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The mysterious Speedmaster hour counter

  1. Archer Omega Qualified Watchmaker Jan 19, 2021

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    I do typically take a photo of the back of each dial, as part of the series of photos I take for each watch I service.

    I have not compiled them in any way...but they do vary in appearance over time certainly.
     
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  2. pascs Jan 19, 2021

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    Thanks for the great detail and explanations :thumbsup:

    One of mine has an odd behavior of the hour reset, the hour hand will creep only occasionally. After I rebuilt the movement, I tested it for a few days without the dial and it was running fine with the hour hand fitted, but when I put the dial and cased the movement it creeps occasionally. I think its because the pusher stem for zero action is sticking slightly and causes the hour hammer to interfere with the hour counter lock lever and prevents it from sitting correctly on the hour wheel. I'll be stripping it down again soon but hopefully this detailed explanation will help me to identify the issue.
     
  3. Archer Omega Qualified Watchmaker Jan 20, 2021

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    So just a word about other chronographs - someone asked about the Cal. 321, and the design on that is very similar:

    [​IMG]

    The parts look a little different, but the mechanism works in the same way. Here is the dial side of an ETA 7750:

    [​IMG]

    It works in the same way, but the drive pinion that is on the mainspring barrel is fixed, and the slipping "clutch" that allows the reset and for the hour recorder to stay put when the barrel is turning and the chronograph is running, are built into the hour counting wheel. Here is that wheel:

    [​IMG]

    And you can see the spring here that contacts the wheel in 3 spots, and this is where oil is applied to make sure that this part slips as it should in use:

    [​IMG]

    So in a recent thread someone mentioned that the hour counting hand would be centered when the reset pusher was pressed, but would move slightly off center when the button was released. There are two common reasons for this:

    1 - Magnetism - if the hammer or cam is magnetized, when the hammer comes down to reset and then lifts off as you let go of the pusher, it can cause the cam to stick to the hammer, and it can cause slight movement of the hour counting wheel. The solution to this is demagnetizing the movement.

    2 - Excess or sticky oil - if the hammer or cam are oiled too much, or the oil is very sticky, it can cause the same thing to happen as in the case of magnetism. The solution there is service.

    There is another one I didn't mention in that thread, because it's not common on newer watches...

    3 - Damage to the hole in the main plate of hour recorder bridge - the hour counting wheel has a pivot that fits in a hole that is made in the main plate of the watch, and the other end sits in a bushing that is in the hour recorder bridge.

    When these holes are worn or damaged and are oversized, the hour hammer will push the hour counting wheel to one side of the hole on reset, but the wheel will move when that pressure from the hammer is released.

    Here is a photo of a bushing that was damaged:

    [​IMG]

    This is easily repaired by replacing the bushing in this bridge. The same problem can happen on the main plate, as shown here:

    [​IMG]

    This is a more difficult problem to fix, so my advice to people is if you find that the reset of your watch is getting to be difficult, requiring more effort, please don't force it - get the watch in to be serviced.

    For the most part the hour counting mechanism works well, but again since the entire thing is based on a friction clutch, note that a sharp shock to the watch could cause the counter to move.

    Anyway, I hope this helps you all understand this part of the watch more completely. If you have any questions regarding this, please ask and I'll do my best to answer.

    Cheers, Al
     
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  4. reverbtime Jan 21, 2021

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    Thank you for this informative post!
     
  5. noelekal Home For Wayward Watches Jan 21, 2021

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    We're grateful that you're here on the Forum. In this thread I learned that Speedmaster hour hands can creep when the chronograph is not activated as well as learning why.

    It's plain to see that Archer is passionate about his craft.
     
  6. chaw6125 Jan 21, 2021

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    Al - thanks for the insight. This is a great post.

    With a worn bushing like that would you replace it with another or would you instead install a jewel?
     
  7. Blackdog Jan 21, 2021

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    Excellent post ! Always wondered how the hour counter actually worked. Not being visible indeed made it mysterious to me !

    Many thanks for a very didactic post !
     
  8. Archer Omega Qualified Watchmaker Jan 21, 2021

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    No, just a bushing. Keep in mind this rotates very slowly...once every 12 hours. The damage is more from someone pressing too hard than it is actual wear.
     
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  9. W210 Jan 21, 2021

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    Wonderful post, thanks Archer !!!
     
  10. newairplane Feb 4, 2021

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    Archer - very nice work!

