Türler clock

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The Türler clock (general view)

The Türler clock is an astronomical clock that the family company "Türler - Uhren & Juwelen" had made and set up in its shop in Zurich on Paradeplatz . It is a synchronized multiple model of the cosmos , which stands in the tradition of astronomical clocks built since the end of the Middle Ages and was designed and manufactured from 1986 to 1995 by the clock designer Ludwig Oechslin and the master clockmaker Jörg Spöring. The Türler watch has been on loan at MIH in La Chaux-de-Fonds since October 2017 as a loan of at least five years .

The Türler clock is on a columnar granite base. Around the central weight drive and the clock pendulum there are five movement blocks for displays on dials and for generating movement in models of the sky. Four of the blocks form a horizontal cross, the fifth is placed in the middle and drives a terrestrial globe and the surrounding spheres.

These are the following blocks or displays or sky models:

The clock, calendar and planetarium also appeared in various combinations in the old astronomical clocks. However, the calendar is new in the form presented. The “horizon” is also new, but is similar to the astrolabe , a special component of astronomical clocks ( astrolabe clocks ). A tellurium was probably added to an astronomical clock here for the first time. The combination with a terrestrial globe surrounded by movable spheres is completely new (a single terrestrial globe surrounded by movable spheres was also not previously known).

The clockwork blocks are 30 cm by 30 cm square on their circumference. The front dials have a diameter of 45 cm. When viewed from above, they fit into a square with an edge length of around 100 cm. The total height of the clock is around 220 cm to the highest point of the outer sphere around the globe.

Drive, gear regulator, components and materials

The clock is driven by a large weight that hangs between the side walls of the base and is wound by an electric motor about every 4 hours. It moves all moving parts every minute. Only the second hand jumps every second synchronously with the deflections of the second pendulum used .

A smaller second weight is used so that the rate control by the pendulum does not have to constantly work against the unsteady force caused by the clockwork blocks. This is pulled up by the heavy weight once every minute. The gear control mainly only has to inhibit the relatively even drive coming from it, because this only moves the second hand directly. The inevitable consequence of the rewinding mechanism for the small weight is that the large weight has a weak effect on the gear control, but only in a ratio of about 1:10. The special construction of the rewind is the reason that all watch parts are moved almost abruptly every minute.

The seconds pendulum is a quartz rod . Because of the low temperature expansion coefficient of quartz (almost zero), the period of oscillation is practically independent of temperature. The accuracy is still checked with time signals every second, which are received from the German time signal transmitter DCF77 . For this purpose, an electromagnet located in the bottom part acts to accelerate or decelerate the swinging pendulum if necessary.

The pendulum works in conjunction with a Strasser anchor escapement .

The clock consists of a total of 251 wheels on 155 axles and only uses levers sparingly:

  • 12-hour clock and calendar: 58 wheels on 35 axles, 1 shift finger, 1 relay roller
  • Horizon: 47 wheels on 31 axles, 5 crank loops
  • Planetarium: 50 wheels on 29 axles
  • Tellurium: 45 wheels on 30 axles, 1 crank
  • Earth globe and celestial spheres: 51 wheels on 30 axes, 2 crank loops

The quality of the watch as a modern precision engineering instrument can also be seen in the fact that, in addition to some ruby jewels, mainly ball bearings and plain bearings made of Teflon are used: 60 ruby ​​bearings, 58 thin-section ball bearings, 86 ball bearings, 62 mini-ball bearings and 49 teflon bearings. Pointer tubes that are inserted into one another are Teflon-coated.

Almost all metal parts of the clock are made of brass and are gold-plated .

12 hour clock and calendar

With its 12-hour dial, the Türler watch is initially a normal watch with hour and minute hands. The rotation in 12 hours generated in the working block is used to drive the four other working blocks after the translation to 1 rotation in 24 hours via shafts and deflection gears.

Within the hour and minute scale there are four smaller dials arranged in a cross shape for the following calendar displays:

  • left: weekday (Monday, Tuesday, ..., Sunday)
  • above: day of the month (1, 2, 3, ..., 31)
  • right: month (January, February, ..., December)
  • below: year (outside, up to 9999) and second (inside, 1, 2,…, 60).

It is a perpetual calendar that follows the Gregorian calendar : it inserts a leap day every four years and leaves it out three times in 400 years.

Like the time of day, the calendar displays change continuously in order to make the time generally tangible as a flowing continuum. Instead of changing calendar dates abruptly and displaying them in narrow windows, bands of data flow steadily through under display marks. In the weekday display, the minute jump generally contained in the clock, which is practically no longer recognizable, is highlighted. The data disks of the month and year display are rotated in daily steps, which is practically perceived as a constant flow.

