ELECTRIC CLOCKS AND BATTERIES.
Electric clocks may be divided into three kinds, or principal
divisions. Of the first-class are those in which the pendulum is driven
directly from the armature by electric impulse, or by means of a weight
dropping on an arm projecting from the pendulum. In this case the
entire train of the clock consists of a ratchet wheel and the dial work.
The second class comprises the regular train from the center to the
arbor. This class has a spring on the center arbor, wound more or less
frequently by electricity. In this case the aim is to keep the spring
constantly wound, so that the tension is almost as evenly divided as
with the ordinary weight clock, such as is used in jewelers’ regulators.
The third system uses a weight on the end of a lever connected with
a ratchet wheel on the center arbor and does away with springs. One
type of each of these clocks will be described so that jewelers may
comprehend the principles on which the three types are built.
[Illustration: Fig. 123. Gillette Clock (Pendulum Driven).]
In the Gillette Electro-Automatic, which belongs to the class first
mentioned, the ordinary clock principle is reversed. Instead of the
works driving the pendulum, the pendulum drives the train, through
the medium of a pawl and ratchet mechanism on the center arbor. The
pendulum is kept swinging by means of an impulse given every beat by an
electromagnet. This impulse is caused by the weight of the armature as
it falls away from the magnet ends, the current being used solely to
pull back and re-set the armature for the next impulse. Any variation
in the current, therefore, does not affect the regulation of the clock,
as the power is obtained from gravity only, by means of the falling
weight. Referring to the drawings, Figs. 123 and 124, it is seen that
each time the pendulum swings the train is pushed one tooth forward.
A cam is carried by the ratchet (center) arbor in which a slot is
provided at a position equivalent to every fifth tooth of the ratchet.
Into this slot drops the end of a lever, releasing at its other end
the armature prop. Thus at the next beat of the pendulum the armature
is released and in its downward swing impulses the pendulum, giving it
sufficient momentum to carry it over the succeeding five swings.
The action of the life-giving armature is entirely disconnected and
independent of the clock mechanism. It acts on its own accord when
released every tenth beat and automatically gives its impulse and
re-sets itself. It is provided with a double-acting contact spring (see
Fig. 125) which “flips” a contact leaf from one adjustable contact
screw to the other as the action of the armature causes the spring to
pass over its dead center. Thus, when the armature reaches the lowest
point in its drop (Figs. 126 and 127) the leaf snaps against the right
contact screw, the circuit is completed, the magnet energized and
the armature drawn up. As the armature rises above a certain point,
the dead center of the flipper spring is again crossed and the leaf
snaps back against the post at the left. In the meantime, however, the
armature prop has slipped under the end of the armature and retains it
until the time comes for the next impulse.
[Illustration: Fig. 124. Side View.]
In adjusting the mechanism of this type of clock the increasing
pendulum swing should catch and push the ratchet before the buffer
strikes and lifts the armature from the prop. The adjustment of the
“flipper” contact screws (with ¹/₃₂ inch play) should be such that as
the armature falls the contact leaf will be thrown and the armature
drawn up at a point just beyond the half way position in the swing of
the pendulum. The power of the impulse can be regulated by turning the
adjusting post with pliers, thus varying the tension of the armature
spring, the pull of which reinforces the weight of the armature. Care
should be taken, however, that the tension is not beyond the “quick
action” power of the electromagnet. It is much better to ease up the
movement in other ways before putting too great a load on the life of
the battery.
The electrical contacts on the leaf and screw are platinum tipped to
prevent burning by the electric sparking at the “make” and “break.”
This sparking is also much reduced by means of a resistance coil placed
in series connection with the magnet coil, Fig. 127, to reduce the
amount of current used. If this coil is removed or disconnected the
constant sparking and heat would soon burn out the contact tips.
Care should be taken to see that the batteries are dated and the
battery connections are clean at the time of sliding in a new battery.
The brush which makes connection with the center or carbon post of the
battery is insulated with mica from the framework of the case. The
other connection is made from the contact of the uncovered zinc case
of the battery with the metal clock case surrounding it. The contact
points should be bright and smooth to insure good contacts.
These clocks need but little cleaning of the works as _no oil whatever
is used_, except at one place, viz., the armature pivot. Oil should
_never_ be used on the train bearings, or other parts. This clock ran
successfully on the elevated railway platforms of the loop in Chicago
where no other pendulum clock could be operated on account of the
constant shaking.
In considering the electrical systems of these clocks, let us commence
with the batteries. While undoubtedly great improvements have been made
in the present form of dry battery they are still very far from giving
entire satisfaction. Practically all of them are of one kind, which
is that which produces electricity at 1½ volts from zinc, carbon and
sal-ammoniac, with a depolarizer added to the elements to absorb the
hydrogen. The chemical action of such a battery is as follows:
[Illustration: Fig. 125.]
The water in the electrolite comes in contact with the zinc and is
decomposed thereby, the oxygen being taken from the water by the zinc,
forming oxide of zinc and leaving the hydrogen in the form of minute
bubbles attached to the zinc. As this, if allowed to stand, would shut
off the water from reaching the zinc, chemical action would therefore
soon cease and when this happens the battery is said to be polarized
and no current can be had from it.
[Illustration: Fig. 126. The Electric Contact.
Fig. 127. The Wiring System.]
In order to take care of the hydrogen and thus insure the constant
action of the battery, oxide of manganese is added to the contents of
the cell, generally as a mixture with the carbon element. Manganese
has the property of absorbing oxygen very rapidly and of giving it off
quite easily. Therefore while the hydrogen is being formed on the zinc,
it becomes an easy matter for it to leave the zinc and take its proper
quantity of oxygen from the manganese and again form water, which is
again decomposed by the zinc. As long as this cycle of chemical action
takes place the battery will continue to give good satisfaction,
and usually when a battery gives out it is because the depolarizer
is exhausted, for the reason that the carbon is not affected at all
and the zinc element forming the container is present in sufficient
quantity to outlast the chemical action of the total mass.
There are great differences in the various makes of batteries; also in
the methods of their construction. It would seem to be an easy matter
for a chemist to figure out exactly how much depolarizer would serve
the purpose for a given quantity of zinc and carbon and therefore to
make a battery which should give an exact performance that could be
anticipated. In reality, however, this is not the case, owing to the
various conditions. There are three qualities of manganese in the
market; the Japanese, which is the best and most costly; the German,
which comes second, and the American, which is the cheapest and varies
in quality so much as to be more or less a matter of guesswork. We
must remember that in making batteries for the price at which they are
now sold on the market we are obliged to take materials in commercial
quantities and commercial qualities and cannot depend upon the
chemically pure materials with which the chemists’ theories are always
formulated. This therefore introduces several elements of uncertainty.
