|
THE
TOURBILLON
The following article has
been prepared for Europa Star by an expert
in the field, Jean-Claude Nicolet, master
watch-craftsman and professor in La Chaux-de-Fonds.
His
study of the Tourbillon is certainly food for
thought, and may solicit some controversy among
our readers. It is not Jean-Claude Nicolet's
intention to contest the exceptional, professional
qualities it takes to construct a hand-crafted
Tourbillon. Mr. Nicolet wanted to focus on certain
inappropriate qualities which are often attributed
to it
This
said, it is important to note that there exists
"tourbillons" and "Tourbillons".
In other words, this important watch-making
technique may vary in quality. There are a number
of differences between a hand-crafted cage,
and certain industrially fabricated creations.
We look forward to your comments on this important
matter.
0
 |
Tourbillon
mounted on a piece with a diameter of 66
mm. A very fine work started by Robert Gafner
and finished by his successor Paul Vuilleumier,
both teachers at the Watchmaking School
of La Chaux-de-Fonds. The piece is fitted
with an ingenious independent seconds system
imagined by Rober Gafner. |
|
History
Of
all the prestigious mechanisms invented by watch-makers
over the centuries, the tourbillon enjoys a
very special reputation. There are two essential
reasons for this: The invention belongs, unquestionably
to the most famous watchmaker of all times,
Abraham-Louis Breguet, who has rightly been
called the "watch-maker of kings and the
king of watch-makers". The second reason
is because the tourbillon is a mechanism which,
even in its most conventional version, is extremely
hard to manufacture. At a time when all tools
were still somewhat primitive, the production
of a tourbillon watch was a certificate of competence
far more appreciated than the diplomas awarded
by the best watchmaking schools.
Over
the generations of watch-makers, since Breguet,
there were probably fewer than 250 able to execute
such a masterpiece. Richard Meis, in his book
"The Tourbillon", a work that can
serve as historical reference, quotes 120 names.
On
the 3rd Nivose of year 9 in the Napoleonic calendar
(23rd December 1800), Breguet applied to the
French Minister of the Interior for a patent
to protect the tourbillon. But the invention
goes still further back. Sir David Salomons,
Breguet's biographer situates it in the year
1795.
Since
Breguet, several great watchmakers, especially
those who had dedicated themselves to the research
of precision, have created tourbillon movements.
The tourbillon regulator is supposed to improve
watch precision in a decisive fashion. We'll
see more about it further on.
Definition of the Tourbillon
Regulator
What
may be referred to as a tourbillon regulator,
or more simply a tourbillon, is a mechanical
device consisting essentially of a rotating
cage carrying at least the balance and the escapement.
The
cage is driven in rotation by the gear-train.
It turns co-axially to a toothed crown fixed
on to the plate. This crown serves to maintain
the oscillator by means of a pinion carried
by the cage. In conventional tourbillons, this
pinion is that of the escape wheel, but this
is not obligatory.
In
a variant of tourbillon called "carousel",
the cage is driven by the medium pinion, while
the third wheel drives the second pinion which
is co-axial to the carousel cage. There is no
fixed crown in this system, but the angular
speed of the second wheel is increased by that
of the cage carrying it. This must be taken
into account in calculations. We owe the invention
of the carousel, in 1895, to the Dane, Bonniksen
(1859-1935).
The
existence or not of a crown wheel fixed on the
plate makes it possible to distinguish the tourbillon
from the carousel.
Use of the Tourbillon
In
the tourbillon as in the carousel, every time
the balance receives an impulse, the cage undergoes
a slight rotating movement with all the elements
it contains. While the watch is immobile, the
oscillator on the other hand changes its position
continuously. In the vertical positions of the
watch, exclusively, where the residual defect
of equilibrium of the organ causes perturbations,
this constant rotation of the oscillator keeps
up a continual agitation of the rating results.
Successive day by day observations in different
vertical positions, do not reveal marked differences
of rate. One deduces that the tourbillon compensates
the effects of gravity as Breguet had anticipated.
A Practical Example
A
practical example will help to explain this
phenomenon. Suppose we observe four times in
succession a good pocket watch at 24 hour intervals
in four vertical positions.
