A modification of Peaucellier linkage proposed in 1877 by A. B. Kempe, London.
Length of blue bar: a
Length of blue bar of 3 joints: 0.75a + 0.25a
Length of yellow bars: 0.5a
Length of orange bars: 0.25a
Axle distance between the two fixed revolution joints 0.75a
The grey disk is fixed to the upper yellow bar. On this disk all points laid on small circle of diameter a (in pink) move along straight lines that are diameters of a big circle of 2a diameter (in cyan). The small circle rolls without slide in the big one. They are of Cardano.