A new detailed study of notes and
sketches done by the infamous Leonardo da Vinci has identified a page of scribbles, a tiny
notebook as the place where Leonardo first recorded the laws of friction. The
research also shows that he went on to apply this knowledge repeatedly to
mechanical problems for more than 20 years.
Scribbled notes and sketches on a page
in a notebook by Leonardo da Vinci, previously dismissed as irrelevant by an
art historian, have been identified as the place where he first recorded his
understanding of the laws of friction.
The research by Professor Ian
Hutchings, Professor of Manufacturing Engineering at the University of
Cambridge and a Fellow of St John's College, is the first detailed
chronological study of Leonardo's work on friction, and has also shown how he
continued to apply his knowledge of the subject to wider work on machines over
the next two decades.
It is widely known that Leonardo
conducted the first systematic study of friction, which underpins the modern science
of "tribology", but exactly when and how he developed these ideas has
been uncertain until now.
Professor Hutchings has discovered that
Leonardo's first statement of the laws of friction is in a tiny notebook
measuring just 92 mm x 63 mm. The book, which dates from 1493 and is now held
in the Victoria and Albert Museum in London, contains a statement scribbled
quickly in Leonardo's characteristic "mirror writing" from right to
left.
Ironically the page had already
attracted interest because it also carries a sketch of an old woman in black
pencil with a line below reading "cosa bella mortal passa e non
dura", which can be translated as "mortal beauty passes and does not
last". Amid debate surrounding the significance of the quote and
speculation that the sketch could represent an aged Helen of Troy, the Director
of the V & A in the 1920s referred to the jottings below as
"irrelevant notes and diagrams in red chalk".
Professor Hutchings's study has,
however, revealed that the script and diagrams in red are of great interest to
the history of tribology, marking a pivotal moment in Leonardo's work on the
subject.
The rough geometrical figures
underneath Leonardo's red notes show rows of blocks being pulled by a weight
hanging over a pulley – in exactly the same kind of experiment students might
do today to demonstrate the laws of friction.
Professor Hutchings said: "The
sketches and text show Leonardo understood the fundamentals of friction in
1493. He knew that the force of friction acting between two sliding surfaces is
proportional to the load pressing the surfaces together and that friction is
independent of the apparent area of contact between the two surfaces. These are
the 'laws of friction' that we nowadays usually credit to a French scientist,
Guillaume Amontons, working two hundred years later."
"Leonardo's 20-year study of
friction, which incorporated his empirical understanding into models for
several mechanical systems, confirms his position as a remarkable and
inspirational pioneer of tribology."
Professor Hutchings's research traces a
clear path of development in Leonardo's studies of friction and demonstrates
that he realised that friction, while sometimes useful and even essential, also
played a key role in limiting the efficiency of machines.
Sketches of machine elements and
mechanisms are pervasive in Leonardo's notebooks and he used his remarkably
sophisticated understanding of friction to analyse the behavior of wheels and
axles, screw threads and pulleys, all important components of the complicated
machines he sketched.
He wanted to understand the rules that
governed the operation of these machines and knew that friction was important
in limiting their efficiency and precision, grasping, for example, that
resistance to the rotation of a wheel arose from friction at the axle bearing
and calculating its effect.
"Leonardo's sketches and notes
were undoubtedly based on experiments, probably with lubricated contacts,"
added Hutchings. "He appreciated that friction depends on the nature of
surfaces and the state of lubrication and his use and understanding of the
ratios between frictional force and weight was much more nuanced than many have
suggested."
Although he undoubtedly discovered the
laws of friction, Leonardo's work had no influence on the development of the
subject over the following centuries and it was certainly unknown to Amontons.
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