Reduction circle
The reduction compass or proportional compass is a special compass that is used to divide, enlarge and / or reduce distances in a certain ratio . It can also be used to divide the circumference into equal parts. In addition, various special constructions can be made, such as the division of a line according to the golden ratio or the “ squaring of the circle ” (ie the construction of a square that is approximately the same area as a given circle).
The reducer consists of two legs that are connected by a movable adjusting screw (usually with a vernier ). It has two points at each end. One pair is used to pick up the initial dimension, the second to knock off the size to be constructed. With precisely manufactured devices, an accuracy of ± 0.1 mm can be achieved.
The third part of the Tractatus primus instrumentorum mechanicorum by Levin Hulsius deals with the reduction circle, which can not only be seen on the title page, but is also explained in detail in the following text. Hulsius said in 1603 that he saw the proportional circle for the first time at the Reichstag in Regensburg. After all, Hulsius attributed the invention of the proportional circle to the instrument maker Jost Bürgi and complained that other craftsmen had simply recreated its circle. Even today, Jost Bürgi is sometimes considered the inventor of the reduction circle. In fact, reduction circles were already known in antiquity. A primitive form with a fixed angle that allows transfers in a ratio of 1: 2 is preserved among the bronze finds from Pompeii . The reduction circle was further developed into the proportional circle by Fabrizio Mordente (with shares from Federigo Commandino ) and later Galileo Galilei .
The reduction circle is also used by stone sculptors , whom they also call "reduction pliers", when they transfer and work on models enlarged or reduced in natural stone .
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Individual evidence
- ↑ Ralf Kern: Scientific instruments in their time / Volume 2. Cologne, 2010. P. 278.
- ^ Filippo Camerota, Il compasso di Fabrizio Mordente. Per la storia del compasso di proporzione , Olschki, Florenz 2000, illustration Ia (Naples, Museo Archeologico Nazionale, inv. 76684), cf. ibid p. 6, p. 14
- ^ Galileo Sector, Galileo Project