In practice the Japanese manganese will stand up for a far longer
time than any other that is known and it is used in all special
batteries where quality and length of life are considered of more
importance than the price. The German manganese comes next. Then comes
a mixture of American and German manganese, and finally the American
manganese, which is used in making the cheaper batteries which are
sorted afterwards, as we shall explain farther on. These batteries are
sealed after having been made in large quantities, say five thousand
or ten thousand in the lot, and kept for thirty days, after which they
are tested. The batteries which are likely to give short-life will
show a local action and consequent reduction of output in thirty days.
They are, therefore, sorted out, much as eggs are candled on being
received in a storage warehouse, for the reason that after a cell has
been made and put together it would cost more to find out what was the
matter with it and remedy that than it would to make a new cell. Many
of the battery manufacturers, therefore, make up their batteries with
an attempt to reach the highest standard. They are sorted for grade in
thirty days and those which have attained the point desired are labeled
as the factories’ best battery and are sold at the highest prices.
The others have been graded down exclusively and labeled differently
until those which are positively known to be short-lived are run out
and disposed of as the factories’ cheapest product under still another
label.
When buying batteries always look to see that the tops are not cracked,
as if the seal on the cell is broken, chemical action induced from
contact with the air as the battery dries out, will rapidly deteriorate
the depolarizer and sulphate the zinc, both of which are of course
a constant draft on the life of the battery, which contains only a
stated quantity of energy in the beginning. Always examine the terminal
connections to see that they are tight and solid.
Batteries when made up are always dated by the factory, but this does
the purchaser little good, as the dates are in codes of letters,
figures, or letters and figures, and are constantly changed so that
even the dealers who are handling thousands of them are unable to read
the code. This is done because many people are prone to blame the
battery for other defects in the electrical system and many who are
using great quantities would find an incentive to switch the covers
on which the dates appear if they knew what it meant. This is perhaps
rather harsh language, but a good many men would be tempted to send
back a barrel of old batteries every now and then with the covers
showing that they had not lasted three months, if they could read these
signatures.
Practically the only means the jeweler has of obtaining a good cell,
with long life, is to buy them of a large electrical supply house,
paying a good price for them and making sure that that house has trade
enough in that battery to insure their being continuously supplied with
fresh stock.
The position of the battery also has to do with the length of life
or amount of its output. Thus a battery lying on its side will not
give more than seventy-five per cent of the output of a battery which
is standing with the zinc and carbon elements perpendicular. Square
batteries will not give the satisfaction that the round cell does. It
has been found in practice by trials of numerous shapes and proportions
that the ordinary size of 2½ × 6 inches will give better satisfaction
than one of a different shape—wider or shorter, or longer and thinner;
that is for the amount of material which it contains. The battery
which has proved most successful in gas engine ignition work is 3¾ × 8
inches. That maintains the same proportions as above, or very nearly
so, but owing to local action it will give on clock work only about
fifty per cent longer life than the smaller size.
It has been a more or less common experience with purchasers of
electric clocks to find that the batteries which came with the clock
from the factory ran for two or three years (three years not being at
all uncommon) and that they were then unable to obtain batteries which
would stand up to the work for more than three weeks, up to six months.
The difference is in the quality and freshness of the battery bought,
as outlined above.
[Illustration: Fig. 128. Fig. 129.]
In considering the rest of the electrical circuit, we find three
methods of wiring commonly used and also a fourth which is just now
coming into use. The majority of electric clocks are wound by a magnet
which varies in size from three to six ohms; bridged around the contact
points, there has generally been placed a resistance spool which
varies in size from ten to twenty-five times the number of ohms in the
armature magnets. See Fig. 128. This practically makes a closed circuit
on which we are using a battery designed for open circuit work.
If we use an electromagnet with a very soft iron core, we will need
a small amount of current, but every time we break the contact, we
will have a very high counter electro-motive force, leaping the
air gap made while breaking the contact and therefore burning the
contact points. If our magnet is constructed so as to use the least
current, by very careful winding and very soft iron cores, this counter
electro-motive force will be at its greatest while the draft on the
battery is at its smallest. If the magnet cores are made of harder
iron, the counter electro-motive force will be much less; but on the
other hand much more current will be needed to do a given quantity of
work with a magnet of the second description; and the consequence is
that while we save our contact points to some extent, we deplete the
battery more rapidly.
If we put in the highest possible resistance—that of air—in making
and breaking our contacts, we use current from the battery only to do
useful work; but we also have the spark from the counter electro-motive
force in a form which will destroy our contact points more quickly.
If we reduce the resistance by inserting a German silver wire coil of
say sixty ohms on a six-ohm magnet circuit, we have then with two dry
batteries (the usual number) three volts of current in a six-ohm magnet
during work and three volts of current in a sixty-six ohm circuit while
the contacts are broken, Fig. 128. Dividing the volts by the ohms, we
find that one twenty-second of an ampere is constantly flowing through
such a circuit. We are therefore using a dry battery (an open circuit
battery) on closed circuit work and we are drawing from the life of our
battery constantly in order to save our contact points.
It then becomes a question which we are going to sacrifice, or what
sort of a compromise may be made to obtain the necessary work from the
magnet and at the same time get the longest life of the contact points
and the batteries. Most of the earlier electric clocks manufactured
have finally arranged such a circuit as has been described above.
The Germans put in a second contact between the battery and the
resistance with a little larger angular motion than the first or
principal contact, so that the contact is then first made between the
battery and resistance spool, B, Fig. 129, then between the two contact
points of the shunt, A; Fig. 129, to the electromagnet, and after
the work is done they are broken in the reverse order, so that the
resistance is made first and broken after the principal contact. This
involves just twice as many contact points and it also involves more or
less burning of the second contact.
[Illustration: Fig. 130. Fig. 131.]
The American manufacturers seem to prefer to waste more or less current
rather than to introduce additional contact points, as they find that
these become corroded in time with even the best arrangements and they
desire as few of them as possible in their movements, preferring rather
to stand the draft on the battery.
One American manufacturer inserts a resistance spool of 60 ohms in
parallel with a magnet of seven ohms (3½ ohms for each magnet spool)
as in Fig. 130. He states that the counter electro-motive force is
thus dissipated in the resistance when the contact is broken, as the
resistance thus becomes a sort of condenser, and almost entirely does
away with heating and burning of the contacts, while keeping the
circuit open when the battery is doing no work.
It has been suggested to the writer by several engineers of high
attainments and large experience that what should be used in the
above combination is a condenser in place of a resistance spool, as
there would then be no expenditure of current except for work. One
of the clocks changed to this system just before the failure of its
manufacturers, but as less than four hundred clocks were made with the
condensers (Fig. 131), the point was not conclusively demonstrated.
