Twice the specific power of regular engines, half the cost, half the weight, 30% more fuel efficient.

With hundreds of millions of small internal combustion engines produced yearly, there is a need for simple and cheap to produce 4-stroke engines. Small part count and simple manufacturing with forgiveness for production tolerances combined with proper sealing, cooling and lubrication are mandatory.

The orbox engine has no gears or valves, but maintains proper sealing, cooling and lubrication. All parts are 2-dimensional simple/cheap to manufacture parts, and can be easily balanced for high speeds. Large openings allow high gas flow and high power density, and simple on-the-fly variable compression allows fuel optimizing and high efficiency. See http://www.orbox.be

The idea is based on the little known geometric law that a straightedge orbiting an ellipse describes a circle. This allows for a rotating elliptical body and a pivoting straightedge to confine a variable volume. To our knowledge (and patent search) this has never been applied.

The geometry can be used as pump or compressor, and the rotor shape can be adjusted for high pressure or high volume gas/fluid pumping or compression, if needed also using the four secondary cavities. http://www.youtube.com/watch?v=dKFrFbefVTo

But as it can be properly sealed, it is also most suitable as geometry for (HCCI) combustion engines.
http://www.youtube.com/watch?v=srmPNq16A5E