Chronometry: Kuhn Selectable Break Ckt (M21)

Discussion in 'Chronometers' started by DeweyC, Nov 16, 2017.

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  1. DeweyC

    DeweyC Registered User
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    A customer is sending me an M21 fitted with the Kuhn selectable break circuit. Kuhn was a watchmaker here in Baltimore and I personally have been looking for one for years. He did very nice work. I saw 4 in one place but they were sold with the estate lot to a single buyer.

    Anyway, he is sending it to me for service and I told him I would do some research on the patent. From what I know, there are fewer than a dozen known. These were all done post WWII production prior to the 1960s. Now you know all I know. I think U.S. Coast and Geodetic Survey commissioned them. This was after market work and there would be no Hamilton records on them that I know.

    Does anyone have any info on this? Thanks.
     
  2. Tom McIntyre

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    My son in law has one of the dual break instruments that were made for Cal Tech's seismic work. Those are mentioned in Whitney's book on the Marine Chronometer. Do you know the serial number of the one coming to you? (Or the ones in the prior sale?) Are the numbers clustered? i.e. were they purchased as a lot from Hamilton?
     
  3. DeweyC

    DeweyC Registered User
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    Tom.,

    To my understanding they were all after the late 1940s so not in the blocks reserved for USN or US Maritime (many people feel to realize there is about a 1200 unit blank between the USN and those reserved for Maritime Commission).

    The 4 I saw were in a the estate of a local talented watchmaker who used to work at the Navy Research Lab. I suspected he got them for a surplus sale or otherwise. Do not know the numbers but the execution is fantastic.

    I need to the archive inventory for the Hamilton stuff and I guess the patent database is offline and I have to up?
     
  4. Tom McIntyre

    Tom McIntyre Technical Admin
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    The patent database is second in priority to getting this site cleaned up. I lost the machine it was working from and that software package was obsolete, so it is not reasonable to reload it. The database is intact but there is no front end right now.

    Google patents works fairly well for name lookups of patents. Once you have the patent number, either Google or the US Patent Office will provide the images.
     
  5. Paul Regan

    Paul Regan Registered User
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    The one that was on Ebay yesterday morning was 2E12157. That could be the one. I left my computer screen a short while and when I came back to buy it it was GONE! It also was Sidereal.
    Paul
     
  6. DeweyC

    DeweyC Registered User
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    Yes, that seems to be where he got it. When I get it I will upload some pics. Very annoyed at the price he paid. The serial number agrees with my understanding of when and how these were made. Did find a blurb in the 1950 JCK about the patent.
     
  7. Paul Regan

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    I'm equally annoyed Dewey however at least I had a chance but decided a bathroom break was a better move at the time. Bad move!
     
  8. burt

    burt Registered User
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    #8 burt, Dec 4, 2017
    Last edited: Dec 4, 2017
    Ok.....I looked at this post today and here is the information you have been searching. If Paul is correct 2E12157 and from the Hamilton ledgers was finished in April 1952 with no other information listed . The inventor of the Break Circuit device,you are discussing, is J.A. Kuhn Sr., he applied for the patent on Oct. 4,1950 and it was granted Sept. 28,1954 #US2690482A I believe this is the only patent he ever applied for so this is probably correct.

    Hope this helps out?

    US2690482-0.png US2690482-1 (1).png US2690482-2 (1).png
     
  9. burt

    burt Registered User
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    #9 burt, Dec 4, 2017
    Last edited: Dec 4, 2017
    According to Whitney,Hamilton used their own system for the break circuit design of their chronometers. They were referred to as their Model 21BC but were not marked as such. I'm guessing on the instruments and maybe even in the ledgers? That would be a bummer for researchers! The movement is the same as the regular 21 but has 15 jewels the extra being the one on the break circuit detent. In stead of designing a different detent, Hamilton utilized the beryllium copper spring detent,which was the same type used on their regular later built chronometers.

    As of December 13,1956 Hamilton completed 201 single break circuit and 5 selective (dual) break circuit chronometers. The single B.C. models were put into production in 1945 and the selective (dual) in 1955.

    I don't think Hamilton patented their design. Negus were the first in America to build a break circuit chronometer in 1874. Kulberg designed one prior to 1890 and Mercer in 1905.
     
