[time-nuts] I now have a clock accurate to 10E-6!!!

J. L. Trantham jltran at worldnet.att.net
Tue Aug 26 04:17:34 UTC 2008


Folks,

I, too, had a great weekend.

The Thunderbolt arrived, plugged it in, and it promptly found it's self.  I
can't wait to put it to work.  Thanks to all (TAPR, time-nuts, etc.) for
their effort on my behalf.

My father (now deceased) collected and repaired clocks for 60 years leaving
my brother and I some unique pieces.  

My prize is a 'FASHION' clock made by the Southern Calendar Clock Company,
St. Louis, Mo, patented March 18, 1879.

It is a two faced clock with two about ten inch diameter faces, one on top
and one on the bottom.  The top face displays hours, minutes and seconds,
all with 'hands'.  The bottom face displays the day of the month, 1 through
31, with a hand that points to the periphery and the month and day of the
week in two rectangular openings on either side of the center of the dial.

The unique feature is that it keeps long months, short months, and every 4
years, gives February 29 days.  It is all mechanical, has two 'springs' for
power, one for time and the other to strike the hour of the day.  It runs
for a week on a single 'wind' and keeps reasonable time.  Not to 1 in 10E6
though.

Its shortcomings are leap seconds and Daylight Savings Time.  Fully manual
on those I'm afraid.

It is completely mechanical with no electric parts.  None the less, quite a
piece of work for the 1800's.

Thanks again to all for all the work that resulted in the Thunderbolt.  I am
sure I will have questions in the future but none tonight.

Joe

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Jim Palfreyman
Sent: Monday, August 25, 2008 2:40 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] I now have a clock accurate to 10E-6!!!

Hi Folks,

Well I've had the best weekend since I've just acquired a pendulum clock
that used to be a telecommunication time standard in the 50s. It is a German
made Siemens pendulum master clock that is about 150cm high and has a
full-length seconds pendulum which is about a metre long. It is powered by
48V to automatically wind the weight up and will maintain time for about 8
hours without power.

The pendulum has an adjustment to raise and lower the 7.5kg weight to
calibrate the clock. One full turn of this knob will advance or retard the
clock by 40 seconds per day. It is graduated into 100 divisions enabling you
to adjust it within 0.4 seconds per day. Half way up the pendulum is a
little tray where you can deposit small weights for your final adjustment
(and most importantly without stopping the pendulum!)

Even though it's a master clock it is also designed to be synchronised to
another master clock and so there is an armature on the pendulum that can be
steered by a magnetic coil. I have no documentation on this bit, but when I
figure it out I naturally shall be driving it from a 1PPS reference. (See
photo.)

There are numerous contacts that are designed to open/shut at various times
including every second, every thirty seconds and minute. The photo shows the
mechanism behind the clock face.

By connecting the seconds contact up to my 5370B I tuned it quite quickly to
be accurate to about a second a day. Which is about 10 microseconds per
pendulum swing! I'm impressed a tick tock clock can do that. (Although it
pales into insignificance compared to what Harrison accomplished.)

It is beautifully constructed and now one of my prized possessions!

(I'll put some more photos in another post.)

Regards,

Jim





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