Leonardo and the Artes Mechanicae

Chapter 2

Machinae ad majestate imperii and textile manufacturing machines

M

y primary aim in this chapter is to appraise the thesis of Bertrand Gille, summarized at the end of the previous chapter, regarding the originality and uniqueness, for the age, of Leonardo da Vinci’s interest in the textile manufacturing cycle. I propose to do so by conducting a preliminary survey of the way the subject is dealt with in the technical literature that flourished in the late Middle Ages and the Renaissance, which, irrespective of its by no means unequivocal aims and readership, offers direct information about techniques, and details of machines, tools and procedures. The sources are heterogeneous, ranging from the manuscript tradition of the late Middle Ages and the fifteenth century (which also saw the advent of the first print versions, as with the treatises of Valturio and Alberti) through to the print genre of the theatre of machines.

They reveal the new attention devoted to machines and also testify to the social ascent of the mechanical arts and of some new intellectual and professional figures. For the most part, these sources are primarily iconographic in nature: the visual illustration of machines and mechanisms is in fact what distinguished such literature at least from Villard de Honnecourt onwards. The extensive use of drawing, technical culture’s own particular form of expression, was already in itself a symptom of change.

1. Historia ordinis Humiliatorum Manuscript G. 301 inf., f. 3r, detail (fig. 11)

1. “Machine” literature and textile manufacturing Let’s look first of all at a group of documents dating to the late Middle Ages and early fifteenth century, which also circulated throughout Europe, In the thirteenth-century album of drawings by Villard de Honnecourt, besides various architectural drawings, the prevailing interest is in machines and mechanisms for building sites, civil works in general (bridge construction, modifications to city walls, pilework in water), and siege weapons and machines. But there is also a lively curiosity for clock-making, mechanisms for automatons, and a study of a wheel for perpetual motion, all connected together. Also worth studying are the sections on machines in the Texaurus of Guido da Vigevano (fourteenth century); the Bellifortis of Konrad Kyeser from the very beginning of the fifteenth century, which had an exceptionally wide circulation;1 the manuscript known as Anonymous of the Hussite Wars (from 1430, though according to some, from 1470–90) and one of the related texts, such as the Spencer 104 in the New York Public Library (mid fifteenth century); the Bellicorum Instrumentorum liber and the Secretum de thesauro experimentorum ymaginationis hominum by Giovanni Fontana (first half of the fifteenth century); and De re militari by Roberto Valturio (the editio princeps dates to 1472).2 Alongside the extensive and sometimes exclusive treatment of fortifications, machines and equipment for siege and defence warfare (fig. 2), there are building-site hoisting machines, water devices and conduits, water craft, bridges, mills, pumps and siphons; fanciful wind-powered vehicles and other marvellous machines; bearings, various gears, including mechanisms for transmitting and converting motion. In Fontana, who was discernibly influenced by Arab and ancient sources, we can see a whole imaginative and fascinating tumult of ideas: the labyrinth, and then clocks and clepsydras; oil lamps, candelabra, lanterns and magic lanterns; alembics, fountains, hydraulic, mechanical and pneumatic musical instruments and other pneumatic devices; toys, masks, and machines and 31

Part III Section I

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BUILDING-SITE MACHINES AND TEXTILE MACHINES Construction technology from the cupola of Santa Maria del Fiore

I.1 Mechanical arts and liberal arts

The series of reliefs along the base of the Campanile of Florence Cathedral, started in 1334–36 and completed in 1437–39, depict personifications of various kinds of human labour, defined by Lorenzo Ghiberti in his Commentaries (1447–55) as “troubadours of the arts”.

The representation develops along an evolutionary line running from the Creation and early agricultural and pastoral activities, evoked on the base of Genesis, to the eminently intellectual activities.

The series of panels does not, however, rigidly respect the traditional hierarchical division established in the medieval period between the “noble” liberal arts, in other words intellectual activities, and the “inferior” mechanical arts, which also included artistic and technical activities. Indeed, the figure of the architect appears twice in the panels of the bell tower, first as the dominus of the whole building site and then as an intellectual figure alongside the painter and the sculptor at the top of the 1334–36 series of panels. Painting and Sculpture were moved to the north side in 1347–49, and

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later the reliefs of Luca della Robbia (1437–39) depicting the finest liberal arts were placed alongside them. Daedalus, the symbol of technical endeavour, was placed from the outset on the same side as the quintessential intellectual activity, astronomy.

