Mine is bigger than yours: Shop A/C notes

In the shop I like the daylight tubes.

I was even going to quote it to sound knowledgeable. :)

Actually, tho, it does make some chemical sense. Crystal structures do change without effectively altering the base atom (ergo heat treating, diamonds, etc), and they do so with subtle shifts in orbital structure, more like orbital angle changes, rather than true quantum leaps'n'shit. This orbital bending sort of "precedes" the orbital changes you see in true covalent bonding.... uh, Bottle....

entropic3.14decay at optonline2.718 dot net; remove pi and e to reply--ie, all d'numbuhs

Sorta what I thought. Negotiating temperature? Please, gimme a break. More fukn PhDs tryna justify dey salary.

Proly 68 F was some sort of mean of all the industrial climates, so's shops could basically make shit in the open air. And, I think it's a little above the mean, reflecting the fact that back then, you didn't have A/C, so you could heat up a shop easier than you could cool it down.

Or mebbe it reflected an avg of climates where machined stuff was likely to be used. Barring cylinder liners, etc. :)

Musta been a long negotiation. :)

Isnt it 300 kelvin on the nose?

"Proctologically Violated©®" wrote in message news:k21ui.351$ snipped-for-privacy@newsfe12.lga...

I believe it had more to do with maintainable temperatures in an already-standardized industrial process. For much longer before the measurements standards were promulgated - way, WAY before 1931 - the standard temperature for photographic processing was 20C.

Cellars are reasonably easy places to light-proof, and where many darkrooms exist even today. They run cooler than the superstructures of their buildings.

LLoyd

Brent:

Close but not quite. 68 degrees Fahrenheit = 293.15 kelvin

PV:

Did you read the full article?

No, I figgered Cliff read it right, and I then concurred. :)

Lloyd has it right, I think, and since I was more or less saying what Lloyd said, iffin yer not disputing him, then you shouldn't be disputing me. But mebbe it's just reflex... :)

I mean, really, what else could the logic be? Pick a temp that's not too expensive to maintain, adjust it by whatever ergonometrics are appropriate, and bing, you got yer standard.

The argering/negotiating likely comes from the Texans vs. Minnesotians, so you figgered they split the difference, mebbe weighted for population/number of machine shops, etc.

Well, mebbe not quite an equal split, since Texans have all those fukn guns.

PV:

Heh welll, I'd be REAL careful who you let do your thinking for you. You don't even know if HE read the whole article. He's stated before that he has an aversion to PDF files.

I don't know Lloyd, but his comments seemed to come from a photographic processing perspective. But still, Lloyd didn't claim that the article didn't explain how or why 20C was chosen.

Wouldn't it be more informative to read the article yourself so you don't have to speculate, or depend on the interpretations of others, about what was said?

Well, Since YOU read the article, mebbe you could just tell us/me!!!!!

AND, If you read Lloyd's post *very very carefully*, you'll see he made reference to "maintainable temperatures".

That WAS the gist of the article, wadnit? Oh, let me guess, yer gonna make *me* read the article....

LOL

Easy,

They put seven engineers (like Cliff) on a committee, they argued for twenty years, six of them died, number six died on April 15, 1931.

Tom

Tom:

Well there ya go. You can always be counted on to drill down to the bedrock of a matter. At 20C, of course.

LOL LMAO ROTFLMAO

and that's a LOT of rollin' and laughin'

PV:

No, I'm not going to make you read the article. It was just a bit of history that I thought would be interesting to those that like that sort of thing. The article is long and not of much use in a practical sense. Other than you realize that inspections are normally done at 68 degrees, and I'm sure you understand that now.

So what WERE the reasons for 68 F??????

Man, my nuts were receding when the shop was 70 F! 'course, in Minnesota, 68 F is a heat wave....

How come, then, is the Standard Temp. 59 degrees F or 15 deg. C. ? One group of Scientists not talking to the other group of engineers?

