Le Rhône 9
Le Rhône was the name given to a series of popular rotary aircraft engines produced in France by Société des Moteurs Le Rhône and the successor company of Gnome et Rhône. They powered a number of military aircraft types of the First World War. Le Rhône engines were also produced under license worldwide.
The copper induction tubes had their crankcase ends located in different places on the 80 and 110 horsepower (60 and 82 kW) versions – the 80 hp versions had them entering the crankcase in a location forward of the vertical centerline of each cylinder, while the 110 hp version had them located behind the cylinder's centerline. This resulted in the 80 hp version's intake plumbing being "fully visible" from the front, while the 110 hp version had the lower ends of its intake tubes seemingly "hidden" behind the cylinders.
A complicated slipper bearing system was used in the Le Rhône engine. The master rod was of a split-type, which permitted assembly of the connecting rods. It also employed three concentric grooves, designed to accept slipper bearings from the other cylinders. The other connecting rods used inner-end bronze shoes, which were shaped to fit in the grooves. The master rod was numbered as number one and the shoes of numbers. two, five and eight rode in the outer groove, the shoes of three, six and nine in the middle groove and four and seven in the inner groove. Although this system was complex, the Le Rhône engines worked very well.
The Le Rhône engines used an unconventional valve actuation system, with a single centrally-pivoting rocker arm moving the exhaust valve and the intake valve. When the arm moved down it opened the intake valve and when it moved up it opened the exhaust value. To make this system work a two-way push-pull rod was fitted, instead of the more conventional one-way pushrod. This feature required the cam followers to incorporate a positive action, a function designed in by using a combination of links and levers. This design functioned but it did prevent the incorporation of valve overlap which limits power output. Due to the structural and cooling limitations of the overall engine design the Le Rhône engines produced as much power as they were capable of, regardless.
As well as production by Société des Moteurs Gnome et Rhône, which had bought out Société des Moteurs Le Rhône in 1914, the Le Rhône was produced in Germany (by Motorenfabrik Oberursel), Austria, the United Kingdom (by Daimler), Russian Empire and Sweden.
Le Rhône 80 hp (60 kW) engines were made under license in the United States by Union Switch and Signal of Pennsylvania, and the 110 hp (82 kW) Oberursel UR.II rotary engine used by Germany in World War I, in such famous fighters such as the Fokker Dr.I triplane, was a close copy of the 110 hp 9J version.
First run in 1916, the Le Rhône 9C is a nine-cylinder rotary aircraft engine produced in France by Gnome et Rhône. Also known as the Le Rhône 80 hp in a reference to its nominal power rating, the engine was fitted to a number of military aircraft types of the First World War. Le Rhône 9C engines were also produced under license in Great Britain by several companies, and in the United States. British production amounted to 1,088 examples.
In common with other Le Rhône series engines, the 9C featured highly visible telescopic copper induction pipes and used a single push-pull rod to operate its two overhead valves.
Oberursel produced the 110 hp model, supposedly without authorization in Germany. The Oberursel Ur.II was a straight copy of the Le Rhône, but the Le Rhône was preferred over the Oberursel due to the materials used in the French product. However, by July 1918 there was a shortage in Germany of castor oil, a plant-derived lubricant that the rotaries required as it could not be easily dissolved into the fuel, and because it possessed lubrication qualities superior to mineral oils of the day. A new Voltol-based lubricant, derived from mineral oil, was substituted and was blamed for engine failures on rotary-engined German fighters such as the Fokker E.V which used the Oberursel Ur.II. It has been suggested that without proper lubricants, the Le Rhône rotary would have been equally failure-prone.
A few examples of the 9C engine remain airworthy both in Europe and North America, one powering a vintage Sopwith Pup biplane in England, and a small number of others having powered reproduction WW I-era aircraft at Old Rhinebeck Aerodrome.
Le Rhône Type 9C
Le Rhône Type 9J
Le Rhône Type 9Ja
Le Rhône Type 9Jb
Le Rhône Type 9Jby
Le Rhône Type 9R
Le Rhône 9Z
Le Rhône K
Le Rhône L
Le Rhône M
Le Rhône P
Le Rhône R
Le Rhône 9C