, come to think of it, what if you'd answered in furlong/firkin/fortnight units? That teacher reaction might have been fun to see.
On the other hand, I remember a cautionary tale from a teaching seminar somewhere: in an elementary math class, the teacher wanted to know how many "numbers" there were between two integers, say 6 and 9. A student answer -- key to this is that demeanor, tone of voice,etc. were lamentably absent, as with much Christian Scripture -- was 'five', and upon being told that was wrong and to explain their answer, said "6.5,7,7.5,8,8.5" The teacher reportedly told him to sit down and shut up as a wiseass. The seminar presenter was aghast that such a lovely teaching moment had been wasted (shades of those teachers in "Despotism"!) I had the uncomfortable realization that the student might have understood more about mathematics, but was more interested in making the teacher look bad... balancing truth and discipline has often been something of a problem in the Western tradition...
The immediate question is whether the Canadians who still use mpg are tying it to Imperial gallons. I'm still old enough to remember Esso receipts from fishing trips (to the Cabonga reservoir, which then still had plenty of pike longer than I was tall no matter what units of length you used) and was struck by just how much bigger the imperial gallon seemed.
Strange that Canadians don't use 'liter numbers' for drink sizes; perhaps because Americans tend to love their soft drinks (and perhaps also because there might be some validity to that wretch Bloomberg's assertion that supersize sodas can cause deleterious mental effects) the recognition of 'two-liter bottles' as a vernacular term is just about pervasive. You'll still have 16-ounce size (in part due to conflation of fluid and avoirdupois measures in the American tradition) but it helped that 500ml is a "bonus" size, and what American doesn't love the sense of getting a little for free (especially Cajuns who have a special word for the thing).
Nixon and Congress missed a sure bet, and the Carter administration, really dropped the ball on getting distance metricization adopted for roads here. If we had to have an arbitrary reduction of speed limit (for fuel consumption, although of course spun to the marks as "safety") it should have been set relative to effective truck gearing, somewhere around 62.5mph and not asinine 'double nickels' supposedly easier to remember. Now, everyone loves and respects 'the ton' in the way folks used to use the expression 'going like sixty', and here was a convergence of events on that nice, round 100km/h (or kph as we said at the time). Instead we got a memorable 88, then went to the enforcement strategy of encouraging cops with a speed-trap mentality to assist our national priority, and no, America didn't decide to come along. I no longer often see km/h equivalents on Interstate signage, which indicates for the nonce that the 'popular transition' to a system adopted here almost 150 years ago now is once again stalled.
I don't look at the Mars lander thing nearly as forgivingly as you and many others do. Engineers know to pick consistent units, define their terms properly, and periodically check. What they were doing with English measure for orbital calculations is still something I can't figure ... and a great many people evidently made the same assumption, that decimal calculations would be in 'scientific' metric units. Now there are some stupid metric conventions, too, like there being no nomenclatural safeguards at all between notation in mks and cgs (perhaps typically, the answer coming out of Switzerland was to deprecate the system most actual scientists were using) and when I first heard about the incident I thought that ws the cause. For it to be English calculations assumed to be metric was bad comedy indeed ... but that wasn't the worst part. Folks from JPL being involved in such a thing was the inconceivably bad part.
Getting back to slab-track junctions, and the original question that all the 'blather' came out of:
PDN was wondering about various motions and deflections at the joints in slab-track systems, and used a Cartesian axis 'convention' that didn't account for some of the potential motions. Since we have one of the world experts in specification of degrees of freedom of mechanical systems not only present in these forums but reading this thread, let me ask this:
What would be the BEST convention to use in specifying axes and degrees of freedom for railroad track analysis? PDN saw this looking down on the track in plan, I think x being nominally longitudinal and Z being normal to the plane of the track as measured, say, across the railheads. That simple convention, as he noted, didn't account for rotation of the slab ends if the slabs were to bow or otherwise deflect on expansion, which could be considered as being relative to other defined axes. What should the framework or conventions be for best fit of model with intended purposes?
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