KIPS 5

[darron]

I am drawing a blank in converting a KIP into a load specvified in Kn.

Can anyone supply a ratio or give me a clue0n how to convert

 

[LPPE]

jheidt - right on with #3.

 

[BigH]

Do I miss something? - we don't want to use the "metric" system - we want to use the SI system (System Internationale) (although I still like the "English&quot. Force is in kN, not kg-f. I happen to like using kPa rather than kN/m2 because, well, the formatting is easier if you want to superscript the 2 in m2. I've used both. As I've stated in other threads - whatever system is used - SI, say - we need to use consistent units . Some use MPa (my preference) and others will quote N/mm2 - then you have to go through the gyrations of dimensional cross-outs to see if they are equivalent.

 

[Focht3]

jheidt2543 is right - in those immortal words of rural wisdom, "don't fix it if it ain't broke."


I go back and forth between the units, and see advantages to both. But to say that no part of the SI system is difficult or confusing - even when you are conversant in it - is simply wrong.


And as to the "rest of the world is right so the U.S. should change" argument: the last time I looked, WE were the ones doing most of the buying (hence our balance of trade problem.) Seems to mee that you'd use OUR measurement system - if you want us to buy your products!

 

[Ingenuity]

Curious...why does the US medical profession use non-English units (e.g. cc - cubic centimeter, mg - milligram etc)?

 

[Qshake]

All,

Please help me here as I am trying to recall a recent book on the introduction of the SI system. Since I am trying desperately from memory to recall the issue I just can't put my finger on it...But wasn't there some error in the SI system for the meter?

Or did this have something to do with a survey of some land that was off due to an incorrect measurement...

It seems to me that two fellas set off to chart or record something and had a great deal of difficulty.

Well, I'm off to look that book up - I'll Be Back!

I just thought it might had some history to this thread.

 

[Qshake]

All right, back again as promised.

The book is titled "The Measure of All Things" by Ken Alder.

Here is an excerpt of a review on Amazon...

"Alder delivers a triple whammy with this elegant history of technology, acute cultural chronicle and riveting intellectual adventure built around Delambre's and Mechain's famed meridian expedition of 1792-1799 to calculate the length of the meter. Disclosing for the first time details from the astronomers' personal correspondences (and supplementing his research with a bicycle tour of their route), Alder reveals how the exacting Mechain made a mistake in his calculations, which he covered up, and which tortured him until his death. "

Any comments, perspectives, historic views?

I was quite surprised to see this and have never known about it as long as I've worked with SI in grade school.

 

[Focht3]

I do, too - in my lab. The units of measurement are convenient for measuring relatively small soil samples.

But I report soil unit weight in pcf and stress in ksf. All of my other "typical" reporting values are dimensionless!

 

[kenvlach]

Any comments about the standard Kilogram losing weight?
It seems that the platinum-iridium kilogram standard kept in France is losing weight (cold-fission? champagne fumes?) by about 3 parts in 10⁸ per century.
Does this mean the collapse of all Kg-based standards?

Abstract of NY Times article:
“Science Desk | May 27, 2003, Tuesday
Scientists Struggling to Make the Kilogram Right Again
By OTTO POHL (NYT) 1546 words
Late Edition - Final , Section F , Page 3 , Column 2

"In these girth-conscious times, even weight itself has weight issues. The kilogram is getting lighter, scientists say, sowing potential confusion over a range of scientific endeavor.
The kilogram is defined by a platinum-iridium cylinder, cast in England in 1889. No one knows why it is shedding weight, at least in comparison with other reference weights, but the change has spurred an international search for a more stable definition.” (

http://query.nytimes.com/gst/abstract.html?res=F30E15F83C550C748EDDAC0894DB404482)

A more scientific story from NIST and efforts to create an electronic-based kilogram standard is at

http://www.eeel.nist.gov/811/elec-kilo.html

Some Internet commentary is at

http://www.metafilter.com/mefi/26061

 

[sc]

Just to add a novel twist to the discussion how does the clothing industry measure sizes?

I've seen size 40 shirts (40" or 101.6cm) that actually ranged in size from 38" to 44".

What about shoes, are the sizes related to length? Nope, well cannot possibly be when a size 10UK is about a size 12US which is about a size 9.5Aus.

