How good is good enough?

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  • #50234
    dan a
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    After reworking a clock, what is your target for “acceptable” time keeping? I’ve heard the best to expect is maybe 1 or 2 minutes a week for these old clocks, but the best I have been able to do is maybe 1 or 2 minutes in 3 days. I’m not sure what the general customer is expecting either.

    #65294
    Anonymous
    • Topics Started: 14
    • Total Posts: 129

    Hi Dan,
    What kind or make of clock do you have? American, European or other? Also is it a pendulum and if so recoil or dead beat or is it a lever or possibly a cylinder balance wheel escapement? These can all make a difference in expected accuracy when it comes down to restoring old timepieces.
    Normally timing irregularities are the result of improper escapement adjustments or a rough or faulty escapement.

    Best, Dan

    #65295
    drichards
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    • Topics Started: 3
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    I concur Dan (or Dans)!

    If you have adequate and CONSISTANT pendulum swing and or balance amplitude and still not able to time it out to a decent rate then problem likely with escapement. If you notice periodic drops in pendulum motion or balance amplitude then a train defect such as a bent pivot or bent gear tooth or even a lodged piece of gunk might be suspect. If swing or amplitude is low then could be drop in power transfer through the wheels to the escapement (I’m including escape wheel here as part of escapement) or could be the escapement, or both.
    Of course something could be slipping somewhere in the train too such as the canon or hand but the rate will usually fluctuate.

    Just a thought. Best Dean

    #65296
    dan a
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    • Topics Started: 2
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    Thank you Dan and Dean. Thank you for the feedback on this clock. It’s a Sessions mantle clock I found on eBay that did not run when I got it. After cleaning, polishing all the pivots and replacing 7 bushings it started working again but I could tell it wasn’t beating well because the BPH counts on the TimeTrax were all over the place. I noticed the pallet arbor pivots were quite worn so I decided to bite the bullet and fix that problem. Since I couldn’t rebush those holes I decided to repivot both sides of the arbor with a larger diameter pivot wire and I thought that went very well as far as I could tell. The pallet arbor fits very nicely now and the BPH measurements on the TimeTrax are fairly tight, within 2-4 beats out of 9724 beats per revolution of the escape wheel. (Does that sound reasonable?)

    Two things I have noticed with this clock: 1) It seemed to speed up after the first few days of running, I suspect from either the lubrication getting to where it was needed or the pivots were settling in, and 2) a full wind of the mainspring only lasted 4 days instead of 7, which could mean the mainspring is weak or the clock is loosing excessive power somewhere. All the wheels look great, with lots of end shake and they are free spinning, so my hunch is to focus either the escape wheel itself or the pallet? Any ideas on how to narrow down the problem(s)?

    And I’m still curious about “how good is good enough” when dealing with a customer’s clock? How do you manage the customer’s expectations?

    Thanks!

    Dan A.

    #65297
    Anonymous
    • Topics Started: 14
    • Total Posts: 129

    Hi Dan
    Looks like you’re doing a very good job bringing the clock back to life.
    Knowing what type of clock you’re dealing with helps a lot with answering the question about customer expectations.
    So IMHO I would say that your estimate of between 1 to 2 minutes per week is a good one for your sessions mantle. That’s a target that I can usually hit when working with these older American and Euro mantle and shelf clocks. Spring driven wall clocks using longer pendulums will often time in closer than that; eg less than a minute.
    Weight driven wall clocks like Viennas easily within a minute. This especially applies to clocks using dead beat escapements like Viennas. Tall case weight driven floor clocks 19th. to 21st. century also easily within 1 minute.
    Letting customers know up front that these clocks are now old and bringing them up to their full timekeeping potential they had at time of production is often not possible without doing a great deal of restoration and even then might fall short of the mark is always a good policy and can avoid possible trouble later.
    Many of the clocks brought into shops are from elderly folk who quite possibly remember growing up with it in their home and also remember it keeping very accurate time. That same accuracy might be expected after servicing even though the clock might be worn out and has been sitting in storage for many years. I believe it’s always a good idea to discuss with a potential customer what they expect from a repair and then convey to them what you believe is possible and practical.
    I have to head out of here for an appointment for a few hours but will check to see if Dean jumps in to discuss the timing concerns when I return. If not then I’ll be back with some probably not so clever ideas! :D Oh also did you mean ‘Center’ wheel rather than ‘Escape’ wheel when you said “9724 beats per revolution of the escape wheel”? I might be misunderstanding what you are saying though.
    Dan

    #65298
    drichards
    Participant
    • Topics Started: 3
    • Total Posts: 35

    Hi Dan,
    That’s good info thanks!
    Yes you might be right. Do check the Escape wheel teeth, pinion and pivots as well as the rest of the escapement action.
    I’ll make mention of a couple of other possible things that I check just in case.

    For now I’m going to assume the same as Dan about you meaning one revolution of the center wheel per 9724 BPH and not the escape wheel. So rounding off to 9720 would give 162bpm. So with an error of 4 BPH and using some quick math would put the rate error somewhere in the neighborhood of 4+minutes for seven day run. So yes your 3 day rate variation ranging from 2 to 4 BPH is dead on. So,,, if that’s correct then we’ve actually determined two things here; your clock is getting close and I can still count! 😆

    Now for the clock only running half of it’s intended 8 day run, well that’s a problem that needs to be addressed for sure. Could definitely be a set or incorrect mainspring as you suggest or something like a slightly bent tooth somewhere in the train. A slightly bent tooth can be difficult to detect and often won’t reveal itself by manually moving the train. Also it takes some force for the time train to activate the strike so there could be an issue there too. Something that I do when this sort of thing happens, and it does, is at the point when the clock stops I place a small mark with a marker pen or whatever at the point where all teeth mesh with one another in the time train. I then deactivate the strike by either running the movement without the strike train installed or by raising the lifting lever so it’s out of action. Then fully wind and let it run until it stops again. If any of the marks line up perfectly then that tooth or teeth are suspect. If the marks are close but maybe not exactly in line then it’s possible there’s a slightly bent pivot on the meshing wheel or pinion arbors. Finally if the clock runs through to the end and the mainspring looks good then check to see if someone replaced the original spring with one the wrong size. This is common especially with vintage and antique watches. If you figure out why it’s stopping prematurely and fix that problem you might also find that the clock rate levels off enough to time it within the 2 minutes or less which should be acceptable by most customers for this type of clock.

    That’s pretty much the way I go about it but I’m sure others have different techniques they use for solving these problems. The order that I do things can always be changed around to fit your own needs and likes.

    I’m mostly a watch guy going all the way back to the 1960s. In fact Bob and I met in the early 1970s when we worked together at a Hamilton repair center in Woodland Hills Calif. Whew! So you will find other more qualified clockmakers up here. Many of these same techniques apply to both though so I hope it helps Dan.
    Please keep us posted on how you make out. Best, Dean

    #65299
    dan a
    Participant
    • Topics Started: 2
    • Total Posts: 5

    Wow, very thoughtful responses! Thank you. I will pull the movement out of the case again and put it back on the test stand so I can try some of your suggestions. This is the first clock I have ever brought back to life so it deserves as much attention as possible to get it “right”. The second clock I just completed is a Korean Schoolhouse clock and so far it is turning out to be much better as far as time keeping goes. I’m still tweaking it but right now it seems to be well within 1 minute per week.

    I’ll report back on the Sessions mantle clock when I have something to report.

    Also, thank you for the insight on handling customer’s expectations.

    Dan

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dan aHow good is good enough?