Zenith caliber 1724 /1724c/1725/1725 ...or the wonders with the planetary gear
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Thread: Zenith caliber 1724 /1724c/1725/1725 ...or the wonders with the planetary gear

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  1. #1
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    Zenith caliber 1724 /1724c/1725/1725 ...or the wonders with the planetary gear

    We are in the mid to late 1960s. State of the art for wristwatches were the automatic movements. The ladies' movements, no matter how small, were a great challenge for the movement manufacturers. The most "famous" automatic movement is certainly the Eterna matic golden heart: bidfun-db archive, published in 1966: Wristwatches: 689: DAU Eterna-Matic Golden Heart, miniature automatic, 1966. Zenith also set a lot in motion to develop its own ladies' movement. Small makes things complicated. The men's movement 2522P, based on the Martel automatic, had already been launched in the market since 1960. In 1967 the first automatic movement for ladies' watches and a very soecial one with 7.35 lines (17.2x4.35 mm) was ready:

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    Fine adjustment, Inca-bloc shock protection and a rotor - so far everything is inconspicuous and modern. With date, the caliber was named 1724C and looks simular
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    This movement ticks in this case in the quite well known serial model "Respirator". For size comparison I have put the watch next to a "corpse remainder" out of the flea market in almost same age men's watch:
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    and a wrist shot for a better immagination. Isn't she lovelely this little Baby Respirator ?
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    The movement was also called 1725 and 1725c with small second and was also built since 1967.

    So far there is no reason to see why this movement deserves an own thread . Then let's venture into the innermost part, which a good and extremely curious friend of Peter's has documented very well. He made the pictures especially for us .
    Usually, an automatic movement uses the kinetic energy of the rotor to wind up the energy storage via a reduction system, i.e. the spring in the mainspring barrel. This spring then transfers its power to the gear train in a restrained manner. For whatever reason, probably to save parts, Zenith came up with this ladies' watch movement and only with these movements did they come up with the idea of passing on the rotor power to the gear train or the spring, depending on the requirements.

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    Without rotor and restlessness everything still seems to follow the usual structure. If one dismantles a little further
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    everything still remains inconspicuous. But now you can see the small change gear whose pin engages into the tension wheel. If one removes further bridges it becomes very strange:
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    What's happening? I'm copying Peter's text so I don't have to twist something: The minute wheel has been replaced by a strangely designed wheel. This is the differential, which has the task to distribute the power from the selfwindig mechanism and the mainspring to the movement. We also have an extra wheel between the differential and the mainspring barrel. (DIFF= differential; EXTRA= extra wheel; KBR= third wheel; SEK= fourth wheel) When winding up the car, we get the strange situation, that the mainspring barrel moves backwards, but the watch still runs
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    The two tension wheels, one with a long pinion which engages in the upper gear rim of the differential. The differential and the extra wheel taken up from the side. The upper diff wheel (red) is always turned up in the clockwise direction by the car elevator. The force from the mainspring comes through the extra wheel to the lower wheel of the differential (blue) and always tries to move this wheel in the counter clockwise direction. The blue wheel also moves in this direction when the car elevator is not working. At least this force can be overcome by the car-lift and the wheel will move backwards. The green wheel in the middle is where the force comes out to the drive, and this wheel always moves counterclockwise.

    Here a schematic representation of the plate gear in which the wheels were marked by Peter identical to the pictures:
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    If in fact the original idea was to save space by doing without two reduction wheels, this has gone wrong in the design. Because of the extra wheel and the crown wheel, which is additionally needed for crown winding to get the actually wrong direction of rotation, it is a zero-sum game. However, the initial considerations of this concept are not known to me. It becomes interesting, if you put this watch on the timegrapher. Peter found an extremely interesting addition in the technical data sheet. Here is described, that there are curved - and wavy lines showing even if the real movement is excellent. He explains it by the fact, that it is caused by the toothing of the small wheels in the differential. These wheels always work in a power flow and "jagged" their way forward. With the tiny dimensions and the given play of the parts to each other, no absolutely even flow is achieved despite precise manufacturing.

