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VICTORIAN NANOTECH
Part 0ne
I didn’t 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 didn’t run,
and when I opened the case I thought some small worm had got trapped
inside. On closer inspection it wasn’t 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 – 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 aren’t 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 – they make
picking up something tiny like a human hair really easy. The danger is
that because they are so hard, it’s easy to scratch the watch – I
scratched a few parts, maybe decreasing the value of my heirloom.
You aren’t supposed to touch anything with your fingers. Ian says I’m
a good pupil apart from this failing – 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 couldn’t 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 Ian’s
guidance. With the help of the photos, it wasn’t 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 can’t 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 –
the catch that locks the movement in the case. Ian’s 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 hadn’t 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 ‘tick’ 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 ‘pull’ 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 – 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 doesn’t do anything and that I don’t
understand, I now own a slightly less valuable scratched watch, but I know
what makes it tick. I’m sure my aunt would have approved.
Victorian
Nanotech part two |
