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Hispano-Suiza aero engines

Jan den Das

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The following information is taken from Wikipedia. Other details can be obtained by connection to Internet under the voice "Hispano Suiza"


The Hispano-Suiza 8 was a water-cooled V8 SOHC aero engine introduced by Hispano-Suiza in 1914 and was the most commonly used engine in the aircraft of the Entente Powers during the First World War. The original Hispano-Suiza 8A was rated at 140 hp (102 kW) and the later Hispano-Suiza 8F reached 300 hp (220 kW).

HS-8 engines and variants produced by Hispano-Suiza and other companies under licence were built in twenty-one factories in Spain, France, Britain, Italy, and the U.S.[1] Derivatives of the engine were also used abroad to power numerous aircraft types and the engine can be considered as the ancestor of another successful engine by the same designer, the Hispano-Suiza HS-12Y (and Soviet Klimov V12 derivative aero-engines) which served in World War II.

The Hispano-Suiza 12Y was an aircraft engine produced by Hispano-Suiza for the French Air Force in the pre-WWII period. The 12Y became the primary 1,000 hp (750 kW) class engine and was used in a number of famous aircraft, including the Morane-Saulnier M.S.406 and Dewoitine D.520. Its design was based on the earlier and somewhat smaller, 12X. A further development was underway, the 12Z, but ended due to the German occupation of France.

The 12Y was also produced under Hispano-Suiza licence in the Soviet Union as the Klimov M-100. This design later spawned the highly successful Klimov VK-105 series that powered the Yakovlev and Lavochkin fighters as well as the Petlyakov Pe-2 bomber. Licensed production of the early models was also undertaken in Czechoslovakia as the Avia HS 12Ydrs.



When World War I began, the production lines of the Barcelona based Hispano-Suiza automobile and engine company were switched to the production of war materiel. Chief engineer Marc Birkigt led work on an aircraft engine based on his successful V8 automobile engine.[2] The resulting engine, called the Hispano-Suiza 8A (or HS-8A), made its first appearance in February 1915.

The first 8A kept the standard configuration of Birkigt's existing design: eight cylinders in 90° Vee configuration, a displacement of 11.76 litres (717.8 cu in) and a power output of 140 hp at 1,900 rpm. In spite of the similarities with the original design, the engine had been substantially refined. The crankshaft was machined from a solid piece of steel. The cylinders were cast aluminium with steel liners. The SOHC cylinder heads were also made of aluminium, using a rotary driveshaft (tower gear) coming up from the crankcase along the rear end of each cylinder bank, with the final drive for each cylinder bank's camshaft accommodated within a semicircular bulge at the rear end of each valve cover. Aluminium parts were coated in vitreous enamel to reduce leakage. All parts subject to wear, and those critical for engine ignition were duplicated: spark plugs for dual ignition reliability, valve springs, magnetos, etc.

Engine reliability and power to weight ratios were major problems in early aviation. The engine and its accessories weighed 185 kg (408 lb), making it 40% lighter than a rotary engine of equivalent power. The new engine was presented to the French Ministry of War in February 1915, and tested for 15 hours at full power. This was standard procedure for a new engine design to be admitted into military service. However, because of lobbying by French engine manufacturers, the Spanish made engine was ordered to undergo a bench test that no French made engine had yet passed: a 50-hour run at full speed. The HS-8A was therefore sent back to Chalais-Meudon on July 21, 1915 and tested for 50 hours, succeeding against all expectations. The design also promised far more development potential than rotary engines which, in spite of being the most common type then in use for aircraft, were getting close to the limits of their potential. Rotary engines of increased power generally had increased weight, which in turn increased the already serious gyroscopic torque generated by the engine's rotation. A further increase in torque was considered unacceptable, and the power to weight ratio of the new rotary engines under development did not appeal to aircraft designers.

French officials ordered production of the HS-8A to be started as soon as possible and issued a requirement for a new single-seat high-performance fighter aircraft using the new engine. The SPAD VII was the result of this requirement and would allow the Allies to regain air superiority over the Germans.



The 12Y was a fairly traditional in construction, a 36-litre water-cooled V-12 with the two cast aluminium cylinder banks set at 60 degrees to each other. The cylinder heads were not removable, instead the entire block could be quickly removed from the engine. This made it somewhat famous for being leak-proof, a design feature that was considered by other designers and almost became a part of the Rolls-Royce Merlin. The major design change from the earlier 12X was to use a master-articulated connecting rod system, instead of the fork-and-blade type. A single overhead camshaft (SOHC) drove the valves, which were filled with liquid sodium for cooling. Only a single intake and exhaust valve were used, unlike most designs of the era which had moved to three or four valves per cylinder. A single-stage, single-speed supercharger was standard, although the art of designing a useful intake was not as well developed as in other countries, and high altitude performance was always lacking.

The first 12Y test articles were constructed in 1932, and almost immediately the entire French aviation industry started designing around it. At the time the engine developed only 760 hp (570 kW), but it was clear it had potential to the 1,000 hp (750 kW) class. An early modification led to the Hispano-Suiza 12Ycrs which used a hollow propeller shaft to allow a 20 mm cannon to fire through the propeller spinner (a combination known as a moteur-canon). All later designs shared this feature. The 12Ydrs was the next major series, with a basic rating of 836 hp (623 kW) at sea level with a compression ratio of 5.8:1.

The Armée de l'Air changed their nomenclature, so the next version was the Hispano-Suiza 12Y-21, which increased the compression ratio to 7:1, when running on 100 octane gasoline. This boosted power to 867 hp (647 kW). In 1936 the connecting rod design was changed slightly to create the 12Y-31, but the lower 5.8:1 compression ratio was retained and the power was increased only slightly over the drs model to 850 hp (630 kW). Nevertheless this became one of the most used engine designs of the pre-war era, used in almost all French fighter designs and prototypes.

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