Month advance on AS 1315?
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  1. #1
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    Month advance on AS 1315?

    After a long period of not wearing my Croton Hourmatic, I've recently had it in for service and am putting some time on it. It's a fun little triple date bumper automatic. It had gotten so dirty that it stopped one night when rolling over to the next day. A trip to my local watchmaker now has it keeping super good time (I REALLY like that guy!). However, I noticed last week that the day of the week and day of the month rolled over, but the month did not change. I can't recall if it did before, and don't want to take it back to my repair guy if it's doing what it's supposed to. The movement is stamped Croton, but best I can tell it's an AS1315 (search the Ranfft pages, I'm new enough I can't post a link). Can anyone confirm whether the month SHOULD advance, or is that manual advance only? I've read that some of the old triple dates didn't move the month themselves, and I just can't remember whether this one did before the service or not.
    Thanks all!
    Shrewboy

  2. #2
    Zenith Forum Co-moderator
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    Re: Month advance on AS 1315?

    I suspect that the month is supposed to advance by itself. If it was just a display that you have to advance manually, Ranfft usually mentions that but this isn't the case here....

    bidfun-db Archiv: Uhrwerke: AS 1315

    Hartmut Richter

  3. #3
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    Re: Month advance on AS 1315?

    If the month is supposed to advance itself then it would be termed a 'perpetual calander'.

    The perpetual calander complication is a very expensive complication, it is seen on watches by Patek Philippe,
    Vacheron & Constantin and othery high end makers.

    To have the month change automaticaly and correctly then it would have to know how many
    days in that month and also take into account leap years, aperpetual calander only needs set once in a millenium.
    A serious horological challange which is solved with all manner of complex gearing, cams and springs.


    Looking at the AS1315 movement in Hartmuts link, it can be seen that your watch is not a perpetual
    calander and so you should set the month manualy.
    busmatt and Shum like this.

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  5. #4
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    Re: Month advance on AS 1315?

    That is unfortunately not true. In a perpetual calendar, the month advances by itself - but the same is true for a semi-perpetual calendar, an annual calendar or even just a full calendar display. My El Primero Cal. 410 has a full calendar display and I don't have to push anything at the end of the month.

    The difference between a full calendar and a perpetual calendar is that the latter compensates for the number of days in the month (as well as the leap years having 29 rather than 28 February days) whereas the full calendar display always shows 31 days. But this doesn't affect the month display. There are some watches where the month or othger features are just for decoration. E.g. the Durowe Cal. 7528 has a complex calendar display:

    bidfun-db Archiv: Uhrwerke: Durowe 7528 (INT)

    ...which nevertheless has to be adjusted manually for each month. This is noted by Ranfft in his text. Since the AS 1315 is missing any such additional remark, I suspect that the month is supposed to advance by itself.

    Hartmut Richter

  6. #5
    Member radger's Avatar
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    Re: Month advance on AS 1315?

    Quote Originally Posted by Hartmut Richter View Post
    That is unfortunately not true. In a perpetual calendar, the month advances by itself - but the same is true for a semi-perpetual calendar, an annual calendar or even just a full calendar display. My El Primero Cal. 410 has a full calendar display and I don't have to push anything at the end of the month.

    The difference between a full calendar and a perpetual calendar is that the latter compensates for the number of days in the month (as well as the leap years having 29 rather than 28 February days) whereas the full calendar display always shows 31 days. But this doesn't affect the month display. There are some watches where the month or othger features are just for decoration. E.g. the Durowe Cal. 7528 has a complex calendar display:

    bidfun-db Archiv: Uhrwerke: Durowe 7528 (INT)

    ...which nevertheless has to be adjusted manually for each month. This is noted by Ranfft in his text. Since the AS 1315 is missing any such additional remark, I suspect that the month is supposed to advance by itself.

    Hartmut Richter
    Your El primiro must differentiate between the length of the months if it advances automatically and you don't need to
    push anything at the end of the month.

    To be honest I don't see that this movement is any kind of comparison to your ElPremirio and can see no kind of auto advance
    mechanism on the pic on Ranffts site.

    But as you say that this watch should advance the month automatically then back to the watchmaker it must go I suppose.

  7. #6
    Member sempervivens's Avatar
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    Re: Month advance on AS 1315?

    The AS 1315 was built in a period (c. 1950) when surely the month did not change automatically. You had (have) to push a button to change the month (each month).