The exception is the day of the month, the display of which changes rapidly every day and appears in a narrow window. The formal reason for this is that the day of the month - significantly more than the day of the week that does not have a number - is perceived as a counted unit and can be represented accordingly. The practical reason is that the months of different lengths (28 to 31 days) would require several gears in order to be evenly divided. The chosen digital solution avoided a major technical effort.

The month disc is rotated in normal years with 365 day steps, in leap years with 366 day steps. This causes a negligible display error on the monthly scale. Its rotation is on average 1 / calendar year.

The year is displayed on four concentric rings from the inside to the outside, in order to deliberately indicate the higher tens decade, century and millennium.

The second hand rotates in the center of the annual rings above its own scale.



In this part of the display, the Türler clock resembles an astrolabe clock built between the late Middle Ages and the beginning of the Renaissance . However, the celestial sphere and horizon are not projected from the north celestial pole onto the plane of the dial ( stereographic projection ), but the so-called azimuthal equidistant projection was used. The picture was created by placing the celestial sphere with its south pole on the picture plane and rolling it repeatedly along its longitude . The two heavenly tropics are equidistant from the celestial equator circle between them . With this method, however, the horizon as the dividing line between the day and night sky is not exactly represented as a circle. A special feature of the Türler clock is the superimposition of this mathematical horizon line with the contour of the natural horizon, as it is captured at a low height from Paradeplatz over the roofs of the neighboring houses with a fisheye lens . The mathematical horizon line is basically the same for all locations on the geographical latitude of Zurich.

The type of projection used leads, like that in astrolabe clocks, to a clear representation of the sun and moon movement from the eastern to the southern to the western horizon. The linear image scale on the meridians simplified the adjustment to be made in the clock to the daily changing orbit of the sun and moon.

The pointer surrounding the sun symbol (three times the diameter instead of true to scale) indicates the time of day in astrolabe clocks on a 24-hour scale as mean local time (MONT). The revolving sun in the sky represents the so-called true time, the deviation of which, which fluctuates over the year , is described by the equation of time . The true course of the sun is reproduced in the Türler clock. The horizon block is driven by an output shaft of the 12-hour clock with calendar with a steady rotation every 24 hours. With an equation device , the construction of which goes back to Jost Bürgi and uses two crank loops connected in series, the uneven - albeit apparent - course of the sun is realized. The uneven flow of solar time is established, which is actually caused by the ellipticity of the earth's orbit around the sun and the inclination of the earth's axis on this orbit. The elongated sun pointer shows on the outside of the 24-hour scale the true local time (WOZ) of Zurich and all places with the same geographical longitude.

The sun's daily orbit, which varies over the year, is also a result of the obliqueness of the earth's axis. The sun symbol changes its distance from the center of the image accordingly with an oscillation period of one year. The pointer carrying the symbol at its tip changes its length telescopically by using a crank loop, so that the symbol moves back and forth between the tropics of the sun.

The movement of the moon is reproduced more precisely in the Türler clock than in the well-known astrolabe clocks. Of the causes that make the course of the moon uneven, the following are considered:

  • the elliptical shape of the lunar orbit leading around the earth,
  • the perigee rotation of the lunar orbit (in the clock 1 rotation in 8.8481 years),
  • the inclination of the lunar orbit against the ecliptic (about 5.1 °, shown in the clock for didactic reasons with about double the value) and
  • the rotation of the nodal line around which the lunar orbit is inclined (in the clock 1 rotation in 18.6134 years).

The first two lead to an uneven orbital speed of the moon, which is achieved with a gear unit with two epicycles . The other two causes mean that the altitude of its daily orbit not only fluctuates in the same way as that of the sun, but that this fluctuation is also superimposed on an altitude fluctuation resulting from the orbit inclination. The rotation of the nodal line means that the oblique lunar orbit stumbles. Both fluctuations therefore do not take place synchronously. The pointer carrying the moon symbol (three times the diameter instead of true to scale) at its tip changes its length telescopically in two slightly different periodic movements. The symbol can run both above the Tropic of Cancer and below the Tropic of Capricorn . The length of the moon hand, which is telescopically changed in the Türler clock, is achieved with two crank loops connected in series (the first already for the sun hand). Since the moon lags behind the sun for about 48 minutes every day, the phases of the moon change , which is reproduced in the Türler clock in a manner known from the astrolabe clocks by turning the small moon ball around the lunar stick.

In contrast to astrolabe clocks, the Türler clock does not show stars. There is no rotating zodiac to represent the stars near the ecliptic.



