Junkers L1

{{Infobox aircraft begin

| name=Junkers L1

| image=File:Junkers T 19 mit Junkers L1 Motor (Ans 05338-01-222-AL-FL).jpg

| caption=The L1 engine used on the Junkers T 19

}}{{Infobox aircraft engine

|type=Four-stroke petrol six-cylinder air-cooled inline

|manufacturer=Junkers Motorenbau GmbH (Jumo)

|designer=

|national origin=Germany

|first run=1921

|major applications=

|produced=Small production run started in 1925

|number built=

|program cost=

|unit cost=

|developed from=

|variants with their own articles=

}}

The Junkers L1 was the first engine manufactured by Junkers to fly. It was an air-cooled, upright six-cylinder inline four-stroke petrol engine only produced in small numbers and largely used for research, but led to the successful L5 and its V-12 development, the L55.

Design and development

Hugo Junkers' early engineering experience was with stationary opposed-piston two-stroke diesel engines for industrial applications and this arrangement was eventually adapted for aircraft use. Nonetheless, his company's first aero engine was a petrol-fuelled four-stroke, the six-cylinder inline air-cooled L1. L was Junkers' notation for petrol engines from the L1 to the L10, which became the Jumo 210 in 1931. It first ran in 1921 and was the subject of much static testing, but the intention was always to produce a flight engine. The first aircraft to test fly the L1 was the Junkers T 19; this aircraft first flew in 1922, but the date of its first flight with the L1 is uncertain.

Notable features were the four large valves per cylinder, two inlet and two exhaust; the ball race main bearings; and the double ignition system, with twin magnetos and two sparking plugs per cylinder.

Operational history

The L1 was largely an experimental engine, but a small production line was set up in 1925. Reliability was not high, however and only a few aircraft, themselves built only in small numbers, used the L1 and its variants. The large diameter, circular blower fitted to the L1a resulted in a flat fronted, circular cross section cowling, particularly noticeable on the Junkers T 19 and 26.

Variants

L1 Original version.
L1a Larger bore diameter and a large circular blower, gear driven, mounted at the front of the engine to enhance high altitude power.
L1b

Applications

Specifications (L1a)

{{pistonspecs|

|ref=Kay (2004) p. 263

|type=6-cylinder air-cooled upright 4-stroke

|bore={{convert|100|mm|in|abbr=on}}

|stroke={{convert|120|mm|in|abbr=on}}

|displacement=5.65 L (345 cu in)

|length={{convert|1.115|m|ftin|abbr=on}}

|diameter=

|width={{convert|700|mm|ftin|abbr=on}}

|height={{convert|790|mm|ftin|abbr=on}}

|weight={{convert|128|kg|lb|abbr=on}}

|valvetrain= two large inlet and two large exhaust valves per cylinder, operated by overhead camshaft

|supercharger=

|turbocharger=

|fuelsystem=

|fueltype= petrol

|oilsystem=

|coolingsystem= air-cooled; finned cylinder heads

|power=cruise {{convert|75|hp|kW|abbr=on}}; take-off {{convert|85|hp|kW|abbr=on}}

|specpower=

|compression=

|fuelcon= 26 kg/h (44 lb/hr)

|specfuelcon=

|oilcon=

|power/weight=

|designer=

|reduction_gear= none:direct drive

|general_other=

|components_other=Ignition system: twin magnetos and two sparking plugs per cylinder

|performance_other=

}}

{{aircontent

|see also=

|related=

|similar aircraft=

|lists=

}}

References

{{Reflist|refs=

Kay (2004), p. 223

Kay (2004), pp. 41, 54

Gunston (2006), p. 112}}

=Bibliography=

{{cite book |last1=Gunston |first1=Bill |title=World Encyclopedia of Aero Engines: From the Pioneers to the Present Day |date=2006 |publisher=Sutton |location=Stroud, UK |isbn=0-7509-4479-X |edition=5th}}
{{cite book |title= Junkers Aircraft & Engines 1913–1945|last=Kay|first=Antony| year=2004|publisher=Putnam Aeronautical Books |location=London |isbn=0-85177-985-9}}