Or did their dart boards have different numbers on it?

:)

John

"Proctologically Violated©®" wrote:

PV:

=============================================================

1. Reference Temperature for IndustrialMeasurementsThis choice did, however, present a problem for indus-trial measurements which are almost never made at sucha low temperature. The basic problem is that if the stan-dard reference temperature is 0 °C, two mating parts ofdifferent materials, say steel and brass, will actually betheir nominal size at 0 °C. If the parts are, instead,assembled at 20 °C, the parts will grow by their coeffi-cients of thermal expansion (CTEs) times the tempera-ture difference from the reference temperature. Since theCTE of steel is about 12 × 10?6/°C and brass is about24 × 10?6/°C, the brass part will expand much more thanthe steel part and assembly may not be possible. Sinceparts are assembled, on average, at around room temper-ature it would seem practical to have the part lengthmeasurement refer to the assembly temperature as close-ly as possible.The obvious way to overcome this problem would beto take some temperature near room temperature, say20 °C, as the reference temperature for industrial meas-urements and then make a reference bar which wouldhave the same length at 20 °C as the InternationalPrototype Meter has at 0 °C. To accomplish this we needto know the thermal expansion of either the InternationalPrototype Meter or the new standard between 0 °C and20 °C. To use the International Proto-type Meter was nota reasonable choice because to preserve its length it wasused as little as possible, as shown in the BIPM responseto Dr. Stratton of the Bureau of Standards. Dr. Strattonwrote to ask if the U.S. could send its meter to BIPMfor comparison to the International Prototype Meter.Dr. Guillaume, Director of BIPM wrote back (Bureautranslation) [2]

But comparisons cannot be made with Inter-national Prototype. The International PrototypeMeter as well as the kilogram, and their certifi-cates, are shut up in a depository, which is underthe charge of the Inter-national Committee, andclosed by three locks, one key of which is in myhands, the second is deposited in the Archives ofFrance, and the third is in possession of thePresident of the Committee, Prof. Foerster atBerlin. The depository which is a deep cave underour laboratory, is inaccessible to me as well as toall the world. It cannot be opened and much morethe prototype can not be taken out except by adecision of the Committee in session.Thus, the CTE studies had to be made on the replicameters made for routine work at BIPM and for themembers of the Commission. These studies were per-formed, off and on, for the next 30 years at BIPM aswell as other countries National Metrology Institutes(NMIs). As late as the 7th International Conference in1927 there were still major publications on this subject.The work was slow for both technical and bureaucraticreasons. The thermal expansion coefficient was neededto very high accuracy from the melting point of waterup to 20 °C, which is a difficult task made more diffi-cult because at a time the temperature scale itself wasunder serious study. Also, since the InternationalPrototype is not generally available, the studies focusedon the 29 nearly identical copies that were made at thesame time out of the same batch of the Platinum-Iridium alloy. These copies were distributed to themembers of the Convention of the Meter; meter bar No.27 was the legal standard for length in the United Statesuntil the redefinition in terms of the wavelength of lightin 1960. Simply getting the bars back to BIPM formeasurements was time consuming. Efforts began in1921 and continued for 15 years [3].From a modern perspective, the basic question is thatof uncertainty. Since the meter was defined as the dis-tance between two lines of the International Prototypewhen held at 0 °C, a second meter bar, even if com-pared directly to the International Prototype at 0 °C willhave a larger uncertainty when used at 20 °C: larger bythe uncertainty of the change in the length of the barwhen heated. The size of the uncertainty depends on the temperature measurement. For ordinary gagesmeasured in a lab environment, the knowledge of theCTE of the gage and the accuracy of the thermometerswould add considerable uncertainty to the gage at20 °C =============================================================

And it goes on and on from there.

John:

I assume you meant to say *isn't*, instead of "is", correct?

You want me to summarize 23 pages of PDF file into one sentence? No Way, if I suffered through reading the whole thing, so can you. LOL