SETH THOMAS SONORA CHIME
This clock has two mechanisms. The one closest to the front of the clock powers
the strike and the time gear trains. It also trips the chime. The chime mechanism is
closest to the back of the clock. The chime mechanism has a huge mainspring and mainspring
barrel. Pay very close attention to the teeth on this barrel; if this mainspring or
barrel lets go , it will do much damage th the mechanism and possibly to someone’s finger.
Most of these clocks are not self correcting on the chime or the strike.The
mechanism that runs the strike and the time is very similar to the 8 day
time and strike american
clock mechanisms. The chime usually is sounded on a row of bells mounted above
a resonating box. These clocks have a beautiful sound in my opinion. The hammer
sequence is different on these clocks than on the modern German w/c self correcting
mechanisms.
The time and strike mechanism is activated by the chime mechanism ,
however ,the chime mechanism is activated by the trip lever and the trip cam in the
time and strike mechanism. Be absolutely sure to check the ratchet dog system on
the chime mechanism; I have seen many of these loose when they come in for repair.
If one of these lets go , the results will be disastrous indeed. There is usually
a pin on the inside of the ratchet that the click spring pushes on to make the click
work. Be sure to check this pin very carefully , it must not be loose , or the
ratchet system will fail.
The pendulum on these mechanisms usually will have at lease 2 inches of
swing, and the pendulum bob is one of the heavier (2 ¾ ounces typically) types.
Before getting too far on the repair of one of these clocks . it is very wise to check
the gear teeth on the chime mainspring barrel. If the barrel is bad , there is no point
in doing the rest of the work until the barrel problem can be resolved. If the chime
mechanism won’t work , then neither will the strike . The hammer throw is critical
on these clocks ; it may have to be reduced if it has been tampered with . Take the
hammer =assembly out , take it apart and clean it thoroughly. I have frequently seen
these mechanisms bind up because of excessive hammer friction due to too much
throw or gummy oil.
The hammer sequence on this mechanism is different than usual. It is as
follows: looking in the back of the clock and assigning numbers to the four bells
used for the quarter hour melody starting with the bell closest to the back door
and calling it #1 and the one next to it #2 ,Then #3 and finally #4 , not counting the
bell used for the hour strike or course , the order for the quarter hour chime (down
the scale westminster) is ; 2 ,4 ,1 ,3 . This same sequence would also apply to the
3rd measure of the ¾ hour chime.