  10. burt

    burt Registered User
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    #10 burt, Dec 5, 2017
    Last edited: Dec 5, 2017
    So who built the first break circuit chronometer? That was debated as early as 1887. I found in the publication "The Observatory" (volume 10 page 427) a monthly journal of astronomy, A Professor A.Young Phd.,R.A.S. who credits Parkinson and Frodsham in 1869 with the first. In the next issue that statement was challenged by a Astronomer from the Melbourne Observatory a R.L.J. Ellery who credits the Robert Molyneaux firm of building #1438 in 1860. Either way it was not Negus who probably was, as I said in my last post,the first American company.

    I found out that the Molyneaux #1438 was used on a expedition of the December 6,1882 transit of Venus as was my own Negus #1273. Not together but in separate locations.These expeditions and their timed transits were critical in determining the distance from the earth to the sun or the "Astronomical Unit".The break circuit chronometer was first developed for Astronomers and then its use was adapted in other areas.

    Just want to make clear a point about the Hamilton selective break circuit chronometer. This instrument was capable of any combination of teeth omitted not just two.For example a chronometer could be modified to break circuit ever 10 seconds or any combination up to 60 or whatever was required.
     
  11. DeweyC

    DeweyC Registered User
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    Thanks Burt. Kuhn's patent was discussed in an issue of JCK in which they said it was evaluated by the USGS. Given I have seen four, and this may be the 5th, I would not be surprised if Hamilton used Kuhn's patent for the California Geophysical Institute. I will try to get up to Columbia over the Holidays and look thru the archives.

    The instrument is now here and it will be several months before I service it. With the patent no. I could retrieve the entire patent. Will definitely provide a copy of the patent. THANKS!!
     
  12. burt

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    How is this? Patent US2690482 - Chronometr

    Whitney doesn't say that but the time line would certainly fit. Of course it wouldn't be the first time I found disparity in his writings.
     
  13. Tom McIntyre

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    i wonder if Bond were taking liberties when they marked their chronometers Bond Break Circuit. It no longer has the device but there are quite a few around that do have it. I had thought these were used in the U.S. Coast and Geodetic Survey work where the Bond telegraphic chronometers (strip chart reorders) were used.
    BreakCircuitInscription.jpg MvtAngle.jpg USAinscription.jpg

    As long as I am at it, here are pictures of my son in law's Hamilton with the break circuit.

    BreakCircClose1.jpg BreakCircClose2.jpg MvtContacts.jpg Movement.jpg Dial.jpg
     
  14. burt

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    Tom,

    If I had to name the Bond firm as to what they made I would first call them clock makers. I believe they were the first to conceive of the idea of the chronograph and received an award in 1851. This device greatly reduced or eliminated the reaction time of a human operator in timing. What I read is Bond used the combination first with clocks.Remember he was director at the Harvard Observatory. So it was probably a sidereal clock that was first connected to Bond's "spring governor" or chronograph. This instrument used a combination of spring governor and weight driven escapement and was accurate to an error of no more than 1/300 of a second. This system worked so well it was modified first by Richard Bond to control or to drive the movement of telescopes to track the stars as the earth rotated. This greatly enhanced the work of astronomer's as now timed exposures were possible and more faint objects could be photographed.

    Whitney doesn't address what they did with chronometers? Nothing I could find under Bond or in his writings on the break circuit chronometer.They certainly had the mechanical skill to incorporate this feature in a chronometer but did they? Maybe they merely copied another that worked? The way your chronometer was engraved doesn't it look like the BC device was added later? Dewey has probably handled more of these than anyone else perhaps he will share his thoughts?

    I hope Dewey can also assess your (excellent ) pictures and perhaps identify who the break circuit device in your son in laws Hamilton was used. Was it Kuhn's or their own? As I said the time line works out that either could be correct.
     
  15. Tom McIntyre

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    I cannot contribute much to this without a lot of digging into papers from quite a few years ago, but my raw recollection from the study I did at the time of the Longitude Symposium is that Bond outfitted the survey teams that mapped the northeaster states and possibly more. (Or, maybe only Massachusetts. I think, if one goes to one of the survey map points and sets up a transit with a telegraphic connection to Harvard, the idea was to get precise common base records.. The break circuit chronometers would have been used to get the local reference time for the observations that were nominally the same as the chronograph in Cambridge.

