How is medium speed engine reverse (without CPP)
In medium speed diesel engines, reversing is achieved by the use of duplicate cams for the air inlet valves, exhaust valves and fuel pumps. Air start distributor timing is also changed by means of camshaft movement or by a directional air supply being admitted to the start air distribution, to reposition cams
To engage correct cams for ahead and astern movements the camshaft slides axially in its bearings. This movement is controlled by the camshaft reversing gear, which is normally a servo piston. Motion of the piston being directly transmitted to the camshaft.
Note: in a slow speed, only duplicate fuel cams required.