A structural arrangement for an internal combustion engine and/or star shaped air compressor, without a crankshaft and connecting rods and with one or more surrounded pistons, being able to use any fuels in the case of the engine, liquid or gaseous including hydrogen and obtain high thermodynamic efficiency. The engine and/or air compressor has an arrangement that makes it possible to transmit linear movement into circular movement by means of a ring together with an eccentric and with a coupling structure, The structure joins the pistons to the ring, which can be polygonal in the case of the use of at least three pistons or welded in the case of one or two pistons.