The widening of the architect’s role to include the invention of machines — a role epitomized by Filippo Brunelleschi — and the profound unity of art and technical studies that distinguished generations of artist-engineers in the Tuscan Quattrocento was affirmed in this primary scene, the visual celebration of a civilization that embraced all forms of work. The panels were conceived by Giotto for a piazza that was later to be dominated by the mira testudo, the extraordinary cupola of the cathedral, which was the fullest expression of technical and architectural maturity.

At the end of the fifteenth century, Leonardo da Vinci affirmed, in his Treatise on Painting, that the dignity of art and technical studies was equal to that of the “human arts”.

1–7 Panels of the Campanile of Giotto, south side: Astronomy, Art of Building, Medicine, Hunting, Weaving, Legislation, Mechanics

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I.2 Places in Florence associated with Leonardo 1464/1469 – 1482

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Leonardo’s father: Ser Piero 1.

The house rented by Ser Piero di Antonio da Vinci from around 1462 until 1479 was behind Palazzo Vecchio, on the corner between Via delle Prestanze (now Via de’ Gondi) and Piazza Sant’Apollinare (now Piazza San Firenze), on the site where Giuliano da Sangallo built Palazzo Gondi in 1490.

2.

The rented lodgings in Via Ghibellina, between Via della Fogna (now Via Giovanni da Verrazzano) and Via de’ Pepi, where Ser Piero lived from 1479 or 1480 till his death in 1504.

3.

The office – on the corner between Via della Condotta and Piazza Sant’Apollinare (now Piazza San Firenze), in front of Palazzo del Podestà (now the Bargello) and near the Badia Fiorentina (where Ser Piero is buried together with his family) – where Ser Piero practised as a notary. He worked with a colleague until at least 1468 and on his own from 1476. A notarial document dated 5 June 1451 indicates that Ser Piero worked in Palazzo del Podestà.

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Leonardo’s master: Verrocchio 4.

The house owned by the Verrocchio family, at least from 1451 to 1470, was in Via dell’Agnolo, on the corner with Via del Malborghetto (now Via de’ Macci) and near the Church of Sant’Ambrogio (where Andrea del Verrocchio is buried).

5.

According to David Alan Brown, Andrea del Verrocchio’s first workshop may have been in Via Ghibellina, on the corner with Via del Malborghetto (now Via de’ Macci), at least from 12 February 1463.

6.

Verrocchio moved his home and workshop to the property (previously rented by Michelozzo and Donatello) owned by the Bischeri family near the Opera del Duomo in the San Michele Visdomini neighbourhood sometime between 1469 and 4 August 1471; he was still living and working there in 1480 and presumably remained till his death in 1488.

Leonardo Leonardo probably started to work in the workshop of Verrocchio, a friend of his father, either in 1464, the year his grandfather Antonio, who had brought him up in the family home in Vinci, died, or in 1469, when Ser Piero is thought to have settled permanently in Florence.

In 1471 Verrocchio built the copper ball placed on the lantern of the cupola of the Cathedral of Santa Maria del Fiore. This is recalled by Leonardo in a celebrated note contained in MS. G, f. 84v (Paris, Institut de France). Leonardo was still working for Verrocchio in 1476, and may have lodged with him as well. Six years later he left Florence for Milan.

1 Stefano Bonsignori, Map of Florence, 1584, detail, etching on copper, 125 ✕ 139 cm Edizione Girolamo Franceschi, Siena, 1594, Florence, Museo Storico Topografico “Firenze com’era”, Inv. MFCE-TOR 2001-3909/OBLA

4 5

2

3

6

1

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I.3.2. Fifteenth-century views of building sites and cranes

1 Beginning of the construction of Berne Cathedral in 1420 In Diebold Schilling, Amtliche Berner Chronik, t. II. 1478 Berne, Burgerbibliothek, Ms. Helv I, 1, S. 451 The miniature shows — with considerable precision, albeit rather naively — another version of fork-shaped raising equipment. The hoisting cable is powered by a bar winch, runs through two pulleys and has a self-closing pincer capable of grabbing the block of stone.

