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Napier Culverin

Water-Cooled Opposed Piston, In-line Diesel

Design E102  1934   Culverin

6-cylinder 4.3/4" bore x 8.1/4" stroke 720 bhp


Design E103 1934   Cutlass

6-cylinder 4.1/8" bore x 6.5/16" stroke 540 bhp

(never built)

Where to see:

    There are no surviving Culverin engines however one  example of the Junkers Jumo 204 is located at

    Wehrtechnische Sammlung, Koblenz, Germany


    There are many more examples of the Jumo 205 engine on display.  In the UK this included

    RAF Museum Cosford

    NMSI Store, Wroughton, Nr. Swindon

Napier Culverin Engine No 85006
press to zoom

In the late 1920's the Air Ministry entered in discussions with Hugo Junkers of Dessau, Germany to produce their new 6-cylinder opposed piston engine which was later designated Junkers 204.  The engine was fuel efficient and, being a diesel, didn't have the inherent risk of fire that petrol engines had.  The Air Ministry identified an immediate use for the engine in airships and long range patrol craft.  Unfortunatey the R101 airship for which it was intended crashed on its maiden voyage .



Initially Vickers were approached however the Ministry turned its attention to Napiers who were asked to produce seven prototype engines under licence from Junkers.  This they completed in 1936 and were fitted in Hawker Horsley J8620 and three in Blackburn Iris seaplane S-1593.  Unfortunately the build up to WWII meant that this engine was swept away to prepare for wartime requirements.  Whilst the Culverin ceased production after only seven engines had been produced all was not lost for the Company.  In 1946 Napiers started to design a revolutionary marine engine based on three Culverin in a triangular layout,  This was the famous "Deltic" engine.


As well as the Culverin which was based on the Junkers Jumo 204, Napiers also had the licence to produce the smaller and much more successful Junkers Jumo 205.  This was designated the name "Napier Cutlass" however it was never developed or produced.