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Re: The 13th Ed. of AISC Manual

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On Dec 22, 2005, at 6:51 AM, Gary Hodgson & Associates wrote:

Seems that whenever they drove into port or landed in
a field and ordered a gallon of fuel, the answer was
"no kipisch".
Getting used to kilos and km and such took me about 3 weeks when I had to, once when I went to Latin America as a kid and again during our flirtation with the metric system in the 80's. Pumps were converted to dispense gasoline by the liter, speed limits started appearing in km/hr, and a few places priced goods per kilo. I think liquor stores still sell wine and hard liquor by the liter--convenient because a liter is only a bit more than a 5th of a gallon, which was the old unit of sale for booze. If I recall correctly pot was wholesaled by the kilo. That sort of conversion is trivial. You buy a set of metric wrenches and soon you're doing the corresponding math in your head. Room temperature is 20C; a cm is the width of your thumbnail and a half kg of stew beef makes a meatloaf. Easy as pie.

When we talk about metrication we really should skip the small potatoes. Conversion from feet and inches is a pain is the ass regardless of whether you convert to meters, cm or inches. It's always been an issue--ISO units or no. The ability to go from centimeters to meters mentally is another non-issue--no different than going from kips to pounds, which we've all done. Besides, that sort of conversion is done so seldom compared to the rest of the units-based arithmetic that engineers go through every day, it's no reason to go metric or stay with imperial units.

The real engineering issues are with hard metrication--fasteners, lumber, sheet metal, wire, and structural shapes, pipe and pipe fittings, just to begin. You don't just switch from imperial to metric by calling a 2.2 lb a kilo. The US has a whole infrastructure, from domestic plumbing to oil refineries and steel mills which have to be maintained and interfaced with US customary replacement parts. You can't just throw away the Palomar telescope when you run out of ASA cotter pins or precision gearing. We're going to be dual dimensioned here for another 50 years.

Like most of us, I do metric arithmetic when I have to. It's no big deal, but I'm still not convinced that the length of Henry Beauclerc's arm is any worse a standard than some Frenchman's guess at the length of the meridian through Paris. I do wish metrication proponents would do something about the infernal practice of naming derived units after dead physicists. I see many more mathematical errors from mixing Megapascals, kilograms, centimeters and dekanewtons than I ever saw converting feet and inches to inches.

 Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw/


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