Primary drives have the task of bridging often large distances between the crankshaft and camshaft(s). In order to prevent oscillation of the chain at the drive level, the chain is guided in the areas between the shafts by means of rails. The chain tensioner transmits its force to the chain via the movable tensioning rail. The other rails (guide rails) are, in contrast, linked rigidly to the engine. The chain slides with little friction and wear over a plastic sliding layer.
Both the available space and the loads acting on the rail are decisive in determining the material to be used for the load-bearing substructure of the rail. The following options are available:
Finite element calculations and related analyses can be used to achieve maximum rigidity while maintaining minimal cost and design space. Mounting on the engine is matched individually to the conditions present.