FULL MARKS to Renato and Franco Zamberlan for their
superbly written and illustrated articles on the great clock. Full marks also
to our editor and his team for presenting them so well. The story is not a happy
one.
To those who know the wonders of the Piazza no word is needed. To those who have
not experienced the artistic wonders of Venice there are no words in any language
of man which can give any idea of those wonders. Unfortunately for the world,
Messrs Brusa and Gorla have stuck their clumsy boots right in it.
I write as a Fellow of the International Institute for the Conservation of Historic
and Artistic Works. Election is by international ballot and I have been one since
1955. The IIC has representatives all over the world. There are about 130 members
in Italy alone. It has a very strict code of ethics concerning what you may or
may not do to an antiquity. Our own BHI code of ethics is based on it. No one
should ever change an antiquity except to preserve it for future generations.
If, like a clock, it has to work, then the only work done should be that required
to keep it working. The fact that things were done to this clock in 1858 should
be of no consequence at all to the conservator — it is part of the history
of the clock and must remain, in as far as this can be done.
The Zamberlans do not have to argue their case. Their photographic evidence is
there for all to see. I am very familiar with the attitude typified by Gorla’s
work. IIC spent the 50s and much of the 60s overcoming such approaches in UK museums.
Some people were persuaded to change, some were moved sideways where they could
do less harm, some retired and some died.
There is always a risk, especially where the ‘restorer’ is self employed,
that corners will be cut and as little work as can be got away with, will be done
in the shortest possible time. If such a man is to be employed then the materials
and the craft methods used must be specified precisely.
Brusa is of course a renowned and very senior horological historian. If he had
the authority to say exactly what should be done, it is to my mind absolutely
inconceivable that he should advocate the basic changes in the digital display
release mechanism and the escapement. Both of these were unnecessary, both cost
a lot of money and both make the machine a worse clock.
It is axiomatic that if you want to let off an intermittent movement from a constantly
moving machine, you trigger that movement from the fastest moving part. The clockmakers
of 1857 were quite right to unlock the 5 minute drum from the escape wheel arbor.
Properly done the energy consumption would be very small and would hardly fluctuate
at all. Why change it if it was working? Or did the changed escape wheel and the
lengthening of the crutch arbor preclude this? There will be irregular motion
lower down the train so however well the new work has been done the let off of
the drums will be less accurate than before. That is what the citizens; of Venice
are going to see, a large sum of money spent to produce a worse result.
The clockmakers who made the long pendulum were absolutely right on three counts.
First they supported it on a wall bracket. It is a bad plan to suspend a heavy
pendulum from the clock frame, however robust it is. Second, the influence of
the escapement on a pendulum depends on the length of the moment arm of torque
on the pallet arbor in relation to the length of the pendulum. A turret clock
must have surplus energy to get it through bad conditions like thick oil in winter.
Small, light, delicate escapements can not be used. The only solution was to use
a long pendulum. Third they used a wooden pendulum rod.
If the pendulum is not temperature compensated, wood, if it has been properly
treated first to keep the damp out, is a good material. For the change of length
of rod between a hot day in summer and a cold day in winter I would expect a time
difference of about 5 seconds a day. Now the rod is steel I would expect an error
of about 13 seconds a day. Is this an improvement? It is a public clock and, unlike
any other great city I know, Venice is not pestered by the noise of traffic. The
strike can be heard at a Great distance, I have often checked it with my watch,
right over on the Zattere. Do the city fathers want to be laughed at, or more
probably hated, after £150,000 has been spent to make this clock a worse
timekeeper? The Temperatore is going to have to check and correct the clock at
least once a day. Surely that was not the aim.
There is another problem which has been introduced which is, to my mind, far more
serious. It is a feature of the dead beat escapement that the escape wheel must
move suddenly from rest when the pendulum, and with it the pallets, are already
moving. Nothing of any mass moves instantly from rest so to get the teeth or pins
to impart the maximum energy to the pallets the escape wheel should be light and
the pendulum should be slow. Gorla and Brusa have produced a worse mechanical
system by making the pendulum faster and escape wheel heavier. With greater inertia
much of the impulse may be lost, to be absorbed with a bang on locking after the
considerable drop. Not content with that Gorla has made the pins from cap screws,
which are not only a soft material but the considerable mass of their heads adds
weight at the rim, the worst possible place. On top of all this, automatic winding
can lead to neglect.
There was a lot of drop in the 1857 wheel, at least half a pin diameter, but then,
and in 1755 the clockmakers could have used a Lepaute wheel. In this the original
diameter of the ping is thicker, the upper half is cut away and part of the lower
half also. This allows maximum impulse and a drop of only 0.5°. The pins of
course would be individually made from good steel, hardened, tempered and polished.
It would be a lot of careful work but the load on the whole going train could
be reduced and the wear would be less.
Gorla and Brusa will get the clock to work by increasing the energy throughput,
which will wear the train more quickly. Do these men not know anything about the
mechanics of horology?
The man I am really sorry for is the last Temperatore, Alberto Peratoner. He grew
up with the clock just as his father did and, I suppose, his grandfather. That
great clock is in his blood. He knows all of it, its lubrication points, its ways.
Yet this one man who knows it all was, we are told, pushed off the Committee.
Of course, every time he went home he was entering a gold mine. I tremble to think
what that flat in the clock tower must be worth in rent at the height of the season.
Is that the reason for it all? It certainly looks like it to me.
That great clock which we all love, needs watching on a daily basis, like ‘Big
Ben’. It is up to every one to see that things are put back the way they
were.
Martin Burgess FIIC, FSA, FBHI
Boreham, Essex.