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Victorian nanotech
Part two
While I was working on my aunt’s pocket watch, my
tutor Ian showed me some of his other watches. The very first watches
appeared in the 1500s and apart from the addition of the balance spring,
their basic design didn’t change much until the 19th century.
Then
they went through a revolution - by 1850 the verge escapement was
obsolete, replaced by the lever escapement.
Verge escapement
Lever escapement
The lever escapement solved a major problem. In a
verge escapement the balance wheel is always
in contact with the watch gearing, so any slight changes in
friction of anything in the watch influences the balance wheel. The genius
of the lever escapement is that the balance wheel (omitted from the shaft
on the right of the drawing above) is completely detached from the rest of
the watch, except at the midpoint of its swing when it releases the
‘lever’ and moves the escape wheel to the next position (making the
tick sound). It’s so much better that it doesn’t need a fusee like the
one inside my aunt’s watch – a lever escapement will keep time
whatever the spring tension.
Shortly after the lever escapement was introduced, an
American engineer called Aaron Dennison developed the first machines to
mass produce watch parts. At first his companies kept going bankrupt, but
somehow the same machines would reappear in the next company. Eventually
named the Waltham watch company, it became well established and continued
to produce
millions of watches until the 1950s. Waltham were really proud of their
achievements, and felt that machine made watches, with interchangeable
parts were ‘scientific’ and greatly superior to European hand made
ones. Their pride is very evident in the elaborate decoration of their
watch movements.
I bought a beautiful Waltham pocket watch on Ebay for
about £100 (a model 645, made in 1908) to take to bits. I thought it was
a hopeless case because I couldn’t pull out the winder to change the
time. Ian immediately solved
this problem. It was classed as a railway watch, and one of the railway
specifications was that it must be impossible to change the time
accidentally. So, instead of pulling out the winder, the dial cover had to
be unscrewed and a tiny lever pulled out. Then the winder moved the hands
perfectly.
Instead of two thin ‘watch plates’, a Waltham
watch is made of thick nickel alloy plates, with spaces milled out to accommodate
the gears. All the screws go in much further and everything feels
satisfyingly solid. It’s a joy discovering how carefully every detail is
designed.
My watch had 21 jewels (pale pink
rubies). Most of them could stay in place but the balance wheel and escape
wheel had a double jewel on each end. One with a hole as the bearing and one
plain disk as an end plate, or thrust bearing. These had to be taken out as
dirt gets in the gap between the two. After cleaning everything we realised
we had lost track of which jewel went where, a bad case of divided
responsibility. It took hours inspecting them all under a microscope and
trying them in different places.
Eventually we got the jewels in the right positions.
The satisfying thing about a lever escapement is it starts ticking
enthusiastically immediately the balance wheel is in place. Sadly it
doesn’t keep ticking for a full day, and is only accurate if it’s kept
flat. Ian
is confident he could he could get it to work properly with enough effort,
but still not bad for a 100 year old watch.
Pocket watches were gradually superseded by wrist
watches in the early 20th century. The movements were exactly the
same, but half the size. The first digital watch was made by the Hamilton
watch company in 1972. It had an LED display that only lit when a button was
pressed for a few seconds to avoid draining the batteries. The enthusiasm
for digital displays didn’t last. Today’s dial watches are electronic
and battery powered (the first watch of this type was introduced by Seiko in
1969). The hands are driven by a stepper motor, and the timing is controlled
by a quartz crystal. ‘Quartz’ watches are typically accurate to within
half a second a day, about 10 times more accurate than any mechanical one.
Now almost everyone has a mobile phone, there’s
no need to have a watch at all, so all today’s watches are basically jewellery. Simple quartz watches are now amazingly cheap. Mechanical watches
are also still made, but it’s a strange business. At one end of the scale
the Chinese mechanical watches on ebay cost less than £10. I bought one and
it keeps good time. The Swiss watches that feature in glossy magazine
adverts (often costing over £10,000) also have traditional lever
escapements. They are beautifully made and every part is hand polished, but
it is weird that people spend that much on a watch that is less accurate
than a simple quartz watch. |
