Junkers L88
The Junkers L88 was Junkers' first geared V-12 engine, appearing c.1930 and based on a pair of 6-cylinder L8s. In 1932 a supercharger was added. It was used in the first pressurised aircraft, the Junkers Ju 49 and, for a while, in the large G 38 airliner and its Japanese built military version.
Design and development
In 1929 Junkers developed their successful Junkers L5 6-cylinder inline 4-stroke aircraft engine into the L8 by increasing its rotational speed and gearing down the output shaft. Just as the L55 V-12 was made by combining two L5s, the L88 combined two L8s into a 60° V-12. This had the same bore, stroke, camshaft operated twin pairs of valves per cylinder, watercooling etc. as the L5, like the L55 driving a common crankshaft in a revised crankcase. An exhaust driven supercharger was added after a year to maintain power at high altitude and this version was named the L88a.[1]
Operational history
Only a few L88 and L88a engines were built. The Ju 49 high altitude research aircraft initially (1932) flew with the L88 and later (1934) with the supercharged L88a.[2] The two G38s used a variety of engines including both the L88 and the L88a.[1] The heavy bomber variant of the G 38, built in Japan as the Mitsubishi Ki-20 was initially powered by L88as. These were replaced, as on the G 38s, by Jumo 504 diesel engines.[3]
Applications
- Junkers G 38, both L 88 and L 88a
- Junkers Ju 49, both L 88 and L 88a
- Mitsubishi Ki-20, L88a
Specifications
Data from Kay (2004) pp.266
General characteristics
- Type: upright V-12 water-cooled 4-stroke piston engine
- Bore: 160 mm (6.30 in)
- Stroke: 190 mm (7.48 in)
- Displacement: 45.8 L (2,795 cu in)
- Dry weight: 510 kg (1,125 lb)
Components
- Valvetrain: two inlet and two exhaust valves per cylinder, one overhead camshaft on each bank
- Supercharger: exhaust gas driven
- Fuel type: petrol
- Oil system: forced
- Cooling system: water-cooled
- Reduction gear: choice between 2.47:1 to 1.44:1
Performance
- Power output: cruise 675 hp (503 kW) at 1,870 rpm, take-off 788 hp (587 kW)
References
- ^ a b Kay, Antony (2004). Junkers Aircraft & engines 1913-1945. London: Putnam Aeronautical Books. p. 266. ISBN 0 85177 985 9.
- ^ Kay (2004) Ibid, p. 95
- ^ Kay (2004) Ibid, p. 88
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