Le Rhône 9J Rotary Aircraft Engine
The Le Rhône was a popular rotary aircraft engine produced in France by Société des Moteurs Le Rhône around 1916. It powered a number of military aircraft of the First World War.
Although not powerful, the largest wartime version gave 130 horsepower (97 kW), they were dependable rotary engines. The Le Rhône 9 was a development from the Le Rhône 7, a seven–cylinder design.
The Le Rhône had a conventional induction system and an unusual method of connecting the link rods to the master rod. In the Le Rhône, the fuel–air mixture went first to an annular chamber at the back of the crankcase and thence, via polished copper pipes, to conventional intake ports and cam–operated valves in the cylinder heads. 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 (82 kW) 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 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. Its master rod was a split–type to allow assembly of the connecting rods, and had three concentric grooves to take slipper bearings from all the other cylinders. The remaining rods carried bronze shoes, shaped to fit in the grooves, at their inner ends. Counting the master rod as no. 1, the shoes of nos. 2, 5, and 8 rode in the outer groove, those of 3, 6, and 9 in the middle groove, and 4 and 7 in the innermost one. Although complex, Le Rhônes worked very well.
The Le Rhônes employed an unusual method of valve actuation. A single rocker arm, pivoted near its center, was made to operate both the exhaust valve and the intake valve. Pulled down, it opened the intake valve; pushed up, it opened the exhaust. To do this, the rocker had to be actuated by a push–pull rod instead of by the usual pushrod. This, in turn, meant that the cam followers had to have a positive action, which was accomplished by a system of links and levers. This system works well enough – some makers used it up to the late 'twenties – but its use makes overlap of valve openings impossible. In an engine designed for high– power and speed, the intake valve begins to open before the exhaust valve is quite closed, but on the Le Rhône, the rocker arm must clear the exhaust valve before it can contact that of the intake. While this put a limit on power output, most Le Rhône models produced all the power that their structural strength and cooling arrangements could cope with.