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2 Girart de Roussillon Girart de Roussillon and his wife Bertha found twelve abbeys in honour of the twelve Apostles, 1447 Vienna, Österreichische Nationalbibliothek, Cod. 2549, f. 164r The legend of Girart and Bertha that, having lost their children, they devoted themselves to founding abbeys and churches, lent itself to the depiction of busy scenes of religious buildings under construction.

This beautiful miniature shows,

perhaps somewhat emphatically, the various phases of construction, ranging from the preparation and dressing of materials on the ground to work carried out aloft. This relied on scaffolding that grew with the buildings and reached considerable heights. On the scaffolding, fork-shaped, loadraising castelli are in operation, consisting of a beam of wood (or a T-shaped crosspiece) reinforced by a stay and equipped with a pulley.

3 Piero di Cosimo The construction of a palace, c. 1515–20 Sarasota, The John and Mable Ringling Museum of Art At the centre of the painting is a development on the stella-type crane. It consists of a wooden crosspiece, reinforced by braces, placed on top of the mast. The mast is held by four cables; two of them are anchored to the ground, while the other two have been slackened in order to allow the shaft to incline, thereby affording a limited

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degree of horizontal movement of the load. The raising is carried out by a wheel, which can presumably be powered either by walking on it or by using pegs fixed along its circumference.

A passage in a seventeenthcentury treatise on architecture gives an account of the identification of the name stella with that of falcone (derrick), which, however, encompassed a broader range of lifting devices: “... a very tall, solidly planted mast with cables inside, and thus kept upright by cables positioned like the rays of a star;

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all the parts resemble the masts of ships... This mast serves as a derrick for turning weights here and there to where they need to go, when the cables on one side are slackened and the ones on the other side are pulled.”

(Vincenzo Scamozzi, L’idea dell’architettura universale, Part II, Book 8, Ch. 30, Venice, 1615, p. 368).

3 Lambert Doormer Cologne Cathedral, c. 1670–73 Cologne, Wallraf-RichartzMuseums, no. 1958/2 The building of Cologne Cathedral, which began around 1248, came to a halt after 1322.

Work started again in 1560 and continued until 1842. A revolving crane dominated the stump of the south bell-tower for about 400 years. Doormer’s drawing seems to indicate that the crane was still on site in the second half of the seventeenth century.

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4 Pieter Bruegel the Elder The Tower of Babel, 1563 Vienna, Kunsthistoriches Museum, GG 1026 The painting almost seems to be a Babel-like catalogue of the various kinds of lifting devices, which, in the middle of the sixteenth century, were evidently still recorded as being in use or at any rate as belonging to a living iconographic tradition.

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I.4 Florence Cathedral building-site machines and equipment

Starting in the fourteenth century, and then above all in the fifteenth century, drawings of machines and mechanisms became more frequent and of increasing quality. Initially there were chiefly to be found in manuscripts about architecture, war machines and fortifications. These drawings reveal both the enduring influence of the legacy of ancient and medieval times and the often imaginative attempts to devise innovative inventions.

A decisive advance in the technology of load-raising machines came with the innovations designed by Filippo Brunelleschi (1377–1446) while he was directing work on the Cupola of Florence Cathedral. The

Chronology of the building of the Cathedral of Santa Maria del Fiore

prolonged period of time the work took, and the fame of the Cupola itself, which was built without the use of centring to support the masonry, enabled generations of artists and technicians to learn directly or indirectly about the fundamental advances of Brunelleschi’s practical mechanics. A more common and effective ability to observe and study the design of mechanisms was also facilitated by the precise, analytic descriptive quality of Florentine and Tuscan drawings, which artist-engineers such as Francesco di Giorgio and then Leonardo da Vinci applied to the study of individual mechanical components, devices and entire machines, with the introduction of perspective, sections and exploded views.

