An investigation of the use of discharge valves and an intake control for improving the performance of N.A.C.A. Roots type supercharger
This is a 1929 NASA technical report, issued by the National Advisory Committee for Aeronautics, on experiments improving the Roots-type supercharger used in aircraft engines. The pictures are engineering line drawings and graphs, with a performance chart of altitude against horsepower and a labelled cross-section of a Roots blower with its impellers and discharge valve. A designer might take from them a clean, technical diagram style: plain black linework, labelled callouts and grid-based charts.
