Exactly why 'conversion' should really never happen, either you work in Metric or you do not. I would not call 25.4 mm a SI unit, call it what it is, an inch. 454 g in not SI it still is a pound, might as well keep it in it's original form, one lbs.
Or shall we just keep all the 1/4-20 screws, nuts, and threads but call them 6.35-20 screw, nut, and thread. Id put my money on the sun and solar energy. What a source of power! I hope we dont have to wait til oil and coal run out before we tackle that. I wish I had a few more years left. -- Thomas Edison♽☯♑ ----- Original Message ----- From: "Kilopascal" <[email protected]> To: "John M. Steele" <[email protected]>, "pat naughtin" <[email protected]> Sent: Saturday, December 11, 2010 2:31:28 PM GMT -05:00 US/Canada Eastern Subject: Re: [USMA:49154] Problems of conversion I don't think I missed the point, I think we are on two different wavelengths. From: John M. Steele Sent: Saturday, 2010-12-11 13:28 To: Kilopascal ; [email protected] Subject: Re: [USMA:49154] Problems of conversion Not at all. I believe you have entirely missed the point of sensible rounding after conversion. 1) 25.4 mm: Yes, if it is some precision fit you may need that. 2) What is the precision of the 182 lb? Probably either 83 kg or 82.6 kg is suitable rounding 3) What is the precision of the 8 miles? I would suggest 13 km or 12.9 km The examples I gave were meant to convey the type of scare tactics that appeared in the media in the '70s to turn the population against metrication. The concept of sensible rounding would have ruined the effect those opposed to metrication were attempting to accomplish. My idea is simply meant to allow those who prefer the old units to be able to continue the use of the old names comfortably and not to resist metrication because they believe they can't. Once the old devices are gone and only metric devices are available, a person can measure out in increments of 25 mm and to their satisfaction that will be an inch and increments of an inch. The fact that 300 mm will be envisioned as 12 inches by them and it won't be a true 12 inches by the old definitions would be immaterial to them. Thus if they stand on a kilogram scale that can display to 0.1 kg, and the number reads 82.4, they can double the number 82 to get 164 and be satisfied with that number as being close enough for their needs. Trying to be "precise" and having to go through the difficulty of converting 82.4 by dividing by 0.453 59..... is going to be frustrating and turn them off to metrication. If they are driving down the street and the sign shows a distance of 46 km, they can easily convert the number in their head to 23 miles by diving the kilometre distance in half if they feel more comfortable with miles. Would they be upset if the number they got wasn't even close? Most likely not. People just feel comfortable with the words. The numbers won't be a problem if they are not quite right. However, those are all rounding decisions based on the apparent precision of the input. The actual conversion factors are 25.4, 0.453 592 37, and 1.609 344 because "exact" is not a problem (to my calculator) and i don't have to worry about "good enough" and using different conversions when converting more precise data. It is rarely possible to get exactly the same precision, so choices may be a little more or a little less, and I have offered the ONLY two logical choices based on my estimate of the input precision. Further precision is "decimal dust." It is permissible (but not worth the trouble) to round the conversion factors to 1-2 guard digits beyond the precision of the input data. (It is worth it if multiplying by pencil and paper or mental arithmetic.) On the first one, if redesigning the product, I would suggest 25 mm increments. If it needs to fit with prior units, use 25.4 as conversion, grin and bear the decimals. In the world of industry, if there is really a need to make an old part from an old drawing, I can see where the exact conversion factor will need to be used, then the number can be rounded to the nearest whole number of millimetres within the range of the tolerance. A dimension of 1.5 inches +/- 1/16 inch can be made to 38 mm +/- 1.5 mm without any problem. I'm sure the Chinese don't worry about the things Americans do and thus don't have to grin and bear it. It is up to us to make it fit. They do it the simple way with rounded metric numbers even if it causes grief here. My idea was not meant for this example, but as a means to metricate society in general where exact conversions are not needed and it doesn't matter if the common citizens estimations of metric amounts in old units is even close. The point is they want to continue to speak and hear these old words and derive comfort from them and if they can't they will resist metrication. But if we make it simple for them to go back and forth, the chances of them resisting becomes slim. Does it really matter if grandma gets 454 g or 500 g when she asks for a pound? Will she really notice? I also feel that the Engineers of the '70s are long gone and the new ones that have replaced them (most likely much less) are more exposed to metric units and would be less resistant if metrication were to happen across the remnant of industry in the US. Journalists for sure would whine and stomp their feet in protest. I really don't expect my idea to catch on anytime soon but when the US is eventually forced to metricate by the economic realities, the average citizen will look for those easy conversion factors as a means to cope. From: Kilopascal <[email protected]> To: John M. Steele <[email protected]>; [email protected] Sent: Sat, December 11, 2010 1:00:26 PM Subject: Re: [USMA:49154] Problems of conversion From: John M. Steele Sent: Saturday, 2010-12-11 11:18 To: Kilopascal ; [email protected] Subject: Re: [USMA:49154] Problems of conversion This is the prime reason why metrication failed in the '70s. Engineers and journalists were running amok telling people that all metrication would do was introduce a whole series of funny numbers. This is because the old numbers would have to be preserved. So if you made things in increments of one inch, you would now have to refer to it in increments of 25.4 mm. A person who weighs 182 pounds would now weigh 82.553 811 34 kg. You drive 8 miles to work and now it will be 12.874 752 km. This scared a lot of people away from metrication and it continues to do so. No virus found in this message. Checked by AVG - www.avg.com Version: 10.0.1170 / Virus Database: 426/3309 - Release Date: 12/11/10