1296

The new cathedral of Santa Maria del Fiore was founded over the preexisting church of Santa Reparata, to a design by Arnolfo di Cambio. Work proceeded very slowly throughout the first half of the fourteenth century.

1331

The government of Florence delegated the supervision of the building of the new cathedral to the Arte della Lana, the city’s powerful wool guild

1333

The Arte della Lana set up the Opera di Santa Reparata, later renamed as the Opera di Santa Maria del Fiore but more commonly known as the Opera del Duomo, to manage the works in their entirety.

1350

The construction of the cathedral gained fresh momentum under the direction of the capomaestro Francesco Talenti.

1367

A committee of experts produced a model of the church and of the Cupola.

1382-1421

Building of the apsidioles and the drum of the cupola.

1420

After a first competition in 1418 failed to produce a winner, the Opera del Duomo organized a second competition and chose the model presented by Filippo Brunelleschi.

Construction of the Cupola began.

On 16 April Filippo Brunelleschi, Lorenzo Ghiberti and Battista d’Antonio were appointed as the provveditori (superintendents) of the Cupola. From 1433 onwards Brunelleschi was given sole responsibility for the work.

1436

Completion of the Cupola as far as the oculus ring.

Approval of the design for the lantern presented by Brunelleschi.

1446

Death of Filippo Brunelleschi.

Construction of the lantern commenced.

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1461

Realization of the model of the pergamena, the upper, spire-like portion of the lantern.

1467

Completion of the pergamena.

1468

The workshop of Andrea del Verrocchio was commissioned to produce the ball for the top of the pergamena.

1471-1472

The ball and cross were put into place and the final construction work on the Cupola was completed.

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1 Anonymous of the Hussite War Revolving derrick with two drive wheels for hoisting, c. 1472–75 Munich, Bayerische Staatsbibliothek, Codex Latinus Monacensis 197, part. 1, f. 1r

3 Bonaccorso Ghiberti Hoist with treadmill and restart mechanism, c.1472–83 Florence, Biblioteca Nazionale Centrale, B. R. 228, f. 94r

2 Mariano di Jacopo called Il Taccola Capstan in conjunction with antenna, or “lignum magnum” Liber tertius de ingeneis ac edificis non usitatis, c. 1427–33 Florence, Biblioteca Nazionale Centrale, Palat. 766, f. 25r

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I.4.1. Hoist

As building work on the Cupola of Santa Maria del Fiore in Florence was gradually completed, the large cranes designed by Filippo Brunelleschi (known at the time as edifici or castelli), which had presumably been in service for a long time, were dismantled, as recorded by a document in the archives of the Opera del Duomo: “The castello that was in the piazza of Santa Maria del Fiore and lifted materials up to the cupola, which was dismantled… December 1472.”

1-3 Hoist and pulley exemplars conserved in the storerooms of the tribune morte of the Cupola of Santa Maria del Fiore, Florence

Various other equipment and more traditional, commonly used hoists remained in service inside the Cathedral, where they were used for the completion of the building work, which was very prolonged, and for maintenance. These included the one still housed in a storage area in the cathedral and the horizontal-axis, shaft hoist like the one on display here, which presumably dates to the eighteenth century. Suitable for lifting moderate weights, they could be used in different ways: mounted on a plat-

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form with an opening in it for the passage of loads raised directly from aloft; installed at ground level with a pulley system for raising the loads; or for use together with capra e stella cranes. They could also be used for a variety of tasks — on building sites, for military purposes, in various branches of work and in domestic environments, for example, for lifting heavy water containers from wells.

The distinctive feature of the hoist on display is the octagonal section of the drum. The most frequently recurrent type found in albums of medieval and Renaissance drawings has a round drum, and is often flared in the middle. Polygonal-section drums are documented in De re militari by Roberto Valturio (1472); in the anonymous Sienese manuscript of machine drawings, S.IV.5 (end of fifteenth – beginning of sixteenth century); in the De re metallica (1556) by Giorgio Agricola; in the Florentine album of sixteenth- and early seventeenthcentury drawings collected by Jacopo and Ottavio Strada; and in Aristotelis Mechanicas Commentarij by Giovanni de Guevara (1627).

