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Need help with a rocket motor ID
On Sun, 4 Feb 2007 12:28:20 +1030, "Dave Kearton"
wrote: wrote in message .. . On Sat, 03 Feb 2007 02:47:10 GMT, "William R Thompson" wrote: I could go on, but I won't. I am the only person in the world completly happy with both systems, and who thinks they are both equally screwed up. Henry H. We all understand the difficulty of migrating from one system to another. So, don't migrate, use what suits, which is what people do, anyway. At least in the U. S. and to my observation, a lot in Europe, too. I use to be involved with some standards activity. (in ordinary language, you could have said I was a mermber of a ISO working group). Some one once told me that the nice thing about standards was that there were so many everyone could have one of their own. After a while, I concluded that the result of having more standards ws that there were more choices, because the old ones don't go away. So, I went away. Australia's change to metrics started on the 14th Feb '66 with the change to decimal currency - dollars and cents. All Aussies over 45 can still remember the TV jingle. A currency based on multiples of 10 makes more sense than one based on 12s (unless your family tree doesn't branch) The US has had decimal currancy for a while. Once that was achieved, switching to Celsius from Farneheit in the mid '70s wasn't such of a chore. The question of temperature scales (very near and dear to me, a mechanical engineer who is suppose to know about thermodynamics) is really quite seperate from the "Metric" issue. The original Metric system didn't even include temperatrue, as the concept was not really established at that time. In promoting the Centegrade scale, the proponents tried to paint Farneheit as being stupid. Who would make a scale that went from 32 to 212 for Gods sake. Well, he didn't. He had variations as the progresed in his work, but basiclly he intended to go from zero to 96 degrees. The zero he had a bit of trouble standardizing, but he intended it to be the coldest temperature that would be expernced. The 96 was suppose t be avrage human body temperature. (Why 96? A bit of numerology, apprently, but it was at least three times a power of two. A power of two is very handy when you are laying out scales. 100 has no advantage.) The fact that water freezes at about zero is handy, maybe. But you have to use negative numbers for ordinary temperatures. Not good in Farneheit's day. Water boiling is not really very relevant. Neither the freezing point or the boiling point have actually be the definitions of the scale for almost almost as long as the scale has existed. The actual definitions now are that there is only one refernce point and that is zero, absolute. The "Celsius" scale is defined in terms of the "Kelvin" or "degree" to ordinary people. The only difference in that and Farneheit now is that a Farneheit degree is 1/1.8 times the size of a Kelvin. Big deal. What is the boiling point of LOX? Who cares what the scale is? At one point, for a couple of years in the early '80s, as I recall, it was illegal to posess for sale rulers with imperial units on them. It was a ridiculous and draconian measure - but effective in getting some of the older farts to consider using metric units. Ridiculous and draconian measure, I say. The law is a fool, I say. Road signs and speeds followed next, closely followed by weights and measures in general. All up, the conversion for the general public was completed by the mid '80s, I'd imagine it was completed a lot faster in specialist industries. Specialist industries in the US converted any time they wanted to, and many, like the drug industry, have been metric forever. The US had a fit of metrication fever about the same time. It got as for as putting up a few speed limit signs. And "kilometer" posts. When people saw those, the said what the F*** is this, and when they figureed out how much money this was going to cost, most states said "Forget it." That was one of those "unfunded mandates" (that is not the right term, maybe). The Federal government mandated it, but the states were going to have to pay for it. I live near the state of Deleware. They not only have mile posts on their turnpike, they have kilo posts, too. In fact, they have HALF kilo posts! Deleware is so small you can almost see all of them at once. There are about 20 or 30 of them. (I am not really sure about the mile posts. They may have the speed limit signs in mph and kph also. They can if they want to.) One thing that I find quirky with the US metric experience is your parochial spelling of metric units. Whereas the rest of the world has adopted the original spelling of Litre, Metre etc, why does the US prefer to use the 'er spelling ? I don't really remember. That has been going on for at least 150 years. I think it has something to do with the idea that we speak, more or less, English here. And we couldn't pronounce "metre." I think that the US was the first country other than France to adopt the meter/metre. A long time before the British. We just didn't make it mandantory. A few years ago, the inch was redefined so that it is now 2.54 cm, EXACTLY. You just don't have to say it in cm. When that happened, the US shrank by 20 feet. No big deal except to those with beach property. In the metrication exercise, there was one part of it that did "catch on." That was that the BATF (Bureau of Alcohol, tobacco and Firearms) did mandate compulsory metric bottle sizes for all Alcoholic beverages. Of course, they completly screwed it up. Actually, they jsut made brand new metric sizes for the old bottle sizes. So they are metric, but wierd metric. The main size is 750 ml, which is very close to the old 4/5 US quart size (746 ml, IIRC). Not worth the effort. "Twice" that is not 1.5 l., as you might suppose, but accordign to the BATF is 1.75 l. Beats me. Just makes it hard to compare prices. The people who squeeled the loudest? The French wine industry, who not only had to change bottle sizes, they had to have STANDARD sizes. 200 years and there was not a standard size for wine bottles! The French said that was because the wine bottle was a standard in its self, the perfect size for two people to consume at a meal! Known to them, even if not to you. There are several "funny" thing about the liter/litre. It has driven the SI guys, who have a lot of time on thier hands, in to various fits of stupid. It is not as simple as I once thought, but the liter got "double defined" like a lot of other stuff in the orginal metric system. The kilometer was the orignal "base" unit, and was 1/40000 the Earths circumference, (Paris meridian, of course. ) Before they even got the survey done, the scratched lines on a bar for a "practical standard". Of course, those don't agree, and on, and on. The kilogram was based on the weight (or mass, take your pick) of 1/1000 of a cubic meter. The liter was either 1/1000 o f a cubic meter or the volume of one kilogram of water, it fluctuated. And, those were not the same, of course. Just a few years ago, the SI banned the liter entirely. No matter how you spelled I think maybe it was out for 6 years. Then they let it back in, with the cobic meter definition. The other oddity of the liter/liter is that the SI says you cannot abreviate it except as "l.". Even though that is very confusing to read often. "L." is not allowed because capitals are resereved for units that are named for people. Some genius tried to fix that by submitting a bio of Andre Litre, the great physicist who was a the son of a wine merchant. The Si woudn't by it. No sense of humor. After haveing been following measurement issues for about 100 years, I got a big surprise lately when I discovred the explanation for the size of the US gallon. I always thought it was just dumb. 231 cubic inches. I had read somewere that the people responsible for the British standars at one time just happened to have a nice cup that size. Not so. In Queen Anne's day, there were several gallons, various sizes, used for various things in various parts of Britian. So , Queen Anne, or her agents, decided to have a new standard, so that there would be one more gallon, "Queen Anne's Wine Gallon." In order to demonstrate their scientific talents they defined that as exactly the volume of a cylinder seven inches in diameter and six inches hight. They picked those numbers because using them, you get an exact whole number for the volume. 231 cubic inches! They also defined the gallon as just that, 231 cubic inches. Problem was, those are only the same on days when pi is equal to 22/7. Most days, pi is closer to 355/113/ That is a differnence of 0.1 cubic incehs, or something. OH, well. Later, after we ran them off, the British tried to catch up with the French by defining yet another gallon, This one equal in volume to 10 pounds of water, at some conditions. Well, happy metrication, and have a good 1/365.24 of a mean solar year. Henry H. |
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