Suspension spring length

Discussion in '400-Day & Atmos' started by JTTrey3, Sep 5, 2018.

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  1. JTTrey3

    JTTrey3 Registered User

    May 20, 2017
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    I have been working on, what appears to be a Kundo standard 55 (Based on Horolovar book). Plate photo included.

    According to the book, this uses suspension spring configuration 3C. I lined up all the parts on the new spring with the diagram in the book, and they match up. However, when I attempt to install the pendulum, the spring is too short. It draws the pendulum top all the way into the locking hole and there is still not enough length.

    Have I miss identified? Thoughts??

    20180727_230305.jpg Plate1371.png spring.png spring-type.jpg
     
  2. etmb61

    etmb61 Registered User
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    What edition is your repair guide (not that it should matter)?

    The diagrams in the 10th ed. are 126.6mm between the center of the hole in the top block to the center of the hole/pin in the bottom block for units 3A thru 3C.

    Also could you show the suspension bracket and the pendulum along with the back plate?

    Eric
     
  3. mauleg

    mauleg Registered User
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    It's possible that you have the bottom block installed upside down?
     
  4. whatgoesaround

    whatgoesaround Registered User

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    Can you slide the bottom block down a little and/or the top block up a tad, still keeping enough of the suspension spring inside to keep the spring tight? Then you might have to adjust the distance of the fork from the new height of the top block. What is important is that it works, not necessarily that everything matches perfectly, although on the "later" models, they should.
     
  5. shutterbug

    shutterbug Moderator
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    There are several errors in the book, and you may have found one. Clearly you'll need a longer suspension spring. Go with your gut on where it will look the best. There will be some adjustment to time keeping perhaps too. You'll have to experiment to see how much.
     
  6. JTTrey3

    JTTrey3 Registered User

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    Thank you all.

    Attached are the requested photos. I am using the 5th edition of the book. Looks like I am just over 125 mm length. I will try to drop it down a tad more.

    I assume I will need enough clearance for the top of the pendulum assembly to be completely clear of the base of the locking hole.

    20180906_113256.jpg 20180906_113305.jpg 20180906_113330.jpg 20180906_114800.jpg 20180906_114821.jpg
     
  7. KurtinSA

    KurtinSA Registered User
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    On some of mine with this type of bottom suspension arrangement, the very top portion of the pendulum actually is within the hole used for locking. Nothing really wrong with that. It further helps with alignment...if the pendulum top is perfectly centered in this hole, you're as aligned as you can get.

    If you're going to be involved in 400-Day clocks, you really should upgrade to the 10th edition. It's not error free, but I'm sure obvious things along the way have been corrected. Could be this is one of them.

    BTW...I measure almost exactly 126mm between the two holes on unit #1.

    Kurt
     
  8. etmb61

    etmb61 Registered User
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    Well everything looks right but you have some extra length in the movement somewhere.

    Anyway, the pin for the bottom block should just rest on the bottom of the hole in the pendulum when the spring is installed and the pendulum is locked. The suspension spring should not be slack when the coil spring and cup are pressing down on the bottom block.
    block1.jpg

    That way when the pendulum is released the pin moves to the top of the hole and you have clearance at the top and bottom of the pendulum.
    block2.jpg

    Eric
     
  9. MartinM

    MartinM Registered User

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    Also, make sure the suspension bracket is square to the back plate and not bent upward. Hard to tell from the angle of the picture.
     
  10. JTTrey3

    JTTrey3 Registered User

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    Thank you. These help quite a bit. I think I finally have it setup, and it has been running for 12 hours. I will probably let it run through the weekend before I put the face and hands back on and begin adjusting the rate.
     
  11. KurtinSA

    KurtinSA Registered User
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    Sounds great! Do you have some sense on how it's running in terms of rate? In other words, will you be able to adjust the pendulum to get to the proper rate. Nominally, these larger clocks will beat 8 times in 60 seconds. The pendulum has built-in adjustments of about 2 seconds per minute either slow or fast relative to the middle position. If you don't have something relatively close to 8 beats per 60 seconds right now, you're going to have to do something to fix that. If you're much faster, say 8 beats in 55 seconds, then you're spring is too thick and needs to be thinned or replaced. Conversely, if it's 8 beats in 65 seconds, you will need to go to a thicker spring.

