Survey: Waltham A13A Aircraft Clock

Discussion in 'Chronometers' started by Jim Haney, Jul 7, 2017.

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  1. Jim Haney

    Jim Haney Registered User
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    #1 Jim Haney, Jul 7, 2017
    Last edited: Jul 7, 2017
  2. Jim Haney

    Jim Haney Registered User
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    I forgot to add that the info stamped on the movement was,

    Waltham Pres Inst Inc.
    Code 79300 compensated
    Type A13A 20 Jewels
    Serial # 168989
     
  3. musicguy

    musicguy Moderator
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    Followed your link to this post, nice clock and very Interesting setting mechanism.

    Rob
     
  4. Tom McIntyre

    Tom McIntyre Technical Admin
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    Those are interesting Jim. I think I have a few around here somewhere. There may be a slight typo in your post since the name was Waltham Precision after the company split in two so the abbreviation would be Prec.
     
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  5. River rat

    River rat Registered User
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    A little late
    Here is a shot of mine when I was repairing the nob
    pRjdUaF.jpg
    And once you start collecting them you can't stop
    K2nwdoC.jpg
    If you got Whitney book military timepieces on page 34 there some info on this make of aircraft clock. They look good mounted in stands I got a US WW1 US Army ASSC Waltham model XA aircraft clock in a wooden stand on my computer desk.
     
  6. grtnev

    grtnev Registered User
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    Quoting from pages 28 and 34 of Whitney:

    "The military specifications MIL-C-6499 defined this timepiece as an unlighted mechanical aircraft clock having a 1-7/8 inch dial and a one-hour elapsed time capability. There were two types:
    a. Type A-13A-1, having fluorescent luminescent hands and dial markings.
    b. Type A-13A-2, having lusterless white hands and dial markings.
    These specifications were amended and/or revised several times between 1953 and July 1970, each change being noted by the addition of an alphabetical letter, beginning with A through E. The Navy's stock number for the above clock was R88C0583-015-000...……..The dial background and the unshaded portion of the hands had a lusterless black finish. The shaded area of the hands and the dial graduations and numerals of the A-13A-1 clock were coated with a fluorescent luminescent material, while the type A-13A-2 clock hands and dial markings were finished in lusterless white."

    "All of the models listed here are fitted with Waltham's well-designed, sturdy, 8-day, 22 size aircraft clock movement, characterized by (1) 20 jewels, (2) 1-hour elapsed time mechanism, (3) unbreakable antimagnetic cobalt mainspring, and (4) adjusted to temperature, position, and isochronism. The movement is fitted with a 1-7/8 inch flat black dial and housed in a standard 2-1/4 inch type aircraft instrument case. The dust and moisture proof case is aluminum and has a lusterless black finish."​

    I was at a car show swap meet this past Thursday and while I was rummaging around, I came across this A-13-A aircraft clock which I picked up for $15. I was pleasantly surprised to find out that it runs and keeps reasonably good time and that the chronograph/elapsed time function works - at least partially. The chronograph/elapsed time function works fine until you get to the 5 minute elapsed time mark when it stops. Obviously no idea when the clock was last serviced, and it obviously could use with a cleaning.

    It is really hard to tell whether or not this clock has fluorescent luminescent or lusterless white dial and hand markings. In some lighting conditions, the numerals and hands look to have a light green tint, in other lighting conditions, they look to be a dull, flat white. In either case, the numerals and hands to not luminesce in the dark. Unfortunately, the label that originally was on the back of the clock has been lost, so until such time that I have it serviced and can determine the movement serial number, I don't have a way to know anything more regarding manufacturer/date.

    Three questions for the forum members:
    1. At least from the mid-1950's through the early 1990's, is it correct to state that these clocks were manufactured by Waltham Precision Instruments?
    2. From specification issuance in 1953 until Waltham Watch Co. was no more in the mid-1950's, were any of these clocks ever manufactured by Waltham Watch Co. prior to its demise?
    3. Whitney states that these clocks were adjusted to temperature, position, and isochronism. Waltham's CDIA aircraft clock from WWII was adjusted to temperature, isochronism and 1 position. I assume the same for this clock; i.e. adjusted to 1 position; i.e. 12 o'clock up?

    Thanks,

    Richard

    DSC03673.JPG DSC03674.JPG DSC03675.JPG DSC03676.JPG
     
  7. Jim Haney

    Jim Haney Registered User
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    Richard,
    Great pickup. When I had the clock apart it had the following,stamped on the plates,so that would indicate to me,that it was a product of this sub company only.

    Waltham Prec Inst Inc.
    Code 79300 compensated
    Type A13A 20 Jewels
    Serial # 168989

    I believe your clock is the A-13-1 because the paint is very thick and if it was the white paint it would not look so fuzzy.

    Have you tried to charge the luminescent with a light for a few hours and then see if it will glow in the dark?

    I don't know how many positions they were adjusted to,maybe the Military specifications sheet would say so?
     
  8. grtnev

    grtnev Registered User
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    Jim,

    I kind of think it is the A1 variant as well, but if the hands and dial numerals were luminescent I don’t see any evidence of it now after being under a bright light for several minutes.

    I’ll know more when I get around to having it cleaned.

    Richard
     
  9. grtnev

    grtnev Registered User
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    A few more notes on this clock:

    1. The clock will run for 8 days, but to improve accuracy, should be wound at least every 4-1/2 days or daily if possible.

    2. From MIL-C-6499E; 7 July 1970; "Military Specification Clock, Aircraft, Mechanical, Type A-13A"

    The clock is tested under the following conditions in one position; i.e. 12 o'clock up:
    • temperature; -35C (-31F) to +55C (131ºF)
    • humidity
    • magnetic field
    • vibration (at multiple frequencies)
    The clock is tested under the following condition in all 6 positions:
    • shock (15g's)
    3. Apparently the luminescent material used in the A1 variant doesn't "glow" in the dark, but rather lights up when exposed to ultraviolet light.

    Richard
     

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