Philly school of horology detent tourbillon model

Discussion in 'American Pocket Watches' started by Travler1, Oct 13, 2019.

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  1. Travler1

    Travler1 Registered User
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    13B609DA-4D4D-4FB0-9F3D-6341391C1531.png 25B31AFE-A1E8-4A55-B4B3-A13E9F3DE010.jpeg F158490B-BCE4-4364-AF8D-89723270DEB4.jpeg 49DA874B-B53B-43F9-B539-3EFD8ADF4545.png

    I’ve been looking for information on the pictured escapement model and the school.

    Of interest/questions are the “D” shaped jewels and their impact on the e/wheel . As only one of them is presently functional . The movement is rotating at 1 revolution per minute and has 2 beats per second. I have discovered that the dial is signed by a past headmaster of the school, and I am guessing the production date, to be apx 1925 plus or minus.

    Any info or thoughts on the school or the movement are greatly appreciated....thanks to all in advance
     
  2. Travler1

    Travler1 Registered User
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    BF8EE16A-0ED6-46EB-A1C6-0AA904931F62.jpeg 4D130842-6A79-41E6-AF2D-889E4D2CDDA1.jpeg 2B76A732-0F7A-44E8-8084-2DE3B1418C87.jpeg 219AC5D3-524C-491C-96B7-EECCC8561FE0.png additional photos ...
     
  3. gmorse

    gmorse Registered User
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    #3 gmorse, Oct 13, 2019
    Last edited: Oct 13, 2019
    Hi Travler1,

    The locking stone looks as though it's been altered at some point, because it shouldn't be at that angle, but very slightly anticlockwise of the radius joining its centre to that of the escape wheel when it's locking that tooth, in order to give a small amount of draw.

    219AC5D3-524C-491C-96B7-EECCC8561FE0_edit.jpg


    The red and blue lines don't give quite the correct picture because the locking stone isn't locking the escape tooth, but I hope it gives some idea. The distance of the locking arm with its stone from the escape teeth seems excessive as well, so perhaps the banking has been altered.

    There's only one jewel on the detent, (the locking stone), there's one on the discharge roller, and there may be one on the impulse roller, but that's often just a cut out in the roller itself.

    Regards,

    Graham
     
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  4. Travler1

    Travler1 Registered User
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    Hi Graham ...nice to hear from you.

    I must apologize for my photos and description of the movement and its action. I’ve have included another photo, which I am thinking will give you a better view of my thoughts, when I say one jewel is inactive on the ewheel. the jewel u mentioned never touches the escape wheel. it’s more of a vanity jewel, or a failed experiment ! ...best John


    .. 3FA99066-CB80-4E4B-B7A0-514F296CB3F2.png
     
  5. Dr. Jon

    Dr. Jon Registered User
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    I can't see enough to be certain but this looks like a Swiss "Grossmann" detent. It is complex story beginning in Glashutte whan Moritz, the German Grossman, got involved in developing a an improved form of pivoted detent.

    The other 2 Grossmann's, who ran the Geneva School of Horology, were inspired to this form. The large jewel and its arm serve two functions. The first is counterpoise, very popular in theory then but now discredited. The other function is to catch the escape wheel if the detent gets dislodged, typically when installing or removing the balance.
     
  6. gmorse

    gmorse Registered User
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    Hi Dr. Jon,

    Ah, I see, the real locking stone was hiding under the detent cock in the original pictures. If part of the other stone's function was to catch the escape wheel if it tripped, it can't have done either the teeth or the stone much good if it had to act in that way, and it must have added to the inertia of the detent. Much simpler just to wedge the train!

    Regards,

    Graham
     
  7. Dr. Jon

    Dr. Jon Registered User
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    HI Graham,

    Same monkeys different tree! I did not do the design but I did read about it, but do not recall where. (I think it is in the 4 volume catalog of th Glashutte Museum) Here is drawing of it I photographed at the Glashutte Museum

    470329-157887a40ee979eb39cd3de1417ef7eb.jpg

    This drawing was done by a student somewhat after M. Grossmann's death, The title translates approximately as detent with safety.

    I agree wedging would be simpler but I think they wer also trying to prevent tripping or at leas reduce the extent of each event. Catching th eforst tooth and on a secondary lock stone minimizes damage and reduces the impacts.

    Whatever the arguments, not many were made.
     

    Attached Files:

  8. Travler1

    Travler1 Registered User
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    “a secondary lock stone minimizes damage and reduces the impacts.”

    Dr. Jon ...I’m blown away with you knowledge of an obscure experiment to improve the spring detent...the drawing was pure icing on the cake.

    Speaking of reducing impacts ...I get that, especially on this oversized (Heavy) school model, as it sounds a tad much, banging away @ 120 RPM
     
  9. Travler1

    Travler1 Registered User
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    Oops ...I hate that, this is not a spring detent ...duhhhh ....please insert pivot detent the next time for me, on this post !
     

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