Expert: Martin Meyer - 6/29/2008

Question
My parents have a Seth Thomas ship's clock.  It is 2 hours fast.  At the top of the clock's face are two adjustment levers: outside of the circle of numbers and between the 10 and 11 is a lever with "STR" and "SIL"; also outside the circle of numbers and above the 1 is a lever with "F" and "S", which we assume to mean fast and slow.

We do not want to manually adjust the hands without knowing that it will not damage the mechanism.

Answer
Hi John,

The levers indicate "strike" - "silent", and "Fast" - "Slow". Moving the lever toward "Slow" makes the clock run slower, and vice versa.

The hands can be adjusted to the correct time by moving the minute hand. This type of clock generally can be set by moving the minute hand either forward or backward, but if you feel a point of resistance when moving the hand backward, stop immediately, and set the clock by turning the minute hand forward only.

It is advisable Not to set the time in the 10 minute period before a strike point; that is, set the time when the hands read between the hour point (after the clock strikes) and 20 minutes after the hour, or between the half-hour and 10 minutes before the hour.

To adjust the Fast-Slow lever: wind both keyholes fully, as far as they will go, and set the clock to the correct time. Let it run the full winding period (one week), before noting the amount of error and adjusting the Fast-Slow lever. Then repeat this process until the clock keeps accurate time, always winding fully and letting the clock run a full week between adjustments. This is because mainspring-driven clocks run slightly faster when fully wound and slightly slower when almost unwound; making adjustments on a weekly basis averages out this error. http://www.clockmasteronline.com