purposes to a crankshaft parallel to the cylinder axis via a slotted guide, provided on the crankcase side of the piston, for at least one crankpin of the crankshaft, characterised in that the crankpin (18) bears against the slotted guide (17) via a roller (19) and the tubular member (1) forming the cylinder and the crankcase (5) is heat-insulated from the exterior.
