Resonance vibrations of aircraft propellers
This 1932 NASA technical report on resonance vibrations of aircraft propellers was issued by the NACA-era Technical Reports Server for engineers and aeronautical researchers. Its pictures are technical graphs of rotational speed against frequency and blade-stiffness curves, with labelled families of lines, and a designer might take from them the restrained grammar of engineering plots: thin black rules, labelled curves, and grid-based axes.
