Piston engine with a fast linear bearing mechanism

A fast linear bearing mechanism, which is connected to the connecting portion connecting the piston and the connecting rod, regulates the movement of the connecting portion, so that it moves in an almost straight line along the axial center line of the cylinder. According to one aspect form the engagement ends of a plurality of substantially straight connection elements, as well as the engaging ends of the nearly straight connecting elements with the connecting portion engages, which connects the piston and the connecting rod, a one-sided support structure that enables the nearly straight support members rotatably to be connected, while they are of a predetermined direction in engagement.