Abstract: A free piston engine wherein a combustion piston directly drives a pumping piston to pump hydraulic fluid to and fro to a linear to rotary motion pump/motor converter which is in the form of a "split cycle" machine.

Abstract: A low compression ratio internal combustion engine with extended dwell at or near piston top dead center to facilitate substantially complete combustion providing a higher engine output power. A pre-combustion chamber passes high temperature and pressure combustion products into the cylinder of the engine.

Abstract: A machine having a piston unit within a cylinder arrangement wherein each piston unit comprises a plurality of in-line pistons within their respective cylinders such that the pistons are in fluid communication with a common compression chamber and where the pistons of each unit move in unison.

Abstract: A radial cylinder machine comprises a number of equispaced lobed shafts (7) which orbit about the central machine axis inwardly of the pistons (13). The lobed shafts (70) also rotate about their individual axes by virtue of planetary pinions on each shaft (7) meshing with a fixed ring gear. The orbiting and rotating lobes (9) act as cams on the inward faces of the pistons (13) whereby there is inter-conversion of reciprocatory motion of the pistons (13) and rotary motion of the lobed shafts (7). The lobed shafts (7) are mounted on a carrier fixed to a central axis input/output shaft whereby torque may be transferred permitting the machine to act as an engine or pump. There is also disclosed a means of maintaining contact between the pistons (13) and the lobes (9).