Expert: John Newman - 8/12/2009

Question
QUESTION: I have a recent-production Stickley 89-85 Mantel Clock containing a Franz Hermie 141-041 unadjusted zero-jewel movement with pendulum ("Made in Germany").  It is my first mechanical-type clock, and I am struggling to adjust the clock so that it will tell time accurately and consistently.  I am frustrated because after nearly a week of daily pendulum nut adjusting, I got the clock to tell very accurate time for a day; then I wound the time and strike/chime with the key...and the clock started running fast (about 5 mins./day).  (1) Is this particular movement capable of keeping extremely accurate time once adjusted?  (2) Is there a detailed (initial and subsequent?) winding and setting procedure that I should be following?  (3) How tightly should I wind the clock each 7-8 days (Stickley's recommended frequency)--e.g., until the key absolutely won't turn further, or stop winding when the key's resistance starts to increase (or...)?  Thank you!

ANSWER: Matt, I'm sorry you are having such a difficulty in rating the clock.  In answer to your questions:

1.  These movements should keep rather accurate time after rating it.  A minute or so a week deviation for a mechanical clock is considered good.  

2. There is not a detailed procedure for winding a clock.  You just wind each mainspring until you feel the resistance increase.  They can be wound in any sequence.

3.  The movement is called an 8-day which means it will run 8 days between windings, so you wind it once a week and you have a extra "day of grace" if you are away or forget to wind it for a day.  Just wind each mainspring until you feel the resistance increase.  You don't need to wind it until it absolutely won't turn any further.  The difference between these two points is maybe a quarter of a turn of the key.

There can be a couple of reasons why the rate is varying.  First, some movements will change rate at first if you wind it until it won't turn any further.  If a pendulum bob of the incorrect weight or a suspension spring (the small leaf spring at the top of the pendulum assembly) of the wrong strength has been substituted, erratic rating sometimes happens. And there can be some mechanical wear or lubrication problems that can add to this.  But let's say the movement is new or has received periodic service and everything is in order.  The way the pendulum works to regulate the clock is that the longer it is the clock runs slower and the shorter it is the clock runs faster.  To rate the clock the pendulum bob should be checked after each adjustment to insure it is seated firmly on the rating nut.  If it is not, the adjustment will not be accurate.  What happens is that when tightening the nut for increased speed, the nut will push the bob up and be firmly seated.  However, when the nut is loosened the bob doesn't always follow it down resulting in an inaccurate adjustment.  So you might have to pull the bob down so it is firmly seated.  

First, when rating a clock it should be done in the middle portion (does not have to be exact) of a winding, not right after winding fully or nearly wound down.  In my opinion I think it's a little easier to rate a clock from slow to fast.  Since your clock is running fast I would start by loosening the nut a couple of complete turns so it runs a little slow.  Set it near the top of the hour and when it strikes check it with an accurate source such as a quartz watch or clock.  Let it run for 24 hours and check it against the source again, using the strike as a reference.  If you listen closely you will hear a "click' just before the strike action begins.  I use this "click" as my reference point.  If it is indeed slow, tighten the nut two complete turns, reset the time and let it run for another 24 hours.  Note the change.  If it is still slow, turn the nut in the same direction again.  Keep doing this until the rate is accurate.  As you get closer, the nut might have to be turned only a quarter of a turn or less.  If you go too far and it is running fast, you would need to back the nut down, maybe one-half of your last adjustment.  Then let it run for a few days or a full week.  If it is off a little, a small tweak of the rating nut might be necessary.  One further item is that the rating will vary slightly by overall temperature changes.  Usually in the winter the inside temperature is warmer than in the summer when it is cooler.  This will affect some clocks over a week's time and they will have to be adjusted slightly twice a year for the season change.  I hope this helps a little and if you have any more questions, get back with me.

John Newman
THE VILLAGE CLOCKSMITH
Old Prattvillage
Prattville, Alabama


---------- FOLLOW-UP ----------

QUESTION: I meant to ask one additional, important follow-up question:

(5) Should the clock's minute hand be moved only forward, or can it also be moved backward without causing damage to the mechanism when setting the time?

Thanks.

Answer
Matt,  5. Your Hermle 141 is a "safe back" clock and the minute hand can safely be turned counterclockwise to set it.

One note, if you have any further follow-up questions, would you send them to my shop email address?  I have a limit on the number of questions on Allexperts each day and sending the questions to my email address will free up the Allexperts queue.  Thank you.

John Newman