Single air supply using hollow piston rod

A linear reciprocating engine comprising:

• a cylinder having a first combustion chamber at a first end and a second combustion chamber at an opposing second end;
• a vestibule located external to the first combustion chamber and proximate the first end;
• a piston slidably mounted within the cylinder;
• a first piston rod portion extending from the piston through the first combustion chamber and into the vestibule, the first piston rod portion including a first passageway flow-connected to an inlet port and at least one first sidewall opening;
• and
• a second piston rod portion extending from the piston through the second combustion chamber, the second piston rod portion including a second passageway flow-connected to at least one second sidewall opening,
• wherein the first passageway is flow-connected to the second passageway,
• and wherein the engine is provided with a single air supply communicating with the vestibule.

A linear reciprocating engine, comprising:

• a cylinder having a first combustion chamber at a first end and a second combustion chamber at an opposing second end;
• a chamber located external to the cylinder;
• a piston configured to be slidably mounted within the cylinder;
• a piston rod including a first piston rod portion and a second piston rod portion, wherein the first piston rod portion extends through the first combustion chamber and the second piston rod portion extends through the second combustion chamber, and the first piston rod portion or the second piston rod portion is configured to extend into the chamber;
• at least one first opening in the first piston rod portion configured to move into and out of the first combustion chamber to selectively communicate gas to the first combustion chamber;
• and
• at least one second opening in the second piston rod portion configured to move into and out of the second combustion chamber to selectively communicate gas to the second combustion chamber,
• wherein the piston rod is configured such that when the at least one first opening is outside the first combustion chamber and the at least one second opening is outside the second combustion chamber, air is supplied to the chamber to build pressure in the piston rod, and
• wherein the piston rod includes an interconnecting flow passageway extending through the piston.