Continue Sun / Moon rise set, dial output drive assemblies, sun drive, hours of daylight and nighttime sub-dials  - July 2017  

This month Buchanan continues with the output drive section of the sun/ moon rise-set module responsible for the sun revolution, sun horizon shutters and moon sphere revolution and rotation.  

We had a clearance problem in the area where four bearings are needed to support the sun and moon hands. These photos show a grinding machine where the four ball bearing supports for the sun and moon output hands were had their widths ground down by 37.5%.  

The difference between the original and altered profiles is shown. The pair of tweezers in the last photo shows how small these bearing are.

These first photo shows the old shaft still inserted into the drive mechanism with the new one on the table note that there is an inner sleeve on that part. The entire part will then fit into where the old one is currently located giving two separate rotating shafts where before there was one. Special care will have to be taken to make sure there is maximum shielding of the bearing since the original factory shielding was ground away.

A while back I had asked Buchanan to machine the large flat areas of the wheel pinion heads. The photo shows how those areas were nicely dished. Buchanan made a new brass disc to replace the original bearing retainer which showed up a clearance issue and a mechanical weakness so he had to remake it in stainless steel with strengthened dimensions. This is now complete. The second photo shows the original small ring, the brass ring and the stainless steel ring on the mechanism. It is very much oversized at this point and will later be skeletonized.

The first photo shows sparking a square hole in one of the transfer pinions and then depthing the pinion.

Next the bearing seat is machined and the pinion positioned.

All that needs to be done now is to drill and tap the holes for the screws that hold the brass bearing cap and the transfer drive will be operational; then cut away the shutter bosses for clearance for the centre dial pillars and the transfer pinion.

The transfer drive for the sun tube is nearing completion. The second two photos show a bit of finishing through the polished dimple on the steel pinion as well as the blued screw covering the empty square hole in the photo above it.

Earlier I had expressed concern about the large steel disc and from this front and rear elevation one can see it has largely disappeared.

Now Buchanan begins the fabrication of the two small day night hours indicator dials. These photos show the initial cutting out of the brass bar stock.

The engraving was applied when the ring was still part of the bar stock and this piece is now cut away. Next the dial ring is fully machined out of the bar stock. Later this ring will be machined into a small sector encompassing only the numbers and and a foot for mounting screws to the center hub.

The pair of dials, one for day and one for night. The day dial will be silvered with black numerals and the night a black background with white numerals. The first photo shows these with the front dial plate support. Next one dial is mounted on the drive assembly.

Whew! Let's take a break and look at what we have on the bench. This is an overview of the module frame. Notice how it closely mirrors the calendar frame which will reside on the clock directly to the left side of where this complication will be positioned. This is another example of Buchanan’s efforts to create continuity in design throughout the machine.

The dial ring being turned in the lathe to its final shape.

The ring has been machined down to a small sector which is mounted to the center hub. In the next photo the second ring is mounted to second hub. One can just see the cylindrical cannon tube below which will slide into the central hole shown in the first photo.

One can see the independent movement of the dials in these two photos. In the first photo both dials are moved to be adjacent to each other at the 10 o’clock position; in the next photo at 3 o’clock. Each dial will be controlled by one of a pair of cams controlling the horizon shutters and indicate the number of hours for daylight and nighttime.

Now the tiny indicator hands begin to be fabricated. The hands have a complex right-angled ‘Z’ profile since they need to tuck behind the center wheel. These photos show the drilling and then the part being cut off from the metal stock.

The second photo shows how the hands must tuck under the center wheel.

The drive assembly has come to a stage where the mockup dials can be attached to get a feel for how the presentation will look on the clock. However I see a problem with the mockup as is. The outer dial is obscuring everything behind it. That dial along with the inner Roman numeral dial and center hub combine to nearly hide everything behind the upper dial work. Every dial on this clock so far has been designed to minimize the footprint yet maximize the information content and legibility. We will explore a glass dial alternative with the information laser-etched on the inner surface.  

The planisphere dial at the bottom is still a mockup piece.

I like this arrangement in the first photo much better. The entire appearance is lighter with the glass mockup than the right photo with the enamel dial mockup. The center length of day and night dial has also been changed to two sector dials, eliminating the solid center 'button'.

I have some experience with glass clock dials and the legibility of the dial when finished is very good. The mockup as shown is a plastic sheet with hand drawn lettering and so does not look as good. Later we will see that the set of horizon shutter cams with a special design will show beautifully through the glass area in the upper left sector.