Abstract: A crank disc is rotatably mounted on a journal fixed to the casing. A planetary wheel is mounted rotatably and eccentric on the crank disc. The planetary wheel is in forced engagement with a sun wheel arranged coaxially with regard to the crank disc. The sun wheel is fixed to the casing and its reference diameter is double or equal to the reference diameter of the planetary wheel. A pin is arranged on the planetary wheel eccentric to the planetary wheel's axis. The pin is encompassed by the connecting rod bearing of a connecting rod. The crank disc meshes with a pinion of a driven shaft. By this development the characteristics of the crank drive can be chosen within a wide range. Combustion and efficiency can be increased upon employment in a piston combustion motor.