It should also be borne in mind that the condenser has been vastly
improved within the last twelve months. With the condenser it will be
observed that there is an absolutely open circuit while the armature
is doing no work and that therefore the battery should last that much
longer, Figs. 130 and 131. As to the cost of the condensers as compared
with resistance spools, we are not informed, but imagine that with the
batteries lasting so much longer and the clock consequently giving so
much better satisfaction, a slight additional cost in manufacture by
changing from resistance to condensers would be welcomed, if it added
to the length of life and the surety of operation.
Electric clocks cost more to make than spring or weight clocks and sell
for a higher price and a few cents additional per movement would be a
very small premium to pay for an increase in efficiency.
The repairer who takes down and reassembles one of these clocks very
often ignorantly makes a lot of trouble for himself. Many of the older
clocks were built in such a way that the magnets could be shifted for
adjustment, instead of being put in with steady pins to hold them
accurately in place. The retail jeweler who repairs one of these
clocks is apt to get them out of position in assembling. The armature
should come down squarely to the magnets, but should not be allowed to
touch, as if the iron of the armature touches the poles of the magnet
it will freeze and retain its magnetism after the current is broken.
Some manufacturers avoid this by plating their armatures with copper or
brass and this has puzzled many retailers who found an electromagnet
apparently attracting a piece of metal which is generally understood to
be non-magnetic.
The method offers a good and permanent means of insulating the iron of
the armature from the magnet poles while allowing their close contact
and as the strength of a magnet increases in proportion to the square
of the distance between the poles and the armature, it will be seen
that allowing the armature to thus approach as closely as possible
to the poles greatly increases the pull of the magnet at its final
point. If when setting them up the magnet and armature do not approach
each other squarely, the armature will touch the poles on one side or
another and soon wear through the copper or brass plating designed
to maintain their separation and then we will have freezing with its
accompanying troubles.
A very good test to determine this is to place a piece of watch paper,
cigarette paper or other thin tissue on the poles of the magnet before
the naked iron armature is drawn down. Then make the connection, hold
the armature and see if the paper can be withdrawn. If it cannot the
armature and poles are touching and means should be taken to separate
them. This is sometimes done by driving a piece of brass into a hole
drilled in the center of the pole of the magnet; or by soldering a thin
foil of brass on the armature. As long as the separation is steadily
maintained the object sought is accomplished, no matter what means is
used to attain it.
Another point with clocks which have their armatures moved in a
circular direction is to see that the magnet is so placed as to give
the least possible freedom between the armatures and the circular poles
of the magnet, but that there must be an air-gap between the armature
and magnet poles.
In those clocks which wind a spring by means of a lever and ratchet
working into a fine-toothed ratchet wheel, or are driven by a weighted
lever, there is an additional point to guard against. If the weight
lever is thrown too far up, either one of two things will happen. The
weight lever may be thrown up to ninety degrees and become balanced if
the butting post is left off or wrongly replaced; the power will then
be taken off the clock, if it is driven directly by weight, so that a
butting post should meet the lever at the highest point and insure that
it will not go beyond this and thus lose the efficiency of the weight.
In the cases where a spring on the center arbor is interposed between
the arbor and the ratchet wheel, it should be determined just how many
teeth are necessary to be operated when winding, as if a clock is wound
once an hour and the aim is to wind a complete turn (which is the
amount the arbor has run down) if the lever is allowed to vibrate one
or two teeth beyond a complete turn, it will readily be seen that in
the course of time the spring will wind itself so tightly as to break
or become set. This was a frequent fault with the Dulaney clock and has
not been guarded against sufficiently in some others which use the fine
ratchet tooth for winding.
When such a clock is found the proper number of teeth should be
ascertained and the rest of the mechanism adjusted to see that just
that number of teeth will be wound. If less is wound there will come a
time when the spring will run down and the clock will stop. If too much
is wound the spring will eventually become set and the clock will stop.
Therefore such movements should be examined to see that the proper
amount of winding occurs at each operation. Of course where a spring is
wound and there are but four notches in the ratchet wheel and the screw
stop is accurately placed to stop the action of the armature, over
action will not harm the spring, provided it will not go to another
quarter, as if the armature carries the ratchet wheel further than it
should, the smooth circumference between the notches will let it drop
back to its proper notch.
There are a large number of clocks on the market which wind once per
hour. These differ from the others in that they do not depend upon a
single movement of the armature for an instantaneous winding. Thus
if the batteries are weak it may take twenty seconds to wind. If the
batteries are strong and new it may wind in six seconds. In this
respect the clock differs radically from the others, and while we have
not personally had them under test, we are informed that on account of
winding once per hour the batteries will last very much longer than
would be expected proportionately from those which wind at periods of
greater frequency. The reason assigned is that the longer period allows
the battery to dispose of its hydrogen on the zinc and thus to regain
its energy much more completely between the successive discharges
and hence can give a more effective quantity of current for hourly
discharge than those which are discharged several times a minute,
or even several times an hour. It is only proper to add that the
manufacturers of clocks winding every six or seven minutes dispute this
assertion.
Another point is undoubtedly in the increased length of life of the
contacts; but speaking generally the electric clock may be said now to
be waiting for further improvements in the batteries. Those who have
had the greatest experience with batteries, as the telephone companies,
telegraph companies and other public service corporations, have
generally discarded their use in favor of storage batteries and dynamos
wherever possible and where this is not possible they have inspected
them continuously and regularly.
In this respect one point will be found of great service. When putting
in a new set of batteries in any electrical piece of machinery, write
the date in pencil on the battery cover, so that you, or those who
come after you, some time later, will know the exact length of time
the battery has been in service. This is frequently of importance,
as it will determine very largely whether the battery is playing out
too soon, or whether faults are being charged to the battery which are
really due to other portions of the apparatus.
Never put together any piece of electrical apparatus without seeing
that all parts are solidly in position and are clean; always look
carefully to connections and see that the insulation is perfect so that
short circuits will be impossible.
All contacts must be kept smooth and bright and contact must be made
and broken without any wavering or uncertainty.
Fig. 132 shows the completely wired movement of the American Clock
Company’s weight driven movement, which may be accepted as a type of
this class of movements—weight driven, winding every seven minutes.
The train is a straight-line time train, from the center arbor to the
dead beat escapement, with the webs of the wheels not crossed out. It
is wired with the wire from the battery zinc screwed to the front plate
H and that from the battery carbon to an insulated block G.
Fig. 133 shows an enlarged view of the center arbor. Upon this arbor
are secured (friction-tight) two seven-notched steel ratchets, E, and
carried loosely between them are two weighted levers pivoted loosely
on the center arbor. Each lever is provided with a pawl engaging in
the notches of the nearest ratchet, as shown. The weighted lever has a
circular slot cut in it, concentric with the center hole and also has a
portion of its circumference at the arbor cut away, thus forming a cam.
Between these two levers is a connecting link D with a pin in its upper
end, which pin projects into the circular slots of the weight levers.
