Hermle 340-020A slow...

joe4227

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Oct 25, 2009
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I have a Bullova Mantel clock. The movement is a Hermle 340-020A.
The A indicates the later floating balance with the "adjuster".

The adjuster is a turnscrew near the top of the movement with a tongue that moves back and forth to adjust the speed.

Strangely, mine has always lost about 5 minutes per day. I can adjust that screw through the full range with zero impact. I see that the tongue does move through the full adjustment range, but it makes no difference to speed.

Any ideas on this?:eek::eek:
 

shutterbug

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Be sure that the spring is touching the groove. It should affect time if it is.
 

joe4227

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See photo (I hope you can make out). The spring is in the grove, the "V" in the tongue is in the thread of the adjuster, as best I can tell - am I understanding you correctly?
-> posts merged by system <-
Be sure that the spring is touching the groove. It should affect time if it is.
Sorry - forgot to attach, here is the image...:eek:
 

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sir_swatch

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I had the same problem with my replacement Hermle 350-060 movement that came with the same kind of new "balance wheel". It would not keep accurate time for any adjustments I made. I replaced it with the original (30+ year old) floating balance from the old movement and it keeps perfect time now. Once I had the "balance wheel" escapement out, I noticed that the hole in the regulating arm (where the spring passes through) is too big, allowing too much play on the dead side of the balance spring, which allows it to move as if the regulating arm were not even there! Pure junk in my opinion. If you can find a clean, older floating balance and swap it out, your problem will go away!
 

joe4227

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I had the same problem with my replacement Hermle 350-060 movement that came with the same kind of new "balance wheel". It would not keep accurate time for any adjustments I made. I replaced it with the original (30+ year old) floating balance from the old movement and it keeps perfect time now. Once I had the "balance wheel" escapement out, I noticed that the hole in the regulating arm (where the spring passes through) is too big, allowing too much play on the dead side of the balance spring, which allows it to move as if the regulating arm were not even there! Pure junk in my opinion. If you can find a clean, older floating balance and swap it out, your problem will go away!
This has been helpful, Thanks! I have seen a few posts discussing issues with the later balance and adjustment. I need to do a little reading on the basic theory before attempting this, but a) is it possible to tweak the regulating arm at all so that adjuster actually works? and b) apparently there are new "old-style" balances still for sale, so these can be substituted?

I need to get a better understanding of the basics before attempting to do either. But even if I took it in for service, it would be nice if I could describe the problem correctly and understand what the service person is saying!
 

Smudgy

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This has been helpful, Thanks! I have seen a few posts discussing issues with the later balance and adjustment. I need to do a little reading on the basic theory before attempting this, but a) is it possible to tweak the regulating arm at all so that adjuster actually works? and b) apparently there are new "old-style" balances still for sale, so these can be substituted?

I need to get a better understanding of the basics before attempting to do either. But even if I took it in for service, it would be nice if I could describe the problem correctly and understand what the service person is saying!

The problem is reducing the size of the hole in the regulator arm while still allowing it to work correctly. On a watch, which basically works the same way but correctly, the regulator has either two wires on either side of the spring, or a post and a wire. The wire allows the gap to be adjusted so that it is tight enough to hold the spring, but loose enough to allow the regulator to slide along the spring during adjustment without taking the spring with it. The spring also needs to stay in a neutral position throughout the entire range of the regulator or the adjustments will not work right. That is probably the reason why the hole is too large (it would be difficult to mass produce the thing right without an actual person having to make the final adjustment). If you can mount a piece of wire (or two) to touch the spring without distorting it, the regulator will work right.

With all that said, there is a 'solution' that isn't really correct and is frowned upon by watchmakers and higher end clockmakers (it's something of a 'botch'), but I suspect that the manufacturers expected the escapement to operate in such a configuration on release from the factory. The 'solution' is to adjust the spring so that one side always rests against the regulator when in a relaxed state. In theory the hairspring shouldn't be distorted in this manner, and in practice the regulation will be less consistent than desired, but it will work. The reason that this will be somewhat inconsistent is that effective length of the hairspring will change as the spring lifts off of the regulator, and the time it is free of the regulator depends on the balance amplitude (which changes as the mainspring winds down) and the distance from the hairspring stud that the regulator is positioned. Also, adjusting the hairspring so that it presses against the regulator too hard will cause the hairspring to distort enough that it will effect balance amplitude and timing (making the balance run too fast).

There is a lot of information that I'm skipping over here, but I think I've supplied enough for you have some understanding of the topic. If you really want to get more in-depth information, a book on watch adjustment or hairspring theory will provide the information.
 

shutterbug

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You might be able to reduce the width of the regulator by squeezing it together. A controlled squeeze with a clamp or vise would be the best way to go. Be sure it's still wide enough to allow unhampered movement on the spring.
 

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