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Royal College of Surgeons, 41-42 (now 35-43) Lincoln's Inn Fields, Holborn, Camden, London, 1805-12 (with James Lewis)
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Reference number
SM D5/3/18
Purpose
Royal College of Surgeons, 41-42 (now 35-43) Lincoln's Inn Fields, Holborn, Camden, London, 1805-12 (with James Lewis)
Aspect
[154] Section showing composite beam with iron butterfly cantilever, and decoration of the ceiling, and plan of composite beam showing timber and iron and method of bolt fixing, 'not executed'
Scale
Scale ½ Inch to the Foot
Inscribed
as above, Not executed like this drawing / The iron Truss is diferent / The Coffers in Circular Sofite are omitted in the work, some dimensions given and (verso, Dance) Section lengthway / of part of Museum / not correct and Incorrect / Section / lengthway / Museum
Verso
Rough interior perspective of part of museum showing junction of dome and piers
Pencil
Signed and dated
- 1805-12
Medium and dimensions
Pen, yellow, raw umber, sepia, pink and blue washes, pencil, partly pricked for transfer on laid paper (515 x 660)
Hand
Dance
Watermark
D&CBxX in cartouche surmounted by fleur-de-lis
Notes
The iron, tapered butterfly cantilever, 14 feet long, strapped to two 14 by 6 inch timbers and supported by a compound pier in its centre was to run lengthwise of the museum across the edge of the gallery. Dance roughed in a butterfly cantilever on [SM D5/3/37].
David Yeomans (correspondence, 2 August 2001) notes that 'this design is different [from preceding designs] and raises the question of a possible difference between intended and actual behaviour. Girders were often trussed with three pieces of timber, the top one being horizontal. It looks as if Dance was doing this with iron but allowing the timber of the girder to act as the central compression part. Of course it would not have worked this way. With the arrangement shown the iron would have acted as a double cantilever effectively reducing the span of the timber. The question is what would happen to the negative moments in the iron flitches. It is all right for those between the two beams as shown here because a load on one beam would be picked up by a transfer of moments to the adjacent beam. The question is, what happens at the ends?'
David Yeomans (correspondence, 2 August 2001) notes that 'this design is different [from preceding designs] and raises the question of a possible difference between intended and actual behaviour. Girders were often trussed with three pieces of timber, the top one being horizontal. It looks as if Dance was doing this with iron but allowing the timber of the girder to act as the central compression part. Of course it would not have worked this way. With the arrangement shown the iron would have acted as a double cantilever effectively reducing the span of the timber. The question is what would happen to the negative moments in the iron flitches. It is all right for those between the two beams as shown here because a load on one beam would be picked up by a transfer of moments to the adjacent beam. The question is, what happens at the ends?'
Level
Drawing
Digitisation of the Drawings Collection has been made possible through the generosity of the Leon Levy Foundation
If you have any further information about this object, please contact us: drawings@soane.org.uk