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  1. #21
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    Re: Longines Prima pocket watch 19.71N

    Thanks eri231 ! That's the high frequency one I had seen ;)

  2. #22
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    Re: Longines Prima pocket watch 19.71N

    See the attachments (quotations from Linder and Lachat Longines books and a small collection of 19.73N balances). All not split, I believe.

    How did Longines attain the different degrees in precision measurement? In what I read (which is not much, unfortunately) I saw no mention of different balance wheels. Just different hairspings?

    On my quest after the fitting balance for my 73N double face I once found a mention of a 73K version – I do not know what K stands for. N is for „new” (t19.73 after 1909).
    Name:  Linder 19.73.jpg
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Size:  208.2 KBName:  Unruhn.jpg
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  3. #23
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    Re: Longines Prima pocket watch 19.71N

    All not split, I believe.
    Actually, some are. It can be a little difficult to seize, but the far right picture on the second row from top and the left pic on the third row are indeed bi-metallic split balances. Look closely, you can clearly see the balance rim is made of two different materials (gray steel and yellow brass) with two cuts near the balance's arm (well, you'll see just one since the second is hidden by the centre wheel). The first picture on top is also a bi-metallic split balance, because it's moving it's all blurry but we can still discern the bi-metallic rim.
    Now look at the following link here : http://watchesforparts.net/vintage-l...-or-repair.php
    You'll notice a third balance type you haven't posted, where the balance is all gold-like. It's a beryllium alloy, usually glucydur.
    I really invite you to learn about temperature compensation in watch history, you'll quickly be able to see the different types of balances.

    How did Longines attain the different degrees in precision measurement?
    Please have a close look at the pics eri231 posted earlier. You'll notice two 19.73N movements where the balance is much smaller than yours. This is how they get higher precision. By reducing the size of the balance and change the gears ratios, more power is delivered to the balance and it can achieve much higher frequencies, like 5Hz (or 36000 beats per hour) for the first from top picture eri213 sent and 50Hz (360000bph) for the third, respectively giving 1/10th and 1/100th of a second readings.

    If my math is good, we are here in presence of at least 5 different balances for the 19.73N
    Last edited by 707mm2; January 16th, 2020 at 21:02.
    SunnyOrange and vaa like this.

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  5. #24
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    Re: Longines Prima pocket watch 19.71N

    Thank you! I found out more in the past weeks than in the whole three years of trying to understand and have my double-face repaired…

    The 50hz / 280 000 bph 19.73N stop watch would run for about half an hour, I guess… But may I jump to the conclusion that a watchmaker could fit any balance to the 19.73N caliber and adjust it to run at its original parameters?

    And even, say – silly as it may sound – fit an Incabloc to my Longines? However technically and historically far-fetched, it might even be useful, what with balance staffs being so fragile and and the Odissey it has been to have mine repaired…

    Here and here are a few pages of the original Longines materials lists.
    I'm happy to share and hope I'm giving a little back for your patience and help

  6. #25
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    Re: Longines Prima pocket watch 19.71N

    But may I jump to the conclusion that a watchmaker could fit any balance to the 19.73N caliber and adjust it to run at its original parameters?
    That is in theory correct, given the balance is of an approximate similar size and weight. You can see from time to time vintage watches whose balances have obviously been replaced by an off-brand one. Before the late 19th century, it was even more common to "upgrade" movements with newer balances or even escapements (you can see here in this link a Breguet watch which not only the balance was changed but the whole escapement was converted from cylinder tu english lever). Of course in the 20th century this operation remained quite rare because thanks to parts interchangeability it's much easier to just fit the correct part than taking time adjusting another one.

  7. #26
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    Re: Longines Prima pocket watch 19.71N

    Before the shockproof days, balances and staffs must have been the most frequently requested spares so I'd expected some might be left over. But it has been impossible to find a 73N balance and almost so to find its technical data.

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