Hamilton 4992B used by the Naval Observatory

Discussion in 'American Pocket Watches' started by Jim Haney, Mar 28, 2015.

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  1. Jim Haney

    Jim Haney Registered User
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    Marvin Whitney built these from a Hamilton 4992 B Military watch to use as a measuring tool at the Naval Observatory.

    The Observatory was using this instrument to see what error was in the TIME signal between the Station in Beltsville, MD (Washington, D.C.) WWV, and the location it was received in, Colorado or anywhere else. The error would be caused by interference in Radio signals in the atmosphere.

    This was the time signal and it had to be correct without any error. They broadcast it in several Megacycles 2.5,5.0,10.0,15.0.

    Some info from Google,

    https://books.google.com/books?id=xAVp8cnrEWMC&pg=PA116&lpg=PA116&dq=WWV+Megacycles+2.5,5.0&source=bl&ots=O2Aet-XLgl&sig=M2ovNspWKfZnEfEo9fLIrZBgMck&hl=en&sa=X&ei=0vsWVeKeEIedgwTV2oDgCg&ved=0CDgQ6AEwBg#v:^nepage&q=WWV%20Megacycles%202.5%2C5.0&f=false

    I got this from a Commander Al Betters a friend of Whitney's and he gave me the letter than Marvin wrote to him presenting this as a gift to him. He supplied photos to Whitney to use in the book Marvin was writing at the time. "Military Timepieces, c 1992.
    Cmdr. Betters was a Navy "Frogman" and his pictures are on page 580.

    I have seen 2 others, one owned by Military parts guru, Larry Crutsinger, http://www.hamiltonparts.com/ & fellow collector Fred Hansen.



    DSCN3380.JPG DSCN3378.JPG DSCN3379.JPG DSCN3381.JPG DSCN3382.JPG DSCN3377.JPG DSCN3383.JPG DSCN3384.JPG DSCN3376.JPG
     
  2. s. smith

    s. smith Registered User

    Oct 13, 2006
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    Jim very nice it,s a beauty.
     
  3. Paul Regan

    Paul Regan Registered User
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    Fantastic watch Jim, with an equally amazing provenance!
    Paul
     
  4. Donovan Martin

    Donovan Martin Registered User

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    That is amazing. Thanks for sharing!
     
  5. terry hall

    terry hall Registered User
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    Apr 12, 2001
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    Great item, and greater provenance... thanks for sharing...

    earlier this year 4c78535 was sold, no box or provenance though.

    Outer chapter 1/100 of a minute....
     
  6. 179

    179 Registered User
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    Thanks for posting Jim. Great item with outstanding provenance. With 3 of these known now maybe another will surface in the future. Looking carefully at these, i believe the mvt.,special dial and hands were supplied to the N.O. for casing at the N.O. in the 4 piece case. Maybe Lucite rather than Plexiglass as it seems to have aged well. The protective box also appears to have been made at the N.O. by some of the construction details. Thanks again!
     
  7. rrstd

    rrstd Registered User
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    The box and documentation that came with Jim's example certainly goes a long way in defining the story behind these devices.

    As an update, I can confirm the existance of 2 additional examples of these devices - bringing the total of known examples to 5.

    Rhett
     
  8. Tom McIntyre

    Tom McIntyre Technical Admin
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    A really neat artifact. It is particularly special to have the documentation from the guy who made it.

    Do these precede or follow the "NATO" 3992B's with a similar dial design for decimal minutes?

    3992Bdial.jpg
     
  9. burt

    burt Registered User
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    Jim,

    I was very impressed with this piece, with its historical providence as well as its special purpose as a timing "check" instrument. Kudos to Hamilton also.
     
  10. rrstd

    rrstd Registered User
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    The two examples below, show some of the variation from piece to piece. As can be seen, the lucite cases are slightly different in size as well as construction details.


    NO4992B_1.jpg NO4992B_2.jpg NO4992B_3.jpg
     
  11. rmw

    rmw Registered User

    May 31, 2005
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    Tom

    The decimal watch dial you show was fairly common. I believe these watches all started life as standard Zenith or Hamilton comparing watches and had new dials put on some time after WWII. The ones I have seen were converted in England. They were used for ease of calculation. In fact so many Zeniths seem to have been converted that the conventionally dialled watch seems to be rarer than the converted version. The original dial is of much higher quality.

    RMW
     
  12. Dave Chaplain

    Dave Chaplain Registered User
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    Rhett, is 4C20179 in a lucite case like the one on the right in post #10 already in your list of 5? :)
     
  13. Clint Geller

    Clint Geller Registered User
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    I am a research physicist at a government lab
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    I am puzzled by the opening post in this thread. The speed of radio waves in air is about the same as it is in vacuum, which is 300 million meters per second, or about 186,000 miles per second. So that means that a radio wave emitted from the ground and reflected from the ionosphere will be received at a point about half way around the Earth in about a tenth of a second. Changes in the time of travel of an electromagnetic wave between any two points on the Earth's surface will result from variations in the height of the ionosphere above the ground - not from radio wave interference (Maxwell's Equations are linear!), nor from Doppler shifting (relativistic Doppler shifts only affect the frequency of an electromagnetic wave, not its speed). Presumably, these variations about the mean value are a couple of orders of magnitude or so smaller than the mean value itself. So that means that the variations one is attempting to measure are on the order of a few milliseconds, or less. So how can one expect to measure variations so small accurately with a timekeeper whose escapement beats only once every 200 milliseconds? The dial of the timepiece is completely incapable of registering time intervals that small. So it seems like the tool is hopelessly mismatched for the intended purpose.
     
  14. grtnev

    grtnev Registered User
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    #14 grtnev, Apr 20, 2017
    Last edited: Apr 20, 2017
    Jim,

    Very, very interesting. Thanks for sharing.

    I did note that the position of the regulator is essentially all the way toward S - which is interesting.

    Richard
     
  15. Jim Haney

    Jim Haney Registered User
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    Clint,
    You would have to start with the box which states the WWV or microwave signals and come up with your own theory based on your doctorate degree.
     
  16. Clint Geller

    Clint Geller Registered User
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    Jul 12, 2002
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    I am a research physicist at a government lab
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    Well, Jim, physicists are trained to perform simple, "back-of-the-envelope" calculations to determine the orders of magnitude of the quantities involved in a scenario, to see if it is plausible, before delving into detailed theories. That's what I just did, and based on my analysis, it does not seem plausible to me that any mechanical timekeeper would be useful for measuring the minute variations in the time delay between the emitted and received radio signals between any two points on the Earth's surface.
     
  17. rrstd

    rrstd Registered User
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    Dave, the recent online sale was a new example. Which puts the total I've recorded at 6.
     
  18. Dave Chaplain

    Dave Chaplain Registered User
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    Hey Rhett, for the list, it looks like 4C101699 in a case that looks like the one on the right on post #10 was sold on the large auction site in May. Are there now 7, or was that one of the first 5 recorded?

    It also appears that the seller has sold two of these in the past couple of months, the other being the one I got, 4C20179 ... :O
     
  19. rrstd

    rrstd Registered User
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    Dave,

    I've been wondering who might have purchased that last example.

    The most recent example makes a total of 7 I've recorded.

    Rhett
     
  20. Dave Chaplain

    Dave Chaplain Registered User
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    -

    Rhett, I wasn't the buyer (unfortunately)! I hadn't even seen it until yesterday when the buyer contacted me to discuss it some ... I must be slipping some ... :p
     
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