Begin Sun/Moon rise/set complication, the variable differentials
- January 2017
This month begins the fabrication of the Sun and Moon rise and set
complication. The first diagram shows the wheel chart specification sheet.
This complication has a total of 54 wheels. Next is the scale drawing
of one of a pair of Janvier style differentials, this one being the
The raw brass plate stock ready to be turned
into a wonderful creation.
The first step is to stress-relieve the
plates, a step repeated throughout the project. Most modern brass is
cold-rolled to achieve the uniform surface and thickness. However that
rolling procedure introduces stress areas within the brass that could
manifest itself as warping once areas are cut out, as in the hub of a wheel
after the spokes have been cut; especially given Buchanan's delicate wheel
and spoke style.
Gear cutting is now well underway. The three bullet-shaped parts toward the
left-middle of the photo are bevel blanks out of which a bevel wheel will
eventually be made.
The two large discs are the main differential slant wheels and they are being fitted with
their roller bearings. The brass retaining rings are see as well as a close
up of both a ring and roller bearing. These slant wheels turn quite slowly
and the general rule in this project is where a bearing point turns slower
than one revolution per hour and is lightly loaded a dry jewel bearing is
used. But here there will be side forces on the wheel as it rotates and a
large center arbor to which the wheel is mounted, making a normal
The first photo shows a steel bevel pinion blank prior to the machining of
the teeth. The next photo shows further completion. Notice the the large
disc in the lower left of the photo with the slice taken out. This and the
three directly below are the sector gears for the Sun horizon shutters.
Now the slant wheel mounting arbor is fabricated on the vertical rotary
The first photo shows the slant wheel attached to the mount. The mount will
later be slimmed. In the next photo the great anomaly (37 degree tilt) and projection anomaly
(23.5 degree tilt) slant wheels
comprising part of those differentials for these complications are shown. The
models for these
based on Antide Janvier's design for differentials that mimic the erratic
movements of celestial bodies were illustrated in the November 2016
the first photo the
pinion and its drive wheel are put together with the
staking tool. Next the jig boring machine is used to check the depthing of
the pinion to the projection slant wheel.
The overall depthing setup on the jig boring machine. Here the secondary drive pinion
to the slant wheel for the projection anomaly is tested.
The first photo shows a depthing gauge attached to the boring machine head
and the gauge feeler contacting the surface of the slant wheel. Here the
wheel is checked for perfect alignment. Next the complex shape needed for
the drive wheel cock begins to take shape.
The initial tilted cock is in place with the secondary drive wheel and pinion.
These photos show the
fabrication of a bevel wheel. First is the bevel blank made from brass rod
stock. Next the area is cut down; next the actual dimensions of the bevel
are cut in addition to a bit of counter-sinking of the bevel wheel face.
Finally the wheel is cut off from the brass rod blank and is seen on the
lower left on the tool bed.
Here are a series of photos showing the steps in
finishing an inserted blue steel pivot. First the pinion is drilled
and then the pivot is pressed in. Then it is rough machined almost to size.
Then it is reduced with a diamond file until the jewel just fits. Then it is
smoothed with a ruby file and finally burnished. The pivot is then filed to
length and the end domed.
Here again is the
staking tool used to mount a pinion onto its mating drive wheel. This is the
primary drive wheel set which is positioned in the same orientation as the rest of the
surrounding wheel train, where the arbors are horizontal. Next the completed
primary wheel set, held by the tweezers, is shown next to the secondary
mating wheel and pinion. The secondary set is
oriented to the same angle as the large slant wheel. The combination of the
primary and secondary drive wheel sets allows power to change to direction to
that of the slant wheel.