Napier Deltic

Animation of a Deltic engine

The Napier Deltic is an unusual type of diesel engine. It was used in boats and railway locomotives. The cylinders are arranged in a triangular form with two pistons in each cylinder. There are three crankshafts which are geared together at one end of the engine. These engines usually had nine cylinders (three banks of three) or eighteen cylinders (six banks of three). These engines were built by D. Napier & Son.

Key to animation

• Green = incoming air
• Orange = burning fuel/air mixture
• Purple = outgoing exhaust gas

Napier Deltic Media

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  Animated diagram of Deltic engine

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  Cylinder firing order of the 18 cylinder Napier Deltic diesel engine: The grid represents triangular cylinder arrangement (banks A, B, C) and rows 1 to 6

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  The Deltic-powered Hunt-class mine countermeasures vessel HMS Ledbury

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  Napier Deltic powered British Rail Class 55 D9017 The Durham Light Infantry starting its engines at London King's Cross in 1966

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  Napier Deltic engine at the National Railway Museum, York