BMW IIIa

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BMW
BMW IIIa

BMW IIIa
BMW IIIa
Production period: 1918
Manufacturer: BMW
Working principle: Otto
Motor design: line
Displacement: 19100 cm 3
Mixture preparation: Carburetor
Engine charging: no
Power: 140 kW
Dimensions: 287 kg
Previous model: none
Successor: BMW IV

The BMW IIIa was a liquid-cooled six - cylinder in - line engine with a displacement of 19.1 liters , which was built as an aircraft engine by the German manufacturer BMW from 1917 . The more powerful BMW IV followed in 1918 as a further development with increased displacement (22.9 l) .

With the name Junkers L 2 , the engine was manufactured under license from Junkers Motorenbau GmbH from 1924 .

history

Max Friz came to Rapp-Motorenwerke in January 1917 and began on May 20th with the construction of the oversized six-cylinder engine Rapp Rp III and the V-12 engine Rapp Rp IVa. In July, Rapp left his company, which from then on operated as Bayerische Motorenwerke . The first test bench runs took place in September 1917. The development had to be stopped for the time being, since BMW was only supposed to manufacture engines under license . Franz Josef Popp managed, however, to convince the Air Force Inspectorate (IdFlieg) that the new engine was being developed. In October 1917 he received an order for the 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 in duration of power output of 140 kW (185 hp) at 1360 was  min -1 and a start capacity of 166 kW (225 hp) at 1400 min -1 achieved. A month later, the first Fokker D.VIIs were equipped with these engines and they were convincing right away. Opel became a licensee in April 1918 and produced 140 engines per month from June 1918. Around 700 engines had been built by the end of the war.

The BMW IIIa performed much better at high altitudes than any other German aircraft engine used in 1918.

construction

The BMW IIIa is a water-cooled six-cylinder in-line engine.

construction

The crankcase of an aluminum alloy is split horizontally. The seven times in bearings mounted crankshaft consists of steel . A thrust ball bearing absorbs the thrust of the directly driven propeller. The steel cylinders are individually attached to the crankcase with clamping claws and have welded sheet steel jackets for water cooling. The aluminum pistons each have three piston rings . The overhead camshaft ( OHC valve control ) is driven by a vertical shaft and actuates the overhead valves via roller rocker arms .

Carburetor

A single BMW “height” carburetor takes care of the mixture formation .

“Since the Bavaria aircraft engine is built as an altitude engine due to its special construction characteristics, it also has a special carburetor, which enables the cylinders to receive the most favorable mixture charge corresponding to the respective altitude at every altitude, up to the highest achievable. [...] While the carburettor works at great heights with full mixture chamber openings, it must be throttled accordingly at lower heights and on the ground, without, however, adversely affecting the operational safety, performance and economy of the engine. With the BMW high-altitude carburetor, this is achieved by dividing it into three mixing chambers, each with a gasoline nozzle, with two groups of throttle valves that can be operated independently of one another. "

- Bayerische Motoren Werke A.-G. Munich : Operating Instructions

Ancillary units

The Doppelzündanlage (two spark plugs per cylinder) consists of two Bosch - magnetos . The firing order is: 1–5–3–6–2–4. The pressure circulation lubrication is maintained with a piston oil pump. A centrifugal pump circulates the coolant.

use

The BMW IIIa was u. a. used as propulsion in the following aircraft:

It was also often used on prototypes and record flights.

On December 30, 1921, an endurance flight record was set in the USA with a BMW IIIa . According to the Fédération Aéronautique Internationale , a Junkers-Larsen 6 (US license for the F 13) set a permanent world record with 26 hours, 19 minutes and 35 seconds. BMW itself stated in advertisements in 1922 that the record was flown over Long Island (as also confirmed by American newspapers and publications: Roosevelt Field, Mineola, Long Island, New York). Takeoff was 8:58:15 a.m. on December 29, 1921, and landed on December 30, 1921 at 11:17:50 a.m. due to a faulty oil or lubricant system. In January 1922, the “Aero Club of America” awarded the two pilots Eddie Stinson and Lloyd Bertaud a medal of honor for this American and world record in endurance flight.

Technical specifications

Parameters Data of the BMW IIIa
design type Liquid-cooled six - cylinder in - line engine ,
vertical ( crankshaft below), without supercharging
Valve control an overhead camshaft ( OHC ), driven
by a vertical shaft,
two valves per cylinder
Displacement ( bore × stroke ) 19.1 liters (150 mm × 180 mm)
Compression ratio 6.3
Dry matter 287 kg
Continuous (travel) performance 185 hp (140 kW) at 1,300 min -1

See also

literature

  • Kyrill von Gersdorff, Kurt Grasmann: aircraft engines and jet engines. Development history of German aviation engines from the beginnings to the European community developments. Bernard & Graefe Verlag, Munich 1981, ISBN 3-7637-5272-2 .

Web links

Commons : BMW IIIa  - collection of images, videos and audio files

Individual evidence

  1. ↑ Altitude carburetor for the BMW IIIa aircraft engine. Functional scheme. BMW AG, 1917, accessed on June 22, 2014 (document in the BMW Group Archive).
  2. ↑ The BMW 6 Cyl. 185 hp. Engine. In: Aviation and Aircraft Journal. Aviation Week, March 21, 1921, pp. 370–371 , accessed on May 13, 2019 .
  3. ↑ Description and operating instructions for the 185 HP Bayern aircraft engine type BMW IIIa. In: BMW history. BMW AG, 1918, accessed on May 13, 2019 (manual with pictures, 69 pages).
  4. ↑ FAI Record ID # 9455. Fédération Aéronautique Internationale, December 30, 1921, accessed June 29, 2014 .
  5. ↑ World Record Non - Stop (1922), Mineola (USA), British Pathé - YouTube video channel, IdNr .: g9sDnVsVVSc, accessed on October 25, 2014 (English).
  6. ↑ Official world records as of December 31, 1921, L'Année aéronautique 1921–1922 (French) - Flugfahrt-Jahresschrift, L. Hirschauer, Ch. Dollfus, publisher : Dunod (Paris), p. 45, signature: ark: / 12148 / cb32694945z / date, Bibliothèque nationale de France, accessed October 28, 2014.
  7. ↑ World record achieved in endurance flight with a Bayern engine. In: Allgemeine Automobil-Zeitung. Austrian National Library, July 9, 1922, accessed on June 29, 2014 (advertisement).