The Hispano-Suiza 18R was an eighteen cylinder high performance water-cooled piston engine, in an 80° W or broad arrow layout, for use in racing aircraft, built in France during the latter half of the 1920s.
Design and development
After failing to enter the Schneider Trophy seaplane race for several years, the French Ministère de l’Air decided to enter the 1929 competition. Two companies were tasked with designing and building floatplane racers to compete with the entries from Italy and Great Britain, resulting in the Nieuport-Delage NiD-450 and Bernard H.V.120, both of which were powered by the specially designed Hispano-Suiza 18R engines. To power the racers Hispano-Suiza married three six cylinder blocks from the Hispano-Suiza 12Nb to a common crankshaft / crankcase, set at 80° to each other. Retaining the bore and stroke of the 12Nb, the 18R had the compression ratio increased from 6.25:1 to 10:1 with a total displacement of 54.075L. Each cylinder aspirated through two valves operated by single overhead cam-shafts with ignition from two spark plugs set on opposite sides of the combustion chamber supplied by magnetos at the rear of the engine. Fuel metering was carried out by nine carburetors each supplying two cylinders. Construction of the 18R was largely of Elektronmagnesium alloy for body components with high strength steels for highly loaded parts such as the crankshaft. In common with many multiple bank and radial engines the pistons were connected to the crankshaft via master and slaveconnecting rods; the central vertical bank was served by the master rod which housed the big-end bearing with connecting rods articulating from this to the other two banks. The 18R was available with or without a Farman reduction gear. Development issues delayed production of the engine, with the first geared drive engine delivered to Nieuport-Delage in October 1929, a month after the 1929 Schneider Trophy race. Despite the effort put into its development the 18R proved to be unreliable and unable to achieve the expected power output. The poor performance of the 18R prompted the development of the 18S, a de-rated version intended for commercial use. Reducing the compression ratio to 6.2:1 at a maximum rpm of 2,000 and replacing the Elektron with aluminium alloy, the 18S was available with or without the Farman reduction gear, but was not a success, only powering the Ford 14A in the pylon mounted central nacelle.
Operational history
The 18R and 18S did not have successful careers, only powering four aircraft types in very small production numbers, proving to be totally outclassed by contemporary racing engines, such as the Rolls-Royce R which powered the Supermarine S.6 family of floatplane racers.
Variants
Data from: ;18R: The original racing engine with 10:1 compression ratio, available with or without the Farman reduction gearing. ;18Sb: The de-rated. 6.2:1 compression ratio, commercial version without the Farman reduction gearing. ;18Sbr: The 18Sb with the Farman reduction gearing.
