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Korean tambour beats too fast

ChimeTime

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Sister-in-law dropped off a Dai Jin mantle clock that hasn't run in several years. It was no trouble to wash and lube the movement, and it started running with a steady beat right off. The problem seems to be the beat rate is right up at 10,000 BPH. The adjuster nut has been inverted to lower the bob another 1/16". Any more and the nut will drag the case. I've added a lead weight to the bottom of the bob and it's still several minutes fast over 90 minutes.

All the pendulum pieces look stock. I think this is the first time the clock has ever been serviced.

So the only thing I'm left with is replacing the suspension spring. It has no visible damage, but the clock was transported to my house with the bob in place which can't be good. So my question is, do I want to go thicker or thinner on the next SS to slow the clock ?

IMG_20210731_173539176.jpg IMG_20210731_154824022.jpg
 

Willie X

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Something has changed. I would guess that the pallet depth is to shallow, either through mis-adjustment or wear. Probably the former. Willie X
 

shutterbug

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I agree. You may be skipping teeth on the escape wheel, and that will damage the wheel.
 

Uhralt

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To answer your question, a thinner suspension spring will give you a slightly lower rate.
How did you come up with the observed beat rate and how do you know what the theoretical beat rate is for this movement? A slipping escapement won't give you a higher beat rate but will speed up the clock significantly.

Uhralt
 

wow

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Chime Time, I have one exactly like yours in my shop. It is easy to bump the tabs that support the anchor arbor and move them so the anchor is too far away from the escape wheel. If so, the problem you are describing can occur. If too far away, a tooth on the escape wheel may skip occasionally. To be sure this is not happening, move the tabs closer to the wheel until the wheel cannot escape when you rock the anchor.Then back them off slightly until the wheel barely passes when you rock the anchor. The pendulum should swing wide.
 

Willie X

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It doesn't have to skip teeth to gain time.

A 'to shallow' dead beat escapement will gain a lot of time. It will also have a low pendulum amplitude.

If the auto-beat is to loose, it will have the same effect as skipping teeth. But both of these problems are rather obvious.

To shallow pallets are not so obvious, except for the short pendulum swing.

Willie X
 

ChimeTime

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Answers....
• Thanks for the tip on the SS. However the spring on this unit is already at 0.002" so there's not going to be one much thinner.
• I'm using the phone app "Clock Tuner" to measure my BPH
• The anchor is making almost full engagement with the escape wheel.
• The pallets are barely clearing the teeth of the escape wheel when operated manually.
• I haven't calculated the optimal beat rate, but know the clock has gained 3 hours in the last 24.

It's continuing to run nicely and has a very steady beat.

Thanks to everyone for all the help. I'll continue to run and watch this clock.
 

eemoore

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I am having the same problem with a movement from Dia Jin close but a school clock with a long pendulum. Very similar movement . Please post a solution if you fine one. thanks.
 

Willie X

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The escapement may be 'flutteting' from time to time. A beat amp (left in place) can ID this problem. 3 hours per day is not going to be a simple adjustment.

More likely it's something like: a slipping anchor, something out of mesh, parts changed, wrong movement, wrong pendulum, stuff like that. The pendulum (if the problem) would need to be about 1/2" longer.

There is really no need for a beat counter on a job like this ...

Willie X
 

JimmyOz

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First thing to do is ask your sister-in-law if it was keeping time before. Next thing would be to take the info on the movement and Google it to see if it is the right one. If both are correct then start to look for slipping anchor, wheels, it is a process of elimination really. 3 hours a day gain something must be obvious?
 

ChimeTime

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1. I can get this movement to keep good time in the stand, but like Willie X said, I had to add 3/4 inch to the length of the pendulum. That length would drag the bottom of the case interior.

2. Then I calculated the rate by counting the teeth and came up with an estimate of 7325 BPH. I have been able to slow the time train down from 10,000 to 8800 with various adjustments. Good, but still no where near slow enough.

3. Based on the extra length finding in 1, the next step was to move the CG of the pendulum lower w/o physically extending the length. This involved fitting a short twin leaf suspension spring in place of the 1" long single leaf. I also removed the top portion of the 50 gram bob weight and lightened the hanger. With the bob adjuster a paper thickness off the case floor, the clock is now only adding about 4 minutes per hour.

4. There is no more room below, so I'm going to need to raise the fixed mount for the suspension spring. There is ample room inside the tambour case to do this. But I need to buy some brass and fashion another mount. The twin leaf was so effective, the new design will be simple and direct, more like a Becker or Mauthe.