With the planetarium, the geocentric (more precisely one at the geographical latitude of Zurich) is abandoned and one outside the solar system is taken. The sun is in the center ( heliocentric view of the world ) and is orbited by the planets on almost a single plane. In the clock, all concentric planetary rings rotate in one plane. The deviations are neglected. A small circular disk with a planetary symbol on the edge rotates on each planetary ring, which results in an eccentric circular path. This approximates the ellipticity of the paths. The circular disks (planet symbols are the tips of the arrows on them) do not rotate in space, they always point in the same direction, which is achieved by a small eccentric mass each. Because of the large orbital ellipticity of Pluto , its small disk had to be replaced by a pointer (the planet symbol is its outer end), since a disk would have collided with the rings of the neighboring planets. The distances from Mercury to Mars were mutually true to scale, from Jupiter to Pluto increasingly scaled down for reasons of displayability.

The rings need between 88 (Mercury) and 90,470 days (Pluto) to orbit. The times achieved are at least equal to the target values ​​with the following decimal places (small difference only with Pluto):

  • Mercury: 87.969 days
  • Venus : 224,701 days
  • Earth: 365.256 days ( sidereal year )
  • Mars: 696.980 days
  • Jupiter: 4,332.59 days
  • Saturn : 10,759.21 days
  • Uranus : 39,685.93 days
  • Neptune : 60,187.64 days
  • Pluto: 90,470.47 days (target 90,470.49 days)

The planetarium work block also contains many wheels (50), although the movements of the slower planets are in part derived from those of faster planets. Direct gears lead from the input rotation (1 / 24h) only to Mercury (further to Venus), Earth (further to Mars), Jupiter and Saturn (further to Uranus, Pluto and Neptune).

The edge of the planetarium is covered by a scale subdivided with the signs of the zodiac , on which the position of a planet or the sun in the zodiac can be seen if you point from the symbol of the earth over the planet or the sun to the scale.



With the tellurium, an also extraterrestrial observation site that is fixed with respect to the sun has been taken. But this is closer to the earth than to the planetarium.

The sun is shown, which is orbited only by the planet earth, but the latter also by its moon. The daily rotation of the earth also takes place in the model. The earth is exaggeratedly large compared to the sun, and the distance between them is exaggeratedly small. The moon is about the right size compared to the earth, but it is immeasurably close to it. Opposite it is a disc as a counterweight, which can also be understood as a fictitious counter moon.

Earth and moon together orbit the sun in a tropical year (365.2422 days).

The earth rotates once around itself on a sidereal day (23 h 56 m 4.1 s = 0.99727 solar days) on its axis inclined to the ecliptic (approx. 23.5 °). The moon moves through its orbit in a tropical month (27.3216 days). Since both revolve around the sun, a rotation of the earth related to the sun lasts 24 hours (1 day) and a moon related to the sun 29.5059 days ( sidereal month ). The representation of the orbital inclination of the moon in relation to the ecliptic was omitted.

The tellurium is surrounded by a sun-proof ecliptic ring that is scaled with the signs of the zodiac and the month names. The pointer opposite the earth revolves with it and shows the position of the sun in the zodiac. There is no need for bearings at the planetarium.

The earth is also surrounded by an ecliptic ring that does not rotate in relation to the sun. The disc with the signature of the builder and the client and the date of the inauguration (June 21, 1995) of the clock is used to balance the weight of the model balls for earth and moon.

The elliptical orbit of the earth is taken into account indirectly because the sun is not exactly in the center of the circular orbit of the earth. The slightly eccentric sun also rotates like the real gaseous sun rotates on average: 1 rotation / 25.38 days; Inclination of the axis of rotation to the ecliptic about 7.25 °.

The ellipticity of the lunar orbit and its perigee rotation are incorporated with the same means as for the horizon (two epicycles, 1 crank loop).

Globe and celestial spheres


This model with the earth in the center represents the old geocentric worldview . In contrast to the horizon model, only the earth's axis remains immobile. The earth rotating evenly around itself is shown as a globe.

The globe axis is inclined relative to the axis of the surrounding solar sphere with the ecliptic angle (approx. 23½ °). The globe is surrounded by five spheres, four of which also rotate. Three of these four spherical shells rotate around a vertical axis.

1. The moon is drawn on the innermost glass bowl (circular area with a hole that represents the moon to scale). Its axis is not completely perpendicular (lunar orbit inclined about 5.1 ° to the ecliptic). The bowl with the moon makes one revolution (360 °) in a tropical month (27.3216 days). The not quite even orbital speed of the moon is simulated in the same way as in the horizon and in the tellurium: 2 epicycles, 1 crank arm. The slightly inclined moon axis is not fixed, but rotates around the vertical axis of the ecliptic with the speed of rotation of the nodal line (1 rotation / 18.6134 years).

