Napier & Son - World War II

World War II

Starting from scratch, Napier decided to use the new sleeve valve design in a much larger H-block 24-cylinder engine, soon to be known as the Sabre. Designed under Frank Halford, the engine was very advanced and proved to be difficult to adapt to assembly line production. Therefore although the engine was ready by 1940, it was not until 1944 that production versions were considered reliable. At that point efforts were made to improve it, leading eventually to the Sabre VII delivering 3,500 hp (2,600 kW), making it the most powerful engine in the world, from an engine much smaller than its competition.

Napier also worked on diesel aircraft engines. In the 1930s they licensed the Junkers Jumo 204 for production in England, which they called the Culverin. They also planned to produce a smaller version of the same basic design as the Cutlass, but work on both was cancelled at the outbreak of World War II.

Napier developed a marine engine from the Lion aero engine, the petrol-driven Sea Lion, which could deliver 500 hp (370 kW) and was used in the "Whaleback" Air Sea Rescue Launches.

During the war (1944) Napier were asked by the Royal Navy to supply a diesel engine for use in their patrol boats, but the Culverin's 720 hp (537 kW) was not nearly enough for their needs. Napier then designed the Deltic, essentially three Culverins arranged in a large triangle (deltoid). Considered one of the most complex engine designs of its day, the Deltic was nevertheless very reliable, and was taken into service after the war as a locomotive powerplant (in British Rail's Class 55) in addition to the torpedo boats, minesweepers and other small naval vessels for which it was designed.

Also during world war two a six-cylinder 300 cubic inch road-vehicle engine was commissioned by the government, but this design was sold to Leyland Motors by 1945.