In an opposed piston, compression ignition engine two crankshafts are single-side mounted with respect to a row of cylinders, which is to say that the crankshafts are mounted so that their axes of rotation lie in a plane that is spaced apart from and parallel to a plane in which the axes of the cylinders lie. Each piston of the engine is coupled to one of the crankshafts by a single linkage guided by a crosshead. The piston has a piston rod affixed at one end to the piston. The other end of the piston rod is affixed to the crosshead pin. One end of a connecting rod swings on the pin and the other end is coupled to a throw on a crankshaft. Each crosshead is constrained to reciprocate between fixed guides, in alignment with the piston rod to which it is coupled.