2. The sun (circular area with a hole, which represents the sun to scale) is on the second glass bowl (vertical axis), the night half of which is less transparent. It orbits the earth in a tropical year (365.2422 days) on the ecliptic circle. Seen from the globe rotating around its own axis, the places with sunrise and sunset are on their day / night boundary (direction in Zurich can be identified with the help of the horizon ring, see 5.). The uneven orbital speed of the sun is reached in the same way as in the horizon . But here only one of the two crank loops is necessary, because the slope of the earth's axis exists in the model. Only what happens as a result of the ellipticity of the earth's orbit needs to be reproduced.

3. The glass bowl with the starry sky follows (vertical axis). When viewed from the outside, the applied constellations are mirror-inverted to the view from Earth. Each star is a gold plate in a milled recess in the glass bowl. The starry sky rotates around the axis of the ecliptic once in a Platonic year (about 25,794 solar years). The reduction ratio between a rotation of the starry sky and a half-oscillation of the seconds pendulum is 813,993,528,636: 1 (the large number is the duration of the Platonic year in seconds). For this purpose, starting from the rotation of the sun bowl, 6 additional gear stages were installed. To reproduce this extremely slow movement is an exaggerated exaggeration, because the viewer will most certainly never notice it.

4. The fourth “bowl” is a fixed wire frame, the main part of which is the horizontal ecliptic / zodiac - that is, the projection of the sun's apparent path over the course of a year onto the stars of the celestial sphere. It serves as a space-fixed reference system and should actually rotate together with the third shell. But one sticks to the custom adopted from astrology of specifying the position of the sun in the ecliptic with the so-called signs of the zodiac - that is, in constellations that are progressively not applicable .

5. The outermost “shell” is again a wire frame that rotates together with the globe (23½ ° inclined axis). It repeats most of the orientation lines found on the globe: the equator, tropics, and arctic circle ; also the meridian , the zenith above and the horizon of Zurich. For the horizon made the great circle of the spheres, one has to imagine the globe so small that its surface with Zurich lies in the center of the spheres.

If the symbols for the sun (2nd shell), moon and opposite moon (1st shell) are on top of each other, an eclipse is displayed:

Traditional classification

Time measurement and calendars are among the oldest branches of astronomy . All units of time that appear natural to humans are determined by astronomical phenomena: the year, the month, the day . The phenomenon “time” has influenced philosophers, astronomers, physicists and the like. v. a. m. never let go. Only in the recent past has an abstract atomic time been defined with the SI second . The spread of mechanical clocks did not take place until the last third of the 14th century. Astronomical clocks, which were made in considerable numbers between the 14th and 17th centuries in German-speaking countries, were intended to stimulate the viewer to think more deeply about time beyond the mere display of the time of day and to make it clear to him that life was not at the discretion of people but is assigned by God. The manufacturers and designers of these watches enjoyed a great reputation in their time. Each watch was a unique piece with a special story.

The Türler clock is in the tradition of such clocks that are "designed either as technical-scientific or scientific-didactic instruments". However, its builders do not consider it to be a classic astronomical clock, "although it ... also fulfills its requirements". It is "a work of art with the aim of conveying a deeper and always current content through a picture."

Notes and individual references

  1. ^ Franz Türler: The Türler clock - model of the cosmos. In: Franz Betschon , Stefan Betschon, Willy Schlachter (eds.): Engineers build Switzerland. First-hand history of technology. Volume 2. Verlag Neue Zürcher Zeitung, Zurich 2014, ISBN 978-3-03823-912-3 , pp. 344-350.
  2. The description is based on the publications listed below and two other, previously unpublished manuscripts by Ludwig Oechslin, one of which is the calculation of the works.
  3. The two epicycles used go back to a solution that Nicolaus Copernicus found while saving the phenomena .
  4. The isolated terrestrial globes are traditionally set up at 23½ °, although the relation to the ecliptic does not play a role here.
  5. Ludwig Oechslin: The Türler clock in Chronometrophilia, N o 52, winter 1996; Page 22: "Your [the stars] own movement is only included here in order to increase the mentally conscious accuracy of the clock".
  6. a b Ludwig Oechslin: The Türler clock in Chronometrophilia, N o 52, winter 1996; Page 15


  • Ludwig Oechslin : The Türler clock. In: Chronométrophilia. No. 52, Winter 1996, ZDB -ID 270878-4 , pp. 14-32.
  • Türler watches & jewels: The Türler watch, the model of the cosmos. Corporate font.
  • Franz Türler (ed.): The unique. Türler clock - the model of the cosmos . Verlag Ineichen, Zurich 2013, ISBN 978-3-033-03839-4 .

Web links

Coordinates: 47 ° 22 '11 "  N , 8 ° 32' 20.8"  E ; CH1903:  six hundred and eighty-three thousand one hundred nineteen  /  247126