    By and large I had understood it and to make the whole thing clear to me Daniel gave me this snow schematic drawing of the gear train:

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    I hope you come along with the german lettering...

    However, I can confirm that my two functioning watches are excellent at keeping time in everyday life and I like to wear them. Unfortunately, this unusual movement was only used in the Zenith ladies' watches until 1969 and then, like many other manufacturers, was changed to the small ETA. After the quartz crisis, the ETA is probably the only remaining swiss manufacturer, which produces smaller mechanical and automatic ladies' watches as a volume product. I would like to be taught a better one. If you find an automatic ladies' Zenith watch, it must be from 1968/69 to contain this movement. This is then model independent. Younger automatic vintage ladies' watches are always driven by an ETA. I already know, why the manufacturers launch big ladies' watches as the big fashion :ok:

    Many thanks my friends to explain this interesting technique to me and I hope I can pass it on here. The watch whose movement was disassembled here I will present when the post office was with me at the Defies with octagonal case The DEfi is 27 mm wide.

    Silke
    Last edited by SilkeN; April 20th, 2020 at 22:05.
    Herold likes this.
    That's what I think about today:https://www.youtube.com/watch?v=vlUGeY7MWVo

  2. #2
    Member sempervivens's Avatar
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    Re: Zenith caliber 1724 /1724c/1725/1725 ...or the wonders with the planetary gear

    That Zenith respirator is particularly nice and flashy, Silke, but the classic steel round one is also a small wonder.
    Vanitas vanitatum et omnia vanitas, praeter ...

  3. #3
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    Re: Zenith caliber 1724 /1724c/1725/1725 ...or the wonders with the planetary gear

    What a wonderful watch - and what a great write up!! I don't quite understand it all yet (maybe I need to see the movement being taken apart for that) but it is certainly an interesting design. The reason why that movement came out when it did is presumably that ladies' movements, being smaller and therefore having relatively more friction than the larger ones, did not wind well without the ball bearing and that had been patented by ETA around 1948 and the patent expired around that time. Not only among ladies movements did most automatics except those made by ETA specifically for Eterna have pin bearings up to the late sixties.

    Hartmut Richter

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  5. #4
    Member SilkeN's Avatar
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    Re: Zenith caliber 1724 /1724c/1725/1725 ...or the wonders with the planetary gear

    THank you both and Hartmut for the information about the ball bearing patent of ETA.I must confess that I also found it very difficult to understand this fascinating bidirectional flow of power, which is why I also took Peter's explanations literally. In the Hampel it is described: "Ball-bearing heavy metal rotor wound on both sides via a sliding pinion changer, direct energy transfer with the help of a planetary compensation gear to the fourth wheel".
    However, I am surprised and fascinated to discover independent developments in such late movements, even if they did not prevail. The production of such a movement must have been quite expensive. In addition, the watchmakers certainly did not like curves in the recording of their timegraphers while adjusting a watch.

    I had misappropriated the space and wheel-saving solution for the Date Module of the 1724c in the Thead, because I wanted to show the unusual ways of using rotor power. So as a supplement the simple solution. The drive is done directly by a drive of the change gear:

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    At least this should be a cheap and smart solution that is easy to understand.

    Regards Silke
    That's what I think about today:https://www.youtube.com/watch?v=vlUGeY7MWVo

  6. #5
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    Re: Zenith caliber 1724 /1724c/1725/1725 ...or the wonders with the planetary gear

    A weird set up! As far as the bidirectional winding goes, I could see very quickly what was going on: it's a rocking mechanism ("Wippenwechsler") just as in the original first bidirectional winding system (Felsa "Bidynator"). I'm not sure whether there are any modern movements using it in favour of the click gear ("Klinkenrad") system but in the old days, quite a few companies employed it.

    Hartmut Richter

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