[Boatanchors] SI units and the rest

[Kludge]

-----Original Message-----
From: boatanchors-bounces at mailman.qth.net
[mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of WA5CAB at cs.com
> Never mind. The speed of light in a vacuum is only approximately 1*10^8. 
> Meaning that the meter is not actually the length that it should have 
> originally been defined as. Another nail...

Basically what happened is that measurements that were picked more or less
at random (What would the meter be if that plate had been somewhere else in
Paris, for example, or had been in Antwerp?) or are the mean of a constantly
varying amount (The second is a prime example although plate tectonics
assures us that the original definition of a meter is a variable as well.)
were then glued down by whatever was convenient to make these arbitrary
measurements more or less stable.  Since the gram, hence the kilogram, is
based on an already arbitrary measure, the meter, it also is arbitrary.
This takes the whole MKS system, which is the basis for the SI, off the
market as being any better than the Imperial system.

Somewhere I remember seeing a comment about the meter being useable in
decimals while inches could only be used in fractions.  Every mechanical
drawing I've ever seen called out tolerances in decimal portions of an inch
while OTs still call the old 220-225 MC band the 1-1/4 meter band and
420-450 MC the 3/4 meter band.  There are other examples of each but those
were off the top of my head.  

Let's take a look at the foot (12".)  It's evenly dividable by 2, 3, 4, 6
and itself.  How convenient of those ignorant savage ancients to have come
up with a measure like that.  Tack three of them together and you have a
yard which has even more convenient divisors.  The yard breaks down into two
cubits, three of which ganged together make one of several standard widths
(54") of yard goods ... which are still called yard goods not meter goods.  

What does all this have to do with boatanchors?  (Magoo, listen up!)  as I
said a long while back, every radio I have pertinent to this group is marked
in MC or KC not MHz or kHz.  The chasses are laid out in inches and
fractions (or decimals, I suspect) thereof not centimeters or, worse,
millimeters.  Some fit 19" racks not 48.26 cm racks.  They use tubes the
transconductance of which are measured in mhos per the tube manuals.  BUT,
no matter what the units used, they all operate on the same basic theory
unless someone here has equipment that uses metric only and simply will not
communicate with the older and more civilized equipment.

Robert, your earlier comments on metric threads are quite accurate.  It's
kind of like using NF where any real engineer would call out NC instead.  I
have found one place metric's good and that's where I need fine adjustment
capability like my watchmaker's lathes.  Metric threads are pretty useful
then although I'm planning to convert at least one cross slide to a fine
decimal pitch.

If you want something really amusing, check out the taps watch makers use
for stems and crowns.  There are, as I recall, five sizes, #8-#11, which are
not in order of size.  Two of those sizes are .97 and 1.13 (1.16?) mm and
the other three are no better.  Further, die plates in the watch making &
repair world aren't consistent manufacturer to manufacturer and it's not
uncommon for the numbers to decrease as the size increases.  If the sizes
and numbers increase together, they may or may not correspond to actual
metric dimensions in mm and tenths.  (The watch industry has been metric for
quite a while.  More or less.)  As a result, I try to stick with one die
plate manufacturer (Martin) and keep the taps made from a particular die
plate together with it.  

So there it is, an exceptionally old and established international industry
going back centuries that has fastened itself to the metric system even in
the US and isn't internally consistent.  Funny how that works, isn't it.

Best regards,
 
Michael, WH7HG BL01xh
http://www.nationalmssociety.org/chapters/NTH/index.aspx 
http://wh7hg.blogspot.com/ 
http://kludges-other-blog.blogspot.com 
Hiki Nô!