Been reading and not getting tangled up. Agree that it seems like a reasonable subject. Though I have no pendulum clocks. I was struck by their beauty up in Canada at TVAs television studios. On the wall was this amazing clock on a huge slab of metal. All it needed was a battery. Other then that it was clean and gently pushing the pendulum seemed to make it work. It was to go into there historical museum someday. I always thought invar was the magic metal. Quartz rod? You can get those at some reasonable cost? What I am curious about is there a wear mechanism on these really good clocks. Does the pendulum just swing on a bending piece of metal or on a bearing?
To the technical side isn't it sort of cheating the wonder of the clock using gps correction. I mean at that point there is no point. I am asking these questions because its sort of the thing I would not mind crafting. Regards Paul. WB8TSL On Tue, Dec 10, 2013 at 7:15 PM, Don Latham <[email protected]> wrote: > 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. > _______________________________________________ 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.
