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.   hunkin

                                                         


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VICTORIAN NANOTECH

  Part 0ne

 

I didnít know much about watches until my aunt died and I inherited an astonishingly beautiful pocket watch from her. Looking online, I found it was made in Switzerland around 1800. It didnít run, and when I opened the case I thought some small worm had got trapped inside. On closer inspection it wasnít a worm but the tiniest chain I had ever seen, a perfect microscopic bicycle chain with links smaller than half a millimetre.

 

I really wanted to take the watch bits to see how it worked but I was nervous because it was obviously worth a lot. So I emailed the local branch of the British Horological Institute with photos of the watch, enquiring if any of their members would be prepare to tutor me. I had several replies saying a beginner should definitely not start with such a valuable piece (I think worth roughly £1,000) but one member, Ian Coote, offered to take me on.

 

The first surprise was the height of the bench, almost at neck level. You rest your wrists on the edge of the bench and the watch movement is clamped in a holding block. The screwdrivers are much more precise than cheap jewellers ones Ė they are colour coded and its important to hold them the right way and use exactly the right size for each screw. Once a screw is free, you remove it with tweezers. But these arenít ordinary tweezers, they have super fine points made of super hard steel (the best ones are made by a company called Dumont and cost about £30). I never realised tweezers could do so much Ė they make picking up something tiny like a human hair really easy. The danger is that because they are so hard, itís easy to scratch the watch Ė I scratched a few parts, maybe decreasing the value of my heirloom. You arenít supposed to touch anything with your fingers. Ian says Iím a good pupil apart from this failing Ė my fingerprints are now on almost every part.

 

With his encouragement I stripped the watch down to a mass of gears, plates, screws and springs. Amazingly nothing was seriously damaged, so it looked as if it might be mendable. Every screw looked different to me so I couldnít see how we could possibly ever put it back together, but I had taken a few photos. Once stripped down, everything had to be put in the cleaning machine. This involved putting all the parts in little wire baskets. Any sense of order I had as to where all the parts fitted was lost at this stage. The cleaning machine immersed the parts and agitated them in a series of different fluids. The process took nearly an hour.

 

I then started re-assembling it with Ianís guidance. With the help of the photos, it wasnít quite so hard working out where everything went as I had thought. It only gradually struck me that all these nanoscale parts had been made by hand. I canít imagine how the delicate minute hand could have been filed, or how any of the parts were made so precisely. We then realised we had lost a part Ė the catch that locks the movement in the case. Ianís workshop is full of stuff, not an easy place to find anything. We spent hours searching and had just given up when it re-appeared in a corner of a dark blue tray where I had put some parts. By this time we were both exhausted so I returned to finish the job another day.

 

I hadnít realised that the escapement was a verge escapement. This is the escapement that was used on the very first clocks. Verge escapements have a very irregular Ďtickí and are never good timekeepers. They were gradually abandoned in clocks after the pendulum was invented in the early 17th century. As it was impossible to mount a pendulum in a watch, the verge remained for another 200 years.

 

The tiny chain I found when I first opened the watch was part of a mechanism to make it a bit more accurate, called the fusee. The more you wind a watch, the stronger the Ďpullí of the spring on the escapement. To even out the spring tension, the chain goes from the spring barrel onto a wheel with a spiral track. The chain had got bent by being squashed against the watch case, so I thought it was no good, but Ian confidently pulled it straight. Fitting it back in place was very fiddly.

 

The other fiddly bit was replacing the top plate. All the gear shafts have reduced ends, called pivots, which fit into holes in the plate. I could fit two but while trying to get the last one in, the others would pop out again. This was a relatively simple watch Ė some chiming watches have 13 pinions to locate. I did finally eventually succeed. The top plate is fixed by three tiny tapered pins, pushed through holes in locating pillars. They can be seen in the photo above. One pin had snapped off, so the pillar (1.5mm diameter) had to be drilled out. Ian set up a .5mm spade bit in his watchmakers lathe, made a centre mark on the pillar with the tweezers and told me to drill by pushing the pillar against the spade bit. I never thought it would work, but it was surprisingly controllable and my hole went perfectly through the centre of the pillar. Then all the bearing holes had to be oiled. Too much oil gums up the works and can suck the oil out of the vital places by capillary action. Watchmakers oilers ingeniously dispense one tiny drop at a time.

 

When we finally got the balance back in place, the escapement showed no inclination to tick, but tweaking two adjuster screws eventually got it going. At the end of the second day it felt very satisfying replacing the dial and case with the escapement merrily ticking. Sadly, having adjusted everything possible, it still runs wildly fast, gaining 3 minutes an hour. Ian thinks the balance spring may have broken and been shortened at some point. It was still a great experience. Rather than owning a valuable watch that doesnít do anything and that I donít understand, I now own a slightly less valuable scratched watch, but I know what makes it tick. Iím sure my aunt would have approved.

Victorian Nanotech     part two

 

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