Napier Deltic

The Napier Deltic engine is a British opposed-piston valveless, two-stroke diesel engine used in marine and locomotive applications, designed and produced by Napier & Son. The cylinders were divided in three blocks in a triangular arrangement, the blocks forming sides with crankcases located in each apex of the triangle.

The term Deltic (meaning in the form of the Greek letter Delta) is used to refer to both the Deltic E.130 opposed-piston high-speed diesel engine and the locomotives produced by English Electric using these engines, including its demonstrator locomotive named DELTIC and the production version for British Railways, which designated these as (TOPS) Class 55.

A single half-sized, turbocharged Deltic power unit also featured in the English Electric-built Type 2 locomotive, designated as the Class 23. Both locomotive and engine became better known as the "Baby Deltic".