Jens Olsen World Clock Copenhagen consisting of 12 clockworks and 15,448 individual parts

Jens Olsen's World Clock, or Verdensur, is a highly sophisticated astronomical clock on display in Copenhagen City Hall. The clock consists of twelve clockwork mechanisms with a total of 15,448 parts. It is mechanical and must be wound once a week.

Besides the time, it displays lunar and solar eclipses, the positions of celestial bodies, and a perpetual calendar. The fastest gear rotates once every ten seconds, the slowest every 25,753 years.

Story

The clock was designed and calculated by Jens Olsen (1872–1945). He was a trained locksmith and later learned the watchmaking trade. He was also involved in the start of the clock's construction and died in 1945, ten years before its completion.[6]

The calculations for the clock were carried out until 1928 and subsequently supervised by the astronomer Elis Strömgren.[4] The drawings for the clock were created between 1934 and 1936, and the actual production took place from 1943 to 1955.

The clock was put into operation on December 15, 1955 by Birgit, the youngest granddaughter of King Frederik IX and Jens Olsen.

Deviations from the expected readings, detected in 1991, were due to increased friction caused by the oil in the pivots, which hardened due to prolonged exposure to sunlight and oxygen. Consequently, the clock was largely disassembled for restoration and modernization.

All brass and bronze parts were regilded.

470 pivot points were modified to accommodate miniature ball bearings that are not visible when assembled.

Some shafts were coated with a low-friction nickel-Teflon mixture. The restoration began in 1995 and was completed in 1997. It was entrusted to the Danish watchmaker and restorer Søren Andersen.[9]

design

aesthetics

The clock is centrally located in a specially designed room, surrounded by smaller, thematically related exhibits and descriptions of various aspects of the clock. It is housed in a large glass case with a wooden and stainless steel frame and stands on a granite base.

The clock faces the room's only entrance but can be viewed from all sides to admire its intricate design. The case has internal lighting and its temperature and humidity are regulated by a ventilation system in the building's basement. The current version is made largely of gilded brass, while the dials are made of rhodium-plated brass.

inhibition

The escapement is a Dennison double triple-leg gravity escapement, a design choice common in later tower clocks that prioritizes accuracy over efficiency. In simpler terms, the escapement itself acts as a remontoire, so variations in input torque are largely decoupled and do not affect the pendulum. However, this design requires a considerable amount of input power (in the case of the world clock, a substantial weight) to compensate for the excess energy that is "dissipated" by the air brake with each tick.

The pendulum is a seconds pendulum and therefore, due to the local gravity in Copenhagen, requires a theoretical length of 994.5 mm. However, due to the distributed mass, the physical pendulum is slightly longer to ensure the correct oscillation period. The choice of materials is meticulous: the pendulum rod is made of Invar, the impulse rods of sapphire, and the clockwork is elaborately set with precious stones. The escapement wheel is a relatively unusual five-tooth design.

Clockworks

The movements are modular, making them easier to identify and the clock's operation easier to understand. This also allows for the removal and maintenance of many movements without having to stop the entire clock. The number of escapements is occasionally given as 11 instead of 12. This ambiguity arises from whether mean time and sidereal time are considered a single movement. All movements except the Equation Works movement have dials on the front, arranged in left, center, and right sections.

Second time

The movement for the intermediate time is located at the top center and has the largest dial of the watch. It displays hours and minutes on a 12-hour dial, as well as a smaller, recessed dial with a seconds display on a 60-second subdial.

Stardate

The sidereal time movement is located directly below the mean solar time movement in the central section and features a 24-hour dial with minute and hour hands. Additionally, there is a smaller, recessed 60-second dial with a seconds hand.

Main calendar

The main calendar is located at the bottom of the central section and comprises five dials for the Sunday letter, the epacts, the solar cycle, the indication cycle, and the lunar cycle. Below this is a calendar display showing the dates of movable feasts, the day of the week for each date, and the dates of the full, new, and quarter moons.

Triple dial

The "triple dial" is located at the top left and consists of three dials set within a larger circle: the equation of time (top), solar time (bottom right), and mean local solar time (bottom left). Each solar time dial has a minute and hour hand on a 24-hour scale.

Synchronoscope

The synchronoscope is the left-hand dial in the left-hand section and displays the time for any location in the world. This is achieved using a fixed map (in the form of a south pole projection) around which a 24-hour dial rotates. This module also generates the pulse signal for the Gregorian calendar (directly below it) and the modules for the Julian period.

Sunrise/Sunset

The sunrise/sunset indicator is located on the far right of the left-hand side and includes movable louvers that display the times of sunrise and sunset throughout the year. These can be read from an inner, fixed 24-hour dial for solar time or an outer 24-hour dial for mean solar time (taking mean solar time into account).

Gregorian calendar

The Gregorian calendar is located at the bottom left. It displays the year, month, day of the month, and day of the week. These displays change discontinuously at midnight and otherwise remain unchanged.

starry sky

The "Starry Sky" movement is located on the upper dial of the right-hand section and displays the current celestial sphere above us. The representation is achieved using stereoscopic projection (similar to an astrolabe) with fixed threads that indicate reference lines for the meridian and zenith in the local reference frame, as well as the tropics, equator, and circumpolar circle in the celestial reference frame. The precession circle of the poles is also shown; it represents the slowest movement of the clock.