[Illustration: Fig. 132.]
[Illustration: Fig. 133.]
The lever F is pivoted to the front plate of the clock and carries at
right angles a beveled arm which projects over the ratchets E, but is
ordinarily prevented from dropping into the notches by riding on the
circumferences of the weighted levers. When one lever has dropped down
and the other has reached a horizontal position the cut portions of
the circumferences of these levers will be opposite the upper notch of
the ratchets and will allow the bar projecting from F to drop into the
notches. This allows F and G to connect and the magnet A is energized,
pulls the armature B, the arms C D, and thus lifts the lever through
the pin in D pulling at the end of the circular slot. As the lever
flies upward, the cam-shaped portion of its circumference raises the
arm out of the notches, thus separating F and G and breaking the
circuit. A spring placed above E keeps its arms pressed constantly upon
E in position to drop. The wiring of the magnets is shown in Fig. 130.
[Illustration: Fig. 134.]
The upper contact (carried in F) is a piece of platinum with its lower
edge cut at an angle of fifteen degrees and beveled to a knife edge.
The lower point of this bevel comes into contact first and is the
last to separate when breaking connection, so that any sparking which
may take place will be confined to one edge of the contacts while the
rest of the surface remains clean. (See Fig. 134.) Ordinarily there
is very little corrosion from burning and this is constantly rubbed
off by the sliding of the surfaces upon each other. The lower contact,
G, consists of a brass block mounted upon an insulating plate of hard
rubber. The block is in two pieces, screwed together, and each piece
carries a platinum tipped steel spring. These springs are so set as
to press their platinum tips against each other directly beneath the
upper contact. The upper and lower platinum tips engage each other
about one-sixteenth inch at the time of making contact. The lower block
being in two pieces, the springs may be taken apart for cleaning, or
to adjust their tension. The latter should be slight and should in
no case exceed that which is exerted by the spring in F, or the upper
knife edge will not be forced between the two lower springs. The pin
on which F is pivoted and that bearing on the spring above it must be
clean and bright and _never be oiled_, as it is through these that the
current passes to the upper contact in the end of F. The contacts are,
of course, never oiled.
The two weighted levers should be perfectly free on the center arbor
and their supporting pawls should be perfectly free on the shoulder
screws in the levers. Their springs should be strong enough to secure
quick action of the pawls. This freedom and speed of action are
important, as the levers are thrown upward very quickly and may rebound
from the butting post without engaging the ratchets if the pawls do not
work quickly.
The projecting arm, C, of the armature, B, has pivoted to it, a link,
D, which projects upward and supports at its upper end a cross pin.
The link should not be tight in the slot of C, but should fit closely
on the sides, in order to keep the cross pin at the top of D parallel
with the center staff of the clock. This cross pin projects through D
an equal distance on either side, each end respectively passing through
the slot of the corresponding lever, the total length of this pin being
nearly equal to the distance between the ratchets. When the electric
circuit is closed, and the magnets energized, B, C and D are drawn
downward; the weighted end of one of the levers which runs the clock,
being at this time at the limit of its downward movement, see Fig.
135, the opposite or slotted end of said lever, is then at its highest
point, and the downward pull in the slot by one end of the above
described crosspin which enters it will throw the weighted end of the
said lever upward. The direct action of the magnets raises the lever
nearly to the horizontal position, and the momentum acquired carries
it the remainder of the distance. By this arrangement of stopping
the downward pull of the pin when the ascending lever reaches the
horizontal, all danger of disturbing the other lever A is avoided. The
position is such that the top of the ascending lever weight is about
even with the center of the other weight when the direct pull ceases.
[Illustration: Fig. 135.]
Before starting the clock raise the lever weights so that one lever
is acting upon a higher notch of the ratchet than the other. They are
designed to remain about forty-five degrees apart, so as to raise only
one lever at each action of the magnet. This maintains an equal weight
on the train, which would not be the case if they were allowed to
rise and fall together; keeping the levers separated also reduces the
amount of lift or pull on the battery and uses less current, which is
an item when the battery is nearly run down. If these levers are found
together it indicates that the battery is weak, the contacts dirty,
making irregular winding, or the pawls are working improperly. See that
the levers rise promptly and with sufficient force. After one of them
has risen stop the pendulum and see that the butting post is correctly
placed, so that there is no danger of the lever wedging under the post
and sticking there, or causing the lever to rebound too much. The
butting post is set right when the clock leaves the factory and seldom
needs adjustment unless some one has tinkered with it.
The time train should be oiled as with the ordinary movements, also
the pawls on the levers. The lever bushings should be cleaned before
oiling and then well oiled in order to avoid friction on the center
arbor from the downward pull of the magnets when raising the levers. In
order to clean the levers drive out the taper pin in the center arbor
and remove the front ratchet, when the levers will slip off. In putting
them back care should be used to see that the notches of the ratchets
are opposite each other. Oil the edges of the ratchets and the armature
pins. Do not under any circumstances oil the contact points, the pins
or springs of the bar F, as this will destroy the path of the current
and thus stop the clock. These pins must be kept clean and bright.
HOURLY WINDING CLOCKS.—There are probably more of these in America
than of all other electric kinds put together (we believe the
present figures are something like 135,000), so that it will not be
unreasonable to give considerable space to this variety of clocks.
Practically all of them are made by the Self Winding Clock Company and
are connected with the Western Union wires, being wound by independent
batteries in or near the clock cases.
Three patterns of these clocks have been made and we will describe
all three. As they are all practically in the same system, it will
probably be better to first make a simple statement of the wiring,
which is rigidly adhered to by the clock company in putting out these
goods. All wires running from the battery to the winding magnets of the
movement are brown. All wires running from the synchronizing magnet to
the synchronizing line are blue. Master clocks and sub-master clocks
have white wires for receiving the Washington signal and the relay for
closing the synchronizing line will, have wires of blue and white plaid.
[Illustration: Fig. 136.]
By remembering this system it is comparatively easy for a man to know
what he is doing with the wires, either inside or outside of the case.
For calendar clocks there are, in addition, two white wires running
from the calendar to the extra cell of battery. There is also one other
peculiarity, in that these clocks are arranged to be wound by hand
whenever run down (or when starting up) by closing a switch key, shown
in Fig. 136, screwed to the inside of the case. This is practically an
open switch, held open by the spring in the brass plate, except when it
is pressed down to the lower button.
The earliest movement of which any considerable number were sent out
was that of the rotary winding from a three-pole motor, as shown in
Fig. 137. Each of these magnet spools is of two ohms, with twelve ohms
resistance, placed in parallel with the winding of each set of magnet
spools, thus making a total of nine spools for the three-pole motor.
[Illustration: Fig. 137.]
