Expert: Martin Meyer - 9/6/2008

Question
Our 30 day key crank up clock use to chime on the hour and ONCE on the half hour. NOW all of sudden it chimes the hour correctly but chimes and EQUAL amount of times on the half hour. What can I do to get it to go back to chiming correctly?
thanks,

Answer
Hi Carol,

Unfortunately this problem involves more than a simple adjustment, and will probably require the services of a professional clock repairer.

The mechanism that controls the strike is called a "rack and snail". I have attached a photo to help explain its operation (this is a different clock, but the general operation is similar). The snail is mounted on the hand shaft, and behind it, mounted to the hand shaft, is a star wheel with a long point and a shorter point. Just before the clock strikes, one of the points on the star wheel raises a lever which causes the rack hook to move away from the rack, thus allowing the rack to drop. At the hour, the long point of the star raises the rack hook higher, letting the rack fall all the way until the rack tail stops it at the correct step on the snail, making the clock strike the correct number of hours.

At the half-hour, it is the short point of the star which triggers the strike, and this point is only able to lift the rack hook part way, so the rack only drops a small amount, allowing the clock to strike only one time.

On your clock, some part of this fairly complicated assembly is out of adjustment or bent, causing the rack to drop all the way to the snail even when it is the short point of the star which triggers the mechanism. Exactly which part is incorrect can be difficult to determine, and experimenting with bending or adjusting parts usually makes the problem worse rather than better. A professional clock repairer can locate the problem and correct it.  http://www.clockmasteronline.com