The 1864 Otto & Langen engine was a free piston atmospheric engine (the explosion of gas was used to create a vacuum and the power came from atmospheric pressure returning the piston).
Injini ya Otto & Langen ya 1864 ilikuwa injini ya anga ya pistoni isiyolipishwa (mlipuko wa gesi ulitumiwa kuunda utupu na nguvu ilitoka kwa shinikizo la anga kurudisha pistoni).