Clocking

[Carl S Zimmerman]

At 10:09 +0100 on 2002/09/28, jim phillips asked (in relation to the 
great steel bell of St Peter's Italian Church):

>... As the bell was clocked I write to ask the question whether 
>'clocking' a steel bell can ever crack it?

The term "clocking" must be a very ancient one, dating from the days 
when the hours were struck manually by a city watchman on duty in the 
church tower, using a sand-glass (or hourglass) before the 
development of mechanical clocks. I say this because the action 
associated with this word (pulling the clapper against the bell by 
means of a rope tied to its flight) is totally different from that of 
any clock-hammer I have ever seen.

Clock hammers are a form of drop or trip hammer. At rest, a clock 
hammer lies on a flat spring, with its head very close to the surface 
of the bell. The clock mechanism lifts the hammer away from the 
bell, then drops it free. The force of the hammer's fall overpowers 
the flat spring sufficiently to allow the hammer head to strike the 
bell. When the impetus of that blow has been absorbed, the spring is 
then able to hold the hammer away from the bell, in the original rest 
position.

The details of the hammer layout vary somewhat. For a single-purpose 
clock bell which is hung dead, the hammer mechanism can be placed 
anywhere about the rim of the bell. For a clock bell which also 
swings, the hammer typically is placed to operate through the frame 
side opposite the wheel; no special action is required when swinging 
the bell other than to insure that the clock does not strike. In 
both of these layouts, the hammer pivot is below the head. 
Drum-driven automatic carillons in the Low Countries have their 
hammers suspended from above, but the principle of operation is the 
same. In all cases, the result is a clean blow of short duration, 
exactly analogous to what happens with a free-swinging clapper inside 
a swinging bell.

Does this description apply to tower clocks (or turret clocks) in the 
UK? Or do they have a different sort of striking mechanism? 
(Unfortunately, during my stay in the UK I never had the opportunity 
(or the desire!) to investigate the details of any tower clocks.)

As is well known, the danger of "clocking" is that the human at the 
end of the rope may carelessly hold the clapper against the bell, 
thus preventing its free vibration and setting up the unusual and 
uneven stresses that may lead to its cracking.

Given this extreme disparity between the action of "clocking" and the 
action of a clock hammer, could we find (or invent) a more accurate 
and less ambiguous word to refer to the former?

-- 
=Carl Scott Zimmerman= Co-Webmaster: http://www.gcna.org/
Voicemail: +1-314-361-5194 (home) mailto:csz_stl at s...
Saint Louis, Missouri, USA - 19th c. home of up to 33 bell foundries