User talk:Bobblewik/units of mass

Mass versus weight in metric

I hope I've done the right thing, I've updated the standard for thrust/weight ratio for metric.

Weight in metric is correctly measured in *newtons*. Kilograms are a unit of *mass*. Hence thrust/weight ratio is a dimensionless constant that (fortunately enough) is numerically equal to the imperial number. This seems to be the way that NASA does it, as best I can tell, and it's the most logically correct. There's probably manufacturers out there that do the wrong thing... but they do the wrong thing. (by User:Wolfkeeper)

You've "updated" what, where?

Get real. See the example I just posted shortly before you posted here on Talk:SABRE, and the rest of the discussion there:

Here's a specific example which explains it about as clearly as it possibly can. This is from NASA's web page titled The Apollo Spacecraft - A Chronology. Vol. I, Part 3 (1962 1st quarter) at http://www.hq.nasa.gov/office/pao/History/SP-4009/v1p3b.htm

"Agreement was also reached at this meeting on a vacuum thrust level of 20,000 pounds for the engine. This would maintain a thrust-to-weight ratio of 0.4 and allow a considerable increase in the lunar liftoff weight of the spacecraft."

Gene Nygaard 08:46, 21 Mar 2005 (UTC)

units of mass in weapon ratings

Hi - just one detail. I think it's no use to write: "32 pounder (15 kg) cannons". As for "continental" Europe, pounds are understood for old cannons, but I've never encountered kg in this manner. An equivalent might be calibre in mm, if it is known. Pibwl 15:22, 31 Dec 2004 (UTC)

I did think about whether it is possible to provide an equivalent in mm, but I am not able to do the conversion myself. I have not come across the phrase '15 kilogrammer' and I know that pounds (of various weight values) were in widespread use around the world. But units used in the past are not understood today. A cannon is described as x pounder on the basis that the projectile weighs x pounds, therefore a conversion from x pounds to y kg is reasonable. I can't see any downside to providing the information for the benefit of metric readers. Thanks for the feedback. Bobblewik (talk) 13:14, 1 Jan 2005 (UTC)

One problem is that, especially in the 20th century, "pounds" as a measure of gun caliber bears only a rough approximation to the actual projectile weight. --Carnildo 22:22, 18 Jan 2005 (UTC)

That probably because it actually is a measurement of bore. Is it the inverse of gauge in shotguns, so if a 12 gauge shotgun is the diameter of a lead (ρ = 11.34 g/cm³) ball of 12 lb^-1, a "6-pounder" would have a diameter ³√72 = 4.1 times the diameter of a 12 gauge shotgun (which is about 0.73 in, or 18.5 mm)? And a 15-pounder a bore ³√180 = 5.65 times that of a 12 gauge shotgun, or the same as a 105 mm howitzer? Gene Nygaard 00:10, 19 Jan 2005 (UTC)

Looks like I guessed wrong, on the details at least, with most 15-pounders I can find being 3 inches in bore. Gene Nygaard 09:42, 20 Jan 2005 (UTC)

Conversion of British "n-pounder" guns

The appropriate conversion is not from lbs to kilograms but to the equivalent calibre eg 2- pounder is 40 mm. Except when actually talking about the shell weight. GraemeLeggett 11:09, 10 Jun 2005 (UTC)

The issue has been mentioned before. See User_talk:Bobblewik#units_of_mass_in_weapon_ratings. I was under the impression that 'pounder' is a reference to the weight of the projectile. Projectile weight and gun calibre are different things, of course. It appears to me that some descriptions involve weight units and some descriptions involve length units. I know how to convert weight (lb -> kg) and length (in -> mm), so the conversion task is relatively simple.

I have supplemented non-metric weight terms with metric weight terms. I have supplemented non-metric calibre terms with metric calibre terms. If the pound is not a unit of weight and is a unit of calibre, then that is surprising but nevertheless fine by me. All I need to know is how to do the conversion from pounds to millimetres.