On the front end of the armature drum arbor is a commutator having six
points, corresponding to the six armatures in the drum. There are three
magnets marked O, P and X; each magnet has its own brush marked O′, P′
and X′. When an armature approaches a magnet (see Fig. 137) the brush
makes contact with a point of the commutator, and remains in contact
until the magnet has done its work and the next magnet has come into
action. When properly adjusted the brush O′ will make contact when
armatures 1 and 2 are in the position shown, with No. 2 a little nearer
the core of the magnet than No. 1; and it will break contact when the
armature has advanced into the position shown by armature No. 3, the
front edge of the armature being about one-sixteenth of an inch from
the corner of the core, armature No. 4 being entirely out of circuit,
as brush X′ is not touching the commutator.
The back stop spring, S, Fig. 137, must be adjusted so that the brush
O′ is in full contact with a point of the commutator when the motor is
at rest, with a tooth of the ratchet touching the end of the spring, S.
Sometimes the back stop spring, S, becomes broken or bent. When
this occurs it is usually from overwinding. It must be repaired by
a new spring, or by straightening the old one by burnishing with a
screwdriver. Set the spring so that it will catch about half way down
the last tooth.
Having explained the action of the motor we come now to the means of
temporarily closing the circuit and keeping it closed until such time
as the spring is wound a sufficient amount to run the clock for one
hour; as the spring is on the center arbor this requires one complete
turn.
This is the distinguishing feature of this system of clocks and is
not possessed by any of the others. It varies in construction in the
various movements, but in all its forms it maintains the essential
properties of holding the current on to the circuit until such time
as the spring has been wound a sufficient quantity, when it is again
forcibly broken by the action of the clock. This is termed the “knock
away,” and exists in all of these movements.
To start the motor the circuit is closed by a platinum tipped arm, A,
Fig. 138, loosely mounted on the center arbor, and carried around by a
pin projecting from the center wheel until the arm is upright, when it
makes contact with the insulated platinum tipped brush, B. A carries
in its front an ivory piece which projects a trifle above the platinum
top, so that when B drops off the ivory it will make contact with the
platinum on A firmly and suddenly. This contact then remains closed
until the spring barrel is turned a full revolution, when a pin in the
barrel cover brings up the “knock-away,” C, which moves the arm, A,
forward from under the brush, B, and breaks the circuit. The brush, B,
should lie firmly on its banking piece, and should be so adjusted that
when it leaves the arm, A, it will drop about one-thirty-second of an
inch. Adjusted in this way it insures a good, firm contact.
The angle at the top of the brush, B, must not be too abrupt, so as to
retard the action of the clock while the contact is being made. Wire
No. 8 connects the spring contact, B, to one of the binding plates at
the left hand side of the case; and wire No. 6 connects the motor, M,
to the other. To these binding plates are attached brown wires that
lead one to each end of the battery.
When the clock is quite run down, it is wound by pressing the switch
key, Fig. 136, from which a wire runs to the plate. The switch key
should _not_ be permanently connected to its contact screw, J. See that
all wires are in good condition and all connections tight and bright.
The main spring is wound by a pinion on the armature drum arbor,
through an intermediate wheel and pinion to the wheel on the spring
barrel.
At stated times—say once in eighteen months or two years—all clocks
should be thoroughly cleaned and oiled, and at the same time inspected
to be sure they are in good order.
Never let the self-winding clocks run down backward, as the arm, A,
Fig. 138, will be carried back against the brush, B, and bend it out of
adjustment.
[Illustration: Fig. 138.]
To clean the movement, take it from the case, take out the anchor and
allow it to run down gently, so as not to break the pins, then remove
the motor. Take off the _front_ plate and separate all the parts. Never
take off the back plate in these clocks. Wash the plates and all parts
in a good quality of benzine, pegging out the holes and letting them
dry thoroughly before reassembling. The motor must not be taken apart,
but may be washed in benzine, by using a small brush freely about the
bearings, commutator and brushes. Put oil in all the pivot holes, but
not so much that it will run. The motor bearings and the pallets of the
anchor should also be oiled.
Inspect carefully to see that the center winding contact is right and
that the motor is without any dead points. Dust out the case and put
the movement in place. Before putting on the dial try the winding by
means of the switch, Fig. 136, to be sure that it is right; also see
that the disc on the cannon socket is in the right position to open the
latch at the hour, and after the dial and hands are on move the minute
hand forward past the hour and then backward gently until it is stopped
by the latch. This will prove that the hand is on the square correctly.
On account of the liability of the motor to get out of adjustment and
fail to wind, from the shifting of the springs and brushes, under
careless adjustment, various attempts have been made to improve this
feature of these clocks and the company is now putting out nearly
altogether one of the two vibrating motors, shown in Figs. 139 and 140.
In Style C, Fig. 139, the hourly contact for winding is the same as in
the clock with the three-magnet motor, as shown in Fig. 138. The magnet
spools are twelve ohms and the resistance coil is eighty ohms, placed
in parallel, as described in Fig. 130.
The vibrating motor, Fig. 139, is made with a pair of magnets and
a vibrating armature. The main spring is wound by the forward and
backward motion of the armature, one end of the connecting rod, 8,
being attached to a lug of the armature, 2, and the other to the
winding lever, 10. This lever has spring ends, to avoid shock and
noise. As the winding lever is moved up and down, the pawl, 9, turns
the ratch wheel, 11, and a pinion on the ratch wheel arbor turns the
spring barrel until the winding is completed.
[Illustration: Fig. 139.]
The contact for operating the motor is made by the brass spiral spring,
3, which is attached to the insulated stud, 4, and the platinum pin,
5, which is carried on a spring attached to the clock plate. As the
armature moves forward the break pin, A, in the end of the armature
lifts the contact spring, 3, thus breaking the circuit. The acquired
momentum carries the armature forward until it strikes the upper
banking spring, 6, when it returns rapidly to its original position,
banking on spring 7, by which time contact is again made between
springs 3 and 5 and the vibration is repeated until the clock is wound
one turn of the barrel and the circuit is broken at the center winding
contact.
Fig. 140, Style F, is a similar motor so far as the vibrating armature
and the winding is concerned, but the winding lever is pivoted directly
on the arbor of the winding wheel and operates vertically from an arm
and stud on the armature shaft, working in a fork of the winding lever,
8, Fig. 140. It will be seen that the train and the motor winding
mechanism are combined in one set of plates. The motor is of the
oscillating type and its construction is such that all its parts may be
removed without dissembling the clock train.
CONSTRUCTION OF THE MOTOR.—The construction of the motor is very
simple, having only one pair of magnets, but _two sets_ of make and
break contacts, one set of which is placed on the front and the other
on the back plate of the movement, thus ensuring a more reliable
operation of the motor, and reducing by fifty per cent the possibility
of its failing to wind.
The center winding contact also differs from those used in the
three-magnet motors and former styles of vibrating motor movements.
