![]() To pass this limit, the sleeve valve would have to be used, to increase volumetric efficiency, as well as to decrease the engine's sensitivity to detonation, which was prevalent with the poor quality fuels in use at the time. In it, he wrote that traditional poppet valve engines would be unlikely to produce much more than 1,500 hp (1,100 kW), a figure that many companies were eyeing for next generation engines. ![]() ![]() In 1927, Harry Ricardo published a study on the concept of the sleeve valve engine. This called for radical changes and while many companies tried to build such an engine, none succeeded. A typical large engine of the era, the Pratt & Whitney R-1830 Twin Wasp, developed about 1,200 hp (895 kW) from 1,820 cubic inches (30 litres), so an advance of some 50 percent would be needed. This power output was needed to propel aircraft large enough to carry large fuel loads, for long range flights. In these new designs, Napier chose air cooling but in service, the rear cylinders proved to be impossible to cool properly, which made the engines unreliable.ĭuring the 1930s, studies showed the need for engines capable of developing one horsepower per cubic inch of displacement (about 45 kW/litre). Since the cylinders are opposed, the motion in one is balanced by the motion on the opposing side, leading to no first order vibration or second order vibration. The H-block has a compact layout, consisting of two horizontally opposed engines, lying one atop or beside another. Napier followed the Lion with two new H-block designs: the H-16 (Rapier) and the H-24 (Dagger). By the late 1920s, the Lion was no longer competitive and work started on replacements. Their most famous was the Lion, which had been a very successful engine between the World Wars and in modified form had powered several of the Supermarine Schneider Trophy competitors in 19, as well as several land speed record cars. Prior to the Sabre, Napier had been working on large aero engines for some time. The rapid introduction of jet engines after the war led to the quick demise of the Sabre, as there was less need for high power military piston aero engines and because Napier turned its attention to developing turboprop engines such as the Naiad and Eland. Other aircraft using the Sabre were early prototype and production variants of the Blackburn Firebrand, the Martin-Baker MB 3 prototype and a Hawker Fury prototype. The first operational aircraft to be powered by the Sabre were the Hawker Typhoon and Hawker Tempest the first aircraft powered by the Sabre was the Napier-Heston Racer, which was designed to capture the world speed record.
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