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A program is described here that analyzes the behaviour of roller-follower valve gear. The motion is computed from a kinematic analysis; the instantaneous radius of curvature and the pressure angle are determined, so that the contact force and stresses can be evaluated at the cam/follower interface. The validation of the software is discussed. Also analyzed, is the hydrodynamic lubrication of the roller-follower journal bearing. A case study is described in which journal and bearing wear are attributed to inappropriately sited oil feed holes. It is shown that there is a region where no hydrodynamic pressure develops, thus providing an appropriate location for the oil feed holes. The assumptions in the hydrodynamic analysis are discussed.

This study investigates the wear characteristics of a variable valve timing (VVT) system used to vary the phasing of the inlet valve events on a medium speed marine diesel engine. The running-in properties of critical components within the system are examined. The effect of surface finish and surface hardness upon wear is examined. It was found that in order to prevent excessive wear between the roller and tappet follower then the roller should be harder than the tappet. Tappet and roller hardness values of 60 and 70 Rockwell Hardness ‘C’ (HRC) respectively were found to be satisfactory.