    I remember spending at least half an hour at the symposium staring at the Bond two train regulator with the conical pendulum and the gravity escapement acting as a remontoir (I thought). Here is a picture of the one that was for many years in the Bond shop window. Below is also a video of 394 in the Harvard collection.
    the-bond-shop-astronomical-regulator-no-396.jpg

     
  16. burt

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    #16 burt, Dec 5, 2017
    Last edited: Dec 5, 2017
    Tom,

    In looking at Hamilton 2E11659 it appears to confirm that these "selective break circuit chronometers" were not marked as such as stated by Whitney. I also check the ledgers and no special notation is recorded either. So he got that exactly correct.The plates are not marked as 15 jewels either. They appear as regular chronometers in both plate marking and ledgers.If anything they look as if Hamilton pulled instruments from regular production and then modified them or had them modified before sending them to Cal.Tech.? I noticed they were completed as a three chronometer order and two single orders. Yours in the three chronometer order has a different invoice number (49601) than the two single instruments. That also confirms Whitney as to the production of five. That is a bummer for researches, as without the actual instruments, it doesn't look like the ledgers will be of any assistance in finding more if they did exist or any other "special production pieces"?

    I noticed,as a personal note, that the next two chronometers in line after yours were shipped to Baker Lyman & Co. the marine supply company who serviced my Mercer.

    I think the Bond shop clock sold for $539,000.fairly recently.
     
  17. DeweyC

    DeweyC Registered User
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    Burt,

    Tom's break circuit is not selective, it is a single interval instrument and from what I can see of the cam on the 4th wheel, it is a 10 second interval. Also Tom,every break circuit chronometer has two electrical connections from the instrument to thumbscrew connectors on the case. If you hook up a 9 v battery and a light or a buzzer to the two connections, you will can see how it in operation. Generally the chron sent a pulse to a prick pen on a recording chrongraph. An observer had a hand swtich that operated a second prick pen and by comparing the two prick marks the time of an observed event could be accurately determined.

    I am still not clear how the selective break circuits were used for seismology. But I will get there. Will try to upload a photo of the Kuhn tonite/tomorrow. Lot of fires in my life at the moment.

    The Hamilton Archive inventory contains a project file specific to Kuhn. Hopefully I will get to Coumbia soon and look at that file.


     
  18. burt

    burt Registered User
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    #18 burt, Dec 5, 2017
    Last edited: Dec 5, 2017
    Dewey,

    Thanks for solving that one. Now Tom knows what he has.One thing learned is the ledgers (at least the two we checked) are not marked as break circuit chronometers of either type. Without the chronometers themselves to examine it appears we will not be able to identify them with the records? I attempted to check the ledgers for a known selective break circuit that was owned by Whitney. He states he has in his collection 2E12457 but unfortunately the ledgers run out at 2E12300. I guess we will just have to see with what you come up with at Columbia? If Hamilton does have a file on Kuhn I think you are right on track with your assumption. I was wondering if the one you have in the shop (2E12157) is marked in any special way or as actually being 15 jewels as Whitney reported them to be? No one ever said solving an old mystery is easy but we are getting there.
     
  19. DeweyC

    DeweyC Registered User
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    OK, here is a pic of dial. When I get the chance I will do a BC page on my website showing various break ckts I have serviced.

    View attachment 409609

    IMG_0037.JPG
     
  20. DeweyC

    DeweyC Registered User
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    OK, here is a pic of dial. When I get the chance I will do a BC page on my website showing various break ckts I have serviced.

    View attachment 409609
     
  21. burt

    burt Registered User
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    Dewey,
    Thanks for taking time to do the picture! I see it's Sidereal so it probably had a career in Astronomy?I know your busy so I looked into how these BC chronometers might be used in Seismology?

