Strike and repeat control assemblies, main strike fly fan detents - February
Shown above is a strike detent assembly. There are two of these, one for the quarter
and one for the hour strike trains. Each are connected to their respective racks; which
will control the duration of the striking sequence of each train. At this point it looks
awful as it appears to be merely 'stuck on' the side of the lintel's end. The lintel as
well as the detent frame will be machined to correct this. The encircled area in the last
photo is the detent and is shown below. A second detent will be attached to the left side
of the horizontal lentil to control the hour strike train.
The detent is enlarged above. This device is what will release and then
engage the strike train fly fan assembly whip (the long, straight piece seen slightly
blurred in lower right hand corner); mediating the duration of the strike sequence. Note
that we continue our bird design carried through from the escapement and the seesaw rack
gathering assemblies. The red area will be the bird's jeweled beak. All of the various
components making up the strike system are currently fabricated in brass. Once the system
is thoroughly tested and debugged, these components will be re-machined in steel and the
majority of the components blued.
Buchanan now draws out the rough outlines of what he believes will be the
component layout of the strike control system. The first photo shows the pair of mounts
holding the rack fall-arresting fly fan assemblies. Also shown are the strike racks and
the hour fly fan detent. The second photo shows the beginnings of strike and repeat
initiator; also containing a pair of small fly fans. All of these fly fans provide
cushioning of the various strike components as they are activated. But more importantly,
(remember the number one rule of this project - visual impact), there will be a
cascading effect of these flies; beginning with the uppermost and smallest fly connected
to the initiator, then proceeding downward to the strike racks and finally to the release
of the strike train fly fan mounted to the base of the movement frame. This cascade of
events leading to the release of the strike train fly should last approximately two
seconds. Plenty of time to catch the viewer's attention.
The strike initiator cam has four arms with jeweled rollers on each. This
will be mounted to the same arbor as the quarter strike snail. This can be seen on the
last photo with the rough-machined snail in the foreground.
Shown are a few of the various components of the strike/ repeat initiator.
Note the machined collar, third photo, which attaches the pinion to the wheel. This
component is out front; in a prominent place so we do not use the conventional method of
simply attaching the pinion adjacent to the wheel hub. Another example of Buchanan's
uncompromising standards. The solid wheels will later be spoked.
The various parts are assembled and the assembly is shown positioned
approximately where it will reside within the movement.
Finally this month I had completed an article to be published in the April
issue of the Bulletin of the National Association of Watch and Clock Collectors
(NAWCC) titled Halfway Point for the Astronomical Skeleton Clock. This describes
the progress of the clock up to August 2010 by which time construction of the movement had
been underway for three years. Shown is the galley of the rear cover for the issue. This
makes the second rear cover article published in the Bulletin, the first having
been published August 2007 describing the scope of the project, its initial design and
mockup work. You can read the on-line versions of these articles here: Original
presentation paper on the Astronomical Skeleton Clock. and Halfway
point for the construction of the Astronomical Skeleton Clock, Year Three .
For those who cannot use the built-in viewer I have added the YouTube
The first video shows a test of the quarter strike sequence. The second shows a
close-up of the gathering pallets used to raise the quarter strike rack. As with
everything else in this project we chose a much more visually fascinating way to do this.
A conventional clock would have a simple single or double bladed pinion to raise the rack
in conjunction with a rack hook to keep the rack in place. We use two jeweled pallets, a
rocker arm and cam to drive the rocker.
Here we test for the first time the quarter and hour strike sequences. There are still
many parts to be added to for these components to not only strike in a conventional manner
but to also posses a full repeat on demand function.