    Compare with the famous Tri-Compax (the first wristwatch chronograph with full calendar and moonphase): you have to change the month manually (each month).

    You can't go by what Ranfft says for these details: as he can't know everything nor does he mention everything. This is a detail which he never mentions.

    For instance for the Tri-Compax, until a couple of years ago the Ranfft database mentioned that a common button was used for setting the month and the moonphase. Which is not true. He has corrected that (now still says that it was designed ' to apply a common pusher for month and moonphase (pushing deeper) but it is unknown whether this was ever realized. )

    However that may be: it is not mentioned that the Tri-Compax needs changing the month manually (each month). Nor does Ranfft mention this for any other vintage full calendar movement; although surely it is the general rule for all full calendar watches before 1972 (i.e. before the El Primero-Espada). Durowe 7528 was built from 1972 onwards, but still the month does not advance automatically (at least I believe Hartmut, when he says it doesn't - but I don't see that noted by Ranfft in his text).
    Last edited by sempervivens; February 14th, 2016 at 20:51.
    Vanitas vanitatum et omnia vanitas, praeter ...

  8. #7
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    Re: Month advance on AS 1315?

    You mean to tell me, I own a watch with not only the world's very first automatic chronograph movement but also the world's first full calendar display with a month display that automatically flips forward?! WOW, I am beginning to appreciate this watch (currently on my wrist) more and more by the day.....

    But seriously, although I admit that I don't know about the AS 1315 for certain, the technical implementation of a month display that automatically shifts over when the date flips from "31" to "1" is so simple that I find it very hard to believe that noone managed it until 1972. Just like the ordinary hour gear controls the date and only flips it over when you get to midnight, the date can control the month and only advance it when you get to a new "1". The real difficulty lies in making system recognise whether the month should flip at "30" or "31", depending on the length of the month (in an annual calendar - or recognising the "28" for February in a semi-perpetual calendar - or the "28" or "29" in a perpetual calendar).

    I think that there are three options here:

    1. Accept it the way it is and push that button once a month
    2. Get a watchmaker to partially disassemble the watch to see whether some spring (or other part) is broken - if not, radger must be correct
    3. Ask someone who knows the movement. And Dr. Ranfft might be a good first person to try IMO

    Hartmut Richter

  9. #8
    Member sempervivens's Avatar
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    Re: Month advance on AS 1315?

    Quote Originally Posted by Hartmut Richter View Post
    You mean to tell me, I own a watch with not only the world's very first automatic chronograph movement but also the world's first full calendar display with a month display that automatically flips forward?! WOW, I am beginning to appreciate this watch (currently on my wrist) more and more by the day.....
    Yes, that is what I firmly believe.

    Now maybe there are some none chronographs with full calendar made in the 1960's, which do have a month that automatically changes at the end of the month... I don't know... but I seriously doubt it.

    The fact that it technically does not seem difficult, is not an argument. A bicycle also is not so difficult to make, once you've got a spoked wheel. Yet it still took about 4 thousand years after the spoked wheel to invent the bicycle.

    And BTW a spoked wheel also doesn't seem so difficult. Yet it took about 7 thousand years after the invention of the wheel, before human beings arrived at a spoked wheel.

    And BTW a wheel in itself also is not really so difficult....yet it took our ancestors at least 30 thousand years to invent a wheel.
    Vanitas vanitatum et omnia vanitas, praeter ...

  10. #9
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    Re: Month advance on AS 1315?

    Well, as a further indication, the Venus Cal. 222 definitely doesn't have a self advancing month indication. You have to push that little button. Now, Ranfft specifically mentions this in his datasheet on that calibre:

    bidfun-db Archive: Watch Movements: Venus 222

    There is no such indication for the AS 1315 - or for many other calibres with a month (but without annual or perpetual calendar). Hence I would assume that there were at least some such movements with self advancing month indication before 1969.

    However, by no means take my word for it: look under the dial for a damaged spring or ask someone with plenty of experience with that movement.

    Hartmut Richter

  11. #10
    Member sempervivens's Avatar
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    Re: Month advance on AS 1315?

    Thanks Hartmut. Good to know that Ranfft does mention it for at least one of the calibres with full calendar; presumably a calibre which he has handled himself.

    However for all the others he doesn't mention it, like the Venus 200, the Tri-Compax, and note that also the famous Valjoux 72 C doesn't have it as people who have experience with the movement can tell; for instance here.
    Last edited by sempervivens; February 16th, 2016 at 08:05.
    radger likes this.
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