[R-390] Slide rule calculations

[Gregory W.Moore]

GA, All,

The discussion concerning the good old slipstick, along with one's book
of logs and trig functions brought back some great memories.  Bob, you
are dead right that the larger the sliderule, the greater the order of
magnitude while solving equations.

This being said, and having learned my Engineering on a Pickett 12" rule
and having solved many, many equations with same, including beating the
pants off a guy using one of the early scientific calculators, I can
truly say that you can get 5 places of accuracy if you look closely
enough.  Also, with the advent of calculators we have become "place
obsessed" running equations far beyond what is necessary to satisfactory
to solve any equation. If it was good enough for aircraft, well, I don't
think anyone would have any complaints.  The other discussion was
concerning the great E-6-B "computer", which actually was a circular
slide rule used for aviation calculations such as Ground Speed, True Air
Speed, correction for altitude and compressibility, and the reverse held
a very neat device for figuring the wind triangle. I used one for 43
years until I lost my medical, and never had a bit of trouble with same.
I blew some coin of the realm on an electronic E-6-B, and frankly,
hitting the small keys while holding the yoke with your knees was not a
particularly easy, or pleasant experience (flying with no autopilot)..

While I agree that any electronic calculator will give you many, many
places of accuracy, it really is meaningless,for one reaches a point
where the precision just isn't necessary, and confusing to boot.

Give me a good slide rule or E-6-B (or one of it's many cousins) and I
will calculate with no problem at all.. using a calculator, especially
the one that comes up on your computer screen is frankly, a pain in the
butt..

just my .02 on the subject of slipsticks and circular rules,

73 de Greg "GW" Moore

w9ya wrote:
> Hey Bill and the gang;
> 
> Well while the way most people are taught to use a slide rule you can go
> between 3 to 4 places of accuracy; There IS a way to increase that at least
> one order of magnitude for most calculations !! And a larger slide rule also
> helps.
> 
> Further this problem can be calculated without regard to the first several
> levels of magnitude anyways.
> 
> Bob
> w9ya
> 
> On Thu, Dec 4, 2008 at 6:19 PM, Bill Hawkins <bill at iaxs.net> wrote:
> 
>> George,
>>
>> You can't do it with a slide rule, because you can't read it to one
>> part in a thousand. For ten times the cost, you might be able to
>> read it to one part in 10,000 with a magnifier.
>>
>> Four beats per second means your generator is 4 Hz either above or
>> below WWV's 2.5 MHz. On the plus side, that's 2.500004. Multiply
>> that by 4 and get 10.000016 MHz, or 1.6 parts in 10 to the sixth
>> power (which is 1 millionth or 1E-6, where E is exponent of ten).
>> You'll get the same answer if you divide 4 by 2.5, but it'll take
>> longer.
>>
>> So your accuracy is 1.6E-6 or 1.6E-4 percent, or 0.00016%. This is
>> very good for something set by a dial. But you get 2.5000005 or
>> 2.5E-7 when you move 10 Hz on the dial. You were only off 4 Hz
>> before, so I'd guess that you went from being below to being above,
>> and made a tiny error in setting the dial.
>>
>> WWV on a bad propagation day is good to 1E-7.
>>
>> Was that what you're looking for?
>>
>> Bill Hawkins
>>
>>
>> -----Original Message-----
>> From: george stringe
>> Sent: Thursday, December 04, 2008 12:47 PM
>>
>> OK so here is a test for all the slide rule junkies: I have my Wavetek
>> sig gen all warmed up and my BA Hallicrafter SX-71 tuned to WWV at
>> 2.5Mhz.
>> When the generator is set at  2.50000 Mhz, I am guessing that I get 4
>> beats/second,  if I set the gen at 2.50001, I get 2 seconds per beat.
>> So, what is my generator accuracy percentage?
>>
>>
>> _____________________________________________________________
>> R-390 mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/r-390
>> Help: http://mailman.qth.net/faq.htm
>> Post: mailto:R-390 at mailman.qth.net
>> Unsubscribe: http://mailman.qth.net/mailman/options/r-390
>>
> 
> 
> ------------------------------------------------------------------------
> 
> _____________________________________________________________
> R-390 mailing list
> Home: http://mailman.qth.net/mailman/listinfo/r-390
> Help: http://mailman.qth.net/faq.htm
> Post: mailto:R-390 at mailman.qth.net
> Unsubscribe: http://mailman.qth.net/mailman/options/r-390