HAMMERS, GONGS AND BELLS.
Just as the tone of a piano depends very largely upon the condition
of the felts on the hammers which strike the wires, so does the tone
of a clock gong or bell depend on its hammer action. The deep, soft,
resonant tone in either instance depends on the vibration being
produced by something softer than metal. Ordinarily this condition is
reached by facing the hammer with leather. The second essential is that
the hammer shall immediately rebound, clear of the bell, so as not
to interfere with the vibrations it has set up in the bell, wire or
tube. As the leather gets harder the tone becomes harsher and “tinny,”
sometimes changing to another much higher tone and entirely destroying
the harmony. The remedy is either to oil the leather on the hammers,
or if they are much worn to substitute new and thicker leathers until
the tone is sufficiently mellowed, so that a vigorous blow will still
produce a mellow tone of sufficient carrying power. A piece of round
leather belting will be found very convenient for this purpose.
The superiority of a chiming clock lies in its hammer action. If this
mechanism is not perfect, only inferior results can be obtained. The
perfect hammer is the one that acts with the smallest strain and is
operated with the least power. Heavy weights create a tremendous
strain on the mechanism and bring disastrous results when one of the
suspending cords break. The method of lifting the hammer is one of
importance, and the action of the hammer-spring is but seldom right on
old clocks brought in for repairs, especially if it be a spring bent
over to a right angle at its point. If there are two springs, one to
force the hammer down after the clock has raised it up, and another
shorter one, fastened on to the pillar, to act as a counter-spring and
prevent the hammer from jarring on the bell, there will seldom be any
difficulty in repairing it; and the only operation necessary to be
done is to file worn parts, polish the acting parts, set the springs a
little stronger, and the thing is done. But if there is only one spring
some further attention will be necessary, because the action of the
one spring answers the purpose of the two previously mentioned, and to
arrange it so that the hammer will be lifted with the greatest ease and
then strike on the bell with the greatest force, and without jarring,
requires some experience. That part of the hammer-stem which the spring
acts on should never be filed or bent beyond the center of the arbor,
as is sometimes done, because in such a case the hammer-spring has
a sliding motion when it is in action, and some of the force of the
spring is thereby lost. The point of the spring should also be made to
work as near to the center of the arbor as it is possible to get it,
and the flat end of the spring should be at a right angle with the edge
of the frame, and that part of the hammer-stem that strikes against the
flat end of the spring should be formed with a curve that will stop the
hammer in a particular position and prevent it jarring on the bell.
This curve can only be determined by experience; but a curve equal to a
circle six inches in diameter will be nearly right.
The action of the pin wheel on the hammer tail is also of importance.
The acting face of the hammer tail should be in a line with the center
of the pin wheel, or a very little above it, but never below it, for
then it becomes more difficult for the clock to lift the hammer, and
the hammer tail should be of such a length as to drop from the pins of
the pin wheel, and when it stops be about the distance of two teeth
of the wheel from the next pin. This allows the wheel-work to gain a
little force before lifting the hammer, which is sometimes desirable
when the clock is a little dirty or nearly run down. We might also
mention that in setting the hammer-spring to work with greater force
it is always well to try and stop the fly with your finger when the
clock is striking, and if this can be done it indicates that the hammer
spring is stronger than the striking power of the clock can bear, and
it ought to be weakened, because the striking part will be sure to stop
whenever the clock gets the least dirty.
Gong wires are also the cause of faulty tones. In the factories these
are made by coiling wires of suitable lengths and sections on arbors in
a lathe. They are then heated to a dull red and hardened by dipping in
water or oil. After cooling they are trued in the round and the flat
like a watch hairspring and then drawn to a blue temper. The tone comes
with the tempering, and if they are afterwards bent beyond the point
where they will spring back to shape the tone is interfered with. Many
repairers, not being aware of this fact, have ruined the tone of a gong
wire while trying to true it up by bending with pliers. When the owner
is particular about the tone of the clock, a new gong should always be
put in if the old one is badly bent.
The wires are soldered to their centers and if they are at all loose
they should be refastened in the same manner if it can be done without
drawing the temper of the wire. When this cannot be done a plug of
solder may be driven in between the wire and the side of the hole so as
to stop all vibration or the solder already in place may be driven down
so as to make all tight, as any vibration at this point will interfere
with the tone.
[Illustration: Fig. 121. The pins in the chiming barrels.]
TUNING THE BELLS.—Bells only very slightly out of tone offend the
musical ear, and they may easily be corrected to the extent of half
a tone. To sharpen the tone make the bell shorter by turning away
the edge of it if it be a shell, or by cutting off if it be a rod or
tube; to flatten the tone, thin the back basin-shaped part of the bell
by turning some off the outside. Bells which are cracked give a poor
sound because the edges of the crack interfere with each other when
vibrating. They may be repaired by sawing through the crack to the end
of it, so that the edges will not touch each other when vibrating. If
there is danger of the crack extending further into the bell, first
drill a round hole in the solid metal just beyond the end of the crack,
and then saw through into the hole; this will generally prevent any
further trouble.