    What I found was Seismology is the study of earthquakes and seismic waves that travel through and around the earth. These waves can be caused also by volcanoes or major explosions. While seismographs located at various remote ( similar to the chronograph as it uses a recording drum) record the events there seems to be a critical element of measuring these waves, as to their speed, to identify as to which type and would require a portable accurate measurement of time. (The P wave travels at 6.4km per second and the S wave at 3.2km per sec.etc.) The science seems to require accurate measurement of time in many other aspects of its work. Caltech, who ordered the 5 BC chronometers from Hamilton has been doing this work from 1921.

    I was reading Kuhn's patent and I now better understand the advantage of a BC chronometer with selective breaks.

    Seismogram.gif
     
  22. Tom McIntyre

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    It is interesting that seismometers are essentially very long period pendulums that integrate the vibrations of the environment. They get lots of additional gear to make it possible to calibrate them.

    You could think of the action as recording variations in gravity as is done by gravimeters in survey work to explore underground structures. The connection to clocks is that precision clocks also measure the variation in gravity due to the tides. Since you need to compute the Allan Deviation of the clock to see the tides, it is not a fast recording device.

    To me, it seems unfortunate, that the physicists and geologists who do this work do not generally consider themselves horologists. It reduces the visibility of horology as a serious area of study.
     
  23. Paul Regan

    Paul Regan Registered User
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    I wonder what these were boxed in. This one still has the gimbal hardware however it had some foam pasted to the bottom of it and for those sad souls that saw the auction it came as just a movement/tub.
     
  24. burt

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    #24 burt, Dec 6, 2017
    Last edited: Dec 6, 2017
    Paul,

    I wonder if they were boxed like the chronometers used in aviation? Not in gimbals but secured in the box with an outer "shock" ring to protect the instrument.

    Tom,

    I think your (son in laws) chronometer a most interesting and desirable/collectible instrument to own as it was used at a prestigious institution of note and it would have contributed to such an important science and research work. Think of all those thousands of Hamilton's built we probably will never know where they were used ,for what function or by whom?
     
  25. Tom McIntyre

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    Thanks Burt. I think we may need to distinguish between adjustable break and dual break circuit. As I recall the Cal Tech instruments had a constant hour circuit and an adjustable minute circuit, but the minute circuit was generally set for each instrument to allow the operator to know from the arrival minute which instrument was reporting.

    Here is the external wiring picture with the labels.

    BoxContacts.jpg TubContacts.jpg TubWiring.jpg
     
  26. burt

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    #26 burt, Dec 7, 2017
    Last edited: Dec 7, 2017
    Tom,Dewey,Paul et al.

    I'm trying to put into perspective just what we have found and what we need to explore. As to the Hamilton break circuit chronometer Whitney identifies only two models. A single break of which they made 201 units starting in 1945 and a selective (multiple) which they made 5 units starting in 1955. These totals are as of December 13,1956.Compounding the problem is that some of these selective models were produced after that date so we really don't know how many were made. (Whitney's own example 2E12457 was presented at Hamilton on Oct.21,1957) We now have to consider the Kuhn multiple break circuit (1954 or later) of which Dewey has seen 4 examples of and believes there are less than a dozen. Did Hamilton actually convert chronometers to the Kuhn device? Then we have Toms example that we have 5 known shipped to Cal. tech in which may be a different type than those described as before?

    So do we have 4 different type of break circuit chronometers Hamilton may have produced/modified/ or had modified? When Whitney stated only 5 selective models were produced were they in addition to the Kuhn models or inclusive of them? I place a lot of weight on Dewey's assessment that maybe a dozen of the Kuhn were made and the additional fact that a Hamilton file exists on it. So are the selective BC chronometers Whitney wrote about actually Kuhn's? That now seems very plausible and something the Hamilton file should confirm. What category did Whitney classify Tom's?

    Then there is the limited help from the ledgers as they don't appear to specify if a BC feature was installed on a specific chronometer and that many of the instruments we are discussing were late production pieces and their serial numbers run later than the records include. Can we get anyone to help us out with examples of these instruments to solve these questions?

    Well is this pretty much the mystery we are trying to solve and this is what I call real research.
     
  27. Tom McIntyre

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    I think the dial holds the key. There is a provision in the dial to adjust the break circuit on the Kuhn. There is no such provision on the ones shipped to Cal Tech. Mercer also made a very large group of adjustable break circuit chronometers. I have seen those sell at a substantial discount to a regular Mercer chronometer. I think that is because they just cut a window in the dial and had the mechanism on the plate.