Are the sizes related to metric or english? Are the sizes related to ego?

Thank god (or whoever you belive in) that we engineers have settle on two systems only, where an inch is an inch (which is 25.4mm) and where a kilogram is a kilogram (or 2.204622622 lb according to my HP15c), but hang in there I've also heard of a gallon and a US Gallon!


bye
sc

 

[Ron]

The metric system was adopted by Congress as the "official" system of measurement in the United States in either 1875 or 1876 (no, that's not a typo...1800's). I suppose we are a bit slow to come around.

 

[redhead]

Lots of phun and quips with Kips sir,
But what about "slugs" to make the mix stir.
These weighty things have lost their "g's",
For the masses just to please.

 

[Sparweb]

In Canada, we have the opposite problem: Our bureau of measurement thought that our Kilogram "copies" of the French prototype were getting heavier. Now that France thinks that theirs might be getting ligher, nobody can tell which masses are going which way!



STF

 

[Binary]

I believe that the US is officially on the SI system. I remember back in grade school when it first was rolled out (Carter, I think...that's what you get with an engineer as President). We started to see traffic signs go up with km as well as miles and speedometers started showing km/h along with mph.

Certainly ANSI defines all units in terms of SI.

The big problem is that the general population sees no value in switching units and, as previously stated, many industries are completely tooled in English units so the cost of changing is drastic.

As an aide, I worked for a company developing a new inspection system and we were going to be progressive and do it all in SI. The problem is that it was hard/expensive to get material in nominal SI units so we either ended up with lots of decimal cm/mm dimensions or having to machine material that we'd have normally used with stock dims.

Also, I once worked as a machinist at HP and everything we did was in mm.

A final difficulty: I now work for a micro-company whose products are mostly sold in SI countries. However, I still dimension everything in inches because we don't have DRO's on our mills and my machinists would keel over if they had to multiply/divide by 25.4 everytime they dialed in a table movement.

From a calculation viewpoint, I can't see why anybody would want to use English units.

Finally, I learned about kips in Strength of Materials in 1986...I never saw it in any of my ME courses, books, or handbooks - seems to be a CE unit mostly.

 

[DaveVikingPE]

Way to go, redhead.

Slugs are your garden variety masses...

 

[redhead]

Nice one Dave.

Redhead

 

[curvbridger]

From my perspective, since having multiple clients "officially" switch to SI and then back again, I am tired of the debate.

I think that SI is better for ease of use and precision, but Imperial units "rule" for proportioning and layout. Hasn't anybody else muttered curses under their breath at the French when dividing something into three (equal?) parts????

Curvbridger

 

[fmathis]

And all the precision in the world doesn't mean anything if it isn't accurate!

And if an engineer doesn't have a "feel" for things like the correct order of magnitude, then it's just a matter of time before they get into trouble on some design because they were precise and wildly inaccurate.

That's one thing the slide rule forced you to do and something that calculators and software don't do. We certainly need to take advantage of technology, but at the same time we need to know what it's doing and be able to recognize when accuracy is obscured (maybe even lost) in lots of precise calculations -

 

[Focht3]

To quote the 1989 Terzaghi lecturer (an ASCE award given annually to an outstanding geotechnical engineer),

"It is better to be approximate and correct than precise and wrong."

 

[BigH]

I love threads like these. They are fun and informative - well, it shows that Engineers do have a sense of humour too!! to all!!

Two items from my ezperience with SI system. 1) I saw dock "caissons" being designed (roughly 40m long) to riduculous numbers like 41131mm. 2) I saw an article in a national engineering/construction magazine where the title was something like "304mm of sand and gravel covers site for working platform for piling contractor" "Wow", I said. I would never know that working platforms are so "precise". Did the writer get the site engineer's comment as "a foot", then used his jim-dandy calculator and change 1ft to 12 inches, then 12 inches x 2.5 to get mm but, yeah, it should be a bit higher so I'll make it 304!!? Probably. ASCE has always sugested 305 as the equiv of a foot. But, then who's foot. Like the kg losing "mass", there are a number of different definitions of "foot", too.

Focht3 on his post previous to this has it right!


to all.

 

[Rowland33]

Personaly I prefer the slug, rod, pole or perch system. But there, I admit I am somewhat conservative.