Large two stroke marine diesel engine camshafts are driven either by gears or chains. In the case of gear drive, a train of gear wheels is fitted, which transmits the drive from the crankshaft to the camshaft. Appropriate speed and direction is achieved, by suitably arranging the intermediate gears in different positions and sizes. Unlike a chain, the gear does not lose tension; however, gears are subject to damage and difficult / expensive to replace.
Large super long stroke engines have Moment Compensators fitted to the gears. the balance weights rotate at the full engine speed or twice the engine speed, in synchronization with the crankshaft to take care of the primary and secondary vibration.
Reference and Images
“Marine Engineering Practice” by Vikram Gokhale and N. Nanda