    I just purchased a circa 1969 Speedmaster mark II with racing dial. My local jeweler installed a new crystal, lubricated some parts and adjusted it so it keeps excellent time. The watch looks great. The reset for the chrono does not work right though, the "hour hammer operating lever" seems to get stuck in the depressed state, even though its pusher is fine. The little spring loaded pin that is actuated by the hammer moves freely and the spring seems ok. It seems to be a sticky "hour hammer operating lever". I have carefully removed the back cover to take a look. Problem 2: The hour dial at 6:00 position moves along with the hour hand even if the chrono is stopped. It never resets. Do you have any suggestions for how I might go about having this repaired? I am not good enough to tear down the mechanism and would not attempt it.

    Thanks

    Rick

     
  11. Archer Omega Qualified Watchmaker Feb 4, 2021

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    Hi Rick,

    It really sounds like you need to find a proper watchmaker to look at this. You won't see much from the back, as the hour recorder parts are under the dial as I've illustrated.

    The hour hammer operating lever is pushed back out by the hammer itself. The hammer is moved by the hour hammer spring - I recently had another watchmaker email me as he was having trouble with the hour recorder mechanism, and a similar issue to what you describe. The hour hammer wasn't returning back out to the home position, and eventually I figured out that he hadn't hooked the hour hammer spring into the hour hammer properly. So for this specific issue, that's where I would start.

    However the description you gave about what was done - lubricating a few points and then regulating - that's not a full service, so unless you have a known service history for this watch, you should get it fully serviced. This involves complete disassembly, cleaning, replacing/repairing parts as needed, fresh lubrication in all areas. As I've noted above, your second issue (hour recorder creep) is usually solved by just a proper service.

    Cheers, Al
     
  12. pdxleaf ... Feb 20, 2021

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    This is my issue, (no creep).

    My watch is new (now a year old 1861). Since new, the hour counter shows more time passed than the minutes. For example, for the first 30 mins, the hour counter is past the half way mark. For the second half hour, the hour counter is near to the first hour mark. Once the hour has elapsed, the one hour mark is (generally) aligned with the one hour indicator.

    The problem is that it makes it a bit tricky to discern whether the i am coming up on the first 30 mins or whether i am on 31 plus mins.

    I had accepted this as normal for 1861s.

    Here is the question: are you saying this is not normal and (in the case of a new watch) a result of inaccurate alignment at the factory? If so, then is this something covered by the warranty and also something an owner should expect to be corrected by returning it to Omega?

    If yes (it should be corrected), is it worth the risk that incurs whenever a watch is opened and taken apart? It is functional as i have learned its quirk. It's a bit annoying but is the adjustment for this one small tick worth the effort of taking apart a new watch?

    Sorry for the delayed post. I wanted to read this for awhile but wanted the time to sit and absorb it, which is this Saturday morning.

    Thanks Al. Hope you guys are staying warm.

    Dave
     
  13. Archer Omega Qualified Watchmaker Feb 20, 2021

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    So is this another way of saying that the counter is too far ahead the whole time?

    I'm not sure I 100% understand the issue...
     
  14. rob#1 Feb 20, 2021

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    Very informative, thanks @Archer . Took me a few goes to get my head around it but it makes sense now. I can only imagine what it would have been like designing and testing these mechanisms all those years ago...
     
  15. jaguar11 Sep 26, 2021

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    Outstanding post and one which I have only just caught up with!
     
  16. Pazzo Sep 26, 2021

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    +1
    @Archer Thank you very much.
     
  17. Nyrmala Aug 9, 2023

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    Very informative post.

    It seems like I've got a similar issue with the hour hand regarding my 3594.50 Broad Arrow.
    1861 movement and while everything runs perfectly fine, I realized that when the chronograph is running for more than an hour, If I stop it and hit the reset pusher, everything goes back to 12 except the hour hand that doesn't fully reset.
    It goes back but stops on the way and If I want to fully reset it, I need to hit the reset pusher a second time.

    What could be the problem here ?
    Other than the reset part, the hour hand runs fine while the chronograph is also running.

    Should I send it to Omega for full service or would a local watchmaker be enough for this particular issue ?

    Thanks @Archer
     
  18. Archer Omega Qualified Watchmaker Aug 9, 2023

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    If it has been more than say 7 years since it was serviced, it likely needs a full service.

    You could use Omega or an independent that is certified by Omega, and has access to all parts that might be needed.