With
a watch without tourbillon, the readings will
be as follows:
| Day |
Condition |
Daily
rate |
Position
of pendant |
|
| 0 |
0 |
- |
above |
| 1 |
+5 |
+5 |
above |
| 2 |
+5 |
0 |
on
left |
| 3 |
0 |
-5 |
below |
| 4 |
0 |
0 |
on
right |
| |
|
The
average daily rate is: |
|
| |
|
+5
-5 +0 +0 |
|
| |
|
avd
= -------------- = 0 |
|
| |
|
4 |
|
The
greatest difference between the average daily
rate and one of the rates is 5 (difference of
0 to +5 or of 0 to -5).
The
same watch fitted with the same oscillator but
equipped with a tourbillon will give the following
results in the same conditions.
| Day |
Condition |
Daily rate |
Position
of pendant |
|
| 0 |
0 |
- |
above |
| 1 |
0 |
0 |
above |
| 2 |
0 |
0 |
on
left |
| 3 |
0 |
0 |
below |
| 4 |
0 |
0 |
on
right |
The
average daily rate is equal to zero as in the
first case but the difference corresponding
to a position change is nil. The watch seems
markedly better. Is it really the case?
Was Breguet right?
In
his application for a patent, the famous watchmaker
mentions several advantages of the tourbillon,
which he summarizes below:
"By
means of this invention, I have succeeded in
canceling through compensation the anomalies
caused by the different positions of the centers
of gravity of the regulator movements, to distribute
frictions on all parts of the circumference
of this regulator's pivots and of the holes
in which these pivots move, so that the oiling
of the friction surfaces is always even, in
spite of oil coagulation, and finally to cancel
many other causes of error influencing movement
accuracy, which could only be attained until
now by constant trial and error and often even
without any certainty of success." Afterwards,
Breguet mentions only the compensation of the
effects of gravity due to changes of position.
He
is careful not to say that the tourbillon does
not correct the rate variations in the "pendant
up" and "dial up" positions.
This is how timers define the rate variations
between the two horizontal positions and the
three vertical positions usually controlled
in the observatories.
Finding the Right Position
As
a result, a watch laid flat at night and always
placed in the same vertical position during
the day does not provide better results when
fitted with a tourbillon regulator. It's more
the contrary that is true, because in a vertical
position the tourbillon watch gives an average
rate while the watch without a tourbillon gives
only the rating result corresponding to the
position it occupies.
It
can easily be arranged that one of these vertical
positions - as chosen - gives much the same
result as the horizontal positions. The possible
advantage of the tourbillon then shows only
if the watch changes occasionally its vertical
position during the day. If this change of position
is very frequent, the "mixing" of
positions occurs of itself.
In
view of this, it is certain that, when worn,
a wristwatch with a tourbillon is not more accurate
than a conventional watch.
Why is there so much
admiration for the tourbillon?
If
what you have just read is true, it is difficult
to understand the veneration in which the tourbillon
has been held by watchmakers for some two centuries.
There
are several reasons for this. First of all,
the unquestioned and deserved prestige of Breguet,
the inventor.
Secondly,
all the tourbillon watches presented in the
observatories were manufactured by watchmakers
or renowned companies.
Thirdly,
the manual production of a tourbillon watch
can be carried out only by particularly skilled
watchmakers and its successful execution is
an unquestionable certificate of mastery.
Finally,
the superiority of the tourbillon becomes evident
only in observatory controls where the pieces
are tested for 25 days in five successive positions,
2 horizontal and 3 vertical ones. The watches
are treated with the greatest care. The length
of observation between two reports is exactly
24 hours. It's the only way to act in order
to show the variations due to position changes
but these conditions are far from being the
same as when the watch is worn. Tested in this
manner, tourbillon watches benefit from a marked
advantage. They possess a little mischievous
imp - the tourbillon - who is always modifying
the vertical positions so that all the efforts
of the testers, to show the position differences,
are thwarted.
The
tourbillon does not correct position variations;
it only prevents their being detected in the
usual testing conditions. But when placed on
the vibrograph, the tourbillon reveals its weaknesses
immediately.
