Expert: Martin Meyer - 7/11/2008

Question
Hi, I have a carriage clock with rack and snail, at 1 it strikes 12, at 2 it strikes 1 and at all other hours it strikes correctly, any ideas what is wrong? Thanks a lot.

Answer
Hi Steph,

The snail on your clock is indexed incorrectly to the minute wheel. At 1:00, the rack tail should fall to land on the highest step of the snail. Instead, it is falling onto the lowest step, that is, the 12:00 position. To correct this problem, the snail must engage with the minute wheel (the offset gear and pinion next to the center shaft and snail) one or two teeth counterclockwise.

These gears are on the front plate of the movement, and behind the dial, so you must remove the movement from the clock, and remove the hands and dial from the movement.

The snail is prevented from lifting, and thus losing its indexing, by the minute hand and, usually, also by a washer on the minute wheel. The washer on the minute wheel will be held on by a taper pin or E-clip. Remove the pin or clip, then remove the washer. Now, use a pencil to mark exactly the teeth on the snail gear that mesh exactly with the teeth on the minute wheel pinion. Hold the minute wheel steady so that it does not turn, while you carefully lift the snail straight off its shaft. You must be very careful that the minute wheel does not disengage from the gear on the minute hand shaft (cannon pinion), or the minute hand will then be incorrectly indexed, and the clock will strike when the minute hand is not pointing directly to the "12". Then replace the snail, rotated one tooth counterclockwise, onto its shaft and engaging with the minute wheel pinion. Check your pencil marks to make sure that the snail gear is one tooth farther counterclockwise on the minute wheel pinion than it was before. Now replace the washer and pin or clip.

Check your adjustment by replacing the minute hand and turning it to the 1:00 position. The clock should strike one time. If it still strikes 12 times, and the rack tail still falls onto the lowest step of the snail, then you will need to repeat the procedure, moving the snail gear one more tooth counterclockwise.

The other hours should now all strike correctly. If they all strike one hour too many, you may have have inadvertently moved the snail too many teeth.  http://www.clockmasteronline.com