A rotation rod assembly comprising: a first linkage rod having a first annular body portion fixedly secured to and extending axially therefrom, the first annular body portion having an inner surface defining a first bore axially extending partially into the first annular body portion, the first annular body portion having a first axial end and second axial end, the first axial end being closed and the second axial end having an opening with a plug adjustably secured therein, the plug having a second bore extending therethrough, the first linkage rod being fixedly secured to a frame; a second linkage rod having a piston section extending axially therefrom, the piston section being coaxial with the first linkage rod and the plug, the piston section being disposed for rotation in the first bore, the inner surface surrounding the piston section, the second linkage rod extending through the second bore and rotatable relative to the plug, the piston section being axially restrained by the first end and the plug; the piston section having a first bushing and a second bushing secured to at least one outer surface of the piston section, the first bushing and the second bushing having a lubrication groove (141Y, 141X, 143Y, 143X) formed in an axially and a radially outer surface thereof, at least one of the first bushing and the second bushing being in sliding engagement with portions of the inner surface, the first end and a portion of the plug; a barrier (141, 142E, 142D) for preventing flow of the grease inside the piston section; and a flow path for conveying grease around the piston section, the flow path comprising a first radial circuit in the first bushing, a first axial circuit in the first bushing, a second axial circuit around a radial outer surface of the piston section, a third axial circuit in the second bushing, and a second radial circuit in the second bushing. a first linkage rod having a first annular body portion fixedly secured to and extending axially therefrom, the first annular body portion having an inner surface defining a first bore axially extending partially into the first annular body portion, the first annular body portion having a first axial end and second axial end, the first axial end being closed and the second axial end having an opening with a plug adjustably secured therein, the plug having a second bore extending therethrough, the first linkage rod being fixedly secured to a frame; a second linkage rod having a piston section extending axially therefrom, the piston section being coaxial with the first linkage rod and the plug, the piston section being disposed for rotation in the first bore, the inner surface surrounding the piston section, the second linkage rod extending through the second bore and rotatable relative to the plug, the piston section being axially restrained by the first end and the plug; the piston section having a first bushing and a second bushing secured to at least one outer surface of the piston section, the first bushing and the second bushing having a lubrication groove (141Y, 141X, 143Y, 143X) formed in an axially and a radially outer surface thereof, at least one of the first bushing and the second bushing being in sliding engagement with portions of the inner surface, the first end and a portion of the plug; a barrier (141, 142E, 142D) for preventing flow of the grease inside the piston section; and a flow path for conveying grease around the piston section, the flow path comprising a first radial circuit in the first bushing, a first axial circuit in the first bushing, a second axial circuit around a radial outer surface of the piston section, a third axial circuit in the second bushing, and a second radial circuit in the second bushing.