Mechanically complete Sun / Moon rise set
module; horizon shutter cams, movable dial plaques -
Today I prepared to start the cams. I needed a dial to work from for the
shutter settings so I drew up a scale to print on paper. By the time I had
drawn it up I realised that I was only one step away from engraving so I
engraved it onto the dial plate. Just like they do on the front plate of a
complicated watch movement.
Look at this engraving, it is beautiful and after the outer bezel is fitted
will never be seen again!
The readings around the rim will be used to
gauge the accuracy of the cams as they are slowly filed until the readouts
match the tables of when the sun rises and sets at the latitude of Chicago.
I had to remake the collet that held the cams as I had an unacceptable
wobble. I have removed the roller on a cam follower and replaced it with a
mushroom head that is flat enough to pass the side of the cam. I am now in
the process of scribing around the mushroom head every five days to obtain a
rough idea of the cam shape. I have attached a long pointer to the edge of
the shutter to read of the edge of the engraved dial plate.
That process involves
the laborious iterations needed to refine the cam shape as the errors are
eliminated by reading the result of each cam trim on the dial rim. This is the same
process used to make the equation kidney cam. Both types of cams rotate once
per year. There are 73 readings around the cam’s perimeter, each
encompassing a five day period for a 365 day year. It takes ten to twelve
entire sets of readings and trimmings to bring the cam’s shape to acceptable
73 x 12 = 876 individual readings. The second photo shows the rough
outline of the cam following the initial scribe marks produced from the cam
follower; the individual scribe lines are just barely visible. The table in
the background is the sunrise and sunset times for the latitude of Chicago,
Illinois which are used to correlate the readings on the engraved dial
perimeter with the cam follower arm, and then each scribe is made on the
face of the cam for each five-day period.
A cam in the vise being hand filed. One can see the individual readings as
dots along the perimeter of the cam, second photo
In this video the cams controlling the shutters are manually rotated through
their one year cycle to show the extent of the day and night changes
throughout the year.
Last month designs for
the horizon cams were discussed. These are Buchanan’s renderings and I think
once again he has delivered a beautiful and functional design. These two
cams each control the sun rise, left hand shutter, and sunset, the right
hand shutter. They will rotate once per year. So for the sunrise, why not
use a depiction of the sun rising? Of course one could see the sun setting
with the same design so the night sky was depicted, no confusion there!
The cams are now
complete. Look, Mr. Sun has his own set of eyes as represented by the
insertion of two small steel ball bearings! So this sun joins the one from
last month in having eyes, one blue set and this one silver.
Our use of allegorical design has been used in cam work before. These three
cams were made earlier, the equation of time cam, left, indicating sun time, was
made with sun rays in October 2014 and the hour and quarter strike snail cams made in the image
of a Nautilus shell cross section in January 2014.
The movable plaques
that hover over the glass dial portion are fabricated, and next shown just
before removal from the brass blank.
The first photo shows
the very small size of these plaques, even smaller than the sunrise, sunset
plaques. And this very small size demanded that block lettering be used as
they are too small for script and due to the nature of the glass dial
layout, could not be made larger. There is now a question of whether the
mixture of script and block letter is a good one. An argument could be made
for it all being in block, but then the script on the center-hub dial must
be changed, and this looks quite nice as is. One could also say that block
lettering is located outside the white enamel dial referring to the moon
with script on the inside referring to the sun, and that is what we have
settled on. Look at the style of these plaques, no simple flat engraved
surface, but a raised picture framing edge, another in the many nice
Now starts the
finishing of the shutter assemblies. So far the blue glass is still
temporary plastic inserts.
The two steel pointers are now fitted to the
sunrise, sunset plaques.
Next the pointers positioned over the enamel
The first photo shows the machining of the
pair of dual steel pointers for the hours before and after moon rise and
set. Next the pointers are blued.
All of the plaques that refer to the moon have block lettering are given a
French silvered finish and are located outside the enamel dial. French
silvering gives the finish a frosted surface and enhances legibility. All of
the plaques referring to the sun are written in script on yellow brass, and are located inside
the enamel dial, second photo.
The left illustration
is the artwork for the glass dial that has the moonrise, moonset and angle
hour information. The photo shows a plastic mockup with this illustration
printed onto it and inserted into the dial bezel.
The artwork will
eventually be fed into a computer controlled laser for etching onto the rear
of the glass dial
First a close up detail
of the moon sphere opening for the glass dial. Next the dial mockup mounted to the mechanism with the moon located
within the dial gap.
Note the dual dial pointers now attached to the
movable plaque to the right each reading a separate ring of numbers.
All of the dial components are now present. Only the transparent dial and
the moon sphere are still mockups.
The main components of the sunrise/moonrise-set module. Parts count at about
550 is approximately that for the perpetual calendar.
The sunrise/moonrise-set module is now mechanically complete.
In this video we demonstrate the module with both dials for this as well as
the tellurian module below to give the viewer the full compliment of the
complex wheel works beneath. The clear dial is still a plastic mockup and so
has a bit of a wobble.