Pendulum design

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The pendulum and it's suspension assembly was missing when I acquired the movement. The fabricator did a beautiful job of blending the design of the pendulum assembly to the design of the movement. There were several special challenges to this design since it had to swing behind the dial. It had to have two "key holes" in it's rod to accommodate the cannon pinion holding the dial hands as well as the going train winding square. I had decided on a bob constructed from dual glass jars to hold mercury.

              pendulum1a.jpg (98489 bytes) The first two drawings show the design of the pendulum rod against that of the going train frame. Efforts were made to make the design of the pendulum look as if it was a part of the original design.
              pendulum2a.jpg (95742 bytes)  
              Brass tower clock-Saff (12a).jpg (346652 bytes)     Shown are the pendulum as well as the bell support frame mockups in brass-painted wood. At this point the bell pulls are not yet in their final design iteration their levers still outside the frame.
              Brass tower clock-Saff (11).jpg (348795 bytes) Overall look of the clock on mockup stand, weights and pendulum assembly.
              pendulum-a.jpg (605610 bytes) Original pendulum bob design. This was later changed to avoid the use of a threaded ring that was glued to the glass upon which the lids would screw down.

The total volume used for mercury at 4/5ths level is 640 ml - about 9.1 kilos or 20 lb of mercury.

              Brass tower clock-Saff (15).jpg (347425 bytes) First wooden mockup of the bob using the thumbprint jars provided
Brass tower clock-Saff (19).jpg (524476 bytes) Early production.
              Final product. Here the threaded rings glued to the glass are eliminated. The lids (with a leather gaskets) now rest upon the top of the glass jars and are pinned into place with the pair of four-armed handles attached to threaded screws. When loosened, the entire assembly swings away supported by the side rods attached to the lower pivots.

The center knurled nut is for fine adjustment, a scale delineated in seconds/day will be mounted behind this. The nut below is for coarse adjustments. Upon reflection, the fine adjustment should have been done in the conventional manner through the upper suspension mount, thus being able to do this without stopping the pendulum.

The jars are shown filled with tungsten powder to simulate mercury. Upon delivery the two jars were filled with 10 lbs. of mercury into each jar.

              Brass tower clock-Saff (10).jpg (350288 bytes) Early wood mockup of pendulum support system. Notice the consistent use of curvilinear design for the new pieces to match the old. The parts are then spray painted to match the extant brass parts. We used this method extensively in the next project I enlisted the Buchanan firm in, the astronomical skeleton clock.
              Brass tower clock-Saff (74).JPG (844516 bytes) Final support. Adjustments have been included for left to right and front to back.

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