The year 1919 became a turning point when the journal "Engineering" published a detailed report on the engine invented by William Joseph Still. This publication publicly confirmed that this hybrid mechanism had achieved a thermal efficiency of 40 percent. It was a technical triumph, significantly surpassing the 30–33 percent efficiency rates prevalent at the time. The engineering world watched as steam and diesel combined in a single block.
The Still engine was not a simple device, but a complex double-acting piston mechanism. The upper side of the piston performed the work of a two-stroke diesel combustion cycle. The lower side functioned as a steam engine, utilizing waste heat. The system was constructed from massive steel and cast iron, occupying a huge area in factory spaces or ship hulls. Every detail required the precision demanded by William Joseph Still’s rigorous blueprints.