Expert: Martin Meyer - 6/12/2009

Question
QUESTION: I am trying to adjust my wife's Sligh mantel clock. I am wondering just exactly how many tick/tocks per minute it should have. It seems to be 75, is this correct?

On the bottom is a tag with:
Model 0503-1-AN
Movement 2962
Reg


ANSWER: Hi Alan,

The beats per minute is determined by the pendulum length of the clock. I am not able to determine this from the numbers you gave me, and Sligh is no longer in the clock business, so you will not be able to find it from them. If you send me a followup with all numbers and information stamped on the back movement plate, I may be able to provide you with this information.

But, note that the final regulation should be done by winding the clock fully, as far as it will go, running it for a full week, then noting the error and making a regulating adjustment. This process will take several adjustments and some patience. The beat rate will get you in the ballpark, but mainspring clocks run slightly faster when fully wound and slightly slower when almost unwound, so regulating requires a bit of averaging out for a weekly acceptable accuracy.  http://www.clockmasteronline.com

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

QUESTION: Thanks,
Since I sent the question, I discovered the notations on the movement inside.
It says:
87
Franz Hermle
Two (2) jewels
unadjusted
made in West Germany
1050-021

It has a balance wheel rather than a pendulum. Thanks for your time.
Looking forward, Al Shinn

Answer
Hi Alan,

The beat rate of the 1050 movement is 9,000 Beats Per Hour. Your number of 75 per minute = 4,500 per hour, so I assume that you are counting two "ticks" as a "tick-tock". The beat rate is always calculated by individual ticks, so your number is correct. I would note that, even using a clock timing machine, the final accuracy of timekeeping is always a matter of observation over a full running cycle (8 days), rather than simply a count of the beat rate.  http://www.clockmasteronline.com