4 Hoist. c. seventeenth–eighteenth centuries Elm, 183 ✕ 162 ✕ 185 cm Vinci, Museo Leonardiano Provenance: Florence area Carbon dated to the fourteenth century: University of Rome “La Sapienza”, Department of Earth Sciences, Radiocarbon Laboratory

I.5.3. Revolving crane

1 Leonardo da Vinci Right: “stella” crane on carriage Codex Atlanticus, f. 138r, c. 1480–82 Milan, Biblioteca Ambrosiana (facsimile reproduction)

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The classic “stella” cranes were undoubtedly used for a long time on the Cathedral building site. Presumably attempts were made to refine them, as can be seen in the following drawings by Bonaccorso and Leonardo.

2 Bonaccorso Ghiberti Revolving crane, c. 1472–83 Florence, Biblioteca Nazionale Centrale, B. R. 228, f. 107 v (facsimile reproduction)

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The crane had a vertical pingear wheel which drove a winch for raising light loads, and a screw platform for moving the raised weight.

3 Bonaccorso Ghiberti Two “stella” cranes on a carriage, c. 1472–83 Florence, Biblioteca Nazionale Centrale, B. R. 228, f. 95 v (facsimile reproduction)

4 Leonardo da Vinci Sketches of revolving crane with a block and tackle mechanism aloft Codex Atlanticus, f. 847r, c. 1480 Milan, Biblioteca Ambrosiana (facsimile reproduction)

5 Leonardo da Vinci Revolving crane Codex Atlanticus, f. 105 bv, c. 1480 Milan, Biblioteca Ambrosiana (facsimile reproduction) 6–7 Revolving crane Wooden and digital model based on: Leonardo da Vinci, Codex Atlanticus, f. 105 bv Vinci, Museo Leonardiano Project and realization: Luigi Boldetti, 1966 This revolving crane with hoist had just one pin-gear drive wheel in the centre of the horizontal crosspiece. This made it possible to move both the load and the pulley linked to the drum, thereby balancing the forces.

Leonardo’s drawing is not entirely clear regarding the position of the worm screw and the drive wheel. In the wooden model on display here, Luigi Boldetti opted to place the screw alongside the crosspiece.

However, this means that the load would have weighed directly on the screw,

compromising its resistance and durability. This raises some doubt, because the screw was the most delicate of the components and at the time was more expensive than the structure. The drawing also permits another solution, namely that the screw was inside the crosspiece in keeping with the classic Brunelleschian model. However, this would seem to require a break in the crosspiece and consequently two pieces (and would even have involved fitting a pulley in the cavity of the mast). This would have weakened the structure.

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I.5.4. Revolving crane with counterweight

With this crane the load and the counterweight could be moved at the same time (in divergent or convergent mode with respect to the central axis), so the crane remained stable on its vertical shaft.

Movement was effected by means of two independent worm screws: one was inside the crosspiece, controlling the slide of radial movement of the vertical screw, while the other was on the beam underneath. The vertical shaft of the crane was guided by a long rudder and could turn 360°. The wheel at the foot of the shaft served to reduce the friction caused by the rotation on the base platform. The weight was raised and lowered by means of a vertical screw equipped with three turnbuckles to keep the load on an even plane. Four teams

1 Bonaccorso Ghiberti Counterweighted revolving crane, c. 1472–83 Florence, Biblioteca Nazionale Centrale, B. R. 228, f. 106r (facsimile reproduction) 2 Leonardo da Vinci Counterweighted revolving crane Codex Atlanticus, f. 965r, c. 1478–80 Milan, Biblioteca Ambrosiana (facsimile reproduction)

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of workmen were required to operate the crane: one turned the crane, two turned the screws for the radial displacement of the load and counterweight, and the fourth team moved the vertical screw.

In Leonardo’s drawing, there is a ring in the middle above the crosspiece. This may have been for attaching the support cables. Historical literature offers contrasting views on the position and use of this crane. The fact that the raising of the load relied on the use of a screw, necessarily rigid and with a limited load capacity, suggests that the crane was used for precision positioning. Furthermore, in the drawings, the load appears to be a block of marble for the lantern.