Comparing two Options
In
order to make a valid comparison between the
two types of watches, those without a tourbillon
should be placed in a vertical position, in
a rotating cage with a rotating speed of about
1 r.p.m. or else one should give up observing
the vertical positions. Under these conditions,
the advantage would go unquestionably to the
watches without tourbillon. We'll see why later.
The
admiration given to the tourbillon is of the
same nature as that given to a clever conjuror
who causes an elephant to vanish! What we think
we see is a mere optical illusion.
From Doubt to Certainty
The
first doubts regarding the efficiency of the
tourbillon were felt quite early on but the
inventor's halo prevented them from being expressed.
If the tourbillon had an effect comparable to
that of the hairspring applied to the balance,
the difficulty of its design would not have
seemed so great. The small number of tourbillons
made is another factor that reveals the system's
lack of efficacy.
In
a remarkable study that was published in issue
number 22 of the "Revue de Association
française des amateurs d'horlogerie ancienne"
Messrs Droz and Florès make a few apt
criticisms that we are reproducing with authorization.
A Subject of Controversy
Claudius
Saunier, editor of the "Revue Chronométrique"
for almost 60 years (1855-1914), seems almost
to ignore the system. There are practically
no articles devoted to it. A laconic remark
at the bottom of a page says: "The tourbillon
is no good, Breguet recognized the fact..."That
is an extreme opinion. In the Revue Chronométrique,
the tourbillon by Benoît is presented
as "a modern tourbillon".
In
a short article, Maillard Salins, shop manager
of the Leroy firm, expresses the greatest doubts
on the efficacy of the tourbillon and carousel
systems.
In
"Pendule, Spiral, Diapason", a book
published in 1920, H. Bouasse, professor at
the Science Faculty of Toulouse, France, writes
in tome 11: "In order to cancel the centering
errors of the balance, someone had the ingenious
idea of making it turn: this resulted in the
tourbillon escapement, but its high price and
problematic advantages reduced it to being a
historical curiosity.... Experience shows that
in the end, the use of this "perfected"
system involves considerable costs. It is ingenious
but far too complicated."
Other
authors, such as Marius Favre in the "Journal
Suisse d'Horlogerie", issue No 3/1905,
analyses some results obtained in the observatories
and gives the preference to fixed escapements.
His analysis is particularly apt.
Defining Criteria
The
table below presents the respective rankings
of 706 observatory pieces of which 174, that
is 25%, are fitted with a tourbillon. This 25%
obtained 59% of the first places. At priori,
these results speak in favor of the tourbillon.
However, if one remembers that one of the criteria
among the most difficult to satisfy - the one
concerning positions - does not enter into consideration
in the assessment of the tourbillons, one is
somewhat disappointed with these results. The
other criteria need to be unfavorable to them
for tourbillons not to obtain systematically
the first places. A detailed examination, criterion
by criterion, confirms this hypothesis.
| Table
of results of some observatory tests in
the first half of the 20th century. |
| The
first column shows where the tests took
place and the category of watches examined.
The second, the years when the tests were
carried out. In the third column, you find
the number of chronometers listed and in
the fourth the number of tourbillons. Columns
five and six show the rank obtained by the
best and the least good tourbillon. When
only one tourbillon undergoes the test,
it is both the best and the least good! |
| Locations |
Year |
Number
of items |
Chronometers
with tourbillons |
|
| Kew |
1894 |
55 |
11 |
1 |
27 |
| Kew |
1904 |
57 |
41 |
1 |
56 |
| Kew |
1906 |
58 |
29 |
1 |
50 |
| Kew |
1907 |
52 |
14 |
5 |
47 |
| Geneva |
1906 |
82 |
1 |
69 |
69 |
| Geneva |
1907 |
101 |
3 |
14 |
68 |
| Geneva
(pocket) |
1928 |
32 |
5 |
1 |
16 |
| Geneva
(clock) |
1928 |
53 |
3 |
1 |
5 |
| Geneva
(clock) |
1944 |
22 |
13 |
1 |
20 |
| Geneva
(pocket big) |
1944 |
20 |
14 |
1 |
20 |
| Geneva
(pc. small) |
1944 |
4 |
1 |
4 |
4 |
| Geneva
(clock) |
1945 |
32 |
18 |
2 |
27 |
| Geneva
(pocket big) |
1945 |
15 |
12 |
1 |
15 |
| Geneva
(pc. small) |
1945 |
4 |
1 |
2 |
2 |
| Neuchâtel |
1905 |
63 |
3 |
1 |
33 |
| Neuchâtel |
1906 |
45 |
1 |
3 |
3 |
| Neuchâtel |
1941 |
11 |
4 |
1 |
4 |
Why are tourbillons
disappointing?