The center winding contact piece, 13, has no ivory and no platinum.
The hourly circuit is not closed by the current passing through this
piece, but it acts by bringing the plate contact spring, 16, in
metallic connection with the insulated center winding contact spring,
17, both of which are platinum tipped. It will thus be seen that no
accumulation of dirt, oil or gum around the center arbor or the train
pivots will have any effect in preventing the current from passing from
the motor to the hourly circuit closer.
[Illustration: Fig. 140.]
The operation is as follows: As the train revolves, the pin, 12,
securely fastened to the center arbor, in its hourly revolution
engages a pin on the center winding contact piece, 13. This piece as
it revolves pushes the plate contact spring, 16, upward, bringing it
in metallic connection with the center winding contact spring, 17,
which is fastened to a stud on an insulated binding post, 18, thereby,
closing the hourly circuit. The current passes from the binding post,
18, through the battery (or any other source of current supply) to
binding post 19, to which is connected one end of the motor magnet
wire. The current passes through these magnets to the insulated stud,
4. To this stud the spiral contact spring, 3, is fastened and the
current passes from this spring to the plate contact spring, 5, thence
through the movement plate to plate contact spring, 16, and from there
through spring, 17, back to the battery.
The main spring is wound by the forward and backward motion of the
armature, 2. To this armature is connected the winding lever, 8. As
the winding lever is oscillated, the pawl, 9, turns the ratchet wheel,
11, and a pinion on the ratchet wheel arbor turns the winding wheel
until the pin, 15, connected to it engages the knock-away piece, 14,
revolving it until it strikes the pin on the center winding contact
piece, 13, and pushes it from under the plate contact spring, thereby
breaking the electric circuit and completing the hourly winding.
The proper position of the contact springs is clearly indicated in Fig.
140. The spring, 16, should always assume the position shown thereon.
When the center winding contact piece, 13, comes in metallic connection
with the plate contact spring, 16, the end of this spring should stand
about one-thirty-second of an inch from the edge of the incline. The
center winding contact spring, 17, should always clear the plate
contact spring one-thirty-second of an inch. When the two springs touch
they should be perfectly parallel to each other.
ADJUSTMENTS OF THE ARMATURE.—In styles C and F, when the armature,
2, rests on the banking spring, 7, its front edge should be in line
with the edge of the magnet core. The upper banking spring, 6, must be
adjusted so that the front edge of the armature will be one-sixteenth
of an inch from the corner of the magnet core when it touches the
spring.
When the contact spring, 3, rests on the platinum pin, 5, it should
point to about the center of the magnet core, with the platinum pin at
the middle of the platinum piece on the spring.
To adjust the tension of the spiral contact spring, 3, take hold of
the point with a light pair of tweezers and pull it gently forward,
letting it drop under the pin. It should take the position shown by the
dotted line, the top of the spring being about one-thirty-second of an
inch below the platinum pin. If from any cause it has been put out of
adjustment it can be corrected by carefully bending under the tweezers,
or the nut, 4, may be loosened and the spring removed. It may then be
bent in its proper shape and replaced.
The hole in the brass hub to which the spring is fastened has a flat
side to it, fitting a flat on the insulated contact stud. If the
contact spring is bent to the right position it may be taken off and
put back at any time without changing the adjustment, or a defective
spring may readily be replaced with a new one. When the armature
touches the upper banking spring the spiral contact spring, 3, should
clear the platinum pin, 5, about one-sixteenth of an inch. Both
contacts on front and back plates in style F are adjusted alike. The
circuit break pins “A” on the armature should raise both spiral contact
springs at the same instant.
If for any reason the motor magnets have become displaced they may
readily be readjusted by loosening the four yoke screws holding them
to the movement plates. Hold the armature against the upper banking
spring, move the magnets forward in the elongated slot, 20, until the
ends of the magnet cores clear the armature by one-sixty-fourth of an
inch, then tighten down the four yoke screws. Connect the motor to the
battery and see that the armature has a steady vibration and does not
touch the magnet core. The adjustment should be such that the armature
can swing past the magnet core one-eighth to three-sixteenths of an
inch.
DESCRIPTION OF SYNCHRONIZER.—At predetermined times a current is sent
through the synchronizer magnet, D′, Fig. 141, which actuates the
armature, E, to which are attached the levers, F and G, moving them
down until the points on the lever, G, engage with two projections, 4
and 5, on the minute disc; and lever F engages with the heart-shaped
cam or roll on the seconds arbor sleeve, causing both the minute and
second hands to point to XII. These magnet spools are wound to twelve
ohms, with an eighty-ohm resistance in parallel.
On the latch, L, is a pin, I, arranged to drop under the hook, H, and
prevent any action of the synchronizing levers, except at the hour.
A pin in the disc on the cannon socket unlocks the latch about two
minutes before the hour and closes it again about two minutes after the
signal. This is to prevent any accidental “cross” on the synchronizing
line from disturbing the hands during the hour.
M is a light spring attached to the synchronizing frame to help
start the armature back after the hands are set. The wires from the
synchronizing magnet are connected to binding plates at the right-hand
side of the clock and from these binding plates the blue wires, Nos. 9
and 10, pass out at the top of the case to the synchronizing line.
If the clock gets out of the synchronizing range it generally indicates
very careless regulation. The clock is regulated by the pendulum,
as in all others, but there is one peculiarity in that the pendulum
regulating nut has a check nut.
If the clock gains time turn the large regulating nut under the
pendulum bob slightly to the left.
If the clock loses time turn the nut slightly to the right.
Loosen the small check nut under the regulating nut before turning the
regulating nut, and be _sure to tighten_ the check nut after moving the
regulating nut.
[Illustration: Fig. 141.]
The friction of the seconds hand is very carefully adjusted at the
factory, being weighed by hanging a small standard weight on the point
of the hand. If it becomes too light and the hand drives or slips
backward, losing time, it can be made stronger by laying it on a
piece of wood and rubbing the inner sides of the points with a smooth
screw driver, and if too heavy and the clock will not set when the
synchronizing magnets are actuated, the points of the spring in the
friction may be straightened a little.
If the seconds hand sleeve does not hold on the seconds socket, pinch
it a little with pliers. If the seconds hand is loose on the sleeve put
on a new one or solder it on the under side.