3 Leonardo da Vinci Load-raising device with vertical screw Codex Atlanticus, f. 926v, c. 1478 Milan, Biblioteca Ambrosiana (facsimile reproduction) 4 Francesco Di Giorgio Martini Revolving crane Treatise on architecture Florence, Biblioteca Medicea Laurenziana, Ms. Ashburnham 361, f. 46 r, c. 1481–84 (facsimile reproduction)

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5–9 Counterweighted revolving crane Wooden and digital model based on: Buonaccorso Ghiberti, B. R. 228, f. 106r Leonardo da Vinci, Codex Atlanticus, f. 965r Vinci, Museo Leonardiano Project and realization: University of Florence, Department of Construction Science (1987?)

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10 Detail of the lantern of the cupola of Santa Maria del Fiore, Florence

I.5.5. Lantern crane with central fulcrum

1 Leonardo da Vinci Lantern crane, c. 1480 Codex Atlanticus, f. 808v Milan, Biblioteca Ambrosiana (facsimile reproduction) “4 screws raise this crane, and once raised, there is a firm platform beneath” 2 Leonardo da Vinci Detail of the screw-based raising device installed on the crosspiece of the crane Codex Atlanticus, f. 1083v (enlarged detail), c. 1478 Milan, Biblioteca Ambrosiana (facsimile reproduction)

The crane, mounted on a circular platform and revolving around a central fulcrum, was presumably used (as a note by Giuliano da Sangallo also attests) during the building of the cupola’s lantern.

There is general agreement that it was placed in the centre of the oculus, with the circular platform positioned inside the octagonal perimeter on which the lantern walls were erected. The crane had a screw-based raising and positioning mechanism similar to the one on the counterweighted crane; installed on a slide between the beams of the crosspiece, this device permitted transverse movement of the load. The crane was employed for the lifting and precision positioning of the blocks of marble for the lower part of the lantern. As the walls rose, the support platform was raised by screws.

3 Giuliano da Sangallo Crane for the lantern Sienese notebook, c. 1507 Siena, Biblioteca Comunale degli Intronati, S. IV. 8, f. 12r (facsimile reproduction) “How the dome lantern of S. Liparatta was built” [S. Liparatta is Santa Maria del Fiore] 4 Bonaccorso Ghiberti Lantern crane, c. 1472–83 Florence, Biblioteca Nazionale Centrale, B. R. 228, f. 104r (facsimile reproduction)

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5–7 Lantern crane with central fulcrum Wooden and digital model based on: Buonaccorso Ghiberti, B. R. 228, f. 104r Leonardo da Vinci, Codex Atlanticus, f. 808v Giuliano da Sangallo, Ms. S.IV.8, f. 12r Vinci, Museo Leonardiano Project: University of Florence, Faculty of Engineering, Department of Mechanics and Industrial Technologies, 2004 Realization: Opera Laboratori Fiorentini, 2004 Construction technology from the cupola of Santa Maria del Fiore

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I.6 Lantern crane with annular platform

The machine depicted in the drawings by Bonaccorso Ghiberti (fig. 7) and Leonardo da Vinci (fig.

8), presented here in the form of a functioning model built to a scale of approximately 1:2, is one of the machines designed by Filippo Brunelleschi for the construction of the Cupola of Santa Maria del Fiore in Florence and built after his death in 1446. Documents belonging to the Opera del Duomo indicate that work to build the crane started in June–August 1465, on the basis of two models designed by the goldsmith Bruno di Ser Lapo Mazuoli. It was used for raising the “pyramid”, namely the cone-shaped spire of the Cathedral lantern. The lantern rises from the closing oculus of the Cupola, situated 90 m above ground level, and is a little more than 22 m high, including the ball installed on top. The “pyramid” of the lantern was completed in April 1467.

The crane served to position blocks of marble used in the construction of the spire, which were raised from the lantern terrace and from platforms mounted around it (clearly visible in the enlarged detail of the painting by Biagio d’Antonio, cfr. fig.

