This is the same model as Loops.Engine1b. The only difference is that the central part of the planar kinematic loop has been replaced by the assembly joint "Modelica.Mechanics.MultiBody.Joints.Assemblies.JointRRP". The advantage of using JointRRP is, that the non-linear algebraic equation of this loop is solved analytically, and not numerically as in Loops.Engine1b.
An animation of this example is shown in the figure below.