    I did not expect to have any trouble finding a picture of the Mercer on-line but I have been unsuccessful so far.
     
  28. burt

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    #28 burt, Dec 7, 2017
    Last edited: Dec 7, 2017
    Paul.

    In answer to your question how were they boxed I found this from Whitney: "Although some break circuit chronometers are mounted in the conventional mahogany carrying case with longer lead wires to permit the chronometer to swing free,generally,most of them are fitted in a padded leather or wooden box,or aluminum canister or in a moisture proof case with a shock-proof mount which acts as a shield".


    There is a photo of a break circuit chronometer mounted in a magnetic shield case on page 181 of his book.
     
  29. Dr. Jon

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    I can contribute another Hamilton example. It is number 2E111834. It is in a heavy, probably iron, case (magnet sticks to it) with shock mounts and break circuit. I forget its sequence but do recall it was unlike any other I had read about.

    The dial is unusual in that it has radium spots at the 5 minute markers and at the ten second marks on the sub second dial.


    Here is how it is cased in more detail







    Here are some views of the break circuit area. I marked the ruby pin with a green arrow.

    The case has no markings to indicate who owned it.

    I refer to it as Hamilton's first shock proof, waterproof, anti magnetic Chronometer.

    Front_s.jpg Open_s.jpg Interior2_s.jpg Marked-ruby.jpg
     
  30. burt

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    #30 burt, Dec 7, 2017
    Last edited: Dec 7, 2017
    Doc,

    Yours looks like it's very similar to the one in Whitney's book. Very nice and thanks for posting! I checked 2E11834 and saw the production 1948 date and went to the (64-XXX) U.S. government. As I suspected no additional or special information was noted in the Hamilton ledgers, yet certainly a unusual cased and a single BC equipped chronometer.

    In checking the ledgers did you notice all the "surplus sales" recorded on the page/s and to many familiar makers names and suppliers? Interesting to see Hamilton getting stock out that was no longer required by the government after the war.
     
  31. burt

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    #31 burt, Dec 8, 2017
    Last edited: Dec 8, 2017
    A question and observation. Does anyone have a Hamilton BC chronometer that is marked 15 jewels as Whitney wrote they are? Tom's example is marked 14 so it was probably selected to be modified after the plates were finished? The ledgers only say Mod.21 85 size and no mention of jewel count on any instrument. Is that an indication that chronometers to be modified were selected from completed instruments and not specific built break circuit units?

    So far the evidence seems to be leaning toward Hamilton used their own method of modifying single break circuit instruments as Whitney reported and that the selective break circuit models are equipped with Kuhn's device.I honestly feel Hamilton did both conversions at their facility and clearly give credit to Kuhn's patent on the dial. Hamilton was building single BC units for 10 years but didn't start producing selective chronometers until Kuhn patented his invention.Hamilton has a long history of using outside resources in their watch innovations. Perhaps Dewey ( or anyone else that has one) can supply a movement picture of the Kuhn modified specimen so that we can view how it is marked as to jewel count? These although rare, should be the easiest to identify as they are clearly marked on the dial and have the selective device adjuster positioned there.
     
  32. Tom McIntyre

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    #32 Tom McIntyre, Dec 8, 2017
    Last edited: Dec 8, 2017
    I do not think Hamilton would have marked the jewel count for marketing impact, which would have been the only reason to include a non-timekeeping jewel in the count. I need to ask John Huber (who worked on it) how many jewels Scott's[1] chronometer has, but I thought both of the switch detents were jeweled.




    1. ^My son in law
     
  33. tick talk

    tick talk Registered User

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    Gould credits Dr. Ad. Hirsch, director of Neuchatel Observatory, with the first "make-and-break" electrical attachment in 1866, followed by a similar design in 1868 from Charles Frodsham (pg. 211, The Marine Chronometer Its History and Development, 1923)
     
  34. burt

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    #34 burt, Dec 12, 2017
    Last edited: Dec 12, 2017
    Hey Brother,

    Nice research and a second source conformation on Frodsham as making the second instrument.in 1868-69. As I believe I stated before these instruments, the break circuit chronometers, were developed for astronomers.( Frodsham made the first clock and chronometer for Allegheny Observatory that I posted in the Sidereal thread) It would make complete sense that an astronomer like Dr.Hirsh would find a need for and possibly design or develop a prototype device or work with a chronometer maker to that end. That is in 1866.

