Balance diagonals, poising weights, strike train rear frame, begin snail transfer train - September 2010                         

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This month Buchanan begins on the pendulum balance diagonal braces. These are necessary to stiffen the large, intricate diamond shaped frames and also supply an area for the balance's poising weights; similar to the design in Harrison's H1 marine chronometer. First a drawing is produced to show parts that will secure the diagonals to the existing balance arbors. The following photos show these parts being fabricated with the main arbor attachment structures outlined on the raw brass stock in the last two photos.

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These photos show the parts that will secure the diagonals to the frames themselves. These are made in split halves. They must clamp around the upper and lower center upright of each balance. The last photo shows one of these in place before final closure of the part around the upright.

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Next the diagonals are fabricated. First the raw rails are cut from brass stock. Notice how we do not settle for a simple profile, but chose to have decorative ends. This requires the entire center section to be reduced to allow the larger decorative flares below the end holes. The last two photos show the diagonal attachment parts in place.

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These photos show the diagonals in place. Considering the density of the components in the movement it's amazing we were able to find the free space necessary to allow for the sweep of the diagonals.

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Now begins the fabrication of the poising weight discs. We decided to make these in keeping with Harrison's original design as depicted by the background photos in the last two shots.

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The poising weight frictional supports are made. The rough blanks are made, drilled and sliced. Another set of custom screws are made (most for other parts of the movement). When the screws are loosened from the rear plate the weights can be moved along the the diagonal rail to achieve the ideal balance of the pendulums.

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The weights are now in place. B decided to blue the steel base in addition to the screws. We may later change to a polished steel surface for the plate to give contrast, but this is to be decided later. The last photo shows the upper balance weights in place.

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The rear strike train frame is now fabricated. Notice how the movement has taken on a more vertical 'feel' from that shown before. it's slimmer and more refined. The large blued screws are a taste of what's to come when all the screws are done in this way.

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A milestone is shown here. For the first time we are beginning to place and shape the dials for the movement. Shown here are to the left, the main time dial and on the right the tellurium.

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The design of this movement required that the information pertaining to the the strike train snails be transferred from the left hand side of the movement (as seen from the front) where the time train resided to the opposite side where the strike train was.  Therefore, a set of idler wheels would transmit this information across the rear of the movement. Needless to say, of course, the extra wheels were a welcome extravagance!  The striking mechanism will be a quarter repeater. The first two photos show the wooden mockup of the idler wheel train and frame. Another very important milestone is shown in the third photo. Here we are inserting a wood mockup system into the actual metal movement instead of into the wooden movement mockup for evaluation. The actual movement is now far enough along that the wood mockup is no longer needed. Look carefully at the last photograph. the transfer wheels pass through the area bounded by the pendulum horizontal frames and the diagonal braces! As B said to me, "I want someone to look at some particular feature of my work and ask, 'well now just how did he do that'?"

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This series of photos shows the modularity of the movement design. The lower frame  containing the heavy main frame and wheels is separate from the upper three frames. These are divided roughly between the time train the celestial train and the strike trains. This design makes assembly and more importantly, future servicing much more easier than would be possible in a conventional plate and spacer design.

                                                       

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