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
An vertex of the big kite traces an absolutely straight line (in red).