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