Heliocentric Revolution

The "Heliocentric Revolution" clockwork is located on the right side of the right-hand section and is essentially a planetarium. It depicts the eight planets orbiting a fixed sun and their positions relative to a fixed outer zodiac dial. Pluto was discovered in 1930, shortly after the calculations for the clock were completed. Since the IAU redefined the term "planet" in 2006, the clock now again includes all planets. Planetary motion is constant and circular, and the distance between their orbits is uniform.

Geocentric revolution display.

The sun's position is visible in the upper left and is almost aligned with a lunar node. This lunar node and its complementary node in the lower left exhibit arcs corresponding to the alignment range for total and partial eclipses. The moon's position is visible in the lower right, its phase approaching its third quarter. The lunar perigee is marked with a "P" on the right, and the apogee with an "A" on the left. The outer dial displays the right ascension in degrees, interspersed with the signs of the zodiac.

Geocentric Revolution

The geocentric revolution display is located on the left side of the right-hand panel and shows the ecliptic longitudes of the Sun, Moon, lunisolar nodes, lunar perigee, and lunar phase. These are all complex motions, especially the Moon's position. However, the calculations for these motions are not performed solely within this module. Rather, most anomalies are calculated by the equation function and transferred to the geocentric revolution display, where they are combined with the mean motions via differentials to generate the display.

Julian period

The clock mechanism of the Julian period is located at the bottom right and displays both the Julian year and the Julian day. Both are discontinuous movements, similar to the Gregorian calendar, but with a fluctuation at 1:00 PM CET.

Equation set

The equation mechanism has no display on the front of the watch and is located behind the main calendar in the central section. However, it does have labels explaining its various functions, as well as small adjustment wheels. The equation mechanism generates rotational speeds of astronomical significance, which are either used directly elsewhere in the watch or create a linear motion at these speeds, which is then used elsewhere.

The system of equations uses its own weight as an energy source and is time-regulated by a 36-tooth ratchet wheel, which is driven by an impulse from the module for the mean time.

These values ​​and their uses are listed here in order from left to right (when looking at the front of the watch, or from right to left when looking at the back, where the movement is more visible):

1/2 Tropical Year (182 days, 14 hours, 54 minutes, 23 seconds).
A sinusoidal linear signal is generated via a Tusi pair to account for the skewness in the equation of time. This signal is then added via a pulley to account for the eccentricity effect, producing the equation of time signal. Note: This motion is generated after (and therefore includes) the phase shift due to the anomalistic annual axis.

The rotation rate is directly applied to the sunrise/sunset display. Note: This movement is generated before (and therefore does not include) the phase shift caused by the anomalistic annual axis.
1 Anomalistic Year (365 days, 6 hours, 13 minutes, 56 seconds).

A sinusoidal linear signal is generated using a Tusi pair to account for the effect of eccentricity in the equation of time. This signal is then summed using a roller, taking skewness into account, to generate the equation of time signal.

1 Anomalistic Year (365 days, 6 hours, 13 minutes, 56 seconds).
Using a Tusi pair, it generates a sinusoidal linear signal that accounts for the influence of eccentricity in the equation of time. This signal is then combined with the influence of the obliquity of the ecliptic using a roller to generate the equation of time signal.

Using an eccentricity, it generates a pseudo-sinusoidal rotation, which is added to the half-tropical year preceding the Tusi pair on this wave. This captures the phase shift resulting from the influence of the eccentricity on the obliquity of the ecliptic in the equation of time.

It generates a pseudo-sinusoidal linear signal using a crank, which is then added to the lunar anomalies to model the annual equation.

1/2 Draconic Month (13 days 14 hours 32 minutes 48 seconds)
It generates a pseudosinusoidal linear signal via a crank, which is then added to the lunar anomalies to model lunar reduction.

1/2 Synodic month (14 days 18 hours 22 minutes 1 second)
It generates a pseudosinusoidal linear signal via a crank, which is then added to the lunar anomalies to model lunar variation.

Lunar Nodal Oscillation (173.31001 days)
It generates a pseudosinusoidal linear signal via a crank, which is transmitted to the "Geocentric Revolution" module to be added to the mean precession rate of the lunar nodes and thus to determine the position of the lunar nodes.

Moon apsidal oscillation (205.89744d)
It generates a pseudosinusoidal linear signal via a crank, which is transferred to the geocentric revolution module and added to the mean apsidal precession rate to determine the apsidal line.

Monde Evektion (31d 19h 29m)

It generates a pseudosinusoidal linear signal via a crank, which is then summed to the lunar anomalies to model the evection.
Anomalistic lunar month (27d 13h 18m)

It generates a sinusoidal linear signal via a Tusi pair, which is then summed to form the lunar anomalies in order to model the Great Lunar Anomaly (equation of the center).

Connections between movements
Information is exchanged between movements in three ways, depending on the type:

Rotation information is transmitted via bevel gear sets in the source and target modules, with an intermediate shaft. These rotate continuously (unlimited), although not always at a constant speed. The gear ratio of both modules is always designed so that the shaft rotates at a sensible frequency (e.g., 1 revolution per average day). While this design is not the simplest, it makes it easier to understand – presumably intentionally.

Linear displacements are transmitted via steel tapes. These are analog signals with a limited range, such as the current value of the equation of time or various solar and lunar anomalies. The tapes typically run upwards to the housing cover, where they are moved horizontally across the respective target movement using a bell crank system, from where they can be guided downwards again.

Impulses are transmitted via rods. These are discrete signals that trigger discontinuous events, such as the date change at midnight. The angled lever system in the housing cover is also used here.

Source: Wikipedia