    I'm still leaning toward the Robert Molyneaux firm as the one who made the first in 1860. He is a chronometer maker and is listed as working as early as 1835 at 30 Southampton Row,Wc. Secondly Ellery,also an astronomer, writing much (contemporary writer) earlier in 1887,in a official Astronomical Journal and not being challenged (in a leter issue) I think gives him (Molyneaux) the title. He even identifies the instrument number 1438 which makes me think he knew what he was writing about.

    I appreciate you posting as I only came on to this information when I read that Whitney gave the credit to the Negus brothers which I later learned was not correct. Truth is, I only know what I read, so we always rely and hope that the original source we site as being correct. Good hearing from you.
     
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  35. Dr. Jon

    Dr. Jon Moderator
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    I wonder why an astronomer would use a chronometer as a reference unless in the field, really in the field. Bond was electrically transmitting timing pulses (for which the form won a medal at the 1851 Great Exposition in London. The clock the produced theses pulses was inherently more accurate than any chronometer and adjust daily by use of transit instrument
     
  36. burt

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    #36 burt, Dec 13, 2017
    Last edited: Dec 13, 2017
    Most observatories were not establish to acquire and transmit accurate time. Those that were most certainly used regulator clocks in conjunction with chronographs and transit instruments. Most observatories have multiple telescopes located sometimes in a single large building or scattered on the property. Their clocks were usually placed in special clock rooms.I feel the portable chronometer is the instrument how correct sidereal time was was taken from the clock room to the telescope. Correct time was required to navigate the celestial heavens as the earth rotates.The break circuit chronometer would provide an additional feature when a very precision measurement of time was required to be taken at the telescope. Very precision measurements of time during transits of planets over the sun were used to calculate distances in Astronomy. Many questions, about the universe, were answered by Astronomers during the period these chronometers were used. In the "field" chronometers actually preformed equal or better than pendulum clocks adapted to portable mounts.
     
  37. burt

    burt Registered User
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    #37 burt, Dec 13, 2017
    Last edited: Dec 13, 2017
    Perhaps these pictures better explains and supports my opinion. The first picture is of the Lick Observatory which was founded in 1888. You can see the various telescope domes scattered throughout the property. The second clearly shows the "clock room" location next to the smaller dome in the left portion of the main observatory building. Allegheny observatory would be the second type example with three major telescopes in one building and a single clock room housing two Howard regulators one standard time and one sidereal. If you notice they are mounted on heavy stone pillars, in the observatory "clock room", which continue down to bed rock. I believe it was this clock (pictured on the left) which sent its time signals to the Pennsylvania Rail Road and other customers who "purchased" time as electrical contacts are still visible on the instrument. These clocks were the second generation used at Allegheny and are on display and running. Later the observatory housed a Reifler tank regulator.

    visitor.png LickObservatoryDiagram.jpg ao3.jpg Open house Allegheny Observatory 009.JPG
     
  38. burt

    burt Registered User
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    For those who did not view the Sidereal thread in the second picture is the transit instrument at the U.S.N.O. and a precision regulator in the background of the photograph that Illustrates what Doc Jon was referring to when he posted. The first picture shows the astronomer at the transit instrument and his hand on the switch of the chronograph which would record the exact time the selected "timing" star would be at a certain point on the celestial meridian. In the second picture which is a later and improved transit telescope you can also see the ball governor which would turn the drum of the recording chronograph. The instrument also has much larger setting circles which would allow for more precision in alignment of the instrument. I think pictures are great illustrators of what we try to say in print. (Library of Congress photos)

    download.png download (1).png
     
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  39. tick talk

    tick talk Registered User

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    In hopes of assisting with your research, I scanned copies of The Horological Journal from 1860 to 1866 but could not find a published account of Molyneux and a break-circuit device. Will check later years as time permits :)
     
