This is a development of “Tchebicheff’s four-bar linkage 3”.
Length of yellow bar: a + a
Length of blue bar: 2.5a
Length of orange bar: 5a
Length of pink bar: 2.5a + 2.5a
Axle distance between the revolution joints of the green seat: 2a
Axle distance between the ground revolution joints: 4a
The green seat has horizotal motion (not strictly rectilinear).