IMG_20210809_180637692.jpg IMG_20210809_175842595.jpg IMG_20210809_175523244.jpg IMG_20210809_175410003.jpg
 

ChimeTime

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The point is, you shouldn't have to do all that ... Willie X
Exactly. I've repaired/serviced ~30 clocks and watches in my amateur career and none of them gave me this much "fun". The ST2 stumped me for a couple of days, but that was my first experience with a dead beat escapement. All the others ran slow (or not at all) due to energy loss within the time train. Standard stuff.

Don't get me wrong, I'm enjoying the journey and learning a lot. The SIL has already declared that I should throw it in the trash, but I love a good puzzle. So I'm continuing. This thing will not beat me !!

More history... Apparently this clock was picked up at a thrift store a decade ago and ran for a while, then got passed around and ended up with my SIL. So while the opportunity for swaps and changes are numerous, there are no other clocks in the family to make swaps and changes between. More importantly, there is zero mechanical aptitude within my wife's family, and so there are no suspects !

The quest continues !
 

Keith Doster

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I'm wondering how much more of the bob weight you could remove in order to lower the CoG even further. Surely that bob doesn't need to be very heavy.
 

shutterbug

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Is there any evidence that the movement might have been replaced? That much gain per hour is still huge.
 

ChimeTime

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I'm wondering how much more of the bob weight you could remove in order to lower the CoG even further. Surely that bob doesn't need to be very heavy.
Experimented with a 5 gram lead weight because it was very compact. The movement liked that just fine. So that's how/ why I felt confident cutting the 50 gram bob in half.

That gained about 1/4" in effective pendulum length. There was no need to remove more because of the diminishing returns.
 
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JimmyOz

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Next thing would be to take the info on the movement and Google it to see if it is the right one.
Apparently this clock was picked up at a thrift store a decade ago and ran for a while, then got passed around and ended up with my SIL.
Why was it in the thrift store? maybe because someone bought the wrong repalcement movement and could not get it to keep time?
There seems nothing wrong with the movement apart from that it gains time and when set up on test stand it runs on time with a longer leader. All this say's to me that it is infact the wrong movement!
If you want this movement to work in that case the best way is to just add 3/4' to the feet or replace the feet that are already there, then cut a slot in the base to let the pendulum run, If you do not want to see the pendulum just add a block of the same wood infront of it in line with the corner feet and stain them all to match?
 

ChimeTime

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Although there are no signs of swapped movements, I'm about ready to agree with JimmyOz. This thing runs too good with a longer pendulum to have ever been sold in that tambour case.
 

shutterbug

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And consider that most of the Korean 30 hour clocks are wall clocks running longer pendulums. I think you have a marriage.
 

ChimeTime

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Due to the number of responses and the quality of the very helpful advice received, I thought it only right to tell you the end of the story....

The root issue was indeed the wrong pendulum. Using a movement stand and a pendulum made up of 0.06" wire, experiments were carried out to see at what length good time keeping commenced. The finding was that the original pendulum needed nearly 2 inches longer. Once that was understood, measurements were taken of the tambour case. The finding was that if a short suspension spring was used, then it would just barely fit.

Mounting the original suspension bridge to the top of the case interior gained about 1 inch. With the rate adjuster dragging the floor, another 1/4 inch was needed, and so an elongated hole was cut through the bottom of the case. These steps were rather severe, but mt SIL had already said this Korean clock was going into the trash if it couldn't keep time.

A very short European type suspension spring was used along with a Hermle suspension rod. To the bottom of this, the bob and adjustment from the original pendulum were added. Glad to report that the clock has been keeping excellent time now for 4 days.

Thanks to all !

dia1.jpg dai2.jpg dia3.jpg
 

kinsler33

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I imagine that someone replaced the movement with one from a Korean wall clock, and when that pendulum didn't fit in the tambour case, they found one that would fit. If it was on sale at an antique store they'd have stopped the pendulum until a prospective buyer showed interest. "Oh, it runs fine," said the antique dealer, who starts the pendulum swinging. After the clock ran for 15 minutes or so the prospective purchaser is convinced, never knowing that the clock is way fast.

That's why I avoid dealing with antique dealers.
 
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Willie X

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They have been known to throw away the keys too! "I think it will be fine, it just needs a new key". :oops: Willie X
 

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