Achates Power makes an engine based on opposed-piston principles with a central chamber inside the cylinder between the two pistons.

"Patent drawing"

-The patent, presented in USA and Russia, differs from ordinary engines of this type (Jumo) in a way that the crankshafts are on both sides of the cylinder and a connecting rods attached to the pistons make them rotate.

"With the pistons in different positions"

-It works with the two-stroke system, and is proposed for several vehicles, aircraft included.

-At each end of the cylinder there is a port, on one side the intake and on the other the exhaust.

"Patent Drawings - Expandable Modular Engine"

"Aspecto mas real del Achates"

Some more information about this engine by "Achates", pronounced "Akates".

"Achates mechanism"

-And also a photo of the first practical realization of this engine.

"Completed Achates engine"

The end result:

"Achates two-stroke, opposed-piston engine"