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Atmos Over Rotation

promenade clocks

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Aug 11, 2016
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Thank you for any assistance you can offer. I have looked for hours on this forum. I have an Atmos Calibere 540 that I have cleaned and changed the suspension spring and now it is over rotating. Following suggestions on other threads, I have both opened and closed the fork. I have made sure the fork is poised, and I have checked the poise of balance. These were all tried following the factory manual on how to adjust the fork. I did notice in the manual a test for the spring strength, is this wound too much? How much should it be wound? Also, I made sure the roller is smooth, and the roller spring is not too tight. Also, I have added weight to the balance, which did not help.
 

new_hampster

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Aug 3, 2006
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Adding weight will slow the period, and the clock will not keep good time. Normally, I would open the fork for this issue.

I usually wind 540 4-5 turns, after letting the mainspring down all the way.

When you say 'over rotating', can you elaborate?
 

promenade clocks

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Aug 11, 2016
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Rotating too much in this case, means the balance is turning enough so that the roller hits the fork at the end of the swing. This is about 630 degrees of turn. According to the manual I have, when letting down the mainspring, I should see 14 turns. This must mean turns of the winding arbor? I was turning the ratchet wheel. Are you turning the ratchet wheel 4-5 turns? How much does the bellows end up winding this?
 

new_hampster

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Aug 3, 2006
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14 turns is far too much. The clock is over wound, and will continue to over swing until the mainspring lets itself down, which could take weeks to months.

Here's how to wind. But first, check operation of the chain and carrier pulley. With the movement and bellows removed, there should be no twists nor slack in the chain as the back spring is fully pressed, and there should be no hesitation in back spring return when released. Routine maintenance would include removing the carrier pulley, cleaning it and its arbor (I've seen lots of grime here), oiling the carrier pulley and spring pulley arbors, then reinstalling the carrier pulley, being careful to put at least 2 turns on the pulley spring. You also want to check the height of the back spring, which is controlled by where the chain is pinned. I believe the spec is 45mm for a 540.

When satisfied, let the movement mainspring down all the way by releasing the click spring, using your thumb as a brake. Then re-install the unwound movement. Now what you will be doing is pressing the spring on the back and counting the turns of the mainspring arbor. It helps to put a mark on the mainspring winding wheel in order to count the turns. I put a dot at one point, and then 2 dots 180 degrees away so I can count 1/2 turns.

Notice where your mark is, and start by pushing the back spring all the way in, and then release it. As you release, the mainspring is wound, so notice the movement. Repeat by pushing the back spring again, and releasing, and continue pushing/releasing it until it no longer has any return when you let it go, counting the mainspring wheel turns as you go. When the back spring no longer returns after you push it in, the clock is fully wound - any additional winding at this point will increase balance amplitude, but is not sustainable by the bellows since the back spring is not within range. Equilibrium is usually somewhere between 4 and 5 turns of the mainspring wheel. If you over wind any amount, by either manually turning the winding wheel or by pulling the back spring out, the clock will eventually find its way back to equilibrium. It's a matter of time!

Let us know how it goes. I would be curious where 14 turns of the mainspring is documented.
 
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promenade clocks

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Aug 11, 2016
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Thanks again for the assistance. The 14 turns comes from the factory service manual. Section 8.1 "-Let down the mainspring and count the turns of the lower rachet wheel 4015 (approx 14)." Normally, we push the rear spring in until equilibrium is achieved on all Atmos clocks.
 

coldwar

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May 20, 2009
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This problem is seen from time to time. Assuming all other parts are not altered, you will find the trouble is in the mainspring, its bridle, the barrel or some combination of the parts. I have been reluctant to lubricate the bridle even lightly, referring of course to factory service notes. A given amount of slip is assumed, I cannot recall any spec or repeatable means to uniformly determine the rate at which the assembly in front of you begins to slip. Self winding watches can also overspeed the escapement and balance with the same set of conditions in play, a certain feel based on experience might be the final answer here. Rust, gum from previous lubing in repair attempts, even solidified cleaning solutions have been discovered in my experience, as well as oil, grease and graphited greases causing me to wonder what is factory and what isn't. >>GOD<< going to work on the delicate fork (which a babys breath might wither) is the last thing I ever might have hallucinated over my years as any cause of this known occasionally seen trouble given the slight power involved. Good Luck
 

promenade clocks

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Aug 11, 2016
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Thank you so much! This one seems to be cured. The manual here seems to indicate the wrong part to watch. Watching the mainspring arbor seems to be where the "14" comes in to play. Even at this, the balance rotates quite a bit. Interestingly the pulley chain was put back in the same place it was when it came in, however care should have been exercised to measure the spring on the back. This will be worth the while the next time a 540 comes in to the shop.
 

new_hampster

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Aug 3, 2006
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Ah, that makes sense. The mainspring arbor has 18 teeth, the winding wheel has 55, so if my math is right, to turn the arbor 14 times will mean the winding wheel turns 4.6 times. And of course, the winding wheel is easier to count as you push the back spring. If you service a 560, you will see that the winding wheel now has markings on it from the factory to help with this process.

EDIT: I originally said 'ratchet wheel' should be 'winding wheel'.
 
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