Expert: Martin Meyer - 8/6/2007

Question
I have cleaned and serviced a Kininger 79K 116 cm. in a grandfather clock.  I put it back in the case and it will run for over a full revolution on the escape wheel then when I put the face/moon dial on it wont advance any more just rocks back and forth.

Two years ago I first worked on this movement the clock, it was purchased new in 79 and had never been cleaned or oiled.  At that time it would not run as the movement was gummed up and dry.  I cleaned and oiled it and the bushings did not seem to have much if any wear.  It has ran since then until the chime drum became hard to turn to wind it.  I freed it up and put it back together and now the other problem has started.

If I put a couple of my fingers on the top of the weight on the time train it will run.

Thanks,

Jim

Answer
Hi Jim,

Moon dial problems are caused either by the pin on the gear which advances the moon dial misaligning and jamming on the tip of the moon dial tooth, or by the moon gear on the centershaft not intersecting properly with the moon gear on the moon dial. Your problem sounds like the latter.
    But first, move the gears on the dial to a position where the pin is not in contact with a moon dial tooth. Then mount the dial on the movement. If the clock still stops, this confirms that this was not your problem.
    Now mount the dial and look at the engagement of the centershaft moon gear with the dial moon gear. Make sure that the gears are intersected, and not misaligned with the dial moon gear just pressing on the centershaft moon gear but not engaging it. This is the most common cause of your problem.
    If the gears are properly engaged, then you must check for correct depthing and alignment. The two gears should be fully in contact, that is, one gear should not be at the very edge of the other gear. If this is the case, realign the gears by loosening the set screw on the centershaft moon gear and moving it a small amount to make it align better with the dial moon gear.
    If none of these methods correct the problem, then the cause almost has to be depthing. Reach in and touch the dial moon gear that engages the centershaft moon gear, and move it back and forth gently. You should feel a very distinct slack, or clearance, between the two gears. If you can look closely into the engagement of these gears, you should see both plenty of clearance between the engaged teeth, and ESPECIALLY, neither gear tooth must be bottomed out on the trough of the opposing gear. If the gears are bottomed out, you must find the cause.
    This could be a bent shaft on the moon dial gear, but is far more likely to be caused by a bent centershaft. Remove the dial and look at the movement from the side while you turn the minute hand around through several revolutions. If the centershaft is bent, you will see it moving up and down as you turn it. You can correct this bend by pressing very carefully on the centershaft to bend it back to its correct position. Then turn the minute hand and recheck. It will take several adjustments to make the centershaft run true.
    Thanks for your question.   Martin