The Serpollet steamcars produced very hot high pressure steam, requiring poppet valves, and these used a patented sliding camshaft mechanism, which not only varied the inlet valve cut-off but allowed the engine to be reversed. Aircraft An early experimental 200 hp Clerget V-8 from the 1910s used a sliding camshaft to change the valve timing. Some versions of the Bristol Jupiter radial engine of the early 1920s incorporated variable valve timing gear, mainly to vary the inlet valve timing in connection with higher compression ratios. The Lycoming R-7755 engine had a Variable Valve Timing system consisting of two cams that can be selected by the pilot. One for take off, pursuit and escape, the other for economical cruising. Automotive The desirability of being able to vary the valve opening duration to match an engine's rotational speed first became apparent in the 1920s when maximum allowable RPM limits were generally starting to rise. Until about this time an engine's idle RPM and its operating RPM were very similar, meaning that there was little need for variable valve duration. The first use of variable valve timing was on the 1903 Cadillac Runabout and Tonneau created by Alanson Partridge Brush Patent 767,794 “INLET VALVE GEAR FOR INTERNAL COMBUSTION ENGINES” filed August 3, 1903, and granted August 16, 1904. Some time prior to 1919 Lawrence Pomeroy, Vauxhall's Chief Designer, had designed a 4.4 L engine for a proposed replacement for the existing 30-98 model to be called the H-Type. In this engine the single overhead camshaft was to move longitudinally to allow different camshaft lobes to be engaged. It was in the 1920s that the first patents for variable duration valve opening started appearing – for example United States patent . In 1958 Porsche made application for a German Patent, also applied for and published as British Patent GB861369 in 1959. The Porsche patent used an oscillating cam to increase the valve lift and duration. The desmodromic cam driven via a push/pull rod from an eccentric shaft or swashplate. It is unknown if any working prototype was ever made. Fiat was the first auto manufacturer to patent a functional automotive variable valve timing system which included variable lift. Developed by Giovanni Torazza in the late 1960s, the system used hydraulic pressure to vary the fulcrum of the cam followers (US Patent 3,641,988). The hydraulic pressure changed according to engine speed and intake pressure. The