Feodosiy Michaelovich Fedchenko and his
Astronomic Clock
The genius, the Soviet physics, the most talented
mechanic, constructor and inventor in 1953 became the author-inventor
of the most precise pendulum clock, which overcame the famous
Shorts’s one in their accuracy, reliability and simplicity
of maintaining.
In 1934 the teacher’s college students of Krivoy Rog the
future Physics teacher were taught not only theory but practice
as well. Among them there was Feodosiy Fedchenko. Every future
teacher – students in their senior years of studies - has
to be able to produce some devices to demonstrate experiments,
as there was lack of equipped classrooms at schools in many cities
then. That’s why when Feodosiy Michaelovitch became a teacher
he tackled the task of constructing the devices with schoolchildren,
using any suitable materials. They made a model of Fuko, Maxswell
pendulum and so on.
In 1941-1945 during the WWII, Fedchenko joined
the army and in the tank division he was a mechanic dealing with
high precision instruments, for example with tank clock. He had
to work at different machine-tools, on his own to process complex
details on a lathe and a drilling machines The former teacher
appeared to be an outstanding mechanic, who could “tame”
any most complicated instruments.
After the victory over the fascist Germany, Feodosiy Michaelovitch
demobilized and returned to his home town - Kharkov. He was going
to take up a research work on the following theme: "Researching
of the opportunities to enforce the operation precision with the
help of suspended pendulum of Short’s type". It was
one of the themes there research laboratory was working on. Here
Fedchenko started working and here he got to know about Short
for the first time.
– The thing I began with, – Feodosiy Michaelovitch
told later to a reporter from the magazine "The Soviet
Museum", – was books. I was reading everything, starting
with Guigens. Among different academic issues I came across
an article, which merely startled me. The German astronomer
Hoin was telling how he was researching pendulums suspension.
I need to say that a suspension is one of the most complex details,
though it looks as a very plain thing.
A steel strip or two of them, clenched at the ends with metallic
sidepieces. One end of the suspension is attached this or that
way to the clock case, while to the other end the pendulum is
hung. That’s it. The pendulum oscillates, the spring (or
springs) bends - the losses due to friction are minimum and
this is what you need for astronomic clock.
Well, there was a story connected with a spring suspension:
it was believed that it enhances the isochronism of a pendulum,
that is makes the period of its oscillations less dependable
on the amplitude. They said, it is because the resistance of
the spring acts as if it pushes the pendulum to the position
of balance, and the more the deviation is, the more the effort
is. That it is likely to improve the isocronus. They thought
in this way, and Hoim himself also did.
But if the springs of a suspension are actually helping to isochronism,
so the thicker ones have to have bigger impact. However, everything
went another way round: the suspension with two thin springs
as Hoin used not only ensured the complete isichronus , but
even made the things worse: when the amplitude increased the
period decreased! So it means that by choosing springs we can
reach the full isochronism from the pendulum, can’t we?
I couldn’t believe Hoin and started checking his experiments.
So Fedchenko started doing thousands experiment,
no less. From 1947 up to 1952 he tried using literally all the
existing types of springs: short ones and long ones, and thick
and thin, with variable cross-section along the length and totally
flat ones, – and all that was in vain. Nevertheless, we
can’t say that the scientist wasted time for that five years.
Without this plentitude of experiment Fedchenko couldn’t
have had such confidence, couldn’t have got such a skill,
and such a subtle ability to predict the possible result of any
future innovation. And the big day came, when there was an award
for all the research work fulfilled.
One of the suspensions appeared to be unusual: the pendulum with
it became overcompensated as it was described at Hoin! What had
happened? Fedchenko took out the suspension, automatically, with
his screwdriver, wound up one of the screws, which were clenching
the sidepieces: the screws responded and moved. And at the same
time the pendulum transformed into a usual non-isochronous one,
which followed all the laws. So, Hoin was not right. The core
of the matter lies in the sidepiecies: if they are tightened enough.
And what does it mean - "tighten"? It means that the
spring bends not at its root, but a little higher or lower.
Right after that Fedchenko generated another idea: to make a suspension
not out of one spring, not out of two, but out of three: two of
which are short, and a long third spring is placed between them.
Then at the position approaching to that of equilibrium, the length
of the pendulum will be identified not with the length of the
spring: if it is short or long, but something average between
them; but at the edges of the oscillation movement spans - there
are short ones, while the middle one a sort of switching off from
the process. The element of accidental occurrence will disappear
– that one which is the feature of not well screwed up screws.
The suspension can be tuned up in a way that the pendulum oscillation
will follow a cycloid, as it is required by Guigens. The very
first checking up proved that the idea had been correct. The pendulum
became isochronous: with any change of the amplitude from 30 to
150 angular minutes the period of oscillation remained constant.
The clock, which was installed in, provided the variation of operation
of 1-2 ten thousandth of a second, whereas the usual astronomic
clock, under the same conditions showed the results 50-100 times
worse.
The solid, powerful wall and bases not affected by jerk were not
needed anymore: as Fedchenko’s clock hardly responds to
any rocking. Breaking with all the rules they can hang in a laboratory
on the first floor - and to be as precise as Short’s clocks
hidden in a cellar.
