RT Journal Article T1 Giovanni Canestrini�s models A1 Ian Hutchings YR 2016 VO 6 IS Autumn 2016 K1 Leonardo da Vinci K1 models K1 friction experiments K1 sketches K1 Giovanni Canestrini AB Among the exhibits at the 2016 Leonardo da Vinci exhibition at the Science Museum, London, was one that purported to illustrate Leonardo’s experiments on friction. The models involved were the work of Giovanni Canestrini (1893–1975) who contributed to the 1939 and 1953 Leonardo exhibitions in Milan. This article discusses the original sources and history of these models, in the light of recent research into Leonardo’s work on friction. It concludes that, while being relevant to Leonardo’s study of mechanics, these models seriously misrepresent his experimental investigations of friction. NO Canestrini (1938) p 301, ‘studi sull’attrito di rotolamento’ NO ibid. p 321 NO Canestrini (1939a) p 497, ‘Leonardo è il primo che affronta lo studio sistematico delle cause di attrito sia nel caso di superfici plane, che nel caso dei perni precedendo di due secoli Amontons (1699) e Coulomb (1781), il quale riprodurrà, per le sue esperienze, il banco che troviamo disegnato al fol. 41 recto del Codice Arundel’. This statement should probably not be taken to suggest that Canestrini believed that Coulomb’s work was directly influenced by a knowledge of Leonardo’s sketches. NO Canestrini (1939b) p 145, ‘Banco per esperienze sull’attrito’ NO Canestrini (1939a) p 494, ‘Perni rotanti su rulli’. Canestrini misattributes the diagram to Codex Atlanticus NO Canestrini (1939b) p 157, ‘Studi sull’attrito nei perni. Here he misattributes it to Asburnham MS 2037 NO Mostra di Leonardo da Vinci e delle Invenzione Italiane NO ‘Modello ricostruito di pancone per esperienze nell’attrito radente e volvente’ (from Guida, 1939; the entry in Catalogo, 1939 is essentially the same) NO ‘Modello ricostruito di un apparecchio sperimentale per lo studio dell’azione delle forze e dell’attrito in un sistema rotoide’ (from Guida, 1939); the entry in Catalogo, 1939 is ‘apparecchio sperimentale per lo studio dell’azione delle forze e dell’attrito in un sistema rotoide. Modello ricostruito dal Cod. Atl. f. 390 v.b.’. The catalogue uses the earlier foliation of Codex Atlanticus; the equivalent current folio is 1081v. NO p 147, ‘Ricostruzione del banco per le esperienze sull’attrito secondo i disegni di Leonardo’ NO Catalogo (1939), p 87, ‘Pancone per esperienze di attrito radente e volvente. Modello ricostruito dal Cod. Arundel f.41r’ NO ‘Modello ricostruito – su disegno di Leonardo – per lo studio dell’azione delle forze e dell’attrito in un sistema rotoide’ NO ‘Frizione a cilindri’ NO ‘Rulli reggispinta in un disegno di Leonardo’ NO ‘Sistema di coppie rotoidali con rulli reggispinta ai perni’ NO Probable dates for the manuscripts are derived from the sources listed in Hutchings (2016, p 53) NO ‘la confregazione circolare fia equale alla confregazione retta’ NO Although there is no text describing this sketch, it is clear from other diagrams on the same page and the facing page that the weight is intended to be 2 libbre. The libbra was approximately 0.33 kg (Hutchings, 2016) and a wooden cylinder of this weight with a density of 720 kg/m3 (typical of European oak, ash or beech) with its length twice its diameter would be 84 mm in diameter and 167 mm long. If we are to assume that the sketch does represent a real experiment, then this gives us an indication of the size of the apparatus – the cylinder would be only about one third of the dimensions of Canestrini’s ‘reconstruction’ in Model A. NO Other examples in the context of friction are in Codex Atlanticus ff. 198r, 525r, 532r, Codex Forster II f. 124v. NO ‘figure…del banco che ha servito a Leonardo per le sue esperienze’ NO The extent to which Leonardo performed real, practical experiments to investigate friction, and to what extent his sketches represent concepts or ‘thought experiments’ is a matter of considerable interest, and is discussed more fully in Hutchings (2016, pp 63–65). 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