Renault 90 hp

The Renault 90 hp, or 12A, was the world’s first V12 aircraft engine. The engine was developed in 1911 from Renault’s earlier V8 engines and used the same air-cooled design.

Design and development
By 1911, V12 engines had already been built for boats and automobiles. As with other V12s and straight-six engines, Renault's design had the inherent advantage of primary and secondary engine balance. The 60 deg angle between two rows of 6-cylinders resulted in even firing intervals for smooth power delivery and gave the engine a narrower profile than Renault's 90 deg V8s thereby reducing aerodynamic drag.

The 90 hp model was the first Renault aero engine with articulated master-and-slave connecting rods allowing corresponding cylinders in each row to be arranged directly opposite each other which improved dynamic balance. This arrangement also made the engine crankcase shorter than would have been the case if the "side by side" connecting rods (found on the earlier V8 Renault 70 hp) had been used.

As with Renault's V8 air-cooled models, engines intended for pusher aircraft were fitted with a centrifugal blower while those engines intended for tractor aircraft used a cowl mounted air scoop to feed cooling air over the large finned cast iron cylinders.

Another feature inherited from earlier Renault air-cooled V8 engines was the form of reduction gearing where the propeller was fixed to the end of the camshaft allowing it to turn at half engine speed. This method of gearing allowed the engine and propeller to be run close to their optimum speeds without the additional weight penalty of a gearbox while the reverse rotation of the crankshaft and propeller reduced gyroscopic forces improving aircraft handling.



The Renault 90 hp was first exhibited at the 1911 Salon de l’Aéronautique at the Grand Palais in Paris. The engine was offered at a price of 17,000 Francs (the 70 hp V8 model was priced at 12,500 Francs). By mid 1912 the engine had been fitted to aircraft manufactured by Astra, Farman and Breguet.

The 90 hp engine was quickly followed by a 100 hp model in the summer of 1912.

Applications

 * Astra C
 * Breguet Type IV
 * Farman MF.7