1, p. 218). This crane was used in conjunction with hoists and other devices for raising blocks to the level of the impost of the lantern.

The crane had three degrees of freedom, permitting vertical and horizontal-radial movement of the load; the entire base also rotated around a circular wooden ring that acted as centring. Horizontal translation movement was obtained by means of a screw/lead screw system. A freely rotating wooden disk was fixed to the end of the beam. Here the operator obtained rotation by inserting (and removing) pins into special holes in the sides of the wooden disk. A screw, probably made from bronze, ran inside the disk (lead screw), transmitting the required transverse movement to a slide free to run along the two axes of the beam. The screw and slide are integral. A system of ropes and pulleys for holding the load is attached to the slide.

This crane is presumably a modified version of the one used for building the lantern (part III, I.5.5), but it differs from it and from all the other solutions adopted in building site machines of the period. In fact, the centring for the rotation is not provided by a central fulcrum, but by four bodies positioned on the base circle and rolling on a vertical axis. It was also different from the previous lantern crane because the pulley-slide system replaced the vertical positioning screw that had been used in the former, perhaps because there was now

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a need to position blocks on a sloping rather than on a horizontal surface.

In Leonardo’s design the function of the two winches (there is only one in Ghiberti’s drawing) is not entirely clear. The drums seem to be of equal diameter and do not mesh with each other. The double turn of the rope may therefore have been inserted by Leonardo to prevent the load from rolling and falling rather than to reduce the motion. However, in the absence of clear evidence, it was decided to retain the second hypothesis, advanced in previous interpretations, in the reconstructed model.

In the drawings by Leonardo and Bonaccorso it can also be noted that the screw protrudes from the beam. Nowadays it is customary to use a diametrically opposite screw/lead screw apparatus, whereby the lead screw moves and the screw is fixed so it is not engaged in the transverse movement, thereby avoiding the unnecessary and damaging bending stress to which a protruding screw is inevitably subjected. The choice illustrated in the two drawings may depend on the fact that at the time the precision of working methods was not sufficient to prevent the load weighing on the screw/lead screw, increasing the attrition between them to a disproportionate extent. At the beginning of 1468 the Opera del Duomo decided to place a copper ball and cross on top of the lantern. The ball was installed in 1471. In the middle of 1468 the main responsibility for this undertaking was assumed by the workshop of Andrea del Verrocchio, where Leonardo started to work from around 1469. Evident traces of his involvement can be seen in a group of sheets from the Manuscript G, where Leonardo set about designing a way of building the ignia, presumably a burning glass. The project involved the realization of a very smooth concave plate, lined on the inside with drawn, non-tarnishable sheets of copper ironed with various machines and then welded together. As regards the procedures required to achieve this, Leonardo noted: “Remember the welding used for the ball of Santa Maria del Fiore” (Manuscript G, f. 84v).

In 1601 the copper ball and part of the spire of the lantern were destroyed by lightning, but they had been rebuilt by the end of 1603.

1-4 Lantern crane with annular platform Wooden and digital model based on: Bonaccorso Ghiberti, B.R. 228, f. 105r Leonardo da Vinci, Codex Atlanticus, f. 808r Vinci, Museo Leonardiano Revision and mechanization project: University of Florence, Faculty of Engineering, Department of Mechanics and Industrial Technologies, 2004 Realization: Opera Laboratori Fiorentini, 2004

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5 View of the lantern of the cupola of Santa Maria del Fiore, Florence 6 View of the ball on top of the lantern of Santa Maria del Fiore, Florence 7 Bonaccorso Ghiberti Lantern crane with annular platform, 1472 – c. 1483 Florence, Biblioteca Nazionale Centrale, B.R. 228, f. 105r 8 Leonardo da Vinci Lantern crane with annular platform Codex Atlanticus, f. 808r, c. 1480 Milan, Biblioteca Ambrosiana (facsimile reproduction)

10–12 Leonardo da Vinci Manuscript G, ff. 84v, 82v, 77r, 1510 – c. 1515 Paris, Institut de France (facsimile reproduction) 13 Alessandro Allori (attrib.)

