Hermle 340-020 Adjustment

[Chris]

I'm working on a relatively new Hermle movement; # 340-020 with a hairspring balance. Everything seems fine, except that the "fork" that engages with the pins on the balance wheel seems to lock up with the pins if you move the hands to set the time. What should I start with in the balance assembly to make be best adjustment? Thanks, Chris

[Chris]

I'm working on a relatively new Hermle movement; # 340-020 with a hairspring balance. Everything seems fine, except that the "fork" that engages with the pins on the balance wheel seems to lock up with the pins if you move the hands to set the time. What should I start with in the balance assembly to make be best adjustment? Thanks, Chris

[LaBounty]

Hey Chris-

I sent you and e-mail with copies of a past "Horological Times" article which discusses adjusting the floating balance.

The article is by David Arnold, CMBHI and can be found in the Nov. 1981 issue of the HT.

Good luck with it!

[Doug]

Hi David,

I believe he has a hair spring balance and not a floating balance.

[TonyR]

Hi guys,

I do have an example of the genuine floating balance. I see that to regulate it, you are supposed to move those tiny levers in the direction of the plus and minus marked on the back of the movement. My problem is, moving it in the minus direction (mine runs too fast), often by several of those small holes) seems to make it go faster. Could it be they've got it the wrong way round? I am reluctant to mess around with this too much as it has taken me quite a while to fix the thing and get it running in the first place. Any suggestions, or just loads more experimentation with those awkward little levers?


Regards,


TonyR.

[LaBounty]

Hi Doug-

Thanks for the clarification! Yes, you are correct but the majority of the adjustments are the same. With the hairspring version, you don't have to worry about where the balance "floats" or the condition of the balance wire but you still need to adjust beat, banking pins, fork, etc... I believe Chris's problem lies with a banking pin adjustment and the article I sent goes into detail on how to do it.

Thanks for catching me!

[LaBounty]

Hey TonyR-

The one I have in my hand has a "+" on the right and a "-" on the left, as I look at the back of the movement. The marks are just outside the opening for the balance.

Moving the "fingers" clock-wise, as you look down on the balance, will slow the clock. On mine, this is towards the "-" or left.

If you are moving the "fingers" in what you think is the proper direction and it isn't working, try moving them the other way. If the clock speeds up in both directions, you have a power problem. The balance should be rotating a bit more than 360 deg. or you will experience time keeping errors.

Good luck with it!

[Viv Rose]

Hi Chris

Use the literature that LaBounty sent you. I received the same from him and made sure the escapement was set up exactly according to the document.
I had success within two hours after battling with this thing for a very long time.

One tip - I placed a very small blob of pink lipstick on top of the outer ring of the balance wheel to help me determine the amount of rotation while it is running.
Unless you get 360 degrees or more rotation the movement will gain time that is guaranteed.

[Chris]

Well, here's what I found. I set the beat to a good, strong tick-tock and it kept locking up. Out of curiosity, I loosened the two mounting screws that hold the balance assembly in place (just a fraction of a turn from strong-hand tight). The balance wheel kicked into life and hasn't locked up since. The spin radius of the balance wheel increased as well (when tight, the pins only went side to side a small distance either side of the center shaft when you look straight at it.) Seems to be working well now, but should I leave well enough alone or tighten it up real snug again and adjust the fork? Thanks, Chris

[LaBounty]

Hey Chris-

That's a tough call. The mounting screws should be snug, but not tight to the point of breaking (gorilla tight).

On the other hand, if your screws can come loose you need to tighten them.

Did the balance assembly move slightly when you loosened the screws? Of so, you've shifted the banking pins in relation to the fork and accidentally got it right. It doesn't take much (0.010") to make a difference.

I'd say, slowly snug up the screws and watch to see if the balance assembly shifts as you tighten. Sometimes, just the friction between the head of the screw and the plate is enough to move things out of alignment. You may need to use magnification to see the results.

Most of the time it is easier to just tighten the screws and then adjust the banking pins so the pallets don't dwell too deeply on the escape wheel teeth lock faces. I've found it easiest to adjust the banking pins with a flat-faced stake from my staking set which has just the right sized hole. This will give you sufficient leverage to accurately adjust the banking pins without marring the surface.

In your post you mention adjusting the fork after tightening. Is the fork bent towards the roller to the point the roller pins could bottom on the fork? If so, yes...adjust the fork.

Unfortunately, this is another instance where having the movement "in hand" would make it much easier to diagnose your problem.

Good luck with it!

[TonyR]

Hi,

Thanks for the help, David. Could I possibly get ahold of that Horological Times article, too? Sounds like it would be very helpful -- now and in the future.


Regards,


TonyR.

[LaBounty]

Hey TonyR-

I'd be happy to send it to you! But I'll need your e-mail address since it isn't listed in your public profile. If you send me an e-mail I'll have it and can send the info on.

David Robertson has sent me a copy of the material he prepared a few years ago from Clockmakers Newsletter and Bulletin on the same subject and I'll add that as well.

[TonyR]

Hi,

Thanks, Dave. My address is verity1194@frontiernet.net

Thanks again,


TonyR.

[Carroll Hardin]

Hey David,
I would also appreciate the article you mentioned on the 340-020.Thanks,

Carroll Hardin
wch33527@aol.com

[LaBounty]

Hey Tony R and Carroll-

Your requests have been processed :smile:.

Enjoy!