Matthew Landrus Leonardo Da Vinci's Giant Crossbow

Matthew Landrus Leonardo da Vinci’s Giant Crossbow Matthew Landrus Leonardo da Vinci’s Giant Crossbow With 75 Images Author Matthew Landrus Wolfson College Oxford University Oxford OX2 6UD UK e-mail: [email protected] ISBN 978-3-540-68915-7 e-ISBN 978-3-540-68918-8 DOI 10.1007/978-3-540-68918-8 Library of Congress Control Number: 2010930276 © Springer-Verlag Berlin Heidelberg 2010 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitations, broad- casting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the rel- evant protective laws and regulations and therefore free for general use. Production: Heather King Typesetting and layout: Büro Stasch · Bayreuth ([email protected]) Printed on acid-free paper 9 8 7 6 5 4 3 2 1 springer.com For Mallica Foreword eonardo was both repelled by violence and fascinated by war. One of his “prophecies” Ltells as that, Animals will be seen on earth who always fight amongst themselves with great destruction and by their fierce limbs a great proportion of trees in huge forests will be laid low throughout the universe… Nothing will remain on or under the earth or in the water that will not be persecuted, dislocated and despoiled… Why, earth, do you not open and precipitate them into the fissures of your great cataracts and caverns, and no longer exhibit to heaven such a cruel and despicable monster. (CA 1033va) The “monster” wreaking such destruction is of course man himself. Leonardo’s “prophecies” belong to a literary genre, and were designed to entertain. However, reading this and other pieces in which he writes about man’s wanton destruction of himself and all the creations of nature, we can sense his personal feelings. Why, then, did he devote so much time to the designing of weapons of massive destruction? The obvious answer is that it was his job. He was employed at the Milanese court by Ludovico Sforza as one of his military engineers and was expected to deliver designs and expertise – more readily perhaps than he delivered paintings. In his capacity as an expert on cartography, weapons and fortifications, he subsequently joined the entou- rage of the notorious Cesare Borgia who was rampaging in central Italy on behalf of the pope. Leonardo also served in this capacity for the city of Florence and for his later French employers. However, his engagement with military engineering went beyond what was necessary just to do his job. He became deeply engaged in the way that weapons presented the possibility of harnessing force and deploying the “elements of machines” on a scale that was unthinkable in any other domain of his activity. War-like patrons were continuously attracted to the construction of decisive new weapons and were willing to invest sums of money far beyond any they would spend on the Arts. Leonardo was much concerned with scale. He saw basic continuities in the design of everything in the universe, whether made by god or man and however large or small. The rules of design worked across all scales. This was not just a question of statics, but involved the behaviour of forces. As he knew from his engagement with mediaeval physics, theory tells us that if you propel something with twice the force the performance of the projectile ought to be doubled. A bigger canon with more gun- powder should accordingly send its missile proportionately further than a small one. Or it should send a proportionately bigger missile the same distance. Bigger bangs promised ever bigger blows. A crossbow 20 times the size of one carried by a soldier should in theory produce twenty times the power. But he came to realise that what book theory predicted and what actually happened were two different things. He was, as he repeatedly stressed, a man of “experience” and not of “book learning”. He came to acknowledge that in the material world of real things, the simple law of the multipli- cation of cause and effect did not work quite as stated. He did consider the neat rule that that the distance a missile from a crossbow would travel would be proportionate to the length of withdrawal of the bowstring, but saw VIII Foreword that the bending of the arms of the bow threw this simple geometry out of line. He looked instead to the interior angle subtended by the string at the point of its withdrawal. There must, according to Leonardo’s beliefs, be a mathematical law at work somewhere in the system. He was the first modern engineer to attempt to apply the geometrical mathematics of the laws of motion to the design of machines. His military designs were intended to operate, as he claimed of his flying machine, “in accordance with natural law”. He was also aware, as someone who knew about materials and worked with master fabricators who knew far more about the performance of wood than any modern engineer, that increasing scale brought with it new constructional problems. You could not simply make the arms of a crossbow thicker and thicker and longer and longer. A very thick arm of unitary construction would fracture in its outer layers. He thus looked to laminates and components that could slide over each other. The main drawing at which Matt Landrus is looking with notable intensity tackles these and other of the problems that go with making a weapon of huge proportions in an entirely new way. He shows that the drawing is not some tidy version of a sketched fantasy that could be presented to a patron as a vapid piece of visual boasting. It was the culmination of incredibly concentrated design procedures for the whole and the parts. Only a fraction of the preparatory drawings survive. The process of drafting was meticulously controlled in scale, not least using a series of inscribed lines and compass points that are only visible in a close study of the paper’s surface under raking light. Only by such means can we unravel the “archaeology” of the drawing and recon- struct Leonardo’s design process. The result of Landrus’s researches is that we can now see Leonardo’s finished dem- onstration of the giant crossbow as a new kind of drawing that embeds an enormous amount of precise, measured and measurable information within its graphic compass. Some of Leonardo’s colleagues, like the Sienese engineer Francesco di Giorgo, one of whose manuscripts Leonardo owned, made wonderfully convincing drawings of machines in their full perspectival glory. But their results were very pictorial, designed to show the viewer (above all the patron) what the devices would look like, but they were not engineering drawings in the modern sense, produced to provide precise guidance to the fabricators. Leonardo in his finished drawing of the giant crossbow is working his way towards the kind of descriptive geometry devised by Gaspard Monge in the 18th century. The trick in such a drawing is to render the machine in its full spatial array but also to embody precise information about the dimensions and the construction of its parts. Matt Landrus, through a meticulous and systematic examination of the drawing in its context, shows for the first time the extraordinary degree to which Leonardo pulled off this trick. Martin Kemp Oxford, September 2009 Acknowledgements s this book has taken shape alongside other projects related to Leonardo’s propor- Ation theories, I have had the fortune of advice and encouragement from a large number of friends and colleagues, some of whom I have thanked – although inad- equately – elsewhere in the book. I am especially grateful to Martin Kemp, whose generous support of my work at Oxford University and thereafter made this book possible. He has offered essential recommendations on the original manuscript of this book, and has kindly written a preface. I would also like to thank Pietro C. Marani and James Bennett for their thoughtful advice on the original manuscript. At the outset of my work on Leonardo and ever since, I have had the exceptional, gracious support of Dario Covi. In recent years, J. V. Field, Claire Farago, and Francis Ames-Lewis have been especially supportive. I also wish to thank Thomas Ditzinger, my Editor at Springer, for his insights, guidance and patience. And for her assistance with the editorial process at Springer, I wish to thank Heather King. I am also very grateful to Armin Stasch for his perspicacious work on the index and other essential preparations of the book. Initial research was possible with the help of a Mary Churchill Humphrey Cente- nary Memorial Scholarship from the University of Louisville. For the support of this scholarship and other resources, I am particularly indebted to John W. Shumaker and David Jones. In the UK, David and Pam Emms were most gracious and generous hosts as trustees of the scholarship. I am grateful to the University of Oxford’s Hulm Univer- sity Fund for awarding financial support for the reproductions.

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