Research
Study reveals Leonardo da Vinci’s “irrelevant” scribbles mark the
spot where he first recorded the laws of friction
The sketches and text
show Leonardo
understood the
fundamentals of
friction in 1493
— Ian Hutchings
A new detailed study of notes and sketches by Leonardo da Vinci has
identified a page of scribbles in 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 20year
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 behaviour 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.
“Leonardo da Vinci’s studies of friction” by Professor Ian Hutchings is published in the
journal Wear. The paper can be accessed in full via:
http://www.sciencedirect.com/science/article/pii/S0043164816300588
(http://www.sciencedirect.com/science/article/pii/S0043164816300588)
or http://www.ifm.eng.cam.ac.uk/uploads/Hutchings_Leonardo_Friction_2016_v2.pdf
(http://www.ifm.eng.cam.ac.uk/uploads/Hutchings_Leonardo_Friction_2016_v2.pdf)
A general article on tribology that discusses its importance in modern engineering can be
found at:
http://www.ingenia.org.uk/Content/ingenia/issues/issue66/hutchings.pdf
(http://www.ingenia.org.uk/Content/ingenia/issues/issue66/hutchings.pdf)
(http://creativecommons.org/licenses/by/4.0/)
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