In style F the synchronizing lever, heart-shaped seconds socket and
cams on the cannon sockets are the same as in the old style movements,
shown in Fig. 141. The difference is in the synchronizing magnets
and the way they operate the synchronizing lever. The magnet has a
flat ended core instead of being eccentric like the former ones. The
armature is also made of flat iron and is pivoted to a stud fastened to
the synchronizing frame. The armature is connected to the synchronizing
lever by a connecting rod and pitman screws. A sector has an oblong
slot, allowing the armature to be lowered or raised one-sixteenth of
an inch. The synchronizing lever is placed on a steel stud fastened to
the front plate and held in position by a brass nut. The synchronizing
magnets are 12 ohms with 80 ohms resistance and are fastened to a yoke
which is screwed to the synchronizing frame by four iron screws. The
holes in the synchronizing frame are made oblong, allowing the yoke
and magnets to be raised or lowered one-sixteenth of an inch. The
spring on top of the armature is used to throw it back quickly and also
acts as a diamagnetic, preventing the armature from freezing to the
magnets. A screw in the stud is used to screw up against the magnet
head, preventing any spring that might take place on the armature stud.
Binding posts are screwed to the synchronizing frame and the ends of
the magnet coils are fastened thereto with metal clips.
The blue wires in the clock case are coiled and have a metal clip
soldered to them. They connect direct by these clips to the binding
posts, thus making a firm connection, and are not liable to oxidize.
With the various points of adjustment a pair of magnets burned out or
otherwise defective may readily be replaced in from five to ten minutes.
When replacing a pair of synchronizing magnets proceed as follows:
Remove the old pair and then loosen all four screws in the yoke,
pushing it up against the tops of the oblong holes, then tighten down
lightly. Fasten the new pair of magnets to the yoke with the inner ends
of the coils showing at the outside of the movement. Press the armature
upward until the synchronizing lever locks tightly on the cannon socket
and the heart-shaped cams, then loosen the magnet yoke screws and press
the magnets down on the spring on top of the armature. Then tighten the
yoke screws on the front plate and see that the back of the magnets
clears the armature by one-hundredth of an inch (the thickness of a
watch paper), when the screws in the back of the yoke can be set down
firmly. The adjustment screw may then be turned up until it presses
lightly against the magnet head. When current is passed through the
magnets and held there the armature must clear the magnets without
touching. The magnet coils must then be connected to their respective
binding posts by slipping the metal clips soldered to them under the
rubber bushing, making a metallic connection with the binding plates.
Fasten these screws down tight to insure good connections.
[Illustration: Fig. 142.]
THE MASTER CLOCK.—Is a finely finished movement with mercurial pendulum
that beats seconds and a Gerry gravity escapement. At the left and near
the center of the movement is a device for closing the synchronizing
circuit once each hour. The device consists of a stud on which is an
insulator having two insulated spring fingers, C and D, one above the
other, as shown in Fig. 142, except at the points where they are cut
away to lie side by side on an insulated support. On these fingers, and
near the insulator, are two platinum pieces, E and F, so adjusted as
to be held apart, except at the time of synchronizing.
A projection, B, from the insulator rests on the edge of a disc on the
center arbor. At ten seconds before the hour, a notch in this disc
allows the spring to draw the support downward, leaving the points of
the fingers, C and D, resting on the raised part of the rubber cam on
the escape arbor. The end of the finger, C, is made shorter than that
of D, and at the fifty-ninth second, C drops and closes the circuit by
E striking F. At the next beat of the pendulum the long finger D drops
and opens the circuit again.
The winding is the same as in the regular self-winding clocks, the
motor wire and seconds contact being connected to the binding plates at
the left, from which brown wires lead up to the battery. Two wires from
the synchronizing device are connected to the binding plates at the
left, from which blue wires run out to the line.
Before connecting the clock to the line it must be run until it is well
regulated, and also to learn if the contacts are working correctly.
Regulate at first by the nut at the bottom of the rod until it runs
about one second slow in 24 hours (a full turn of the nut will change
the rate about one-half minute per day). The manufacturers send
with each clock a set of auxiliary pendulum weights, the largest
weighing one gram, the next in size five decigrams and the smallest
two decigrams; these weights are to make the fine regulations by
placing one or more of them on the little table that is fastened
about the middle of the pendulum rod. The five decigram weight will
make the clock gain about one second per day, and the other weights
in proportion. Care must be taken not to disturb the swing of the
pendulum, as a change of the arc changes the rate.
To start the clock after it is regulated, stop it, with the second hand
on the fiftieth second; move the hands forward to the hour at which
the signal comes from the observatory; then press the minute hand back
gently until it is stopped by the extension on the hour contact, Fig.
142, and beat the clock up to the hour. This ensures the hour contact
being in position to send the synchronizing signal.
A good way to start it with observatory time is with all the hands
pointing to the “signal” hour; hold the pendulum to one side and when
the signal comes let it go. With a little practice it can be started
very nearly correct.
Clocks not lettered in the bottom of the case must be wound before
starting the pendulum. To do this press the switch shown in Fig. 136,
which is on the left side of the case and under the dial.
Continue the pressure until the winding ceases. Then set the hands and
start the pendulum in the usual way. If the bell is not wanted to ring,
bend back the hammer.
SECONDARY DIALS.—One of the most deceptive branches of clock work
is the secondary dial, or “minute jumper.” Ten years ago it was the
rule for all manufacturers of electric clocks to put out one or more
patterns of secondary dials. Theoretically it was a perfect scheme,
as the secondary dial needed no train, could be cheaply installed and
could be operated without trouble from a master clock, so that all
dials would show exactly the same time. Practically, however, it proved
a very deceptive arrangement. The clocks were subject to two classes of
error. One was that it was extremely difficult to make any mechanical
arrangement in which the hands would not drive too far or slip backward
when the mechanism was released to advance the minute hand. The second
class of errors arose from faulty contacts at the master clock and
variation in either quantity or strength of current. Another and
probably the worst feature was that all such classes of apparatus
record their own errors and thereby themselves provide the strongest
evidence for condemnation of the system. Clocks could be wound once
an hour with one-sixtieth of the chance of error of those wound once
per minute, and they could be wound hourly and synchronized daily with
¹/₁₄₄₀th of the line troubles of a minute system.
The minute jumpers could not be synchronized without costing as much
to build and install as an ordinary self-winding clock, with pendulum
and time train, and after trying them for about ten years nearly all
the companies have substituted self-winding time train clocks with a
synchronizing system. They have apparently concluded that, since it
seems too much to expect of time apparatus that it will work perfectly
under all conditions, the next thing to do is to make the individual
units run as close to time as is commercially practicable and then
correct the errors of those units cheaply and quickly from a central
point.
It is for these reasons that the secondary dial has practically
disappeared from service, although it was at one time in extensive use
by such companies as the Western Union Telegraph Company, the Postal
Telegraph and the large buildings in which extensive clock systems have
been installed.
Fig. 143 shows one form of secondary dial which involves a screw and a
worm gear on the center arbor, which, it will be seen, is adapted to
be turned through one minute intervals without the center arbor ever
being released from its mechanism. This worm gear was described in the
AMERICAN JEWELER about fifteen years ago, when patented by the Standard
Electric Time Company in connection with their motor-driven tower
clocks, and modifications of it have been used at various times by
other companies.
