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Deutsches Technikmuseum - May

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Exhibit of the Month May 2019

Photo: Shiny brass compasses and other drawing instruments are arranged side by side in the recessed areas of an opened case.

Drawing case containing a compass with interchangeable attachments and further drawing instruments, Nuremberg, circa 1720. © SDTB / Photo: C. Kirchner

Drawing Case, circa 1720

Anyone who has worked with a compass knows that the legs can become misaligned if they are not firmly secured to one another.

Even Leonardo da Vinci (1452–1519), whose 500th death anniversary is observed in May 2019, struggled with the problem of unwanted changes in the aperture angle when using a pair of compasses to measure or draw a circle.

An enlargement of a drawing from the manuscript depicting three compasses is shown here. A type of joint construction that provides more stability to the legs of an open compass can be seen.

Drawings of different compasses by Leonardo da Vinci, around 1515. Credits see below.

Solutions to the problem of unstable compass legs –

around 1515 ...

The sketches by the polymath Leonardo clearly show that he endeavoured to make technical improvements to the compass. Preparatory drawings of different compasses can be seen on the upper right between the mechanical and geometric studies.

These "dividers" were used for measuring and transferring distances and for scribing circles in paper for freehand tracing. In order to prevent the legs from shifting their positions during use, Leonardo devised a multi-part bifurcated joint construction between the legs to create friction between the contact surfaces.

... and around 1720

That the work on unstable compass legs continued to make progress is clearly illustrated by the 1720 drawing case from Nuremberg that is on display here.
The loosening and locking of the compass legs is done with a pin spanner that adjusts the ease of movement of the pair of compasses up at the head section.

The tool case also contains a compass with interchangeable attachments, a version that has been in use since the mid-17th century. The different attachments are locked into place by means of screws on one leg of the compass. It is thus possible to use the compass with a metal needle point for scoring, a drawing pen for directly drawing with ink, as well as with a lengthening bar for making larger circles.

Zoom Manuscript sheet: Leonardo da Vinci: Manuscript sheet (detail and general view) from the Codex Atlanticus, fol. 696r (c. 1515), © Biblioteca Ambrosiana, Repro: Staatsbibliothek zu Berlin, Stiftung Preußischer Kulturbesitz