Le Rhone rotary aero engine

Made in France, Europe, 1918.

This French aero engine was developed from the Gnome rotary engine, which was designed in Germany in 1905. It was one of thousands of engines, of a wide range of designs, manufactured for aircraft that fought on both sides in World War 1. The Le Rhone was one of the most successful engines used in that conflict, the first war contested in the air as well as on the ground.

The design of the rotary engine, with its fixed crankshaft and moving cylinder block being the reverse of the standard type,...

Summary

B2534
This Le Rhone rotary engine has nine finned cylinders arranged radially around its crankcase, to which the propeller is attached. The 'crankshaft' is hollow and designed to be fixed to be body of the aircraft, while the cylinders and propeller rotate. Cylinder bore is 112 mm, piston stroke is 170 mm, compression ratio is 5:1 and power is 90 kilowatts (120 horsepower) at 1200 rpm.

The engine operates on the four stroke cycle, and air is first drawn through the carburettor thence through the hollow crankshaft to an annular chamber behind the crankcase and finally via copper pipes to the engine cylinders. This tortuous passage severely limits engine performance, but this is offset by the low engine mass of the rotary design.

A block-tube carburettor with a simple fuel jet is attached to the rear end of the crankshaft. Since the crankcase volume in a rotary engine does not vary as the cylinders rotate, there is no pumping action to force a fresh mixture into the cylinders. Instead, the cylinder is filled due to the suction generated inside it as the piston travels down after the exhaust stroke. Because the only forces moving the fuel-air mixture through the engine are centrifugal force in the transfer passages and suction generated in the cylinders, rotary engines require a pressurised fuel system to spray petrol into the carburettor.

A single cam-actuated push-pull rod and rocker arm, pivoted near its centre, operates both the intake and exhaust valves. When pulled down it opens the intake valve and when pushed up it opens the exhaust valve. To achieve this action two cams are used, and the positive action of the cam followers is accomplished through levers. This system suffers from the disadvantage that the intake valve cannot open before the exhaust valve has closed, limiting the speed at which the engine can run efficiently. The settings for valve events are: intake opens 18 degrees after top dead centre (TDC) and closes 35 degrees after bottom dead centre (BDC); exhaust opens 55 degrees before BDC and closes 5 degrees after TDC. Ignition occurs 26 degrees before TDC.

A single magneto, driven at 2.25 times engine speed, fires the spark plugs mounted on the side of each cylinder. Ignition occurs in alternate cylinders during each revolution of the engine. The engine was started manually by turning the propeller. It normally ran at full speed, which could only be varied by intermittently cutting the ignition via a 'blip switch' on the control column.

All the connecting rods couple directly with the crankshaft. A split doughnut-shaped ring, which surrounds the crankpin, is provided with three concentric grooves. Into these grooves are fitted slippers of connecting rods 1,4 and 7 in the inner groove, 3,6 and 9 in the middle groove and 2,5 and 8 in the outer groove. This design allows all pistons to experience identical dynamics during the engine cycle.

It is impossible to fit an exhaust system to spinning cylinders, so the exhaust valve on each cylinder opens directly into free air inside the cowling. Because there is relatively little pressure in the cylinder when the exhaust valve opens, the engine is relatively quiet.

Lubrication is a total loss system. Castor oil is injected into the carburettor by an engine-driven pump, and the unburnt residue forms part of the exhaust. The fuel-oil-air mixture flows through the crankshaft and into the crankcase, where it lubricates the bearings before being transferred into the cylinders.

Dimensions

1075 mm
1075 mm
1000 mm
250 kg

Production

The engine was manufactured by Societe Des Moteurs Le Rhone, France, in 1918.

At the 1889 Paris Exposition, Felix Millet displayed a motorcycle driven by a five-cylinder rotary engine mounted in the rear wheel. In the same year, as part of his program for developing powered flight, Lawrence Hargrave designed a three-cylinder rotary engine powered by compressed air. Rotary engines were also trialled in automobiles.

The Gnome rotary gas engine was developed in 1905 by Motorenfabrik Oberursel in Germany. In 1912 Louis Verdet designed a 7-cylinder version, the 7C, which developed 70 horsepower, and he formed Societe des Moteurs Le Rhone later that year. This engine was followed by the larger Le Rhone 9C, a 9-cylinder design delivering 80 horsepower (60 kW).

Some 25,000 engines were manufactured by Le Rhone during World War 1. Another 75,000 were made, under licence, in the USA, England and Sweden. Nine hundred and fifty three Type J engines were manufactured by W H Allen & Son Co Ltd of Bedford and used in a number of British aircraft including those produced by Armstrong Whitworth, Avro, Bristol, Sopwith and Vickers.

Le Rhone was nationalised as a part of Snecma in 1949.
1918

Source

Presented by the University of Sydney, 1983
16 August, 1983

Cite this Object

Le Rhone rotary aero engine 2017, Museum of Applied Arts & Sciences, accessed 22 September 2017, <https://ma.as/213281>
{{cite web |url=https://ma.as/213281 |title=Le Rhone rotary aero engine |author=Museum of Applied Arts & Sciences |access-date=22 September 2017 |publisher=Museum of Applied Arts & Sciences, Australia}}
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