    Kurt
     
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  12. JTTrey3

    JTTrey3 Registered User

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    @KurtinSA , Great question. I used the spring recommended in the book, so I assume it is correct thickness. I plan to build an arduino based beat timer to help with tuning clocks. My goal is to have a minute hand position sensor which I can use in conjunction with a tick counter in order to determine the correct BPH within 1 - 2 hrs. Then, I can simply tune pendulums to match.

    Sounds like it should work, in theory.
     
  13. KurtinSA

    KurtinSA Registered User
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    It's been shown, not often, that some info in the guide is out of date, especially older editions. Mostly, though, it tends to be the pre WWII clocks. That said, using the stopwatch on your smartphone is all you need at this point to figure out if you're in the ballpark. On other clocks which beat much faster, the standard of measurement is BPH. But on 400-day clocks, you're on the lower end of the scale of BPH, so beats-per-minute tends to be more appropriate. That's all I was suggesting!

    Kurt
     
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  14. JTTrey3

    JTTrey3 Registered User

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    @KurtinSA ,

    Thank you very much. I will definitely do the stopwatch method and post the results. The Arduino is something I have been thinking about for some time in the future, if it will even work at all.

    Thank you, again, for all your help!
     
  15. MartinM

    MartinM Registered User

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    #15 MartinM, Sep 7, 2018
    Last edited: Sep 7, 2018
    If you can port javascript to Arduino code, we may have something you can leverage that has been tossed around a few times on the MB. I'd envision it to best work with a sound sensor listening for ticks and tocks, but a light/reflection based sensor on the pendulum could work as well.
    My original post with the code is at:
    Kundo & setting BPH
    Bill Stuntz did some modifications, but I can't find those posts, now.
    I posted a more updated version of the HTML, as well, but just can't seem to find it, now.
    Ah... Found one:
    Kundo & setting BPH
     
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  16. JTTrey3

    JTTrey3 Registered User

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    @MartinM ,

    Thank you very much. I like the idea. My goal is to build it open-source, so that anyone will be able to copy and improve on the design, both hw and sw.

    I am using the same concepts you outlined. The clock will mechanically always tic a certain number of times for a given movement of the hands, whether beats per hour or per minute. If I can count those tics between the time the minute hand passes through a particular point, I will know the desired bph/bpm for the clock. Measuring the time it takes to do so will also tell me what adjustments are needed. I had planned to use an audio transducer for beat input. However, optical would work, too. For a rotating pendulum, we would need to factor in the number of balls, and maybe use two sensors to detect direction of movement, as well.

    Now you really have me thinking. It will be a very fun project. Hopefully, if i get it done, and if it works as desired, it will help many in the community.
     
  17. MartinM

    MartinM Registered User

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    Unless somebody's looking to calculate beat error for these clocks, optical would be fine for most examples with no need to monitor direction because the total rotational amplitude is almost always under 360 degrees.
    I'm thinking a piece of electrician's tape on one of the balls. Something along those lines.
    Given that the price for a Nano is sub three bucks and sensors are under a buck, a display output of some kind would be the biggest deal.
     
  18. JTTrey3

    JTTrey3 Registered User

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    @KurtinSA ,

    Thank you, again, for your help. I timed 8 beats of the pendulum for 5 separate sequences, and they averaged out to 59.45 seconds.

    This calculates out to about 13 minutes fast per day (I think). The pendulum appears to have quite a bit of range left in its adjustment. Based on your numbers above, it seems like this spring should work without thinning.

    Do you agree, or have I goofed something up. I am just a hobbyist, but I am having loads of fun with this.

    Thanks!
     
  19. KurtinSA

    KurtinSA Registered User
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    You should be good to go!

    Kurt
     

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