As
we have seen, the tourbillon does not correct
anything. It only prevents the detection of
an error that still subsists. It does not even
produce a contrary defect able partly to cancel
the first one, as does for instance the recoil
escapement in clocks. This escapement partly
corrects a pendulum's error of isochronism.
The
tourbillon is in fact an additional mechanism
that consumes energy without producing anything
except misinformation. It is a parasitical mechanism.
The energy it consumes is taken from the reserve
destined to the regulator. As a result, the
balance with less energy will have reduced advantages.
All watches established to function in both
manners, with or without tourbillon, always
have smaller balances of less good performance
in tourbillon version.
Energy
distribution is carried out during the rotation
of the escapement wheel. It is at that moment
too that the tourbillon cage turns. It consumes
a great deal of energy to start moving and hardly
is it launched than it stops suddenly against
the escapement pinion whose wheel has just come
to rest. All the energy drawn by the cage is
absorbed by the shock without any advantage.
The light escapement wheel has given back 25%
of its energy to the balance which has done
nothing but shake up all the regulating system.
This is what is described as the "ingenious
invention of Breguet". The latter luckily
has other titles of glory.
The
fineness of the tourbillon cage makes its execution
very difficult. This cage is the work of one
of the three great cage manufacturers of the
end of last century. Messrs Albert Pellaton,
from Le Locle, Roulet and Grether from the Ponts-de-Martel.
Timing and Balance
The
faster the tourbillon cage turns, the more spectacular
its operation and the more it consumes energy
at a loss. The tourbillon would be less harmful
if it turned more slowly because it would consume
less energy and its effect of garbling information
would be identical, as also its uselessness.
Timers
have always sensed the disrupting effect of
the tourbillon. Why did they build cages as
fine as cobwebs? It was to reduce to the maximum
their moment of inertia and not to force the
admiration of connoisseurs.
Why
did they seek to balance the filled cages, if
not to eliminate their unbalance which is always
altering the amplitude of the balance and shows
up the errors of isochrononism.
Other
inconvenience: by integrating all the vertical
positions, the tourbillons make the timing in
the "plat pendu" ("pendant up"
and "dial up") positions more difficult.
This is felt more particularly when the pieces
are small. On the whole tourbillon wristwatches
time less well than conventional wristwatches
of the same size.
In
fact, all traditional wristwatches are fitted
with a free tourbillon deriving its energy from
the wearer and not from the spring. When they
are worn, these watches occupy an infinite variety
of positions and their rating results give an
average of this constant motion.
Eliminating the Gravity
Gravity
is one of the main causes of rate variations
in watches. By creating the tourbillon, Breguet
thought he was eliminating its effects. It was
an error on his part. He succeeded only in masking
them a little. If he had found a way of eliminating
the force of gravity on watches, he would have
realized an improvement comparable to the invention
of the balance-spring. Unfortunately, there
is no way of suppressing gravity on earth, except
by putting watches into artificial satellites.
This has been done, since astronauts wear watches.
It seems however that nobody has thought of
comparing the rate of these watches on earth
and in a weightless atmosphere. We propose this
very interesting experiment to the watch and
clock industry.
After
having observed them on earth according to specifications
to be defined, a few watches of different qualities
would be entrusted to some astronauts. The same
observations to be carried out again in a weightless
atmosphere and comparisons made. An interesting
evaluation could then be obtained on the effects
of gravity.
One
can be pretty sure that the watches would have
a better comportment in a weightless atmosphere.
All errors of equilibrium would disappear as
by enchantment as would the sagging of the balance
spring and the friction's due to the weight
of the mobiles. It can even be surmised that
the rate variations would be more marked with
the least good watches and that, in a weightless
atmosphere, they would behave like chronometers. |
