[time-nuts] Shortt Clock Recent Measurements

[Don Latham]

Brian and Tom: I second as well. It's important to be aware of the past.
Somewhere around here is a 4 ft length of Invar, 1/2 in. diameter. It
was supposed to be a pendulum rod. However, I did read that Invar
displays rearrangement noise of some kind. Kinda like the jumps in a
quartz element?
I think if I were to start designing, I'd use a quartz rod instead,
coefficient of thermal expansion is smaller. I'll bet that a large
majority of time-nuts have at least read about pendulum timekeepers...
The Smithsonian has a Schortt clock, as well as a couple of others. I am
sad that they aren't running.
Don

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
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>


-- 
"The power of accurate observation is commonly called cynicism by those
who have not got it."
 -George Bernard Shaw


Dr. Don Latham AJ7LL
Six Mile Systems LLC
17850 Six Mile Road
POB 134
Huson, MT, 59846
VOX 406-626-4304
Skype: buffler2
www.lightningforensics.com
www.sixmilesystems.com