Siemens-Halske Sh.III

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Siemens-Halske's Sh.III was an 11-cylinder, air-cooled rotary engine developed in Germany during World War I, a larger and more powerful version of the Sh.I. It shared with its predecessor the unusual design feature of having its internal workings (crankshaft, conrods, etc) rotating in a clockwise direction as seen from "nose-on", within the engine, and the crankcase and propeller (still fastened to the crankcase in the usual manner for other rotary engine designs) rotating in the "accepted" counterclockwise direction. Also unusual for a rotary engine was the inclusion of a true throttle control. Power was rated at 120 kW (160 hp).

The advantages of the engine were increased propeller efficiency through the reduction gearing effect of having the engine effectively running at 1,800 rpm for only 900 rpm of the airscrew, and excellent high-altitude performance due to the high compression ratio achieved. An added bonus was the counter-rotating masses tended to cancel out the gyroscopic forces of the engine. A setup of bevel gears housed within the rear end of the crankcase allowed it, and the interior parts of the engine, to spin in opposing directions.

The main disadvantage was that the lower rpm of the cylinders reduced the efficiency of the air cooling, a real problem in a large engine such as this. The cooling problem was exacerbated by the lack of castor oil late in the war. The use of "Voltol," a substitute derived from mineral oil, meant that the Sh.III engines had a life expectancy of only seven to ten hours before pistons began to seize.

pecifications

* Bore: 124 mm (4.9 in)
* Stroke: 140 mm (5.5 in)
* Displacement: 23.5 L (1,434 cu in)
* Power: 120 kW (160 hp) (Later variants produced 200 hp)
* Dry Weight: 430 lb (195 kg)

Applications

* Albatros D.XI
* Pfalz D.VIII
* Roland D.XVI
* Siemens-Schuckert D.II
* Siemens-Schuckert D.III
* Siemens-Schuckert D.IV

External links

* [http://www.idflieg.com/siemens_shiii.htm Idflieg.com's Siemens Sh.III engine photos, by Andi Szekeres]

References

* Gray, Peter L. (1966) "Profile Publication No.86: Siemens-Schuckert D.III & D.IV." Windsor: Profile Publications.

* Gray, Peter & Owen Thetford (1962) "German Aircraft of the First World War." London: Putnam.