BMW IIIa
The BMW IIIa was a liquid-cooled six-cylinder in-line engine with 19.1 liters, which was built as an aircraft engine from 1917 by the German manufacturer BMW. As a further development with larger displacement ( 22.9 liters ) followed in 1918 the more powerful BMW IV
The name Junkers L 2, the motor was manufactured under license as from 1924 by the Junkers engine GmbH.
History
Max Friz came in January 1917 to the Rapp Motor works and began on 20 May with the construction of the six-cylinder engine überbemessenen Rapp Rp III and the V- 12 engine Rapp Rp IVa. Rapp resigned in July out of his company, which changed its name from now on as Bavarian Motor Works. First test runs took place in September 1917. The development first had to be adjusted because BMW only should produce engines under license. Franz Josef Popp, however, managed to convince the Idflieg of the motor new development in October 1917 and received an order for production of 600 engines. Series production began in February 1918 with a target production rate of 150 engines per month. In April 1918, a decrease of 137 kW continuous power was (186 hp ) is reached at 1360 min -1 and a take-off power of 166 kW ( 225 hp) at 1400 min -1. A month later, the first Fokker D.VII were equipped with these engines and convinced at first. Opel was in April 1918 licensees and produced 140 engines a month from June 1918. By war's end about 700 engines were built.
The BMW IIIa brought at high altitude performance is significantly better than any other 1918 used German aircraft engines.
Construction
It is a water-cooled six-cylinder in-line engine. The crankcase of an aluminum alloy is divided horizontally. The crankshaft is made of cast iron, as the crankshaft bearings are seven plain bearings are used. The cast iron cylinders are arranged individually on the crankcase and have welded coats made of sheet steel for water cooling. The pistons have three piston rings. The overhead camshaft ( OHC valve timing ) is driven by a vertical shaft. The hanging valves are actuated by roller rocker arms.
For the mixture formation, a single BMW ensures "ups " carburetor. The Doppelzündanlage ( two spark plugs per cylinder ) consists of two Bosch magnetos. The firing order is: 1-5-3-6-2-4. The Pressure lubrication is maintained with a piston oil pump. A cooling water pump to circulate the coolant.
Use
The BMW IIIa was used inter alia for the following aircraft as a drive:
- Aero A.18
- Dornier Delphin I
- Fokker D.VII
- Junkers A 20
- Junkers F 13
- Palatinate D.XV
- SWS C-1
Even with prototypes and record flights he came often used.
On December 30, 1921 Flight duration record with a BMW IIIa was achieved in the United States. According to the Fédération Aéronautique Internationale flown to a Junkers -Larsen 6 a standing world record of 26 hours 19 minutes and 35 seconds. BMW itself was 1922 in advertisements, which was flown over the record Long - Iceland (as well as American newspapers and publications confirm: Roosevelt Field, Mineola, Long Iceland, New York). Takeoff was on December 29, 1921 8:58:15 and on December 30, 1921 at 11:17:50 you had to land due to a faulty oil or lubricant system. The "Aero Club of America " awarded in January 1922, two pilots Eddie Stinson and Lloyd Bertaud a medal of honor for this American and world record for continuous flight.