Grand Sonnerie Carriage Clock Overhaul

Complete strip down and overhaul of an excellent example of a Grand Sonnerie Carriage Clock.
These are complicated striking carriage clocks, a description of their operation follows below.

Mechanical Description

Grand Sonnerie clocks work off two racks, a full hour rack and a smaller quarter rack which sits behind the hour rack. The rack hook has two steps on its face. On activation both racks drop, the hour rack is wound up however the quarter rack does not engage with the rack hook because of the step and thus keeps dropping back. On completeion of the hour, the rack hook drops of the back of the 1 hour strike and engages the 2nd step with the quarter hour rack which then winds up. In between the hour and quarter hour strikes there is a false strike as a pin on the back of the hour rack lifts a lever which stops the higher pitched bell landing on the gong to allow the hour to sound on only the one gong.

Unfortunately it is very common to see these clocks bodged. The racks and rack hooks have often been altered along with the mechanism which holds one of the hammers back on the hour strike.  These complications were made to an extremely high degree of accurarcy, with no tollerance at all.  Once they have been altered like this it is extremely hard if not impossible to restore the the to full working order.

Description of the Grand Sonnerie strike.

The Grand Sonnerie (french for grand strike) is a complication on a watch or clock.  On each quarter it sounds the quarters on two gongs (a bit like a ting tang) followed by the hours on one gong.

On every quarter-hour it strikes the number of quarter hours on a gong followed by the number of hours since the last hour on a second gong.
For instance,

• 6:15 it would strike strike six times on the lower pitched gong, then once on a high pitched gong and once on the low pitched gong in quick succession,
• 6:30 it would strike then six times on the lower pitched gong, then altertnately twice on the high and low pitched gongs in quick succession,
• 6:45 six times on the lower pitched gong, then three times alternately on the high and low pitched gong,
• 7 it will sound seven times on the lower pitched gong. It may then not strike the quarters at all or sound 4 on the low/high gongs

You will always know the exact time every fifteen minutes just by listening to the striking.

These types of striking clocks are mostly found as French Carriage Clocks, or German three weight Vienna regulators. In addition they can strike the quarters and hours on demand, by activating a repeating mechanism at the push of a button, or the pull of a string. 

Most of the Grand Sonerie Carriage Clocks have a lever to set the clock to strike the full Grand Sonerie, the Petite Sonnerie (which strikes the hours on the hour and just the quarters on the quarter hours) or silent.