Debugging continues, correction for seconds hand finished, world time dial
corrected and finished
This month's installment sees the finishing of the seconds
correction dial. Be sure to compare last month's video before the correction
to the video this month after correction. It was fortunate that we had a
spare main time dial now that true jump seconds were being read out, that
replacement dial had a more accurate seconds spacing to match the hand.
Debugging continues, an error in the positioning of some of the cities in
the world time dial was found, corrected and finished. One of the remontoire counter
weights were moved away from an adjacent wheel to give more comfortable
clearance, center remontoire wheel slightly repositioned to run in the
middle of its mating pinion (this was not a bug but done to look better).
The tellurian was slightly repositioned to give a better fit, a minor
depthing issue to the planisphere drive is addressed. Many other smaller
bugs were dealt with.
The escape wheel parts
now finished, next the seconds drive wheel and the finished count wheel,
The second photo more
clearly shows the skeletonized spring barrel located between the count and
Wheel spoke artistry
simply doesn’t get much better than this, note Buchanan's signature sharp
inner corners and where the connecting points to the outer toothed rim
nearly disappear. The last wheel!
The components of the pallet fork now finished.
The finished pallet fork. Note the paired and unequally sized jewels,
this design is key to the conversion of of each two-second input into a pair
of one-second outputs.
a set of 60 equally spaced lines and printed them out on paper and then
placed the paper dial on the enamel dials; the one with no bezel is the dial
with the two minor cracks that we discarded
(first photo). The other is on
the clock at present. It shows the bad spacing of the seconds lines,
(second photo), compared to the spare.
It was fortunate we had
two dials made by the enamel artisans in China. The one we had thought we
would keep had no imperfections as far as the enamel work. However when
Buchanan made his drawing showing the equal spacing that the seconds hand
will now produce thanks to the revisions made last month, we see that they
do not line up well. The dial we did not use, (below), has much better
spacing and only had a very small crack and blemish near the thirty-two
seconds mark, this was very minor and will be mostly covered with the bezel.
Given how much better the spacing is on this dial we decided to make the
The dial blemish is very small and demonstrates the high standards for this
to be the second choice dial.
The blemish nearly disappears when placed behind the dial bezel. And to
be fair, a very small crack almost always appears somewhere on large
antique enamel dials, in particular those that take the shape of a ring
which are more fragile than the conventional disc shape. Also note the
visually tight and accurate bezels around each individually moving dial ring
between the mean solar, and sidereal hours and minutes ring.
Note the inconsistencies in the rotation of the wheel shown by the
arrows. This wheel used to be the output for the seconds hand. This is now
buffered by the spiral spring (within circle), allowing the indexing seconds
count wheel to accurately display jump seconds from the former erratic two
seconds output wheel caused by the remontoire reloading cycle. By creating
this indexing wheel and spiral spring buffer we have achieved two goals:
First was to have a reliable seconds hand output. However, before this
change the pendulums as they are designed have a two second period (4 second
cycle) meaning that the second hand, even if not erratic, would jump every
two seconds. However, the feedback from the remontoire reloading cycle was
also causing the hand to act erratically, floating, even skipping a second
or going backwards! Not an acceptable situation. The spiral spring and what
looks like an escapement wheel, but is actually an indexing wheel, is now
the output for the seconds hand achieving a reliable period, but even
better, changing the period from a two second to a true one second jump,
making the time dial look like a conventional regulator, even though it has
a two second pendulum. We chose the two second pendulum because it has a
better visual, almost hypnotic effect on the viewer compared to a one second
period and I was content to have the seconds hand jump every two seconds.
But with this design change we have solved the erratic feedback problem and
have given the time dial seconds hand the advantage of a one second readout
without losing the two second pendulum period. A rare win-win in engineering
In this video one sees what looks like an unusual escapement. This is not an
escapement but a count wheel. The pallet fork is controlled by the two
second compound pendulums so it takes four seconds for the fork to make a full back
and forth swing; since the fork has a pair of two separate pallets, these
four pallets divide the four second pendulum cycle into four individual
contacts with the count wheel, that wheel is connected to the second hand
resulting in a true jump seconds from a two seconds pendulum swing (one half
cycle). Think of this as a 'reverse coup perdu' device since a typical coup
perdu creates a one second dial readout from a half-second pendulum, the
words are French for "lost beat" since only every other beat is recorded on
the dial. In this case we have a "gained beat" perhaps the French
translation could be "battement gagné"? A complete explanation can be found
in last month's April
installment Look carefully at the movement of the seconds hand in
comparison to the twin Harrison grasshopper escapement wheels to the right
of the dial and one sees how two jump seconds are generated on the dial for
each two second long beat of those escapements. Also turn up the volume
during the last frame of the video! This is the first video where one can
clearly hear the many different sounds the machine makes, when not striking.
It now has what one would expect as a regular 'tick tock'. The grasshopper
escapement was always virtually silent. The video was taken close up when
the background noise was low so some of the clicking and whirling can be
These two photos show the beginning of Buchanan using a Microset timer
to get the count wheel properly calibrated, the second photo shows the
improvement from the first.
Now Buchanan turns to the world time dial
The first photo shows all the errors on the
international time dial. Buchanan printed out a paper with lines on the
correct position of the hands for each city and placed the faulty dial above
it, (first photo). Paris Moscow and Abu are correct. Bangkok is hopeless.
Sydney, Los Angeles, Chicago and Rio are all an hour out.
We decided to drop Bangkok, Shift Sydney and Beijing
anticlockwise a bit and this will get Sydney into the correct place and Rio,
Chicago and Los Angeles a little clockwise, Honolulu was placed in the space
at the bottom of the dial to keep reasonable spacing. Honolulu only having
one more letter than Bangkok, (second photo).
The new design is seen in the first illustration, next the that design
fresh off the mill.
The finished international time dial. The city depiction ring is plated
in French silvering.
This photo shows one of the myriad of debugging problems. The remontoire
counterweight in the time train was too close to an adjacent wheel, here
Buchanan has reworked the position of the weight to give a better clearance.
The brass trimmed case is being made locally. Fred Widman is a skilled model
engineer located about an hour from my home. Each glass pane has a brass
surround which fits into the main frame and can be secured with the knurled
thumb screws, but is still
fully removable from the main frame allowing access to the entire machine.
The machine is getting very near completion!
Total parts count to date: 7951. This count now includes the parts for
the case. Additional parts will later be added for winding and setting keys.