I am interested in community views on this. Bobblewik (talk) 11:46, 10 Jun 2005 (UTC)

You have to know what the actual calibre of the weapon is (which will be in inches), and work it out, or follow the links back to the gun articles and look for it there. The trouble comes with the changeover from spherical shot to pointed shells, before then poundage can be worked out to calibre, afterwards - well its more complex. The simple answer is to ignore it and leave it too the article writers/readers who generally know the conversions and get around to it in time. GraemeLeggett 12:30, 10 Jun 2005 (UTC)

Units of mass in precious stones

Bobblewik,

Thanks for your help adding unit conversions to my series of articles on diamond and diamond mines. However, a couple minor quibbles -- first, quoting value as "per carat" is industry standard, and is the preferable phrase to "per weight" as you changed it to. Second, I believe that it is preferable, or at least neutral, in the MOS to write out "percent" rather than use the % symbol. I wanted to check with you though before I changed things back. What do you think?

Thanks, - Bryan is Bantman 06:38, May 14, 2005 (UTC)

You are welcome and thanks for the positive feedback. As far as 'per carat' is concerned, I was not entirely sure about what to do. I fully understand that you might think it looks suboptimal. However, I have difficulty in adding gram values and then suggesting that the price per unit weight has increased in a way that excludes grams. If the per carat value has changed, then the per gram value must also change. I did not want to say the 'per carat (gram) value'. I would welcome further input from yourself and anyone else on the topic. Perhaps it should be discussed in a general talk page.

As far as 'percent' versus '%' is concerned, the manual of style recommends matching a symbolic number (e.g. '7') to a percentage symbol i.e. '%'. This very issue was discussed in the relevant talk page quite recently. However, if you want to change that, it is fine by me.

I would also welcome any addition of metric units that you might wish to do in future. Bobblewik (talk) 20:04, 14 May 2005 (UTC)[reply]

I will happily defer to you on the percent / % issue; it sounds like you are much more aware of goings on than I! :) Regarding the gram / carat issue, I recognize your issues, but I think that in this case we should use the industry standard. For whatever reason, trade in gemstones has never moved away from use of carat as the fundamental unit of trade. Everybody -- miners, distributers, retailers, the general public -- uses carat to refer to the size and/or amount of diamonds and other gemstones. Seeing as it has a defined value of exactly 0.2 grams, I think that it is not unlike other quasi-SI units which are preferred in various applications for historical or other reasons. Forcing in the use of gram is probably inappropriate in this case, as nobody uses it and it muddles the data rather than clarifying it -- which is afterall the intent of both standardized units and encyclopedias. "Per weight" is definitely the worst of the three options, as it fails to indicate the scale (by way of denoting the order of magnitude via unit selected) or the industry standard, and does not parallel the "$xx per carat" data found in certain articles (see for example Argyle diamond mine).

I posted this here because I couldn't decide what talk page to put it on! :) If you want to move it go ahead and just let me know. Thanks. - Bryan is Bantman 17:47, May 17, 2005 (UTC)

I can't think of a page where this discussion would be suitable, but perhaps we will come up with one. I would be interested in the opinions of others.

For myself, I certainly think it is useful to know the weight in grams. When I first discovered that the carat was simply 200 mg, I was astonished that it was so simple a conversion. I was not even aware that it was a unit of weight previously, it could have been volume for all I know. The fact that a diamond ring has 'X carat gold' and 'Y carat diamonds' may have added to further to my confusion.

Perhaps like many Wikipedia users, I am fortunate in being surrounded by meaningful gram values. If you are not, then I can understand that they do not add value for you.

I fully accept your statement that those in the gem industry use 'carat' rather than 'gram'. If Wikipedia were a gem specialist publication, then the effort of conversion would be less beneficial. However, Wikipedia is also a reference for those that know nothing of the gem industry. As an example, the Diamond article could simply say that the annual production of diamonds is "130 million carats". However, an editor added "(26,000 kg)". The description in kg is an improvement for me and I believe for others too. I have similar reasoning for descriptions of the weight of individual gems, the production of individual mines and the pricing. Other editors have added SI equivalents to carat values, so I am not alone in thinking that the effort is worthwhile.

