The first Clock


This first clock is in fact a moving star map (planisphere), which original design was  made by Rob Walrecht (c). Take a look at his website! The clock is driven by a 12 hour quarts clock, but the centre arbor is moving in 24 hours. This arbor moves the Sun in mean Time through the ecliptic. The Sky plate is moving in 23h.56m.03,93s it should be 23h.56m.04,0905s, although the wheel work is simple, the offset in time is not large.
In reality the Sun is not moving with the same speed through the year, but sometimes slower sometimes faster.
In later clocks there is only an indication line for the months.
At the picture you can see that the Sun is in the ecliptic and near the western horizon.
It is evening and almost night.





After buying a lathe, I had to learn how to make wheels for the clock. The problem is that many of the wheels in an Astronomical clock have uneven teeth numbers, like 61 or 73. These numbers were not indicated on the dividing head that came with the lathe. That's why I made my own dividing plates.


With this simple tool I made the divisions in cardboard, and the punches in the dividing plates.

Later I bought a better dividing head, and now I can make every wheel, even wheels (with some calculation) that go over 100.

Many other tools like mandrels were made with the lathe.


All the wheels are made from hard brass, it has more strength and machines better than half hard brass. I bought some commercial cutters, but you can also use home made fly cutters.
Much information I found in the book Wheel and Pinion Cutting in Horology from J. Malcolm Wild.
The books of John Wilding were also very useful to make a good start!


 Wheel- crossing- marking- out jig, from the book of
J. Malcolm Wild.



I want to thank C.G.Croce, P. Coleman, P.E.Meulenkamp
(our local clocksmith) and Rob Walrecht, for their inspiring support, H. Noordmans for his nice calculation program and book about the Eisinga Planetarium and A. Lehr for his book: "De Geschiedenis van het Astronomische Kunstuurwerk" (Dutch)


If possible visit the  Eise Eisinga Planetarium !!





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