[time-nuts] Shortt Clock Recent Measurements

[Brian, WA1ZMS]

FWIW....

Let me just second Tom's last comment:
"Some of you readers might wonder why in this GPS age, two time nuts, each
with plenty of atomic clocks at home, would be talking about vintage
pendulum clocks. It turns out that pendulum clocks are still extremely
interesting timekeepers, from an experimental, scientific, and historical
perspective."

About 2 years ago the Time Nut in me became very interested in pendulum
clocks that were made in my home town in Vermont going back as far as 1797.
I now own several and a project is to take one of them that has a dead-beat
escapement (often noted for its better "accuracy" display of seconds with an
10 inch sweep hand in its day) into the 21st century with frequency locking
of the pendulum to the 1PPS from one of my GPS receivers.

Also....An antique clock dealer who is friend of mine was well pleased with
TVB's talk at a recent time conference on the West Coast.  So it is a mix of
old and new for me at this point.   Apologies if this goes OT.

Regards,
-Brian, WA1ZMS/4


-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Tom Van Baak
Sent: Tuesday, December 10, 2013 5:48 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Shortt Clock Recent Measurements

> The Wiki page for the Shortt pendulum clock has a "Recent Measurements"
(1984)  paragraph that's in error.
> http://en.wikipedia.org/wiki/Shortt-Synchronome_clock#Recent_accuracy_
> measurement
> 
> While it's probably true that the clock is stable to 200 uS per day 
> (i.e. 2E-9) I believe Alfred Loomis discovered the effect of the moon on
this clock a long time ago.

Hi Brooke,

The wiki page is correct. The heading is "Recent Measurements" and Pierre
Boucheron's 1984 effort certainly qualifies. Note the wiki doesn't claim
Boucheron was the first. In fact, even 30 years old, it is still the most
recent, and the only Shortt experiment for which we have raw data. See
http://leapsecond.com/pend/shortt/ for details.

One could try claiming that Loomis was the first to make detailed
measurements of a Shortt, but it would take some digging to prove he was
"first" and not just "one of the first". I mean, if you look at the list of
who received the one hundred Shortt's that were manufactured, many
laboratories had more than one, not to mention the ones that William Shortt
himself owned at the factory. Certainly there was a lot of time measurement
going on in the 20's and 30's. It would take a lot of work to uncover what
was known by whom and when. Or who published first or not.

I think Loomis took it a wonderful extreme with his spark chronograph and
quartz oscillator via telephone time transfer setup. And that be bought
three clocks at once is classic and inspiring to any time nut! So I agree,
Loomis deserves mention on the Shortt wiki page.

Unrelated to gravity and tides, is the role that vacuum pendulum and
ovenized quartz clocks had in confirming that earth rotation was itself
irregular at the millisecond level. Credit for that usually goes to Scheibe
and Adelsberger in the late 30's, not Shortt or Loomis. And that of course
blends into the story of the leap second...

See my scan/OCR historical pendulum collection:
http://leapsecond.com/pend/pdf/ And my own precision pendulum-nut articles:
http://leapsecond.com/hsn2006/

Some of you readers might wonder why in this GPS age, two time nuts, each
with plenty of atomic clocks at home, would be talking about vintage
pendulum clocks. It turns out that pendulum clocks are still extremely
interesting timekeepers, from an experimental, scientific, and historical
perspective.

/tvb


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