The N.A.C.A. Optical Engine Indicator
A 1938 technical report from the National Advisory Committee for Aeronautics, issued by NASA's Technical Reports Server, describing an optical instrument for recording combustion pressure inside engine cylinders. The pictures are plain black-and-white engineering graphs of pressure traces against crank angle and a set of mechanical drawings of the indicator's mirror, lens, eccentric and bearing posts. A designer could draw on their clean scientific line work, labelled callouts and dense technical layout for diagrams or infographics.