MARKING THE CHIME BARREL.—The chime barrel in small clocks is of brass
and should be as large in diameter as can be conveniently got in. To
mark off the positions of the pins for the Cambridge chimes, first put
the barrel in the lathe and trace circles round the barrel at distances
apart corresponding to the positions of the hammer tails. There are
five chimes of four bells each for every rotation of the barrel, and a
rest equal to two or three notes between each chime. Assuming the rest
to be equal to three notes, divide the circumference of the barrel into
thirty-five equal parts by means of an index plate, and draw lines at
these points across the barrel with the point of the tool by moving it
with the slide rest screw. Call the hammer for the highest note D, and
that for the lowest note F. Then the first pin is to be inserted where
one of the lines across the barrel crosses the first circle; the second
pin where the next line crosses the second circle; the third pin where
the third line crosses the third circle and the fourth pin where the
fourth line crosses the four circle, because the notes of the first
chime are in the order, D, C, Bb, F. Then miss three lines for the
rest. The first note of the second chime is Bb and the pins for it will
consequently be inserted where the first line after the rest crosses
the third circle, and so on. Where two or more notes on the same bell
come so close as to make it difficult to strike them properly, it is
usual to put in another hammer, as it shown in Fig. 121, where there
are two Fs. In fine clocks the pins are of varying lengths so as to
strike the hammers on the bells with varying force and thus give more
expression to the music.
The following gives the Cambridge Chimes, which are used in the
Westminster Great Clock. They are founded on a phrase in the opening
symphony of Handel’s air, “I know that my Redeemer liveth,” and were
arranged by Dr. Crotch for the clock of Great St. Mary’s, Cambridge, in
1793.
[Illustration: Fig. 122. Westminster chimes.]
In Europe these chiming clocks are sometimes very elaborate, as the
following description of a set of bells in Belgium will show:
“So far as the experience of the writer goes the Belgian carillons are
invariably constructed on one prevailing plan, with the exception that
the metal used for the cylinder is generally brass; here, however, it
is of steel, and consists of a large barrel measuring 4 feet 2 inches
in width and 3 feet 6 inches in diameter, its surface being pierced
with horizontal lines of small square holes about ⅜ inch square. There
are lines of 60 of these in the width of the barrel, while there are
120 lines of them round the circumference, making a total of 7,200
holes. The drilling of these, of course, takes place when the cylinder
is made, and, so far as this part is concerned, the barrel is complete
before it is brought to the tower.
“Into these square holes are fixed the ‘pins,’ adjusted on the inside
of the cylinder by nuts.
“The pins are of steel of finely graduated sizes, corresponding with
the value of the notes of music. Some idea of the precision obtainable
may be gathered by the fact, as the carillonneur told the writer, that
there were no less than 24 grades of pins, so as to insure the greatest
accuracy of striking the bells.
“Over the cylinder are 60 steel levers with steel nibs; these are
lifted by the ‘pins’ and, connected by wires with the hammers, strike
the bells.
“The 35 bells are furnished with 72 hammers, which are fixed as
ordinary clock-hammers outside of the bells; three of the bells (in
the ring of eight) have a single hammer only, the limited space in the
‘cage’ making it impossible to put more, while others are supplied with
two or three apiece for use in rapidly repeating notes of the music. On
a visit some years ago to the carillon at Malines, the writer noticed
that some of the bells there had no less than five hammers apiece.
“Obviously, though there are 72 hammers in connection with the
carillon, only 60, corresponding with the number of levers, can be used
at one time; these are selected according to the requirement of the
tune; in case of new tunes, the wires can easily be adjusted so as to
bring other hammers and bells into use.
“The feature of the Belgian carillons is that instead of the single
notes of the air being struck as with the old familiar ‘chimes’
harmonized tunes of great intricacy are rendered with chords of three,
four or even five bells striking at one time.
“The cylinder here is capable of 120 ‘measures’ of music, but as, a
matter of fact it is subdivided so that half a revolution plays every
hour.
“A march is, as a rule, played at the odd hours, and the national air
at the even, but the bells are silent after 9 p. m. and start again at
8 a. m.
“The motive power is supplied by a weight of 8 cwt., and is controlled
by a powerful fly of four fans artistically formed to represent swans.
It may be mentioned that the keyboard for hand-playing consists of
thirty-five keys of wood and eleven pedals; these, as indeed the whole
apparatus of this part, are entirely separate from the automatic
carillon; in this instance the keys connect with the clappers of
the bells and have no association with the hammers. The pedals are
connected with the eleven largest bells and are supplementary to the
hour key.”
TUBULAR CHIMES are tubes of bell metal, cut to the proper lengths to
secure the desired tones and generally, but not always, nickel plated.
As they take up much room in the clock, they are generally suspended
from hooks at the top of the back board of the case, being attached to
the hooks by loops of silk or gut cords, passed through holes drilled
in the wall of the tubes near the top ends. The hour tube, being long
and large, generally extends nearly to the bottom of a six-foot case,
while the others range upwards, shortening according to the increase of
pitch of the notes which they represent.
This makes it necessary to place the movement on a seat board and
hang the pendulum from the front plate of the movement, so that such
clocks have, as a rule, comparatively light pendulums. On account of
the position and the great spread of the tubes, the chiming cylinder
and hammers are placed on top of the movement, parallel with the
plates, and operated from the striking train by means of bevel gears or
a contrate wheel. The hammers are placed vertically on spring hammer
stalks and connected with the chiming cylinder levers by silken cords.
This gives great freedom of hammer action and results in very perfect
tones. The hammers must of course be each opposite its own tube and
thus they are rather far apart, which necessitates a long cylinder.
This gives room for several sets of chimes on the same cylinder if
desired, as a very slight horizontal movement of the cylinder would
move the pins out of action with the levers and bring another set into
action or cause the chimes to remain silent.
Practically all of the manufacturers of “hall” or chiming clocks import
the movements and supply American cases, hammers and bells. The reason
is that there is so little sale for them (from a factory standpoint)
that one factory could supply the world with movements for this class
of clocks without working overtime, and therefore it would be useless
to make up the tools for them when they can be bought without incurring
that expense.