Damage to the lantern in 1601 Florence, Biblioteca Nazionale Centrale, Ms. 11.1.429, f. 33r 14 Gherardo Mechini Scaffolding and crane used to repair the lantern in 1601–03 Florence, Galleria degli Uffizi, Gabinetto disegni e stampe, No. 248A

9 The terminal cusp of the lantern in the relief drawing of Giovan Battista Nelli, c. 1695

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I.7 The evolution and shortcomings of a crane, and other building equipment

Building work on the Cathedral was very prolonged, lasting several centuries. As a result, a number of types of lifting machines inherited from the medieval building site coexisted alongside new ones designed by Brunelleschi. In other cases there was a slow evolution from one kind of crane to another, with successive attempts to introduce innovations. These developments generally cannot be detected in archive documents but only in drawings. One example is that of the stella-type crane, which dated back to ancient and medieval times; it was extensively documented in the drawings of Leonardo and Bonaccorso Ghiberti, and present throughout the Renaissance.

The information card below and the relative digital animation offer a possible historical and technical reading of the stella crane.

With the stella-type crane, sideways movement of the load could only be achieved by inclining the mast of the crane, which was supported by cables.

A drawing by Ghiberti (B.R. 228, f. 107v) and other sketches by Leonardo (Codex Atlanticus, f. 847r; part III, I.5.3) reveal an attempt to achieve, in addition to rotational movement around a vertical axis, small lateral movements of the load, by means of the typically Brunelleschian device of a carriage mounted on a worm installed on the horizontal crosspiece. The scope of this crane was, however, strongly limited by the impossibility of balancing the forces acting upon the horizontal traverse. In-

1–2 Revolving crane: collapsing of the structure Frames from digital animation Vinci, Museo Leonardiano 3 Leonardo da Vinci Top left, sketches of hoist mechanisms; right, lewis and pincers Codex Atlanticus, f. 38r, c. 1514–15 Milan, Biblioteca Ambrosiana (facsimile reproduction)

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deed, while the radial position of the point where the load is applied could be varied, the pulley for the cable from the drum of the hoist was fixed.

In the crane documented in a drawing by Leonardo (Codex Atlanticus, f. 105bv; part III, I.5.3) — interpreted here (in a different fashion to the model reconstructed by Luigi Boldetti) with the worm positioned inside the traverse — the number and position of the pulleys for the cable could vary, and there was just one drive wheel in the centre of the horizontal traverse. This made it possible to move both the load and the pulley linked to the drum, thereby balancing the forces. However, this solution involved a break in the traverse, which was made from two pieces, with a consequent weakening of the structure (figs 1 and2).

A subsequent development was the counterweighted revolving crane (part III, I.5.4), which had no hoist or pulleys, but a counterweight that could be moved radially. The drives were independent of the lifting movement of the load and its sideways movement, and of that of the counterweight. This crane did not have any functional limits, but required very complex manoeuvring. It was capable of positioning loads very precisely.

Drawings from the period also frequently document equipment and tools used on site, for instance lewises and pincers for clasping loads, turnbuckles and winch mechanisms for receiving loads raised by ground-level hoists.

4 Bonaccorso Ghiberti Turnbuckles, c. 1472–83 Florence, Biblioteca Nazionale Centrale, B. R. 228, f. 117r 5 Bonaccorso Ghiberti Vertical screw with triple turnbuckle and, in the centre, a lewis, c. 1472–83 Florence, Biblioteca Nazionale Centrale, B. R. 228, f. 119r 6 Giuliano da Sangallo Turnbuckles, c. 1500–04 Siena, Biblioteca Comunale degli Intronati, S.IV.8, f. 48v–49r

Construction technology from the cupola of Santa Maria del Fiore

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1 Francesco Di Giorgio Martini Device for reversing direction applied to just one pin-gear wheel, with drum and two-ended rope Treatise on Architecture Florence, Biblioteca Medicea Laurenziana, Ms. Ashburnham 361, f. 44v, c. 1481–84 (facsimile reproduction)

I.8 Other Renaissance machine drawings

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