Heat energy of various ignition sparks
This is a 1920 technical report from the NASA Technical Reports Server collection, presenting engineering plots of spark heat energy measured across engine speeds for several magneto ignition systems. The four charts are plain line graphs with plotted points, labelled joules per spark against revolutions per minute, each titled with a magneto make and timing condition. A designer might borrow their clean grid-and-curve diagram style for minimal data graphics, where a single smooth line with open circle markers reads clearly against a fine rule grid.