__________________
lot more can be narrated about the Fedchenko’s
astronomic clock (AchF). How the author was working out the system
of magnetic drive for his pendulum- at first at some usual relays,
then at some transistors which had just appeared at that time.
We could tell you how he was researching the precision of the
clock operation being affected by the form of the load (as the
size of a load changes with the change of the temperature), how
he found out that Short just intuitively chose the more suitable
combination of length and load diameter than Rifler did, thus
improving the temperature compensation of his pendulum- and how
it was then when Fedchenko calculated the optimum form: the ordinary
sphere. The most interesting thing is how the clock AchF managed
to identify the gravity of the Sun and the Moon.
Our weight depends on the earthen power of gravity. The Moon and
the Sun gravity changes the earthen gravity: twice during 24 hours
it reaches its maximum and the same times it reaches its minimum.
The difference is tiny but, a one-kilogram load changes its weight
0,4 milligram. Fedchenko’s clock respond to the changes
is 40 times less as this. But certainly not because it can weigh
anything up, but due to the difference of the gravity, it starts
to be fast or slow. We need to compare the AchF operation with
that of quartz clock or nuclear ones.
Such subtle effects could have been only traced with gravimeters
before, which are based on a load attached to a spring. It would
stretch out or shrink following the rhythm of the gravity change
- that is the weight of the load. With such sensitivity which
that devices could attain, they perceive not only the variations
of gravity, but the "aging" of a spring metal. The property
of all gravimeters being a very serious disadvantage is "sliding
down/dropping of a zero". The measurement made today can
in a dozen of days differ, though the earthen gravity stayed constant.
"Can" – there is a sort of uncertainty in the
word. A scientist doesn’t know the reason why the changes
have occurred, and has to repeatedly do a tedious task of calibrating.
To monitor for weeks and months, doing its on regular constant
bases is actually impossible, though this kind of measurement
is the most valuable. Fedchenko’s clock don’t need
such careful maintenance.From1968 they have started the observations
of changes in gravity at the Astrophysics Observatory of the Institute
of Physics of the Earth of the USSR Academy of Science.
________________________________________________
The pendulum clock – is not only a time-measuring device
(its better done by nuclear, quant generators), but rather a gravimetric
instrument, with the help of which, by measuring the gravity,
one can identify the precise form of the Earth, create more accurate
maps, discover mineral resources, research the inner structure
of our planet, etc.
Here is the academic description of the AchF clock done by professor,
the director of the Observatory V.A. Krat:
"The invention of Fedchenko places him in
one row alongside with the names of Guigens, Harrison, Lerua,
Rifler, Short and others who updated the highly precise mechanic
clocks. The AchF clock – is a highly precise pendulum
clock with isochronizing suspension and electromagnetic impact
for the pendulum oscillation. The clock pendulum with a copper
load at an invar bar is placed at a vacuum altitude chamber.
The isochronism is provided with the suspension, the construction
of which ensures the shortage of the pendulum length in accordance
with the amplitude of its oscillation. The oscillation of the
pendulum is supported by short electromagnetic impulses, delivered
to it at the equilibrium moments. The form of a copper load
and the place of a stop for it are chosen in such a way that
the temperature changes of the load dimensions don’t effect
the period of the pendulum oscillation. The temperature compensating
elements of the pendulum are located on the suspension and lower
than the load, which ensures temperature compensation with the
variable temperature gradient. AchF is distinguished by its
utmost reliability and precision among other pendulum clocks.
The variation of its operation makes up 0,2-0,3 mls/per 24 hours.
The implementation is as time standards keepers and for researching
of gravity variations. AchF appeared at the end of the 1959-ies,
the beginning of the 1960-ies. It was patented in 1953; named
after its constructor – F. M. Fedchenko. AchF is the best
out of all the existing types of pendulum clock. It is by far
superior in terms of its precision to the best samples of the
clock of the past - the pendulum clock by Short. In many cases
it can replace quartz clocks of an average precision rate, and
they considerably more advantageous in terms of reliability
and the simplicity of handling. The clock has been operating
for many years from 1960 in Pulkovo Observatory and it operated
actually without any fault which occurred because of the clock
construction, while Short’s clock had to be repaired quite
a few times, and, I believe there is no need to compare the
quartz clocks with AchF".
There has appeared some news about the most notable
clocks of the XIX and XX centuries – Rifler and Short at
the pages of the English magazine the «Horological Journal»,
which has been published around 150 years. In 1973 it published
an article by a French physicist M. Pleger about Fedchenko’s
clock:
"The appearance of Fedchenko’s clock
is the most important event, which gives the evidence that the
art of astronomic clock creation has not been lost, that there
are some resources and new inventions and developments. That
is why Fedchenko and his colleagues in Russia are bestowed the
gratitude from the clock-maker all over the world".
The prominent specialist in mechanics, the academician
S. A. Christianovitch, speaking of the invention of the clock
said:
"The Fedchenko’s suspension could have
been invented at the times of Guigens. Actually, to create it
one did not need any latest academic achievements, but only
the profound shrewdness of mind".
The St.Petersburg Watch&Clock Atelier
The Centre of Watch&Clock Restoration
off. 36, Malodetskoselskiy pr.
St.Petersburg, 190013, Russia
phones: +7 (812) 703-17-56
+7 (812) 316-56-39
+7 (812) 911-02-71
mail@clockmaker.ru
