The Siemens-Halske Sh.III was an 11-cylinder, air-cooled counter

rotary engine The rotary engine is an early type of internal combustion engine, usually designed with an odd number of cylinders per row in a radial configuration. The engine's crankshaft remained stationary in operation, while the entire crankcase and its ...

developed in Germany during

World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...

. The engine was a development of the earlier 9-cylinder Siemens-Halske Sh.I.

Design

The Siemens-Halske Sh.III was an 11-cylinder counter rotary engine. The Sh.III's

propeller A propeller (often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon a working flu ...

and

cylinders A cylinder () has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base. A cylinder may also be defined as an infinite ...

were connected, rotating anti-clockwise when viewed from the front of the aircraft (clockwise when viewed from the pilot's seat) while the

crankshaft A crankshaft is a mechanical component used in a reciprocating engine, piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating Shaft (mechanical engineering), shaft containing one or more crankpins, ...

rotated clockwise. The crankshaft was driven at 900 rpm via a set of

bevel gears Bevel gears are gears where the axes of the two shafts intersect and the tooth-bearing faces of the gears themselves are conically shaped. Bevel gears are most often mounted on shafts that are 90 degrees apart, but can be designed to work at oth ...

, located at the back of the engine, with a 2:1 ratio. The cylinders and propeller would have rotated at a speed of 1800 rpm anti-clockwise had the crankshaft been fixed. With the crankshaft rotating at 900 rpm clockwise the net propeller rotational speed was reduced to 900 rpm. The counter rotary design allowed the engine to achieve the benefits of a high-power density from a high rotational speed while the propeller operated at a slower speed optimised for its design. By the end of WW1, operating the propeller at a slower speed than the engine had become normal practice for inline and V block engines but had proved difficult to accomplish on rotary engines. Additional benefits of the counter rotary design were lower aerodynamic losses and reduced

gyroscopic A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rot ...

forces as the net cylinder rotational speed was reduced when compared to a conventional rotary of similar power output. Unlike most rotary engines the Sh.III had a

throttle A throttle is a mechanism by which fluid flow is managed by construction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases (by the use of a throttle), but usually decreased. The term ''throttle'' ha ...

which could reduce engine speed to 350 rpm. The Sh.III was initially designed with a power output of 160 hp. A later variant, the Sh.IIIa, had a power output of 200 hp with some examples developing as much as 240 hp. In operation the Sh.III suffered from poor reliability. The engine tended to overheat as the relatively slow rotation of the cylinders limited cooling air flow. Additionally, seizures of the engine were caused by poor lubrication as the Germans did not have access to

castor oil Castor oil is a vegetable oil pressed from castor beans, the seeds of the plant ''Ricinus communis''. The seeds are 40 to 60 percent oil. It is a colourless or pale yellow liquid with a distinct taste and odor. Its boiling point is and its den ...

which was one of the few oils that could retain its properties after being mixed with

gasoline Gasoline ( North American English) or petrol ( Commonwealth English) is a petrochemical product characterized as a transparent, yellowish, and flammable liquid normally used as a fuel for spark-ignited internal combustion engines. When for ...

Aircraft

* Albatros H.1 * Albatros D.XI * Pfalz D.VII * Pfalz D.VIII *

LFG Roland D.IX The LFG Roland D.IX was a World War I German single seat fighter aircraft, a biplane powered by one of a new generation of powerful rotary engines. Three slightly different prototypes were built but there was no series production. Design and d ...

* LFG Roland D.XVI * Siemens-Schuckert D.II * Siemens-Schuckert D.III * Siemens-Schuckert D.IV * Siemens-Schuckert D.VI

Specifications

References

External links

Idflieg.com's Siemens Sh.III engine photos, by Andi Szekeres

Siemens Sh.III displayed at Museo Storico dei Motori e dei Meccanismi, University of Palermo (in Italian)

Front view
an
rear view
CAD-based animations of Sh.III internal engine components
YouTube 30 May 2020 video of Mikael Carlson's authentic Pfalz D VIII biplane reproduction on its maiden flight, with restored and flightworthy Sh III engine
{{Siemens-Halske aeroengines Siemens-Halske aircraft engines Air-cooled aircraft piston engines 1910s aircraft piston engines Rotary aircraft piston engines

Design

Aircraft

Specifications

See also

References

Further reading

External links