Another donut-like approach
Scottie, a clock mage down in Dallas, sent me the following text and pictures after getting my latest Tech Tid Bit. He wrote:
Since you mention, "novel repair" in your last letter, I share with you someone's alternative to the ubiquitous Donut.
This enterprising blodger made a double size pinion and shoved it over the original and moved the wheel to turn this monthrunner into a two week runner! I held my breath as I removed it thinking it might expose a broken pinion leaf but, WHEW! It yielded with a few light taps and exposed a perfectly good pinion. Then one of his umpteen bushings fell out during bath. SHEESH.
I have been fascinated by the quality of work that has been done on some of the “donuts” I have found – and by the obvious skill necessary to make the double-sized pinion above. The good folk who made these modifications were clearly knowledgeable, clearly able to do complex machining, yet they still could not get their long duration mechanisms to run.
As time has gone by I have slowly realized that the difference between burnished and unburnished pivots in a long duration mechanism is virtually a 50% change in the required drive weight. Give or take, it takes twice the weight to drive a mechanism with “Polished” pivots when compared with burnished pivots. Why do I stress long duration – because they have at least 1 more gear (and therefore two more pivots) in each train. When you get into 6 month and years runners, they have two more gears. All these gears add up to much greater drag from “polished” pivots. I am equating “polished” with buff sticks, or any other form of Emory paper on wood. Even 0000 Emory paper that is well used will leave a surface that will not perform any where near as well as a burnished pivot.
And no, I do not consider pivots polished with very fine diamond powder as any better. Face it, if you can see a bright, shiny pivot you are seeing light reflected from a scratched surface. When I burnish pivots they go from shiny to virtually black – think about it – the reflected light from a truly mirror-like pivot only comes from that very narrow line where the pivot surface is reflecting back at you eye. This is only a fraction of the light reflected from a “shiny” surface, which reflects everywhere there is a scratch – which is the entire surface. One day, when I am set up to do video’s through a microscope, I will be shooting a video of the impact of burnishing. Till then I can only keep pointing out the impact of burnishing and hoping that people today will learn what watchmakers have known forever – burnished beats polished.
Read MoreSince you mention, "novel repair" in your last letter, I share with you someone's alternative to the ubiquitous Donut.
This enterprising blodger made a double size pinion and shoved it over the original and moved the wheel to turn this monthrunner into a two week runner! I held my breath as I removed it thinking it might expose a broken pinion leaf but, WHEW! It yielded with a few light taps and exposed a perfectly good pinion. Then one of his umpteen bushings fell out during bath. SHEESH.
I have been fascinated by the quality of work that has been done on some of the “donuts” I have found – and by the obvious skill necessary to make the double-sized pinion above. The good folk who made these modifications were clearly knowledgeable, clearly able to do complex machining, yet they still could not get their long duration mechanisms to run.
As time has gone by I have slowly realized that the difference between burnished and unburnished pivots in a long duration mechanism is virtually a 50% change in the required drive weight. Give or take, it takes twice the weight to drive a mechanism with “Polished” pivots when compared with burnished pivots. Why do I stress long duration – because they have at least 1 more gear (and therefore two more pivots) in each train. When you get into 6 month and years runners, they have two more gears. All these gears add up to much greater drag from “polished” pivots. I am equating “polished” with buff sticks, or any other form of Emory paper on wood. Even 0000 Emory paper that is well used will leave a surface that will not perform any where near as well as a burnished pivot.
And no, I do not consider pivots polished with very fine diamond powder as any better. Face it, if you can see a bright, shiny pivot you are seeing light reflected from a scratched surface. When I burnish pivots they go from shiny to virtually black – think about it – the reflected light from a truly mirror-like pivot only comes from that very narrow line where the pivot surface is reflecting back at you eye. This is only a fraction of the light reflected from a “shiny” surface, which reflects everywhere there is a scratch – which is the entire surface. One day, when I am set up to do video’s through a microscope, I will be shooting a video of the impact of burnishing. Till then I can only keep pointing out the impact of burnishing and hoping that people today will learn what watchmakers have known forever – burnished beats polished.