As far as your dislike of 'per weight' is concerned, I am sympathetic. I am not so keen on it myself. However, I can't see how a phrase 'per carat' can be used with a gram value. This seems to me to be a solvable point of detail that we can work on. I would be happy to have your further views and those of others. Thanks for discussing it some more. Bobblewik (talk) 21:27, 17 May 2005 (UTC)[reply]

I'm sure we can figure something out; it's always nice to find another person interested in amicably resolving sticky issues. I agree that the conversion you cited (130 m carats = 26,000 kg) is useful, informative, and adds to the article. I think the only thing I am stuck on is the "per weight" phrase. The analogy I have come up with at the moment, under duress -- :) -- is barrels of oil. We know that a barrel of oil is 55 gallons, or about 208 liters, and when saying "company such-and-such produces xx million barrels per year (xxx million liters)", that conversion is appropriate. However, when we talk about the current price of oil on the commodities market, we should quote it in the units it is traded in - $50 USD per barrel is appropriate; $0.95 USD per gallon is meaningless because you can't trade oil as a commodity per gallon. Thus, in my opinion it is more appropriate to say "light sweet crude trades at higher prices per barrel than heavy crude", but not "light sweet crude trades at higher prices per liter (or gallon) than heavy crude". Similarly, gemstones are traded on a per carat basis; the fact that carats have an SI equivalent is irrelevant when referencing the price or value of production in the units used to trade a commodity. Bushels of wheat or pork bellies are other examples, I suppose. So I am comfortable with all your changes (which as paranthetical additions are perfect) except the per-weight issue. - Bryan is Bantman 22:27, May 17, 2005 (UTC)

Hmm. Our mutual discomfort zone is the phrase 'price per weight'. I am happy to park that problem for now. If I understand you correctly, you are suggesting that $100 per carat is better without the addition of ($500/g). I don't agree with you on that but in the interests of cooperation, I am also willing to park it if you want me to.

Incidentally, a barrel of oil is not 55 gallons. It is 42 US liquid gallons or 35 imperial gallons. So instead of 208 litres, it is only 159. I think it would be a good to have a coherent set of units to compare price per unit volume for raw material and finished product. It merely happens to be difficult and obscure with legacy units. Bobblewik (talk) 23:22, 17 May 2005 (UTC)[reply]

I don't mind adding "($500/g)" to "$100 per carat" at all. What I want to do is maintain recognition that diamonds and other gemstones are traded by carat. This is achieved by keeping phrases such as "high value per carat" rather than replacing with "high value per weight". In general, I think it is helpful to add conversions when actual values are used; however when speaking generally, conversions are messier and/or impossible, and in those cases I think the "standard" (i.e. most common, or industry-accepted, or trade-recognized) unit is best. Once we make it clear that the anachronistic unit in common use has a defined SI equivalency, I think it's best to stick with common use as that's what is most informative. - Bryan is Bantman 00:01, May 19, 2005 (UTC)

Looks to me like one problem the both of you are having is the use of a clumsy construction, not normal English. While we would indeed say "per carat" or "per gram" when talking about a specific unit of measure, the normal terminology when talking about the quantity being measured is value "by weight" and not "per weight". (The clumsier "per weight unit" or "per unit of weight" would be poor alternatives.)

Using a unit of measure to stand for the quantity being measured is almost always a bad idea. What you are talking about in those general statements is not unit-dependent. This is something dealt with specifically in some style guides, though I cannot put my finger on one right now.

I think the fact that people do not understand carats (as demonstrated by Bobblewik's testimony about his own experience), but feel comfortable with the word carat, sits well with thie industry. They don't care if people understand it. But adding the conversions does make it very understandable. [User:Bantman|Bryan is Bantman]], you inadvertently made that point abundantly clear by your comfort level with the name barrel, combined with your total misunderstanding of what that barrel is in real money, i.e. in units that people might use outside the esoteric jargon of a particular industry.

The interdisciplinary nature of the SI is just as important as it being the International System of Units. There is no good reason why anybody should have to learn a new system of units in order to understand the measurements of any field of activity. Gene Nygaard 00:50, 19 May 2005 (UTC)[reply]