The worm gear and screw system shown in Fig. 143 has the further
advantage that it is suitable for large dials, as the screw may be run
in a box of oil for dials above four feet and for tower clocks and
outside work. This will readily be seen to be an important advantage
in the case of large hands when they are loaded with snow and ice,
requiring more power to operate them.
[Illustration: Fig. 143. Minute jumper. A, armature; M, magnets;
W, worm gear on center arbor; B, oil box for worm; R, four toothed
ratchet.]
All secondaries operate by means of an electromagnet raising a weight,
the weight generally forming the armature; the fall of the weight then
operates the hands by gravity. Direct action of the current in such
cases is impracticable, as the speed of starting with an electric
current would cause the machine to tear itself to pieces.
This screw gear is the only combination known to us that will prevent
the hands from slipping or driving by and reduces the errors of the
secondary system to those of one class, namely, imperfections in the
contact of the master clock, insufficient quantity or strength of
current, or accidental “crosses” and burnings.
The series arrangement of wiring secondaries was formerly greatly
favored by all of the manufacturers, but it was found that if anything
happened to one clock it stopped the lot of them; and where more than
fifty were in series, the necessary voltage became so high that it
was impracticable to run the clocks with minute contacts. The modern
system, therefore, is to arrange them in multiples, very much after the
fashion of incandescent lamps, then if one clock goes wrong the others
are not affected. Or if the current is insufficient to operate all,
only those which are farthest away would go out of time.
Very much smaller electromagnets will do the work than are generally
used for it, and the economy of current in such cases is worth looking
after, as with sixty contacts per hour batteries rapidly play out if
the current used is at all excessive. Where dry batteries are used on
secondaries care should be taken to get those which are designed for
gas engine ignition or other heavy work. Wet batteries, with the zincs
well amalgamated, will give much better satisfaction as a rule and if
the plant is at all large it should be operated from storage cells
with an engineer to look after the battery and keep it charged, unless
current can be taken from a continuously charged lighting main. This
can be readily done in such instances as the specifications call for
in the new custom house in New York, namely, one master clock and 160
secondary dials.
ELECTRIC CHIMES.—There have lately come into the market several devices
for obtaining chimes which allow the separation of the chimes and the
timekeeping apparatus, connection being made by means of electricity.
In many respects this is a popular device. It allows, for instance, a
full set of powerful tubular chimes, six feet or more in length, to
be placed in front of a jewelry store, where they offer a constant
advertisement, not only of the store itself, but of the fact that
chiming clocks may be obtained there. It also allows of the completion
by striking of a street clock which is furnished with a time train
and serves at once as timepiece and sign. Many of these have tubular
chimes in which the hour bell is six feet in length and the others
correspondingly smaller. They have also been made with bells of the
usual shape, which are grouped on posts, or hung in racks and operated
electrically. It may also be used as a ship’s bell outfit by making a
few minor changes in the controller.
[Illustration: Fig. 144. Chimes of bells in rack.]
[Illustration: Fig. 145. Chimes of bells with resonators.]
Fig. 144 shows a peal of bells in which the rack is thirty-six inches
long and the height of the largest bell is eight inches, and the total
weight thirty pounds. This, as will readily be seen, can be placed
above a doorway or any other convenient position for operation; or it
may be enclosed in a lattice on the roof, if the building is not over
two stories in height. The lattice work will protect the bells from the
weather and at the same time let out the sound.
Fig. 145 shows the same apparatus with resonators attached. These are
hollow tubes which serve as sounding boards, largely increasing the
sound and giving the effect of much larger bells. Fig. 146 shows a
tubular chime and the electrical connections from the clock to the
controller and to the hammers, which are operated by electromagnets,
so that a heavy leaden hammer strikes a solid blow at the tops of the
tubes.
[Illustration: Fig. 146. Tubular electric chimes.]
The dials of such clocks contain electrical connections and the minute
hand carries a brush at its outer end. The contact is shown in enlarged
view in Fig. 147, by which it will be seen that the metal is insulated
from the dial by means of hard rubber or other insulating material, so
that the brush on the minute hand will drop suddenly and firmly from
the insulator to the metallic contact when the minute hand reaches
fifteen, thirty, forty-five or sixty minutes. There is a common return
wire, either screwed to the frame of the clock, or attached to the
dial, which serves to close the various circuits and to give four
strokes of the chimes at the quarter, eight at the half, twelve at the
three-quarter, and sixteen at the hour, followed by the hour strike.
The friction on the center arbor is of course adjusted so as to carry
the minute hand without slipping at the contacts.
[Illustration: Fig. 147. Enlarged view of connections on dial.]
By this means a full chime clock may be had at much less cost than
if the whole apparatus had to be self-contained and the facilities
of separation between the chimes and the timekeeping apparatus, as
hinted above, gives many advantages. For instance, the same clock and
controller may operate tubes inside the room and bells outside, or vice
versa. These are operated by wet or dry batteries purchased at local
electrical supply houses, and the wiring is done with plain covered
bell wire, or they may be operated by current from a lighting circuit,
suitably reduced, if the current is constantly on the mains. As a full
chime with sixteen notes at the hour strikes more than a thousand
times a day, considerable care should be taken to obtain only the
best batteries where these are used, as after the public gets used to
the chimes the dealer will be greatly annoyed by the number of people
asking for them if they are stopped temporarily.
There has lately developed a tendency to avoid the set tunes, such as
the Westminster and the Whittington chimes, and to sound the notes as
complete full notes, such as the first, third and fifth of the octave
for the first, second and third quarters, followed by the hour strike.
This allows them to be struck in any order and for a smaller chime
reduces the cost considerably. The tubes used are rolled of bell metal
and vary in pitch with the manufacture, so that the only way to obtain
satisfactory tones is to cut your tubes a little long and then tune
them by cutting off afterwards, the tone depending upon the thickness
of the wall of the tube and its length. The bells are tuned by turning
from the rim or from the upper portions as it is desired to raise or
lower the tone, and if the resonators are used they are tuned in unison
with the bells.
[Illustration: Fig. 148. Connections and contacts on front of clock
dial.]
Of the ordinary bells, Fig. 144, the dimensions run: First, height four
inches, diameter 5½; second, height four inches, diameter 5¼ inches;
third, height 4½ inches, diameter 5⅝ inches; fourth, height 4½ inches,
diameter 5⅝ inches; fifth, height 4⅝ inches, diameter 6½ inches. For
the tubes the approximate length is six feet for the longest tube and
the total weight of the chimes is 43 pounds. For the controller the
size is nine by eleven by six inches, with a weight of ten pounds. The
hour strike may be had separately from the chimes if desired.
[Illustration: Fig. 149. Connections and wiring on back of clock dial.]
This makes an easily divisible system and one that is becoming very
popular with retail jewelers and to some extent with their customers.