  40. burt

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    #40 burt, Dec 14, 2017
    Last edited: Dec 14, 2017
    It's in "The Observatory" That is a journal that has been published from 1877. The publisher is "Editors of the Observatory" in England ISSN 0029-7704 and it comes out now every two months. We get it at our Carnegie library in Pittsburgh but I know I found that information on line.My notes say (1887) volume 10 page 427. Don't know what I did with the information as I probably deleted it for space. I'm still working with George Meyers on the Adams and Perry project and with the three chronometer articles just can't keep everything. I think maybe Paul Regan had it too? Anyway thanks for whatever you can find and contribute to this subject or anything chronometers. Chronometer collectors in general will benefit as we learn more about the instruments we collect and that these were used for many other reasons than ships navigation. Mercer states in his book "Chronometer Makers of the World" the uses were many and varied for chronometers.Survey(mapping) work being one of the most principal along with Astronomy, exploration ( of the earth) and even the medical profession.
     
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  41. burt

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    #41 burt, Dec 15, 2017
    Last edited: Dec 15, 2017
    As we are addressing the "selective" break circuit chronometer I thought I would attempt to clarify a few points. The first being that there are actually two types of surveying, land and water. With "land navigation" governments or authorities who wish to define their own areas, borders etc.and also to note geographical details get the coordinate information to draw their maps. Here is where the chronometer with a break circuit feature that is single or selective is an important feature and why. To calculate your position a surveyor's chronometer is equipped with a set of contacts fixed to and is actuated by a wheel that is attached to the 4th (seconds) pinion. This wheel can give a signal every second,or (with a selective break) any variation of a minute as the chronometer is set. (such as every 10 seconds,20 seconds 30 seconds etc)These recorded time intervals, can now be printed on a tape chronograph for reference and then compared later with celestial observations, and accurate mapping can be accomplished.

    When these same principals and procedures are applied to the oceans,lakes or rivers it is called "hydrography or a hydrographic" survey. It's my understanding that only the very best timing chronometers were selected for this type of work. This is how marine navigation charts and the mapping of islands was accomplished. My own Negus 1273 was assigned to this type of work with then Lt.Cmdr. George Dewey in 1872 and was used on his surveying expedition of the Pacific Islands including the Marshals,Gilberts,and the Samoans. These Islands would become very strategic and of great importance for the allied interests during World War II.
     
  42. nonosore

    nonosore Registered User

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    Hello Everybody!

    Thank to very much for all of these informations! I have one of these Model 21. Find it in the Geo Adamson metal case.
    So thanks to you I know why is it not exactly the same Model 21 as we can find for US Navy for example.

    41698581302_0893b73361_c.jpg
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  43. nonosore

    nonosore Registered User

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    Hi!

    Do you know how to find year of production for these timepieces?
     
  44. Jim Haney

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    It was sold to contractor ( 64-3038) on 5-24-1950.
     
  45. nonosore

    nonosore Registered User

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    Thank you very much!
     
  46. nonosore

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    Hi!

    I found and bought an other M21 with break circuit... Serial 2E11966.
    40961739450_095a927ba5_c.jpg
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    41872214585_9fa09df3a7_o.gif

    It is possible to abuse and ask you the year of manufacture? Thank you!
     
  47. Tom McIntyre

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    The entry reads finished 3-22-51, but there is no sold date nor any contract number associated with this unit. This is the only one like that on the pair of pages for this run.

    Thank you for using the animated GIF file for your last picture. I think I knew that would work, but I have never tried it. It is fun to see them running.
     
  48. nonosore

    nonosore Registered User

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    Thank you for your answer. Too bad for the lack of information! This second chronometer comes with the first one I presented. They were recovered together and at first sight were used together. One is labeled "Sideral", the second is labeled "Sideral 2 seconds".


    For the gif, I use the live function of Iphone, then a loop as effect. Put on Flickr as a photo it automatically displays the short gif when direct link is used.
     
  49. Tom McIntyre

    Tom McIntyre Technical Admin
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    The GIF actually gets uploaded to the message board, but the software does not preserve the GIF in the thumbnail. All thumbnails are jpg files.

    You can infer from what I posted that the machine was not sold until Hamilton had stopped keeping the records in the ledgers. I do not remember when that was and I am too tired to go look it up right now.
     

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